AI Trajectory

null

{
  "EnableConfigs": [
    "BLOCK",
    "MQ_IOSCHED_DEADLINE"
  ],
  "FocusSymbols": [
    "elevator_switch",
    "elevator_set_default",
    "elv_iosched_store",
    "elevator_change"
  ],
  "KMSANReasoning": "The patch adds a boolean field `no_quiesce` to `struct elv_change_ctx` to conditionally bypass `blk_mq_quiesce_queue()` and `blk_mq_unquiesce_queue()` in `elevator_switch()` when setting up the default elevator before a disk is added.\n\n1. No exposure of uninitialized memory: All instances of `struct elv_change_ctx` across the kernel are initialized using designated struct initializers (e.g. in `elevator_set_default()`, `elevator_set_none()`, `elv_iosched_store()`) or zero-allocated via `kzalloc_obj()` in `blk_mq_alloc_sched_ctx_batch()`. By C language semantics and allocator design, `no_quiesce` is always explicitly initialized to either true or false.\n2. No user-space copy or info-leak: `struct elv_change_ctx` is strictly an internal block-layer control structure and is never copied to user space or exposed via ioctls, sysfs, or netlink.\n3. KASAN vs. KMSAN: Any potential regressions introduced by skipping queue quiesce would manifest as race conditions, request queue state corruption, or use-after-free/double-free, which are the domain of standard locking checks, LOCKDEP, and KASAN. KMSAN checks for reads of uninitialized memory, which is not at risk here. Therefore, a dedicated KMSAN fuzzing session is not warranted.",
  "NeedsKMSAN": false,
  "Reasoning": "The patch modifies the core block layer elevator switching mechanism in elevator_switch() to conditionally skip quiescing the request queue (blk_mq_quiesce_queue / blk_mq_unquiesce_queue) when ctx-\u003eno_quiesce is set, and enables this flag in elevator_set_default(). This alters queue synchronization and quiesce semantics during default elevator initialization upon disk registration. The code is readily reachable via virtual block devices (such as loop or null_blk) and sysfs scheduler controls, making it worth fuzzing for race conditions or state inconsistencies.",
  "WorthFuzzing": true
}

null

{
  "PatchDiff": "commit 520f348d765fae1090e0a7fc5e8fd829a90182fc\nAuthor: syz-cluster \u003ctriage@syzkaller.com\u003e\nDate:   Thu Oct 15 04:07:01 2026 +0000\n\n    syz-cluster: applied patch under review\n\ndiff --git a/block/elevator.c b/block/elevator.c\nindex 2161b6eea680c..80cbac91581b0 100644\n--- a/block/elevator.c\n+++ b/block/elevator.c\n@@ -573,7 +573,8 @@ static int elevator_switch(struct request_queue *q, struct elv_change_ctx *ctx)\n \t\t\treturn -EINVAL;\n \t}\n \n-\tblk_mq_quiesce_queue(q);\n+\tif (!ctx-\u003eno_quiesce)\n+\t\tblk_mq_quiesce_queue(q);\n \n \tif (q-\u003eelevator) {\n \t\tctx-\u003eold = q-\u003eelevator;\n@@ -583,7 +584,7 @@ static int elevator_switch(struct request_queue *q, struct elv_change_ctx *ctx)\n \tif (new_e) {\n \t\tret = blk_mq_init_sched(q, new_e, \u0026ctx-\u003eres);\n \t\tif (ret)\n-\t\t\tgoto out_unfreeze;\n+\t\t\tgoto out_unquiesce;\n \t\tctx-\u003enew = q-\u003eelevator;\n \t} else {\n \t\tblk_queue_flag_clear(QUEUE_FLAG_SQ_SCHED, q);\n@@ -593,8 +594,9 @@ static int elevator_switch(struct request_queue *q, struct elv_change_ctx *ctx)\n \t}\n \tblk_add_trace_msg(q, \"elv switch: %s\", ctx-\u003ename);\n \n-out_unfreeze:\n-\tblk_mq_unquiesce_queue(q);\n+out_unquiesce:\n+\tif (!ctx-\u003eno_quiesce)\n+\t\tblk_mq_unquiesce_queue(q);\n \n \tif (ret) {\n \t\tpr_warn(\"elv: switch to \\\"%s\\\" failed, falling back to \\\"none\\\"\\n\",\n@@ -731,6 +733,7 @@ void elevator_set_default(struct request_queue *q)\n \tstruct elv_change_ctx ctx = {\n \t\t.name = \"mq-deadline\",\n \t\t.no_uevent = true,\n+\t\t.no_quiesce = true,\n \t};\n \tint err;\n \ndiff --git a/block/elevator.h b/block/elevator.h\nindex 3eb32516be0b1..3886d97427e33 100644\n--- a/block/elevator.h\n+++ b/block/elevator.h\n@@ -43,6 +43,8 @@ struct elevator_resources {\n struct elv_change_ctx {\n \tconst char *name;\n \tbool no_uevent;\n+\t/* the disk isn't added yet, so skip quiescing the queue */\n+\tbool no_quiesce;\n \n \t/* for unregistering old elevator */\n \tstruct elevator_queue *old;\n"
}

core

null

{
  "EnableConfigs": [
    "BLOCK",
    "MQ_IOSCHED_DEADLINE"
  ],
  "FocusSymbols": [
    "elevator_switch",
    "elevator_set_default",
    "elv_iosched_store",
    "elevator_change"
  ],
  "Reasoning": "The patch modifies the core block layer elevator switching mechanism in elevator_switch() to conditionally skip quiescing the request queue (blk_mq_quiesce_queue / blk_mq_unquiesce_queue) when ctx-\u003eno_quiesce is set, and enables this flag in elevator_set_default(). This alters queue synchronization and quiesce semantics during default elevator initialization upon disk registration. The code is readily reachable via virtual block devices (such as loop or null_blk) and sysfs scheduler controls, making it worth fuzzing for race conditions or state inconsistencies.",
  "WorthFuzzing": true
}

You are an expert Linux kernel maintainer and security engineer.
Your job is to review a provided patch series and evaluate whether it warrants fuzzing with syzkaller.

IMPORTANT: The changes have ALREADY been applied and committed as the HEAD commit in
your workspace. Do NOT rely on internal assumptions. You must actively use your code access
tools to inspect the actual source code, callers, and surrounding context.

================================================================================
1. CORE TRIAGE PHILOSOPHY
================================================================================
The goal of patch fuzzing is to discover crashes, regressions, exposed latent bugs,
and newly triggered assertions introduced by the patch series.

- REACHABILITY IS THE PRIMARY GATE:
  Fuzzing can only discover bugs in code that can actually execute in standard virtualized
  environments (GCE or QEMU, utilizing software-emulated devices like USB gadgets, netdev, tun/tap).
  If the modified code is structurally unreachable (see Section 2), it MUST NOT be fuzzed,
  regardless of whether it adds assertions or complex logic.

- DO NOT BLINDLY TRUST "NO FUNCTIONAL CHANGE" (NFCI) OR "REFACTORING" CLAIMS:
  Patch authors routinely label changes as "cleanups", "refactorings", or state
  "No functional change intended". Do NOT take these claims at face value.
  Code refactorings that rearrange logic, introduce helper functions, or alter state management
  in core subsystems frequently introduce subtle semantic shifts or uncover latent kernel bugs.
  If reachable executable code is modified or refactored, it MUST be fuzzed.

- NEW OR MODIFIED ASSERTIONS IN REACHABLE CODE MUST BE FUZZED:
  When a patch introduces or modifies runtime checks or assertions (e.g., WARN_ON*, VM_WARN_ON*,
  BUG_ON*, lockdep_assert*) in reachable code paths, it enforces new or stricter invariants.
  Even if the author believes the invariant always holds, fuzzing is essential to verify whether
  an unusual sequence of operations can violate it.

================================================================================
2. WHEN TO RETURN WorthFuzzing=false (NEGATIVE CRITERIA)
================================================================================
Return WorthFuzzing=false ONLY IF all modified code falls strictly into one or more of these categories:

- Non-kernel and non-executable changes:
  * Modifications to Documentation/, comments, or spelling fixes.
  * User-space directories, self-tests, samples, or scripts (e.g., tools/, samples/, scripts/, usr/)
    that do not affect the compiled kernel image (vmlinux) or kernel modules.
  * Purely decorative logging (e.g., message strings in pr_err, printk, dev_info) or tracepoints
    that do not alter control flow or data structures.
  * Build system or Kconfig changes that do not alter compiled C logic.
- Structurally unreachable hardware:
  * Vendor-specific PCIe switches, SmartNICs, or GPU drivers (e.g., mlxsw, pds_core, qed,
    ionic, amdgpu) requiring physical ASIC/PCIe cards not emulated in standard QEMU.
- Unreachable execution paths:
  * Driver teardown callbacks (.remove, .shutdown, pci_unregister_driver) executed only during
    physical PCI hot-unplug or manual sysfs driver unbinding.
  * Code paths exclusive to architectures other than the target architecture.

================================================================================
3. WHEN TO RETURN WorthFuzzing=true (POSITIVE CRITERIA)
================================================================================
Return WorthFuzzing=true whenever the patch touches reachable executable code, including:
- Core Subsystems:
  * Any logic modifications in memory management (mm/), synchronization/locking (kernel/locking/),
    BPF, scheduler, core networking, VFS, or syscall handling.
- Refactorings and Code Cleanups:
  * Any restructuring of reachable data structures, helper abstractions, or algorithm flows.
- Runtime Assertions and Defensive Checks:
  * Any introduction or alteration of assertions (WARN_ON*, VM_WARN_ON*, BUG_ON*, etc.) in reachable paths.
- Reachable Drivers and Protocols:
  * Drivers accessible via virtual buses (virtio, USB gadget, loopback, netlink, binder, sockets, etc.).

================================================================================
4. EXTRACTING FocusSymbols (PREVENTING DILUTION)
================================================================================
When WorthFuzzing=true, you must extract specific kernel functions into FocusSymbols to guide the fuzzer:

- AVOID UBIQUITOUS LIFECYCLE HOT-PATHS:
  Do NOT list generic, ubiquitous functions called by almost every program in the corpus
  (including, but not limited to: general memory allocators and deallocators, page fault
  and trap handlers, or core synchronization primitives; this is not an exhaustive list).
  Listing ubiquitous functions causes the fuzzer to classify thousands of unrelated tests as "focused",
  which severely dilutes fuzzing effort away from the actual changes.

- TARGET SPECIFIC FEATURE LOGIC AND ENTRYPOINTS:
  List functions that specifically implement the logic being added or altered, or direct API entrypoints
  for the subsystem feature under review.

- HANDLING STATIC INLINE FUNCTIONS IN HEADERS (.h):
  Compiler-inlined static functions (such as static inlines in mm/*.h or include/linux/*.h) lack
  distinct symbol addresses in vmlinux and cannot be targeted directly by symbol coverage filters.
  If the changes are primarily in static inline helpers, identify non-static, feature-specific caller
  functions in .c files that exercise them (avoiding ubiquitous lifecycle wrappers).

================================================================================
5. IDENTIFYING EnableConfigs
================================================================================
Identify any specific CONFIG_ options required to properly compile and reach the modified code:
- Inspect Kconfig files and #ifdef guards; do not make assumptions.
- Check "depends on" lines in Kconfig to include any non-standard parent subsystem configs needed.
- Strip any 'CONFIG_' prefix (e.g., return "NET_IPV4" instead of "CONFIG_NET_IPV4").
Prefer calling several tools at the same time to save round-trips.


Use set-results tool to provide results of the analysis.
It must be called exactly once before the final reply.
Ignore results of this tool.

Target architecture: amd64

For your convenience, here is the diff of the changes:
commit 520f348d765fae1090e0a7fc5e8fd829a90182fc
Author: syz-cluster <triage@syzkaller.com>
Date:   Thu Oct 15 04:07:01 2026 +0000

    syz-cluster: applied patch under review

diff --git a/block/elevator.c b/block/elevator.c
index 2161b6eea680c..80cbac91581b0 100644
--- a/block/elevator.c
+++ b/block/elevator.c
@@ -573,7 +573,8 @@ static int elevator_switch(struct request_queue *q, struct elv_change_ctx *ctx)
 			return -EINVAL;
 	}
 
-	blk_mq_quiesce_queue(q);
+	if (!ctx->no_quiesce)
+		blk_mq_quiesce_queue(q);
 
 	if (q->elevator) {
 		ctx->old = q->elevator;
@@ -583,7 +584,7 @@ static int elevator_switch(struct request_queue *q, struct elv_change_ctx *ctx)
 	if (new_e) {
 		ret = blk_mq_init_sched(q, new_e, &ctx->res);
 		if (ret)
-			goto out_unfreeze;
+			goto out_unquiesce;
 		ctx->new = q->elevator;
 	} else {
 		blk_queue_flag_clear(QUEUE_FLAG_SQ_SCHED, q);
@@ -593,8 +594,9 @@ static int elevator_switch(struct request_queue *q, struct elv_change_ctx *ctx)
 	}
 	blk_add_trace_msg(q, "elv switch: %s", ctx->name);
 
-out_unfreeze:
-	blk_mq_unquiesce_queue(q);
+out_unquiesce:
+	if (!ctx->no_quiesce)
+		blk_mq_unquiesce_queue(q);
 
 	if (ret) {
 		pr_warn("elv: switch to \"%s\" failed, falling back to \"none\"\n",
@@ -731,6 +733,7 @@ void elevator_set_default(struct request_queue *q)
 	struct elv_change_ctx ctx = {
 		.name = "mq-deadline",
 		.no_uevent = true,
+		.no_quiesce = true,
 	};
 	int err;
 
diff --git a/block/elevator.h b/block/elevator.h
index 3eb32516be0b1..3886d97427e33 100644
--- a/block/elevator.h
+++ b/block/elevator.h
@@ -43,6 +43,8 @@ struct elevator_resources {
 struct elv_change_ctx {
 	const char *name;
 	bool no_uevent;
+	/* the disk isn't added yet, so skip quiescing the queue */
+	bool no_quiesce;
 
 	/* for unregistering old elevator */
 	struct elevator_queue *old;

gemini-3.8-flash

null

null

							input: 3545
							output: 33
							thoughts: 811
						

**Analyzing the Elevator Switch Patch**

Alright, let's break this down. First, the patch touches `block/elevator.c` and `block/elevator.h` – that's our initial scope. Time to dig into the diff itself. The main focus seems to be the `elevator_switch` function, specifically related to quiescing and unquiescing the request queue.

Looking at the code, it looks like a conditional has been added around the `blk_mq_quiesce_queue` and `blk_mq_unquiesce_queue` calls. Now, they only execute if `ctx->no_quiesce` is false. This `ctx->no_quiesce` flag seems new, judging from the header file modification. Its comment suggests it's related to cases where "the disk isn't added yet, so skip quiescing the queue". This signals an attempt to potentially optimize or handle a specific initialization sequence.

The `elevator_set_default` function is also updated. It's now setting `ctx.no_quiesce` to `true` when setting the default scheduler to "mq-deadline". This is likely where the new functionality will be most visible.

The `out_unfreeze` label is now `out_unquiesce`. That's a cosmetic change but indicative of the name change.

Now I need to understand the scenarios where this `no_quiesce` flag becomes relevant. What's the context in which a disk is *not* "added yet" but scheduler configuration is already being changed? Initialization, perhaps?

I'm thinking this likely has something to do with the early-boot or hot-plug scenarios for block devices. The goal is to avoid unnecessary quiescing of the queue in some context. Let's see if further code analysis reveals where this context is used and why it's a good idea. Next, let's explore the surrounding code with `read-file` or `grepper` and see how this new flag is being used!

{
  "File": "block/elevator.c",
  "FirstLine": 560,
  "LineCount": 50
}

{
  "Contents": " 560:\t * to restore the old io scheduler, so leaving the io scheduler being none.\n 561:\t */\n 562:\tstatic int elevator_switch(struct request_queue *q, struct elv_change_ctx *ctx)\n 563:\t{\n 564:\t\tstruct elevator_type *new_e = NULL;\n 565:\t\tint ret = 0;\n 566:\t\n 567:\t\tWARN_ON_ONCE(q-\u003emq_freeze_depth == 0);\n 568:\t\tlockdep_assert_held(\u0026q-\u003eelevator_lock);\n 569:\t\n 570:\t\tif (strncmp(ctx-\u003ename, \"none\", 4)) {\n 571:\t\t\tnew_e = elevator_find_get(ctx-\u003ename);\n 572:\t\t\tif (!new_e)\n 573:\t\t\t\treturn -EINVAL;\n 574:\t\t}\n 575:\t\n 576:\t\tif (!ctx-\u003eno_quiesce)\n 577:\t\t\tblk_mq_quiesce_queue(q);\n 578:\t\n 579:\t\tif (q-\u003eelevator) {\n 580:\t\t\tctx-\u003eold = q-\u003eelevator;\n 581:\t\t\televator_exit(q);\n 582:\t\t}\n 583:\t\n 584:\t\tif (new_e) {\n 585:\t\t\tret = blk_mq_init_sched(q, new_e, \u0026ctx-\u003eres);\n 586:\t\t\tif (ret)\n 587:\t\t\t\tgoto out_unquiesce;\n 588:\t\t\tctx-\u003enew = q-\u003eelevator;\n 589:\t\t} else {\n 590:\t\t\tblk_queue_flag_clear(QUEUE_FLAG_SQ_SCHED, q);\n 591:\t\t\tq-\u003eelevator = NULL;\n 592:\t\t\tq-\u003enr_requests = q-\u003etag_set-\u003equeue_depth;\n 593:\t\t\tq-\u003easync_depth = q-\u003etag_set-\u003equeue_depth;\n 594:\t\t}\n 595:\t\tblk_add_trace_msg(q, \"elv switch: %s\", ctx-\u003ename);\n 596:\t\n 597:\tout_unquiesce:\n 598:\t\tif (!ctx-\u003eno_quiesce)\n 599:\t\t\tblk_mq_unquiesce_queue(q);\n 600:\t\n 601:\t\tif (ret) {\n 602:\t\t\tpr_warn(\"elv: switch to \\\"%s\\\" failed, falling back to \\\"none\\\"\\n\",\n 603:\t\t\t\tnew_e-\u003eelevator_name);\n 604:\t\t}\n 605:\t\n 606:\t\tif (new_e)\n 607:\t\t\televator_put(new_e);\n 608:\t\treturn ret;\n 609:\t}\n"
}

gemini-3.8-flash

null

null

							input: 5574
							output: 32
							thoughts: 19
						

Here's my analysis of the task and my approach to summarizing the provided text:

**Analyzing `elevator_set_default` and `elevator_switch` Callers**

Alright, so the task is to pinpoint where the functions `elevator_set_default` and `elevator_switch` are being used. Specifically, I need to identify the code paths that call those functions. This is a common and fundamental step in understanding the control flow and impact of any software system, especially when dealing with something as crucial as elevator control. I would initially want to conduct a static code analysis, using tools if available. This would allow me to quickly identify all instances of those function names within the codebase and generate a list of all callers. If static analysis is insufficient, I would need to turn to dynamic analysis, perhaps with a debugger or logging, to trace the calls at runtime. My primary interest is in understanding the context of the calls: what conditions trigger them, what arguments are being passed, and what other functions are being executed in close proximity. This will allow me to reconstruct the elevator's logic and the implications of its "default" and "switch" states. Ultimately, I'm looking to understand how the elevator's behavior is managed, and how changes to these functions might impact the broader system. I suspect, based on the function names, that these will be critical points of control for the elevator's behavior, and warrant very careful attention.

{
  "Expression": "elevator_switch|elevator_set_default",
  "PathPrefixes": [
    "block/"
  ]
}

{
  "Output": "block/blk-mq-sched.c=614=int blk_mq_init_sched(struct request_queue *q, struct elevator_type *e,\n--\nblock/blk-mq-sched.c-666-/*\nblock/blk-mq-sched.c:667: * called in either blk_queue_cleanup or elevator_switch, tagset\nblock/blk-mq-sched.c-668- * is required for freeing requests\n--\nblock/blk-sysfs.c=950=int blk_register_queue(struct gendisk *disk)\n--\nblock/blk-sysfs.c-991-\tif (queue_is_mq(q))\nblock/blk-sysfs.c:992:\t\televator_set_default(q);\nblock/blk-sysfs.c-993-\n--\nblock/blk.h=361=void elv_update_nr_hw_queues(struct request_queue *q,\nblock/blk.h-362-\t\tstruct elv_change_ctx *ctx);\nblock/blk.h:363:void elevator_set_default(struct request_queue *q);\nblock/blk.h-364-void elevator_set_none(struct request_queue *q);\n--\nblock/elevator.c=554=EXPORT_SYMBOL_GPL(elv_unregister);\n--\nblock/elevator.c-561- */\nblock/elevator.c:562:static int elevator_switch(struct request_queue *q, struct elv_change_ctx *ctx)\nblock/elevator.c-563-{\n--\nblock/elevator.c=655=static int elevator_change(struct request_queue *q, struct elv_change_ctx *ctx)\n--\nblock/elevator.c-682-\tif (!(q-\u003eelevator \u0026\u0026 elevator_match(q-\u003eelevator-\u003etype, ctx-\u003ename)))\nblock/elevator.c:683:\t\tret = elevator_switch(q, ctx);\nblock/elevator.c-684-\tmutex_unlock(\u0026q-\u003eelevator_lock);\n--\nblock/elevator.c=702=void elv_update_nr_hw_queues(struct request_queue *q,\n--\nblock/elevator.c-712-\t\t/* force to reattach elevator after nr_hw_queue is updated */\nblock/elevator.c:713:\t\tret = elevator_switch(q, ctx);\nblock/elevator.c-714-\t\tmutex_unlock(\u0026q-\u003eelevator_lock);\n--\nblock/elevator.c-730- */\nblock/elevator.c:731:void elevator_set_default(struct request_queue *q)\nblock/elevator.c-732-{\n"
}

gemini-3.8-flash

null

null

							input: 6596
							output: 33
							thoughts: 25
						

Okay, let's get down to brass tacks.

**Analyzing Elevator Functionality**

Right, so to understand this elevator behavior properly, I need to dive into the core implementation. I'm going to start by examining the `elevator_set_default` and `elevator_change` functions. Based on the file path, `block/elevator.c`, these functions are the essential components that manage the initial state and any subsequent modifications to the elevator's settings or operational parameters. I'll need to pay close attention to the logic within these functions, understanding how they influence the elevator's movement and other related behaviors. I'm especially interested in how they handle edge cases or potential conflicts. It's time to dig in and deconstruct the code.

{
  "File": "block/elevator.c",
  "FirstLine": 650,
  "LineCount": 95
}

{
  "Contents": " 650:\t}\n 651:\t\n 652:\t/*\n 653:\t * Switch this queue to the given IO scheduler.\n 654:\t */\n 655:\tstatic int elevator_change(struct request_queue *q, struct elv_change_ctx *ctx)\n 656:\t{\n 657:\t\tunsigned int memflags;\n 658:\t\tstruct blk_mq_tag_set *set = q-\u003etag_set;\n 659:\t\tint ret = 0;\n 660:\t\n 661:\t\tlockdep_assert_held(\u0026set-\u003eupdate_nr_hwq_lock);\n 662:\t\n 663:\t\tif (strncmp(ctx-\u003ename, \"none\", 4)) {\n 664:\t\t\tret = blk_mq_alloc_sched_res(q, ctx-\u003etype, \u0026ctx-\u003eres,\n 665:\t\t\t\t\tset-\u003enr_hw_queues);\n 666:\t\t\tif (ret)\n 667:\t\t\t\treturn ret;\n 668:\t\t}\n 669:\t\n 670:\t\tmemflags = blk_mq_freeze_queue(q);\n 671:\t\t/*\n 672:\t\t * May be called before adding disk, when there isn't any FS I/O,\n 673:\t\t * so freezing queue plus canceling dispatch work is enough to\n 674:\t\t * drain any dispatch activities originated from passthrough\n 675:\t\t * requests, then no need to quiesce queue which may add long boot\n 676:\t\t * latency, especially when lots of disks are involved.\n 677:\t\t *\n 678:\t\t * Disk isn't added yet, so verifying queue lock only manually.\n 679:\t\t */\n 680:\t\tblk_mq_cancel_work_sync(q);\n 681:\t\tmutex_lock(\u0026q-\u003eelevator_lock);\n 682:\t\tif (!(q-\u003eelevator \u0026\u0026 elevator_match(q-\u003eelevator-\u003etype, ctx-\u003ename)))\n 683:\t\t\tret = elevator_switch(q, ctx);\n 684:\t\tmutex_unlock(\u0026q-\u003eelevator_lock);\n 685:\t\tblk_mq_unfreeze_queue(q, memflags);\n 686:\t\tif (!ret)\n 687:\t\t\tret = elevator_change_done(q, ctx);\n 688:\t\n 689:\t\t/*\n 690:\t\t * Free sched resource if it's allocated but we couldn't switch elevator.\n 691:\t\t */\n 692:\t\tif (!ctx-\u003enew)\n 693:\t\t\tblk_mq_free_sched_res(\u0026ctx-\u003eres, ctx-\u003etype, set);\n 694:\t\n 695:\t\treturn ret;\n 696:\t}\n 697:\t\n 698:\t/*\n 699:\t * The I/O scheduler depends on the number of hardware queues, this forces a\n 700:\t * reattachment when nr_hw_queues changes.\n 701:\t */\n 702:\tvoid elv_update_nr_hw_queues(struct request_queue *q,\n 703:\t\t\tstruct elv_change_ctx *ctx)\n 704:\t{\n 705:\t\tstruct blk_mq_tag_set *set = q-\u003etag_set;\n 706:\t\tint ret = -ENODEV;\n 707:\t\n 708:\t\tWARN_ON_ONCE(q-\u003emq_freeze_depth == 0);\n 709:\t\n 710:\t\tif (ctx-\u003etype \u0026\u0026 !blk_queue_dying(q) \u0026\u0026 blk_queue_registered(q)) {\n 711:\t\t\tmutex_lock(\u0026q-\u003eelevator_lock);\n 712:\t\t\t/* force to reattach elevator after nr_hw_queue is updated */\n 713:\t\t\tret = elevator_switch(q, ctx);\n 714:\t\t\tmutex_unlock(\u0026q-\u003eelevator_lock);\n 715:\t\t}\n 716:\t\tblk_mq_unfreeze_queue_nomemrestore(q);\n 717:\t\tif (!ret)\n 718:\t\t\tWARN_ON_ONCE(elevator_change_done(q, ctx));\n 719:\t\n 720:\t\t/*\n 721:\t\t * Free sched resource if it's allocated but we couldn't switch elevator.\n 722:\t\t */\n 723:\t\tif (!ctx-\u003enew)\n 724:\t\t\tblk_mq_free_sched_res(\u0026ctx-\u003eres, ctx-\u003etype, set);\n 725:\t}\n 726:\t\n 727:\t/*\n 728:\t * Use the default elevator settings. If the chosen elevator initialization\n 729:\t * fails, fall back to the \"none\" elevator (no elevator).\n 730:\t */\n 731:\tvoid elevator_set_default(struct request_queue *q)\n 732:\t{\n 733:\t\tstruct elv_change_ctx ctx = {\n 734:\t\t\t.name = \"mq-deadline\",\n 735:\t\t\t.no_uevent = true,\n 736:\t\t\t.no_quiesce = true,\n 737:\t\t};\n 738:\t\tint err;\n 739:\t\n 740:\t\t/* now we allow to switch elevator */\n 741:\t\tblk_queue_flag_clear(QUEUE_FLAG_NO_ELV_SWITCH, q);\n 742:\t\n 743:\t\tif (q-\u003etag_set-\u003eflags \u0026 BLK_MQ_F_NO_SCHED_BY_DEFAULT)\n 744:\t\t\treturn;\n"
}

gemini-3.8-flash

null

null

							input: 8271
							output: 33
							thoughts: 14
						

Okay, here's my interpretation of that thought process, tailored for an expert audience, and written in the first person:

**Diving Deeper into `elevator_set_default`**

Alright, so the initial thought is to navigate further down into the code, specifically to the function or method `elevator_set_default`. It's pretty straightforward. We need to understand the behaviour of the system at that level. What's actually happening at that point in the lifecycle of this thing? Given we are at least competent and comfortable with the overall context, the thought is, let's stop guessing and start reading. I want to see what's *really* going on. I'm going to look at the implementation of `elevator_set_default`. It is critical to understand the implementation details of this function or method. Let’s get into the nitty gritty and see how it works!

{
  "File": "block/elevator.c",
  "FirstLine": 745,
  "LineCount": 40
}

{
  "Contents": " 745:\t\n 746:\t\t/*\n 747:\t\t * For single queue devices, default to using mq-deadline. If we\n 748:\t\t * have multiple queues or mq-deadline is not available, default\n 749:\t\t * to \"none\".\n 750:\t\t */\n 751:\t\tctx.type = elevator_find_get(ctx.name);\n 752:\t\tif (!ctx.type)\n 753:\t\t\treturn;\n 754:\t\n 755:\t\tif ((q-\u003enr_hw_queues == 1 ||\n 756:\t\t\t\tblk_mq_is_shared_tags(q-\u003etag_set-\u003eflags))) {\n 757:\t\t\terr = elevator_change(q, \u0026ctx);\n 758:\t\t\tif (err \u003c 0)\n 759:\t\t\t\tpr_warn(\"\\\"%s\\\" elevator initialization, failed %d, falling back to \\\"none\\\"\\n\",\n 760:\t\t\t\t\t\tctx.name, err);\n 761:\t\t}\n 762:\t\televator_put(ctx.type);\n 763:\t}\n 764:\t\n 765:\tvoid elevator_set_none(struct request_queue *q)\n 766:\t{\n 767:\t\tstruct elv_change_ctx ctx = {\n 768:\t\t\t.name\t= \"none\",\n 769:\t\t};\n 770:\t\tint err;\n 771:\t\n 772:\t\terr = elevator_change(q, \u0026ctx);\n 773:\t\tif (err \u003c 0)\n 774:\t\t\tpr_warn(\"%s: set none elevator failed %d\\n\", __func__, err);\n 775:\t}\n 776:\t\n 777:\tstatic void elv_iosched_load_module(const char *elevator_name)\n 778:\t{\n 779:\t\tstruct elevator_type *found;\n 780:\t\n 781:\t\tspin_lock(\u0026elv_list_lock);\n 782:\t\tfound = __elevator_find(elevator_name);\n 783:\t\tspin_unlock(\u0026elv_list_lock);\n 784:\t\n"
}

gemini-3.8-flash

null

null

							input: 9079
							output: 19
							thoughts: 23
						

Okay, here's my interpretation of that thought process, assuming I'm an expert in version control and software development:

**Analyzing the Last Commit's Context**

Right, before diving into the specifics of this patch, I need to get the bigger picture. I'm going to quickly pull up the `git log` for the most recent commit. That'll provide the essential context – the commit message, the changed files, and any related information. I want to understand *why* this change was made in the first place. What problem was it trying to solve? Was it a bug fix, a new feature, a refactor, or something else entirely? Knowing the "why" will significantly influence how I understand the patch itself and its implications. Context is key, after all.

{
  "Expression": "no_quiesce"
}

{
  "Output": "block/elevator.c=562=static int elevator_switch(struct request_queue *q, struct elv_change_ctx *ctx)\n--\nblock/elevator.c-575-\nblock/elevator.c:576:\tif (!ctx-\u003eno_quiesce)\nblock/elevator.c-577-\t\tblk_mq_quiesce_queue(q);\n--\nblock/elevator.c-597-out_unquiesce:\nblock/elevator.c:598:\tif (!ctx-\u003eno_quiesce)\nblock/elevator.c-599-\t\tblk_mq_unquiesce_queue(q);\n--\nblock/elevator.c=731=void elevator_set_default(struct request_queue *q)\n--\nblock/elevator.c-735-\t\t.no_uevent = true,\nblock/elevator.c:736:\t\t.no_quiesce = true,\nblock/elevator.c-737-\t};\n--\nblock/elevator.h=43=struct elv_change_ctx {\n--\nblock/elevator.h-46-\t/* the disk isn't added yet, so skip quiescing the queue */\nblock/elevator.h:47:\tbool no_quiesce;\nblock/elevator.h-48-\n"
}

gemini-3.8-flash

null

null

							input: 9617
							output: 29
							thoughts: 695
						

**Analyzing Block Layer Quiescing Behavior**

Okay, so I've been looking at this comment in `elevator_change` around line 672, the one about potentially skipping the queue quiescing in certain scenarios. It's hinting at a performance optimization related to how the I/O scheduler handles new disk additions. The comment mentions a situation where quiescing the queue might introduce long boot latencies, especially with many disks, so freezing the queue and canceling dispatch work is considered sufficient.

My immediate next step would be to dig into the version control history – ideally, I'd check `git log` or `git blame` to understand the context of that specific code change. Since I don't have direct access to `git`, I'll use the available tools to search for related comments and code modifications.

I noticed the connection in `elevator_set_default(struct request_queue *q)`. It's called when a block device queue is registered, like during `add_disk`, and it sets `ctx.no_quiesce = true;`. I've seen that `elevator_switch` checks this `no_quiesce` flag before calling `blk_mq_quiesce_queue` or `blk_mq_unquiesce_queue`. It's essentially conditional quiescing based on the `ctx` context.

Now, my focus shifts to understanding where `elevator_set_default` and `elevator_switch` are actually used. The code is in `block/elevator.c`, which is the heart of the block layer's I/O scheduling. The block layer is *very* core – it's fundamental to Linux, and it's definitely reachable. Think about any block device creation, attachment, opening, sysfs interaction with `/sys/block/*/queue/scheduler`, loop devices, network block devices, null_blk, zram, scsi_debug, virtio-blk, dm, md, everything. I know syzkaller is constantly hitting these paths with loop devices, `null_blk`, scheduler changes through sysfs, and filesystem creation on these devices.

Ah, wait a minute! Let's trace how `elevator_switch` is invoked. It is called from writing to `/sys/block/*/queue/scheduler`, which invokes `elv_iosched_store`, which in turn calls `elevator_change` and ultimately `elevator_switch`. The question now is: does `elv_iosched_store` itself set `no_quiesce`? I will immediately check `elv_iosched_store` in `block/elevator.c` to confirm or disprove my hypothesis.

{
  "Expression": "elv_iosched_store",
  "PathPrefixes": [
    "block/"
  ]
}

{
  "Output": "block/blk-sysfs.c=1036=void blk_unregister_queue(struct gendisk *disk)\n--\nblock/blk-sysfs.c-1049-\t * before removal of existing entries starts, protect against\nblock/blk-sysfs.c:1050:\t * concurrent elv_iosched_store() calls.\nblock/blk-sysfs.c-1051-\t */\n--\nblock/elevator.c=777=static void elv_iosched_load_module(const char *elevator_name)\n--\nblock/elevator.c-788-\nblock/elevator.c:789:ssize_t elv_iosched_store(struct gendisk *disk, const char *buf,\nblock/elevator.c-790-\t\t\t  size_t count)\n--\nblock/elevator.h=185=ssize_t elv_iosched_show(struct gendisk *disk, char *page);\nblock/elevator.h:186:ssize_t elv_iosched_store(struct gendisk *disk, const char *page, size_t count);\nblock/elevator.h-187-\n"
}

gemini-3.8-flash

null

null

							input: 11197
							output: 33
							thoughts: 20
						

Okay, let's dive into this. Here's my take on understanding this code:

**Analyzing `elv_iosched_store` in `block/elevator.c`**

Right, so I need to understand how the I/O scheduler state is being saved. The name `elv_iosched_store` immediately suggests this is the function responsible for persisting the scheduler's internal data, which makes sense. I need to figure out what data is being saved and *how*. Clearly, we're dealing with persistent storage of some kind, likely related to power management or system shutdown/restart. The `block/elevator.c` path tells me this relates to the block layer's elevator, which is the I/O scheduler's core. Given my expertise, I suspect this function is crucial for ensuring I/O performance and fairness isn't lost across reboots. I need to see what structures it's accessing and writing to, and what underlying storage mechanism it's utilizing. Is it writing to a configuration file? NVRAM? Or something else? Let's get to the code.

{
  "File": "block/elevator.c",
  "FirstLine": 785,
  "LineCount": 50
}

{
  "Contents": " 785:\t\tif (!found)\n 786:\t\t\trequest_module(\"%s-iosched\", elevator_name);\n 787:\t}\n 788:\t\n 789:\tssize_t elv_iosched_store(struct gendisk *disk, const char *buf,\n 790:\t\t\t\t  size_t count)\n 791:\t{\n 792:\t\tchar elevator_name[ELV_NAME_MAX];\n 793:\t\tstruct elv_change_ctx ctx = {};\n 794:\t\tint ret;\n 795:\t\tstruct request_queue *q = disk-\u003equeue;\n 796:\t\tstruct blk_mq_tag_set *set = q-\u003etag_set;\n 797:\t\n 798:\t\t/* Make sure queue is not in the middle of being removed */\n 799:\t\tif (!blk_queue_registered(q))\n 800:\t\t\treturn -ENOENT;\n 801:\t\n 802:\t\t/*\n 803:\t\t * If the attribute needs to load a module, do it before freezing the\n 804:\t\t * queue to ensure that the module file can be read when the request\n 805:\t\t * queue is the one for the device storing the module file.\n 806:\t\t */\n 807:\t\tstrscpy(elevator_name, buf, sizeof(elevator_name));\n 808:\t\tctx.name = strstrip(elevator_name);\n 809:\t\n 810:\t\telv_iosched_load_module(ctx.name);\n 811:\t\tctx.type = elevator_find_get(ctx.name);\n 812:\t\n 813:\t\t/*\n 814:\t\t * Use trylock to avoid circular lock dependency with kernfs active\n 815:\t\t * reference during concurrent disk deletion:\n 816:\t\t *   update_nr_hwq_lock -\u003e kn-\u003eactive (via del_gendisk -\u003e kobject_del)\n 817:\t\t *   kn-\u003eactive -\u003e update_nr_hwq_lock (via this sysfs write path)\n 818:\t\t *\n 819:\t\t * Use the writer lock instead of the reader lock of update_nr_hwq_lock\n 820:\t\t * to serialize the two-stage elevator switch steps in\n 821:\t\t * elevator_change(): the core switch step under the elevator lock and\n 822:\t\t * the elevator_change_done() step outside the elevator lock.\n 823:\t\t */\n 824:\t\tif (!down_write_trylock(\u0026set-\u003eupdate_nr_hwq_lock)) {\n 825:\t\t\tret = -EBUSY;\n 826:\t\t\tgoto out;\n 827:\t\t}\n 828:\t\tif (!blk_queue_no_elv_switch(q)) {\n 829:\t\t\tret = elevator_change(q, \u0026ctx);\n 830:\t\t\tif (!ret)\n 831:\t\t\t\tret = count;\n 832:\t\t} else {\n 833:\t\t\tret = -ENOENT;\n 834:\t\t}\n"
}

gemini-3.8-flash

null

null

							input: 12279
							output: 28
							thoughts: 175
						

**My Initial Thoughts on the Scheduler Context**

Okay, let's break this down. In `elv_iosched_store`, I see a `struct elv_change_ctx ctx = {};` initialization. That means `ctx.no_quiesce` starts as false, which makes sense. So, when the code writes to `/sys/block/*/queue/scheduler`, `elevator_switch` is going to execute with `no_quiesce = false`. Got it.

Now, things get interesting. I see that `elevator_set_default(q)` gets called through `blk_register_queue(struct gendisk *disk)`. When that happens, `ctx.no_quiesce` becomes true. That seems like a design choice to manage the quiesce process.

And then, when `elevator_set_none` runs, the context is re-initialized with `struct elv_change_ctx ctx = { .name = "none" };`, which implies `no_quiesce = false` again. So `no_quiesce` can be set to either `true` or `false` based on the elevator setup.

Hold on... I need to see where `blk_register_queue` is actually called. That's the crux of this. Time to trace that call.

{
  "Expression": "blk_register_queue",
  "PathPrefixes": [
    "block/"
  ]
}

{
  "Output": "block/blk-core.c=436=struct request_queue *blk_alloc_queue(struct queue_limits *lim, int node_id)\n--\nblock/blk-core.c-487-\t * Init percpu_ref in atomic mode so that it's faster to shutdown.\nblock/blk-core.c:488:\t * See blk_register_queue() for details.\nblock/blk-core.c-489-\t */\n--\nblock/blk-mq-debugfs.c=797=void blk_mq_debugfs_register_sched_hctx(struct request_queue *q,\n--\nblock/blk-mq-debugfs.c-806-\t * We will be called again later on with appropriate parent debugfs\nblock/blk-mq-debugfs.c:807:\t * directory from blk_register_queue()\nblock/blk-mq-debugfs.c-808-\t */\n--\nblock/blk-sysfs.c=931=static void blk_debugfs_remove(struct gendisk *disk)\n--\nblock/blk-sysfs.c-946-/**\nblock/blk-sysfs.c:947: * blk_register_queue - register a block layer queue with sysfs\nblock/blk-sysfs.c-948- * @disk: Disk of which the request queue should be registered with sysfs.\nblock/blk-sysfs.c-949- */\nblock/blk-sysfs.c:950:int blk_register_queue(struct gendisk *disk)\nblock/blk-sysfs.c-951-{\n--\nblock/blk-sysfs.c-1029-/**\nblock/blk-sysfs.c:1030: * blk_unregister_queue - counterpart of blk_register_queue()\nblock/blk-sysfs.c-1031- * @disk: Disk of which the request queue should be unregistered from sysfs.\n--\nblock/blk-sysfs.c-1033- * Note: the caller is responsible for guaranteeing that this function is called\nblock/blk-sysfs.c:1034: * after blk_register_queue() has finished.\nblock/blk-sysfs.c-1035- */\n--\nblock/genhd.c=427=static int __add_disk(struct device *parent, struct gendisk *disk,\n--\nblock/genhd.c-530-\nblock/genhd.c:531:\tret = blk_register_queue(disk);\nblock/genhd.c-532-\tif (ret)\n"
}

gemini-3.8-flash

null

null

							input: 13414
							output: 26
							thoughts: 1000
						

**Worth Fuzzing: Block Layer Elevator Switch with No-Quiesce Optimization**

Okay, let's break this down.  My initial thought is to trace the flow – `blk_register_queue` gets called in `__add_disk`, which is ultimately triggered by `device_add_disk`.  And `device_add_disk`, that's the kicker!  It's invoked for *every* block device: loop, brd, zram, you name it. And the userspace interface with `/sys/block/*/queue/scheduler` allows runtime elevator changes!

Now, the core of the change is in `elevator_switch`.  Previously, it *always* called `blk_mq_quiesce_queue` and `blk_mq_unquiesce_queue`. The commit makes it conditional on `!ctx->no_quiesce`.  The "aha!" moment is `elevator_set_default`, where `.no_quiesce = true` is now set. This clearly means the author specifically wants to *skip* those quiesce/unquiesce calls when setting the default elevator. And, I see they renamed the `out_unfreeze` label to `out_unquiesce`.

Okay, but why?  Let's refresh the commit message.  "May be called before adding disk, when there isn't any FS I/O, so freezing queue plus canceling dispatch work is enough to drain any dispatch activities originated from passthrough requests, then no need to quiesce queue which may add long boot latency, especially when lots of disks are involved." Okay, they're trying to avoid long boot latencies.

So, here's the crux: `elevator_switch` *used* to quiesce/unquiesce, but now, when setting the default elevator via `elevator_set_default`, it *doesn't*. The author is optimising by skipping the quiesce/unquiesce calls to `blk_mq_quiesce_queue`! This looks like a synchronization/quiescing change for the request queue during disk addition.

Is this fuzz-worthy?  Let's consider the criteria.  Block layer?  Core subsystem.  Modifications to locking/synchronization (quiesce/freeze)? Check.  Restructuring of data flow? Potentially, since we're bypassing certain code paths.  Reachable drivers (virtual buses)? Absolutely.  This is all achievable in a standard QEMU/KVM setup with virtual block devices like loopback, null_blk, etc.  If there are requests queued while the scheduler is switched, especially passthrough requests, we could easily be looking at race conditions or concurrency bugs.

So, yeah, this is definitely worth fuzzing.  WorthFuzzing=TRUE. Now, let's look at the config options and reachable symbols! We need to understand the Kconfig options required for this code to compile and be reachable, so let's check `block/Kconfig` and `block/Makefile`.

{
  "Expression": "elevator\\.o",
  "PathPrefixes": [
    "block/"
  ]
}

{
  "Output": "block/Makefile=6=CONTEXT_ANALYSIS := y\nblock/Makefile-7-\nblock/Makefile:8:obj-y\t\t:= bdev.o fops.o bio.o elevator.o blk-core.o blk-sysfs.o \\\nblock/Makefile-9-\t\t\tblk-flush.o blk-settings.o blk-ioc.o blk-map.o \\\n"
}

gemini-3.8-flash

null

null

							input: 15191
							output: 29
							thoughts: 35
						

Okay, here's my interpretation of that thought process, tailored for an expert audience, and written in the first person:

**Navigating the Kernel Build System: A Quick Dive**

Alright, so `elevator.o` is showing up in `obj-y`. That immediately tells me it's being linked into the image, likely as part of a statically built module or directly into the kernel itself. But the question that *immediately* pops up, is what knobs are actually controlling whether or not the elevator code is included. I need to figure out what configurations are responsible for the block layer or, more precisely, the elevator scheduling code.

My first port of call, naturally, is the `block/Kconfig` file. That's where all the high-level configuration options related to that subsystem should be defined. It'll be a matter of quickly scanning through that file to find the relevant `CONFIG_` options – typically related to I/O schedulers or block device behavior in general – that ultimately gate the inclusion of `elevator.o`. From there, I can trace dependencies if necessary, but that's the core of the investigation: Find the controlling configurations.

{
  "Expression": "MQ_DEADLINE|BLOCK",
  "PathPrefixes": [
    "block/"
  ]
}

{
  "Output": "\nFull output is too long, showing 200 out of 352 lines.\nUse more precise expression or PathPrefixes if possible.\n\nNumber of matching lines per file (19 files in total):\nblock/Kconfig:5\nblock/Makefile:1\nblock/badblocks.c:2\nblock/bdev.c:4\nblock/bio-integrity-auto.c:1\nblock/blk-core.c:1\nblock/blk-mq-debugfs.c:1\nblock/blk-mq.c:15\nblock/blk-mq.h:1\nblock/blk-pm.h:3\nblock/blk.h:4\nblock/bsg-lib.c:1\nblock/genhd.c:8\nblock/ioctl.c:3\nblock/partitions/Makefile:1\nblock/partitions/acorn.c:1\nblock/partitions/core.c:1\nblock/partitions/ldm.c:20\nblock/partitions/ldm.h:2\n\nblock/Kconfig-4-#\nblock/Kconfig:5:menuconfig BLOCK\nblock/Kconfig-6-       bool \"Enable the block layer\" if EXPERT\n--\nblock/Kconfig-26-\nblock/Kconfig:27:if BLOCK\nblock/Kconfig-28-\nblock/Kconfig:29:config BLOCK_LEGACY_AUTOLOAD\nblock/Kconfig-30-\tbool \"Legacy autoloading support\"\n--\nblock/Kconfig=214=config BLK_PM\n--\nblock/Kconfig-217-# do not use in new code\nblock/Kconfig:218:config BLOCK_HOLDER_DEPRECATED\nblock/Kconfig-219-\tbool\n--\nblock/Kconfig=232=source \"block/Kconfig.iosched\"\nblock/Kconfig-233-\nblock/Kconfig:234:endif # BLOCK\n--\nblock/Makefile=40=obj-$(CONFIG_BLK_INLINE_ENCRYPTION_FALLBACK)\t+= blk-crypto-fallback.o\nblock/Makefile:41:obj-$(CONFIG_BLOCK_HOLDER_DEPRECATED)\t+= holder.o\n--\nblock/badblocks.c=673=static bool can_front_overwrite(struct badblocks *bb, int prev,\n--\nblock/badblocks.c-702-\nblock/badblocks.c:703:\tif ((bb-\u003ecount + (*extra)) \u003e MAX_BADBLOCKS)\nblock/badblocks.c-704-\t\treturn false;\n--\nblock/badblocks.c=1049=static bool _badblocks_clear(struct badblocks *bb, sector_t s, sector_t sectors)\n--\nblock/badblocks.c-1130-\t\t\t/* Splitting */\nblock/badblocks.c:1131:\t\t\tif ((bb-\u003ecount + 1) \u003c= MAX_BADBLOCKS) {\nblock/badblocks.c-1132-\t\t\t\tlen = front_splitting_clear(bb, prev, \u0026bad);\n--\nblock/bdev.c=435=static void bdev_free_inode(struct inode *inode)\n--\nblock/bdev.c-448-\nblock/bdev.c:449:\tif (MAJOR(bdev-\u003ebd_dev) == BLOCK_EXT_MAJOR)\nblock/bdev.c-450-\t\tblk_free_ext_minor(MINOR(bdev-\u003ebd_dev));\n--\nblock/bdev.c=827=int bdev_permission(dev_t dev, blk_mode_t mode, void *holder)\n--\nblock/bdev.c-830-\nblock/bdev.c:831:\tret = devcgroup_check_permission(DEVCG_DEV_BLOCK,\nblock/bdev.c-832-\t\t\tMAJOR(dev), MINOR(dev),\n--\nblock/bdev.c=863=struct block_device *blkdev_get_no_open(dev_t dev, bool autoload)\n--\nblock/bdev.c-868-\tinode = ilookup(blockdev_superblock, dev);\nblock/bdev.c:869:\tif (!inode \u0026\u0026 autoload \u0026\u0026 IS_ENABLED(CONFIG_BLOCK_LEGACY_AUTOLOAD)) {\nblock/bdev.c-870-\t\tblk_request_module(dev);\n--\nblock/bdev.c=971=int bdev_open(struct block_device *bdev, blk_mode_t mode, void *holder,\n--\nblock/bdev.c-1017-\t\t    !bdev_test_flag(bdev, BD_WRITE_HOLDER) \u0026\u0026\nblock/bdev.c:1018:\t\t    (disk-\u003eevent_flags \u0026 DISK_EVENT_FLAG_BLOCK_ON_EXCL_WRITE)) {\nblock/bdev.c-1019-\t\t\tbdev_set_flag(bdev, BD_WRITE_HOLDER);\n--\nblock/bio-integrity-auto.c=83=void bio_integrity_prep(struct bio *bio, unsigned int action)\n--\nblock/bio-integrity-auto.c-89-\tbid-\u003ebio = bio;\nblock/bio-integrity-auto.c:90:\tbid-\u003ebip.bip_flags |= BIP_BLOCK_INTEGRITY;\nblock/bio-integrity-auto.c-91-\tbio_integrity_alloc_buf(bio, GFP_NOIO, action \u0026 BI_ACT_ZERO);\n--\nblock/blk-core.c=1269=void __blk_flush_plug(struct blk_plug *plug, bool from_schedule)\n--\nblock/blk-core.c-1283-\tplug-\u003ecur_ktime = 0;\nblock/blk-core.c:1284:\tcurrent-\u003eflags \u0026= ~PF_BLOCK_TS;\nblock/blk-core.c-1285-}\n--\nblock/blk-mq-debugfs.c=185=static const char *const hctx_flag_name[] = {\n--\nblock/blk-mq-debugfs.c-188-\tHCTX_FLAG_NAME(TAG_HCTX_SHARED),\nblock/blk-mq-debugfs.c:189:\tHCTX_FLAG_NAME(BLOCKING),\nblock/blk-mq-debugfs.c-190-\tHCTX_FLAG_NAME(TAG_RR),\n--\nblock/blk-mq.c=281=void blk_mq_wait_quiesce_done(struct blk_mq_tag_set *set)\nblock/blk-mq.c-282-{\nblock/blk-mq.c:283:\tif (set-\u003eflags \u0026 BLK_MQ_F_BLOCKING)\nblock/blk-mq.c-284-\t\tsynchronize_srcu(set-\u003esrcu);\n--\nblock/blk-mq.c=661=struct request *blk_mq_alloc_request(struct request_queue *q, blk_opf_t opf,\n--\nblock/blk-mq.c-695-\tblk_queue_exit(q);\nblock/blk-mq.c:696:\treturn ERR_PTR(-EWOULDBLOCK);\nblock/blk-mq.c-697-}\n--\nblock/blk-mq.c=700=struct request *blk_mq_alloc_request_hctx(struct request_queue *q,\n--\nblock/blk-mq.c-761-\nblock/blk-mq.c:762:\tret = -EWOULDBLOCK;\nblock/blk-mq.c-763-\ttag = blk_mq_get_tag(\u0026data);\n--\nblock/blk-mq.c=1236=static void __blk_mq_complete_request_remote(void *data)\nblock/blk-mq.c-1237-{\nblock/blk-mq.c:1238:\t__raise_softirq_irqoff(BLOCK_SOFTIRQ);\nblock/blk-mq.c-1239-}\n--\nblock/blk-mq.c=1277=static void blk_mq_raise_softirq(struct request *rq)\n--\nblock/blk-mq.c-1283-\tif (llist_add(\u0026rq-\u003eipi_list, list))\nblock/blk-mq.c:1284:\t\traise_softirq(BLOCK_SOFTIRQ);\nblock/blk-mq.c-1285-\tpreempt_enable();\n--\nblock/blk-mq.c=1416=void blk_execute_rq_nowait(struct request *rq, bool at_head)\n--\nblock/blk-mq.c-1430-\tblk_mq_insert_request(rq, at_head ? BLK_MQ_INSERT_AT_HEAD : 0);\nblock/blk-mq.c:1431:\tblk_mq_run_hw_queue(hctx, hctx-\u003eflags \u0026 BLK_MQ_F_BLOCKING);\nblock/blk-mq.c-1432-}\n--\nblock/blk-mq.c=2322=void blk_mq_run_hw_queue(struct blk_mq_hw_ctx *hctx, bool async)\n--\nblock/blk-mq.c-2330-\nblock/blk-mq.c:2331:\tmight_sleep_if(!async \u0026\u0026 hctx-\u003eflags \u0026 BLK_MQ_F_BLOCKING);\nblock/blk-mq.c-2332-\n--\nblock/blk-mq.c=2482=void blk_mq_start_hw_queue(struct blk_mq_hw_ctx *hctx)\n--\nblock/blk-mq.c-2485-\nblock/blk-mq.c:2486:\tblk_mq_run_hw_queue(hctx, hctx-\u003eflags \u0026 BLK_MQ_F_BLOCKING);\nblock/blk-mq.c-2487-}\n--\nblock/blk-mq.c=2516=void blk_mq_start_stopped_hw_queues(struct request_queue *q, bool async)\n--\nblock/blk-mq.c-2522-\t\tblk_mq_start_stopped_hw_queue(hctx, async ||\nblock/blk-mq.c:2523:\t\t\t\t\t(hctx-\u003eflags \u0026 BLK_MQ_F_BLOCKING));\nblock/blk-mq.c-2524-}\n--\nblock/blk-mq.c=4835=int blk_mq_alloc_tag_set(struct blk_mq_tag_set *set)\n--\nblock/blk-mq.c-4879-\nblock/blk-mq.c:4880:\tif (set-\u003eflags \u0026 BLK_MQ_F_BLOCKING) {\nblock/blk-mq.c-4881-\t\tset-\u003esrcu = kmalloc_obj(*set-\u003esrcu);\n--\nblock/blk-mq.c-4930-out_cleanup_srcu:\nblock/blk-mq.c:4931:\tif (set-\u003eflags \u0026 BLK_MQ_F_BLOCKING)\nblock/blk-mq.c-4932-\t\tcleanup_srcu_struct(set-\u003esrcu);\nblock/blk-mq.c-4933-out_free_srcu:\nblock/blk-mq.c:4934:\tif (set-\u003eflags \u0026 BLK_MQ_F_BLOCKING)\nblock/blk-mq.c-4935-\t\tkfree(set-\u003esrcu);\n--\nblock/blk-mq.c=4956=void blk_mq_free_tag_set(struct blk_mq_tag_set *set)\n--\nblock/blk-mq.c-4977-\tcleanup_srcu_struct(\u0026set-\u003etags_srcu);\nblock/blk-mq.c:4978:\tif (set-\u003eflags \u0026 BLK_MQ_F_BLOCKING) {\nblock/blk-mq.c-4979-\t\tsrcu_barrier(set-\u003esrcu);\n--\nblock/blk-mq.c=5282=static int __init blk_mq_init(void)\n--\nblock/blk-mq.c-5290-\t\t\t __blk_mq_complete_request_remote, NULL);\nblock/blk-mq.c:5291:\topen_softirq(BLOCK_SOFTIRQ, blk_done_softirq);\nblock/blk-mq.c-5292-\nblock/blk-mq.c:5293:\tcpuhp_setup_state_nocalls(CPUHP_BLOCK_SOFTIRQ_DEAD,\nblock/blk-mq.c-5294-\t\t\t\t  \"block/softirq:dead\", NULL,\n--\nblock/blk-mq.h=440=do {\t\t\t\t\t\t\t\t\\\nblock/blk-mq.h:441:\tif ((q)-\u003etag_set-\u003eflags \u0026 BLK_MQ_F_BLOCKING) {\t\t\\\nblock/blk-mq.h-442-\t\tstruct blk_mq_tag_set *__tag_set = (q)-\u003etag_set; \\\n--\nblock/blk-pm.h-2-\nblock/blk-pm.h:3:#ifndef _BLOCK_BLK_PM_H_\nblock/blk-pm.h:4:#define _BLOCK_BLK_PM_H_\nblock/blk-pm.h-5-\n--\nblock/blk-pm.h=30=static inline void blk_pm_mark_last_busy(struct request *rq)\n--\nblock/blk-pm.h-34-\nblock/blk-pm.h:35:#endif /* _BLOCK_BLK_PM_H_ */\n--\nblock/blk.h=261=static inline bool bio_integrity_endio(struct bio *bio)\n--\nblock/blk.h-264-\nblock/blk.h:265:\tif (bip \u0026\u0026 (bip-\u003ebip_flags \u0026 BIP_BLOCK_INTEGRITY))\nblock/blk.h-266-\t\treturn __bio_integrity_endio(bio);\n--\nblock/blk.h=723=static inline u64 blk_time_get_ns(void)\n--\nblock/blk.h-735-\t *\nblock/blk.h:736:\t * cur_ktime can be zeroed by pre-emption the moment PF_BLOCK_TS is set.\nblock/blk.h-737-\t */\n--\nblock/blk.h-741-\t\tWRITE_ONCE(plug-\u003ecur_ktime, now);\nblock/blk.h:742:\t\t/* Ensure PF_BLOCK_TS is set after cur_ktime. */\nblock/blk.h-743-\t\tbarrier();\nblock/blk.h:744:\t\tcurrent-\u003eflags |= PF_BLOCK_TS;\nblock/blk.h-745-\t}\n--\nblock/bsg-lib.c=362=struct request_queue *bsg_setup_queue(struct device *dev, const char *name,\n--\nblock/bsg-lib.c-383-\tset-\u003ecmd_size = sizeof(struct bsg_job) + dd_job_size;\nblock/bsg-lib.c:384:\tset-\u003eflags = BLK_MQ_F_BLOCKING;\nblock/bsg-lib.c-385-\tif (blk_mq_alloc_tag_set(set))\n--\nblock/genhd.c=178=static struct blk_major_name {\n--\nblock/genhd.c-181-\tchar name[16];\nblock/genhd.c:182:#ifdef CONFIG_BLOCK_LEGACY_AUTOLOAD\nblock/genhd.c-183-\tvoid (*probe)(dev_t devt);\n--\n\n"
}

gemini-3.8-flash

null

null

							input: 19379
							output: 33
							thoughts: 13
						

Okay, here's my take on those thoughts, tailored for an expert audience:

**Examining the I/O Scheduler Configuration**

Right, let's dive straight in. My first thought is to check the `block/Kconfig.iosched` file. We all know how critical the I/O scheduler is for performance, especially on systems with diverse storage configurations. I need to refresh my understanding of the current options, their default settings, and how they’re exposed to the user. I'm thinking about specific platform implications, potential conflicts with other block layer features, and the overall design philosophy that's shaping these configurations. I'm probably looking for clues about the supported schedulers, their dependencies, and any new schedulers or refinements that have been introduced recently. The Kconfig file is the source of truth, so it's the right place to begin this analysis. Time to get my hands dirty.

{
  "File": "block/Kconfig.iosched",
  "FirstLine": 1,
  "LineCount": 50
}

{
  "Contents": "   1:\t# SPDX-License-Identifier: GPL-2.0\n   2:\tmenu \"IO Schedulers\"\n   3:\t\n   4:\tconfig MQ_IOSCHED_DEADLINE\n   5:\t\ttristate \"MQ deadline I/O scheduler\"\n   6:\t\tdefault y\n   7:\t\thelp\n   8:\t\t  MQ version of the deadline IO scheduler.\n   9:\t\n  10:\tconfig MQ_IOSCHED_KYBER\n  11:\t\ttristate \"Kyber I/O scheduler\"\n  12:\t\tdefault y\n  13:\t\thelp\n  14:\t\t  The Kyber I/O scheduler is a low-overhead scheduler suitable for\n  15:\t\t  multiqueue and other fast devices. Given target latencies for reads and\n  16:\t\t  synchronous writes, it will self-tune queue depths to achieve that\n  17:\t\t  goal.\n  18:\t\n  19:\tconfig IOSCHED_BFQ\n  20:\t\ttristate \"BFQ I/O scheduler\"\n  21:\t\tselect BLK_ICQ\n  22:\t\thelp\n  23:\t\tBFQ I/O scheduler for BLK-MQ. BFQ distributes the bandwidth of\n  24:\t\tof the device among all processes according to their weights,\n  25:\t\tregardless of the device parameters and with any workload. It\n  26:\t\talso guarantees a low latency to interactive and soft\n  27:\t\treal-time applications.  Details in\n  28:\t\tDocumentation/block/bfq-iosched.rst\n  29:\t\n  30:\tconfig BFQ_GROUP_IOSCHED\n  31:\t       bool \"BFQ hierarchical scheduling support\"\n  32:\t       depends on IOSCHED_BFQ \u0026\u0026 BLK_CGROUP\n  33:\t       default y\n  34:\t       select BLK_CGROUP_RWSTAT\n  35:\t\thelp\n  36:\t\n  37:\t       Enable hierarchical scheduling in BFQ, using the blkio\n  38:\t       (cgroups-v1) or io (cgroups-v2) controller.\n  39:\t\n  40:\tconfig BFQ_CGROUP_DEBUG\n  41:\t\tbool \"BFQ IO controller debugging\"\n  42:\t\tdepends on BFQ_GROUP_IOSCHED\n  43:\t\thelp\n  44:\t\tEnable some debugging help. Currently it exports additional stat\n  45:\t\tfiles in a cgroup which can be useful for debugging.\n  46:\t\n  47:\tendmenu\n"
}

gemini-3.8-flash

null

null

							input: 20252
							output: 31
							thoughts: 357
						

**Analyzing the Dependencies of mq-deadline Scheduler**

Okay, so I'm diving into how `mq-deadline` gets enabled. The key seems to be `CONFIG_BLOCK` – it's the top-level config, and `CONFIG_MQ_IOSCHED_DEADLINE`, which defaults to 'y', is the one that actually compiles `mq-deadline`. It looks like `elevator_set_default(q)` sets this as the default elevator.

First, I need to confirm whether `MQ_IOSCHED_DEADLINE` is boolean or tristate. Ah, it's tristate with a default of 'y'. That means if `MQ_IOSCHED_DEADLINE` is set to either 'y' or 'm', deadline is available.

Looking at `elevator_set_default`, I can see a `struct elv_change_ctx ctx` that's set up with the name "mq-deadline". Crucially, there's this bit:

```c
	ctx.type = elevator_find_get(ctx.name);
	if (!ctx.type)
		return;
```

This means that if `MQ_IOSCHED_DEADLINE` is *not* enabled, `ctx.type` will be null, and the function will return early.  Therefore, it's pretty clear that `MQ_IOSCHED_DEADLINE` *must* be enabled to reach the `elevator_change(q, &ctx)` -> `elevator_switch(q, ctx)` calls that actually enable the scheduler within `elevator_set_default`. Got it.

So, `BLOCK` is the enclosing menuconfig. I need to make sure I understand the relationship.

Now let's verify where those configs are defined. `BLOCK` is defined via `menuconfig BLOCK` in `block/Kconfig`, and `MQ_IOSCHED_DEADLINE` is sourced from `block/Kconfig.iosched`, and I assume that file is included *if* `BLOCK` is enabled. Let me verify this.

Okay, let's now check the `block/Makefile` to see if there are any other configuration dependencies at play here.

{
  "Expression": "MQ_IOSCHED_DEADLINE",
  "PathPrefixes": [
    "block/"
  ]
}

{
  "Output": "block/Kconfig.iosched=2=menu \"IO Schedulers\"\nblock/Kconfig.iosched-3-\nblock/Kconfig.iosched:4:config MQ_IOSCHED_DEADLINE\nblock/Kconfig.iosched-5-\ttristate \"MQ deadline I/O scheduler\"\n--\nblock/Makefile=25=obj-$(CONFIG_BLK_CGROUP_IOCOST)\t+= blk-iocost.o\nblock/Makefile:26:obj-$(CONFIG_MQ_IOSCHED_DEADLINE)\t+= mq-deadline.o\nblock/Makefile-27-obj-$(CONFIG_MQ_IOSCHED_KYBER)\t+= kyber-iosched.o\n"
}

gemini-3.8-flash

null

null

							input: 21284
							output: 29
							thoughts: 208
						

Okay, let's see. My first thought is to zero in on those focus symbols. I need to understand exactly what modifications were made and which functions are directly impacted.

Looking at `block/elevator.c`, I see a few key players. The static function `elevator_switch` had a `no_quiesce` check introduced. Then, `elevator_set_default` - that non-static function - also had a change, where `no_quiesce = true` was added. `elevator_change` is there, obviously, as a caller of `elevator_switch`. And, finally, `elv_iosched_store` is that sysfs entry point for altering the scheduler, which is likely where the user interacts with this functionality through `/sys/block/*/queue/scheduler`.

Hold on a second! I need to quickly evaluate a subtle point. Can `elevator_switch` be targeted directly? I need to know if it's inlined, static, or just generally exposed in the symbol table. It looks like with GCC/Clang, `elevator_switch` is called from `elevator_change` and `elv_update_nr_hw_queues`. So, to get a clear picture of its impact, I need to check the exact number of callers `elevator_switch` has within `block/elevator.c`. That will help me understand the scope of these changes.

{
  "Expression": "elevator_switch",
  "PathPrefixes": [
    "block/elevator.c"
  ]
}

{
  "Output": "block/elevator.c=554=EXPORT_SYMBOL_GPL(elv_unregister);\n--\nblock/elevator.c-561- */\nblock/elevator.c:562:static int elevator_switch(struct request_queue *q, struct elv_change_ctx *ctx)\nblock/elevator.c-563-{\n--\nblock/elevator.c=655=static int elevator_change(struct request_queue *q, struct elv_change_ctx *ctx)\n--\nblock/elevator.c-682-\tif (!(q-\u003eelevator \u0026\u0026 elevator_match(q-\u003eelevator-\u003etype, ctx-\u003ename)))\nblock/elevator.c:683:\t\tret = elevator_switch(q, ctx);\nblock/elevator.c-684-\tmutex_unlock(\u0026q-\u003eelevator_lock);\n--\nblock/elevator.c=702=void elv_update_nr_hw_queues(struct request_queue *q,\n--\nblock/elevator.c-712-\t\t/* force to reattach elevator after nr_hw_queue is updated */\nblock/elevator.c:713:\t\tret = elevator_switch(q, ctx);\nblock/elevator.c-714-\t\tmutex_unlock(\u0026q-\u003eelevator_lock);\n"
}

gemini-3.8-flash

null

null

							input: 22130
							output: 193
							thoughts: 691
						

**Analysis of Block Layer Elevator Function Modifications**

Okay, let's break this down. My initial assessment is that we're dealing with modifications to some core block layer functions related to elevator management. `elevator_switch`, which is static and about 45 lines long and called only twice, is the central one. It seems this is the function being directly altered. `elevator_set_default` is a non-static symbol, and I see it's defined as `void elevator_set_default(struct request_queue *q)`. We also have `elv_iosched_store`, which handles sysfs interactions, and `elevator_change` and `elv_update_nr_hw_queues` involved in handling changes.

I quickly confirmed that `elevator_set_default` is indeed defined in `block/blk.h` and is called by `blk_register_queue`. That makes sense - it sets the initial elevator, thus changing the queue quiescing and synchronization semantics during elevator initialization when registering disks. The `elevator_switch` function is the one that's actually modified. `elv_iosched_store` is the sysfs entrypoint, and `elv_update_nr_hw_queues` handles updates for hardware queues.

Now, a crucial question: are these functions ubiquitous, or are they specific to a particular use case? They are not ubiquitous, which is good. They are specifically called when setting up or changing elevators on block devices. That narrows down the scope of impact. They're not lifecycle hot-paths, those are like `kmalloc`, `kfree`, page faults, and locking primitives. These are specific block layer functions.

Let's make sure I've got all the pieces. WorthFuzzing is true, and the focus symbols are `elevator_switch`, `elevator_set_default`, `elv_iosched_store`, and `elevator_change`. The relevant configs are `BLOCK` and `MQ_IOSCHED_DEADLINE`.

So, the reasoning here is pretty straightforward. This patch modifies `elevator_switch` to conditionally skip quiescing the request queue (`blk_mq_quiesce_queue` / `blk_mq_unquiesce_queue`) when `ctx->no_quiesce` is set. This `no_quiesce` flag is set in `elevator_set_default()`. Skipping quiescing is being made possible during elevator initialization when registering disks, changing the queue quiescing and synchronization semantics. This affects core block layer logic and is reachable via standard virtual block devices (like loop, null_blk) and elevator switching.

The real key here is fuzzing. Fuzzing helps ensure that skipping queue quiesce during elevator switch doesn't introduce any nasty race conditions or leave pending dispatch requests in an unexpected state. This change is subtle enough to potentially have surprising side effects that fuzzing is well-suited to catch. All that seems logical and accurate, so it's time to mark the findings.

{
  "EnableConfigs": [
    "BLOCK",
    "MQ_IOSCHED_DEADLINE"
  ],
  "FocusSymbols": [
    "elevator_switch",
    "elevator_set_default",
    "elv_iosched_store",
    "elevator_change"
  ],
  "Reasoning": "The patch modifies the core block layer elevator switching mechanism in elevator_switch() to conditionally skip quiescing the request queue (blk_mq_quiesce_queue / blk_mq_unquiesce_queue) when ctx-\u003eno_quiesce is set, and enables this flag in elevator_set_default(). This alters queue synchronization and quiesce semantics during default elevator initialization upon disk registration. The code is readily reachable via virtual block devices (such as loop or null_blk) and sysfs scheduler controls, making it worth fuzzing for race conditions or state inconsistencies.",
  "WorthFuzzing": true
}

{
  "EnableConfigs": [
    "BLOCK",
    "MQ_IOSCHED_DEADLINE"
  ],
  "FocusSymbols": [
    "elevator_switch",
    "elevator_set_default",
    "elv_iosched_store",
    "elevator_change"
  ],
  "Reasoning": "The patch modifies the core block layer elevator switching mechanism in elevator_switch() to conditionally skip quiescing the request queue (blk_mq_quiesce_queue / blk_mq_unquiesce_queue) when ctx-\u003eno_quiesce is set, and enables this flag in elevator_set_default(). This alters queue synchronization and quiesce semantics during default elevator initialization upon disk registration. The code is readily reachable via virtual block devices (such as loop or null_blk) and sysfs scheduler controls, making it worth fuzzing for race conditions or state inconsistencies.",
  "WorthFuzzing": true
}

{
  "WorthFuzzing": true
}

null

core

null

{
  "KMSANReasoning": "The patch adds a boolean field `no_quiesce` to `struct elv_change_ctx` to conditionally bypass `blk_mq_quiesce_queue()` and `blk_mq_unquiesce_queue()` in `elevator_switch()` when setting up the default elevator before a disk is added.\n\n1. No exposure of uninitialized memory: All instances of `struct elv_change_ctx` across the kernel are initialized using designated struct initializers (e.g. in `elevator_set_default()`, `elevator_set_none()`, `elv_iosched_store()`) or zero-allocated via `kzalloc_obj()` in `blk_mq_alloc_sched_ctx_batch()`. By C language semantics and allocator design, `no_quiesce` is always explicitly initialized to either true or false.\n2. No user-space copy or info-leak: `struct elv_change_ctx` is strictly an internal block-layer control structure and is never copied to user space or exposed via ioctls, sysfs, or netlink.\n3. KASAN vs. KMSAN: Any potential regressions introduced by skipping queue quiesce would manifest as race conditions, request queue state corruption, or use-after-free/double-free, which are the domain of standard locking checks, LOCKDEP, and KASAN. KMSAN checks for reads of uninitialized memory, which is not at risk here. Therefore, a dedicated KMSAN fuzzing session is not warranted.",
  "NeedsKMSAN": false
}

You are an expert Linux kernel security engineer specializing in kernel memory
error detectors (KASAN and KMSAN). Your job is to review the provided patch series and
determine if the code changes justify spawning a dedicated KMSAN (KernelMemorySanitizer)
fuzzing session in addition to standard KASAN fuzzing.

CRITICAL DISTINCTION BETWEEN KASAN AND KMSAN:
- Standard KASAN kernel builds (upstream-apparmor-kasan.config) already enable
  a comprehensive suite of debugging tools and sanitizers, including KASAN
  (out-of-bounds accesses, use-after-free, double free, invalid free), LOCKDEP
  (locking bugs and deadlocks), UB-sanitizers, and memory corruption checks.
- KMSAN (KernelMemorySanitizer) detects reads of UNINITIALIZED memory (stack, heap,
  or page allocations) and kernel-to-user memory info-leaks.

Rule: THERE IS NO SENSE IN RUNNING A KMSAN SESSION IF A BUG CAN BE CAUGHT BY KASAN,
LOCKDEP, OR OTHER STANDARD BUG DETECTORS.
A dedicated KMSAN fuzzing session incurs significant resource costs. You must ONLY
set NeedsKMSAN=true if the code changes introduce or expose UNINITIALIZED MEMORY risks
that are detected ONLY by KMSAN.

Look holistically at the patch series and surrounding code. Even if no direct
uninitialized field accesses or new buffer allocations are added in the diff itself,
a patch may alter control flow, bounds checking, or data length calculations in ways
that change how the rest of the code operates on existing buffers (e.g. allowing
uninitialized stack/heap memory to be read, copied to user space, or used in control
flow). Do not hesitate to use your code access tools to inspect the surrounding code,
called functions, and callers.

Set NeedsKMSAN=true ONLY IF the patch introduces or modifies:
1. Kernel structures sent to user space (via copy_to_user, put_user, netlink skb
   attributes, ioctl output arguments, socket options, or BPF buffers) where fields
   or structure padding might not be fully initialized/zeroed.
2. Conditional logic or branching that depends on potentially uninitialized variables
   or struct fields.
3. Allocation or initialization of complex data structures where uninitialized fields
   could be read later in reachable code paths.
4. Bounds checks, lengths, or logic in a way that allows surrounding code to access
   uninitialized bytes of existing buffers.

Set NeedsKMSAN=false IF:
- The code changes primarily risk out-of-bounds access, array overflows, NULL pointer
  dereferences, locking deadlocks, or use-after-free bugs (these are already caught
  by KASAN, LOCKDEP, or standard bug detectors).
- All stack/heap structures touched or introduced by the patch are fully zeroed
  or initialized (e.g. using = {0}, memset, kzalloc) before being read or copied.
- The patch does not introduce any risk of uninitialized memory usage or info-leaks.

Use your code access tools to inspect the surrounding code if necessary, then provide
detailed KMSANReasoning contrasting KASAN vs KMSAN applicability for this patch.
Prefer calling several tools at the same time to save round-trips.


Use set-results tool to provide results of the analysis.
It must be called exactly once before the final reply.
Ignore results of this tool.

Target architecture: amd64

For your convenience, here is the diff of the changes:
commit 520f348d765fae1090e0a7fc5e8fd829a90182fc
Author: syz-cluster <triage@syzkaller.com>
Date:   Thu Oct 15 04:07:01 2026 +0000

    syz-cluster: applied patch under review

diff --git a/block/elevator.c b/block/elevator.c
index 2161b6eea680c..80cbac91581b0 100644
--- a/block/elevator.c
+++ b/block/elevator.c
@@ -573,7 +573,8 @@ static int elevator_switch(struct request_queue *q, struct elv_change_ctx *ctx)
 			return -EINVAL;
 	}
 
-	blk_mq_quiesce_queue(q);
+	if (!ctx->no_quiesce)
+		blk_mq_quiesce_queue(q);
 
 	if (q->elevator) {
 		ctx->old = q->elevator;
@@ -583,7 +584,7 @@ static int elevator_switch(struct request_queue *q, struct elv_change_ctx *ctx)
 	if (new_e) {
 		ret = blk_mq_init_sched(q, new_e, &ctx->res);
 		if (ret)
-			goto out_unfreeze;
+			goto out_unquiesce;
 		ctx->new = q->elevator;
 	} else {
 		blk_queue_flag_clear(QUEUE_FLAG_SQ_SCHED, q);
@@ -593,8 +594,9 @@ static int elevator_switch(struct request_queue *q, struct elv_change_ctx *ctx)
 	}
 	blk_add_trace_msg(q, "elv switch: %s", ctx->name);
 
-out_unfreeze:
-	blk_mq_unquiesce_queue(q);
+out_unquiesce:
+	if (!ctx->no_quiesce)
+		blk_mq_unquiesce_queue(q);
 
 	if (ret) {
 		pr_warn("elv: switch to \"%s\" failed, falling back to \"none\"\n",
@@ -731,6 +733,7 @@ void elevator_set_default(struct request_queue *q)
 	struct elv_change_ctx ctx = {
 		.name = "mq-deadline",
 		.no_uevent = true,
+		.no_quiesce = true,
 	};
 	int err;
 
diff --git a/block/elevator.h b/block/elevator.h
index 3eb32516be0b1..3886d97427e33 100644
--- a/block/elevator.h
+++ b/block/elevator.h
@@ -43,6 +43,8 @@ struct elevator_resources {
 struct elv_change_ctx {
 	const char *name;
 	bool no_uevent;
+	/* the disk isn't added yet, so skip quiescing the queue */
+	bool no_quiesce;
 
 	/* for unregistering old elevator */
 	struct elevator_queue *old;

gemini-3.8-flash

null

null

							input: 2757
							output: 28
							thoughts: 340
						

**Evaluating the Need for KMSAN Fuzzing**

Okay, so the user wants me to assess whether this patch necessitates a dedicated KMSAN fuzzing run. My initial approach is always the same: let's start with a thorough diff inspection.

Alright, the changes involve `block/elevator.c` and `block/elevator.h`.  I see a new boolean field, `no_quiesce`, has been added to the `struct elv_change_ctx`.  That's interesting. The code then conditionally calls `blk_mq_quiesce_queue` and `blk_mq_unquiesce_queue` based on the state of this new `no_quiesce` flag within the `elevator_switch` function. It seems this flag is being used to prevent quiescing the queue in the specified circumstances. The `elevator_set_default` function is also being altered to set this `no_quiesce` flag to `true` under certain conditions.

Now, I need to understand the scope and impact of this change.  Where is `struct elv_change_ctx` allocated? What other places are initializing or using this struct? Is it used in other parts of the block layer?  I'll use `grepper` (or `read-file` if that's more appropriate, depending on the toolchain) to quickly identify the allocation sites, users, and initialization points of `struct elv_change_ctx` within the `block/` directory. That information will be key to understanding the potential for introducing new KMSAN-relevant issues, such as memory corruption, race conditions, or use-after-free situations.

{
  "Expression": "elv_change_ctx",
  "PathPrefixes": [
    "block/"
  ]
}

{
  "Output": "block/blk-mq-sched.c=445=void blk_mq_free_sched_res_batch(struct xarray *elv_tbl,\n--\nblock/blk-mq-sched.c-448-\tstruct request_queue *q;\nblock/blk-mq-sched.c:449:\tstruct elv_change_ctx *ctx;\nblock/blk-mq-sched.c-450-\n--\nblock/blk-mq-sched.c=472=void blk_mq_free_sched_ctx_batch(struct xarray *elv_tbl)\n--\nblock/blk-mq-sched.c-474-\tunsigned long i;\nblock/blk-mq-sched.c:475:\tstruct elv_change_ctx *ctx;\nblock/blk-mq-sched.c-476-\n--\nblock/blk-mq-sched.c=483=int blk_mq_alloc_sched_ctx_batch(struct xarray *elv_tbl,\n--\nblock/blk-mq-sched.c-486-\tstruct request_queue *q;\nblock/blk-mq-sched.c:487:\tstruct elv_change_ctx *ctx;\nblock/blk-mq-sched.c-488-\n--\nblock/blk-mq-sched.c-491-\tlist_for_each_entry(q, \u0026set-\u003etag_list, tag_set_list) {\nblock/blk-mq-sched.c:492:\t\tctx = kzalloc_obj(struct elv_change_ctx);\nblock/blk-mq-sched.c-493-\t\tif (!ctx)\n--\nblock/blk-mq-sched.c=569=int blk_mq_alloc_sched_res_batch(struct xarray *elv_tbl,\n--\nblock/blk-mq-sched.c-571-{\nblock/blk-mq-sched.c:572:\tstruct elv_change_ctx *ctx;\nblock/blk-mq-sched.c-573-\tstruct request_queue *q;\n--\nblock/blk-mq.c=5049=static void blk_mq_elv_switch_back(struct request_queue *q,\n--\nblock/blk-mq.c-5051-{\nblock/blk-mq.c:5052:\tstruct elv_change_ctx *ctx = xa_load(elv_tbl, q-\u003eid);\nblock/blk-mq.c-5053-\n--\nblock/blk-mq.c=5068=static int blk_mq_elv_switch_none(struct request_queue *q,\n--\nblock/blk-mq.c-5070-{\nblock/blk-mq.c:5071:\tstruct elv_change_ctx *ctx;\nblock/blk-mq.c-5072-\n--\nblock/blk.h-14-\nblock/blk.h:15:struct elv_change_ctx;\nblock/blk.h-16-\n--\nblock/blk.h=361=void elv_update_nr_hw_queues(struct request_queue *q,\nblock/blk.h:362:\t\tstruct elv_change_ctx *ctx);\nblock/blk.h-363-void elevator_set_default(struct request_queue *q);\n--\nblock/elevator.c=554=EXPORT_SYMBOL_GPL(elv_unregister);\n--\nblock/elevator.c-561- */\nblock/elevator.c:562:static int elevator_switch(struct request_queue *q, struct elv_change_ctx *ctx)\nblock/elevator.c-563-{\n--\nblock/elevator.c-610-\nblock/elevator.c:611:static void elv_exit_and_release(struct elv_change_ctx *ctx,\nblock/elevator.c-612-\t\tstruct request_queue *q)\n--\nblock/elevator.c=629=static int elevator_change_done(struct request_queue *q,\nblock/elevator.c:630:\t\t\t\tstruct elv_change_ctx *ctx)\nblock/elevator.c-631-{\n--\nblock/elevator.c-654- */\nblock/elevator.c:655:static int elevator_change(struct request_queue *q, struct elv_change_ctx *ctx)\nblock/elevator.c-656-{\n--\nblock/elevator.c=702=void elv_update_nr_hw_queues(struct request_queue *q,\nblock/elevator.c:703:\t\tstruct elv_change_ctx *ctx)\nblock/elevator.c-704-{\n--\nblock/elevator.c=731=void elevator_set_default(struct request_queue *q)\nblock/elevator.c-732-{\nblock/elevator.c:733:\tstruct elv_change_ctx ctx = {\nblock/elevator.c-734-\t\t.name = \"mq-deadline\",\n--\nblock/elevator.c=765=void elevator_set_none(struct request_queue *q)\nblock/elevator.c-766-{\nblock/elevator.c:767:\tstruct elv_change_ctx ctx = {\nblock/elevator.c-768-\t\t.name\t= \"none\",\n--\nblock/elevator.c=789=ssize_t elv_iosched_store(struct gendisk *disk, const char *buf,\n--\nblock/elevator.c-792-\tchar elevator_name[ELV_NAME_MAX];\nblock/elevator.c:793:\tstruct elv_change_ctx ctx = {};\nblock/elevator.c-794-\tint ret;\n--\nblock/elevator.h=35=struct elevator_resources {\n--\nblock/elevator.h-42-/* Holding context data for changing elevator */\nblock/elevator.h:43:struct elv_change_ctx {\nblock/elevator.h-44-\tconst char *name;\n"
}

gemini-3.8-flash

null

null

							input: 4975
							output: 33
							thoughts: 23
						

Here's a first-person summary, tailored for an expert audience, as requested:

**Diving Deep into `block/elevator.c`**

Alright, let's zero in on `block/elevator.c`. My immediate focus is the region between lines 560 and 800. This is typically where the more intricate aspects of the elevator algorithm are implemented. I'm expecting to find the core decision-making logic: how the elevator scheduler determines which requests to service next, how it handles starvation, and how it potentially optimizes for throughput or latency.

I anticipate seeing the implementation of the request queue data structure, and the logic that manipulates it. Perhaps there's an attempt to minimize disk head movement, a consideration for request priorities, or maybe some form of deadline scheduling. I will be looking closely at the data structures being used to see if the implementation takes into consideration different disk types.

Depending on the complexity of the elevator, I might encounter nested loops or potentially recursion. I'll need to follow the control flow carefully to understand the exact mechanics of the algorithm. I'll be particularly interested to see if there are any edge cases being handled - how the algorithm behaves when the queue is empty, or when there are a large number of requests. Furthermore, I'll be keeping an eye out for any potential race conditions or locking issues, especially if the code uses multi-threading. Let's see what gems are hidden in this section...

{
  "File": "block/elevator.c",
  "FirstLine": 560,
  "LineCount": 60
}

{
  "Contents": " 560:\t * to restore the old io scheduler, so leaving the io scheduler being none.\n 561:\t */\n 562:\tstatic int elevator_switch(struct request_queue *q, struct elv_change_ctx *ctx)\n 563:\t{\n 564:\t\tstruct elevator_type *new_e = NULL;\n 565:\t\tint ret = 0;\n 566:\t\n 567:\t\tWARN_ON_ONCE(q-\u003emq_freeze_depth == 0);\n 568:\t\tlockdep_assert_held(\u0026q-\u003eelevator_lock);\n 569:\t\n 570:\t\tif (strncmp(ctx-\u003ename, \"none\", 4)) {\n 571:\t\t\tnew_e = elevator_find_get(ctx-\u003ename);\n 572:\t\t\tif (!new_e)\n 573:\t\t\t\treturn -EINVAL;\n 574:\t\t}\n 575:\t\n 576:\t\tif (!ctx-\u003eno_quiesce)\n 577:\t\t\tblk_mq_quiesce_queue(q);\n 578:\t\n 579:\t\tif (q-\u003eelevator) {\n 580:\t\t\tctx-\u003eold = q-\u003eelevator;\n 581:\t\t\televator_exit(q);\n 582:\t\t}\n 583:\t\n 584:\t\tif (new_e) {\n 585:\t\t\tret = blk_mq_init_sched(q, new_e, \u0026ctx-\u003eres);\n 586:\t\t\tif (ret)\n 587:\t\t\t\tgoto out_unquiesce;\n 588:\t\t\tctx-\u003enew = q-\u003eelevator;\n 589:\t\t} else {\n 590:\t\t\tblk_queue_flag_clear(QUEUE_FLAG_SQ_SCHED, q);\n 591:\t\t\tq-\u003eelevator = NULL;\n 592:\t\t\tq-\u003enr_requests = q-\u003etag_set-\u003equeue_depth;\n 593:\t\t\tq-\u003easync_depth = q-\u003etag_set-\u003equeue_depth;\n 594:\t\t}\n 595:\t\tblk_add_trace_msg(q, \"elv switch: %s\", ctx-\u003ename);\n 596:\t\n 597:\tout_unquiesce:\n 598:\t\tif (!ctx-\u003eno_quiesce)\n 599:\t\t\tblk_mq_unquiesce_queue(q);\n 600:\t\n 601:\t\tif (ret) {\n 602:\t\t\tpr_warn(\"elv: switch to \\\"%s\\\" failed, falling back to \\\"none\\\"\\n\",\n 603:\t\t\t\tnew_e-\u003eelevator_name);\n 604:\t\t}\n 605:\t\n 606:\t\tif (new_e)\n 607:\t\t\televator_put(new_e);\n 608:\t\treturn ret;\n 609:\t}\n 610:\t\n 611:\tstatic void elv_exit_and_release(struct elv_change_ctx *ctx,\n 612:\t\t\tstruct request_queue *q)\n 613:\t{\n 614:\t\tstruct elevator_queue *e;\n 615:\t\tunsigned memflags;\n 616:\t\n 617:\t\tmemflags = blk_mq_freeze_queue(q);\n 618:\t\tmutex_lock(\u0026q-\u003eelevator_lock);\n 619:\t\te = q-\u003eelevator;\n"
}

gemini-3.8-flash

null

null

							input: 6228
							output: 33
							thoughts: 24
						

Okay, here's my interpretation of what I would be thinking, as an expert, based on that directive:

**Analyzing `block/elevator.c` - Lines 720-810**

Alright, let's zoom in on `block/elevator.c`, specifically lines 720 to 810. My intuition tells me this likely contains the core logic for either dispatching requests or, more likely, managing the elevator's internal request queue, perhaps handling prioritization or conflict resolution. Given the context, I'm expecting to find something about how the elevator figures out what floor to serve next, and in what order. I'll be looking for any hints about the scheduling algorithm used here, whether it’s simple First-Come-First-Served (FCFS), Shortest Seek Time First (SSTF), SCAN/LOOK, or something more sophisticated that considers both passenger requests and current elevator position, direction, and load. I will need to understand what variables or data structures are being used to represent the requests. I also anticipate finding where decisions are made about things like direction changes, door control, and idle states, particularly if any of this code is integrated with external system modules. Are there any edge cases handled? For example, how does the system deal with multiple requests in the same direction? Or what about requests that might be considered "urgent," such as fire alarm activation? I'm anticipating some pointer manipulation, maybe some mutex usage for thread safety if this code is multi-threaded. Ultimately, I'm seeking to understand the elevator's "brain" – the decision-making process that dictates its behavior.

{
  "File": "block/elevator.c",
  "FirstLine": 720,
  "LineCount": 80
}

{
  "Contents": " 720:\t\t/*\n 721:\t\t * Free sched resource if it's allocated but we couldn't switch elevator.\n 722:\t\t */\n 723:\t\tif (!ctx-\u003enew)\n 724:\t\t\tblk_mq_free_sched_res(\u0026ctx-\u003eres, ctx-\u003etype, set);\n 725:\t}\n 726:\t\n 727:\t/*\n 728:\t * Use the default elevator settings. If the chosen elevator initialization\n 729:\t * fails, fall back to the \"none\" elevator (no elevator).\n 730:\t */\n 731:\tvoid elevator_set_default(struct request_queue *q)\n 732:\t{\n 733:\t\tstruct elv_change_ctx ctx = {\n 734:\t\t\t.name = \"mq-deadline\",\n 735:\t\t\t.no_uevent = true,\n 736:\t\t\t.no_quiesce = true,\n 737:\t\t};\n 738:\t\tint err;\n 739:\t\n 740:\t\t/* now we allow to switch elevator */\n 741:\t\tblk_queue_flag_clear(QUEUE_FLAG_NO_ELV_SWITCH, q);\n 742:\t\n 743:\t\tif (q-\u003etag_set-\u003eflags \u0026 BLK_MQ_F_NO_SCHED_BY_DEFAULT)\n 744:\t\t\treturn;\n 745:\t\n 746:\t\t/*\n 747:\t\t * For single queue devices, default to using mq-deadline. If we\n 748:\t\t * have multiple queues or mq-deadline is not available, default\n 749:\t\t * to \"none\".\n 750:\t\t */\n 751:\t\tctx.type = elevator_find_get(ctx.name);\n 752:\t\tif (!ctx.type)\n 753:\t\t\treturn;\n 754:\t\n 755:\t\tif ((q-\u003enr_hw_queues == 1 ||\n 756:\t\t\t\tblk_mq_is_shared_tags(q-\u003etag_set-\u003eflags))) {\n 757:\t\t\terr = elevator_change(q, \u0026ctx);\n 758:\t\t\tif (err \u003c 0)\n 759:\t\t\t\tpr_warn(\"\\\"%s\\\" elevator initialization, failed %d, falling back to \\\"none\\\"\\n\",\n 760:\t\t\t\t\t\tctx.name, err);\n 761:\t\t}\n 762:\t\televator_put(ctx.type);\n 763:\t}\n 764:\t\n 765:\tvoid elevator_set_none(struct request_queue *q)\n 766:\t{\n 767:\t\tstruct elv_change_ctx ctx = {\n 768:\t\t\t.name\t= \"none\",\n 769:\t\t};\n 770:\t\tint err;\n 771:\t\n 772:\t\terr = elevator_change(q, \u0026ctx);\n 773:\t\tif (err \u003c 0)\n 774:\t\t\tpr_warn(\"%s: set none elevator failed %d\\n\", __func__, err);\n 775:\t}\n 776:\t\n 777:\tstatic void elv_iosched_load_module(const char *elevator_name)\n 778:\t{\n 779:\t\tstruct elevator_type *found;\n 780:\t\n 781:\t\tspin_lock(\u0026elv_list_lock);\n 782:\t\tfound = __elevator_find(elevator_name);\n 783:\t\tspin_unlock(\u0026elv_list_lock);\n 784:\t\n 785:\t\tif (!found)\n 786:\t\t\trequest_module(\"%s-iosched\", elevator_name);\n 787:\t}\n 788:\t\n 789:\tssize_t elv_iosched_store(struct gendisk *disk, const char *buf,\n 790:\t\t\t\t  size_t count)\n 791:\t{\n 792:\t\tchar elevator_name[ELV_NAME_MAX];\n 793:\t\tstruct elv_change_ctx ctx = {};\n 794:\t\tint ret;\n 795:\t\tstruct request_queue *q = disk-\u003equeue;\n 796:\t\tstruct blk_mq_tag_set *set = q-\u003etag_set;\n 797:\t\n 798:\t\t/* Make sure queue is not in the middle of being removed */\n 799:\t\tif (!blk_queue_registered(q))\n"
}

gemini-3.8-flash

null

null

							input: 7790
							output: 349
							thoughts: 1004
						

**KMSAN Assessment: No Uninitialized Memory Read**

Okay, let's break this down. My initial thought is to trace the origins of `struct elv_change_ctx` and how it's used. From what I see, it's created in a few places: `elevator_set_default`, `elevator_set_none`, `elv_iosched_store`, and `blk_mq_alloc_sched_ctx_batch`. Critically, I note that in the first three cases, we're either using designated initializers, which zero-initialize unspecified members (standard C behavior) or explicitly initializing all members. The fourth case uses `kzalloc_obj`, which is a zero-allocator. No issues there.

The crucial question is whether this structure is ever communicated to user space. After a thorough review, I can confirm that `elv_change_ctx` is entirely internal to the kernel's block layer and never crosses that boundary. It's solely used within `block/elevator.c` and `block/blk-mq-sched.c`, tracking elevator switching context.

This patch adds a `no_quiesce` boolean field to the struct, and it's initialized in all cases. In `elevator_set_default`, it's explicitly set to `true`. In the other cases, it's either explicitly or implicitly initialized to `false`. There's no conditional logic that depends on an uninitialized value, and there are no instances of the structure's fields being read without initialization.

Now, to address the KMSAN criteria directly:

1.  **No Kernel Structures to User Space:** `struct elv_change_ctx` is never copied to user space. It is only used internally.
2.  **No Uninitialized Variable Dependency:** The `no_quiesce` flag is always properly initialized.
3.  **No Complex Uninitialized Data:** The struct is not complex, and zeroing is ensured.
4.  **No Bounds Check Vulnerabilities:** The patch doesn't alter any bounds checks or buffer lengths that could allow reading uninitialized memory.

This patch primarily seems to be a synchronization/concurrency/queue state management change related to queue quiescing during elevator setup. This could potentially introduce deadlocks or race conditions, but these would be identified by standard kernel testing, KASAN, or LOCKDEP. The change doesn't introduce any risk of uninitialized memory reads or information leaks to userspace. Therefore, this patch does *not* require KMSAN. KMSAN is the wrong tool for this particular task.

{
  "KMSANReasoning": "The patch adds a boolean field `no_quiesce` to `struct elv_change_ctx` to conditionally bypass `blk_mq_quiesce_queue()` and `blk_mq_unquiesce_queue()` in `elevator_switch()` when setting up the default elevator before a disk is added.\n\n1. No exposure of uninitialized memory: All instances of `struct elv_change_ctx` across the kernel are initialized using designated struct initializers (e.g. in `elevator_set_default()`, `elevator_set_none()`, `elv_iosched_store()`) or zero-allocated via `kzalloc_obj()` in `blk_mq_alloc_sched_ctx_batch()`. By C language semantics and allocator design, `no_quiesce` is always explicitly initialized to either true or false.\n2. No user-space copy or info-leak: `struct elv_change_ctx` is strictly an internal block-layer control structure and is never copied to user space or exposed via ioctls, sysfs, or netlink.\n3. KASAN vs. KMSAN: Any potential regressions introduced by skipping queue quiesce would manifest as race conditions, request queue state corruption, or use-after-free/double-free, which are the domain of standard locking checks, LOCKDEP, and KASAN. KMSAN checks for reads of uninitialized memory, which is not at risk here. Therefore, a dedicated KMSAN fuzzing session is not warranted.",
  "NeedsKMSAN": false
}

{
  "KMSANReasoning": "The patch adds a boolean field `no_quiesce` to `struct elv_change_ctx` to conditionally bypass `blk_mq_quiesce_queue()` and `blk_mq_unquiesce_queue()` in `elevator_switch()` when setting up the default elevator before a disk is added.\n\n1. No exposure of uninitialized memory: All instances of `struct elv_change_ctx` across the kernel are initialized using designated struct initializers (e.g. in `elevator_set_default()`, `elevator_set_none()`, `elv_iosched_store()`) or zero-allocated via `kzalloc_obj()` in `blk_mq_alloc_sched_ctx_batch()`. By C language semantics and allocator design, `no_quiesce` is always explicitly initialized to either true or false.\n2. No user-space copy or info-leak: `struct elv_change_ctx` is strictly an internal block-layer control structure and is never copied to user space or exposed via ioctls, sysfs, or netlink.\n3. KASAN vs. KMSAN: Any potential regressions introduced by skipping queue quiesce would manifest as race conditions, request queue state corruption, or use-after-free/double-free, which are the domain of standard locking checks, LOCKDEP, and KASAN. KMSAN checks for reads of uninitialized memory, which is not at risk here. Therefore, a dedicated KMSAN fuzzing session is not warranted.",
  "NeedsKMSAN": false
}