AI Trajectory

null

{
  "EnableConfigs": [
    "LRU_GEN",
    "LRU_GEN_ENABLED"
  ],
  "FocusSymbols": [
    "try_to_free_pages",
    "shrink_all_memory",
    "try_to_free_mem_cgroup_pages"
  ],
  "KMSANReasoning": "The patch removes a conditional block handling unevictable folios in `sort_folio` within the memory management subsystem (`mm/vmscan.c`). It does not introduce any new variables, structures, or allocations that could be left uninitialized, nor does it expose any kernel memory to user space. Any potential bugs resulting from this change would likely be related to incorrect LRU list management, which could lead to use-after-free, out-of-bounds accesses, or general memory corruption. These types of issues are effectively caught by KASAN and standard kernel debugging tools. There is no risk of uninitialized memory reads or info-leaks, so a dedicated KMSAN fuzzing session is not necessary.",
  "NeedsKMSAN": false,
  "Reasoning": "The patch modifies the core logic of the Multi-Gen LRU (MGLRU) page eviction by removing the special handling of unevictable folios in sort_folio(). This is a functional change in the memory management subsystem that affects how pages are reclaimed and should be fuzzed.",
  "WorthFuzzing": true
}

null

{
  "PatchDiff": "commit 1d940b4a5f7af25dd549b47c71c5a041b267129f\nAuthor: syz-cluster \u003ctriage@syzkaller.com\u003e\nDate:   Tue Aug 11 09:46:11 2026 +0000\n\n    syz-cluster: applied patch under review\n\ndiff --git a/mm/vmscan.c b/mm/vmscan.c\nindex 3194da7dcc795..eca5ff64238dd 100644\n--- a/mm/vmscan.c\n+++ b/mm/vmscan.c\n@@ -4648,7 +4648,6 @@ void lru_gen_reparent_memcg(struct mem_cgroup *memcg, struct mem_cgroup *parent,\n static bool sort_folio(struct lruvec *lruvec, struct folio *folio, struct scan_control *sc,\n \t\t       int tier_idx)\n {\n-\tbool success;\n \tint gen = folio_lru_gen(folio);\n \tint type = folio_is_file_lru(folio);\n \tint zone = folio_zonenum(folio);\n@@ -4660,16 +4659,6 @@ static bool sort_folio(struct lruvec *lruvec, struct folio *folio, struct scan_c\n \n \tVM_WARN_ON_ONCE_FOLIO(gen \u003e= MAX_NR_GENS, folio);\n \n-\t/* unevictable */\n-\tif (!folio_evictable(folio)) {\n-\t\tsuccess = lru_gen_del_folio(lruvec, folio, true);\n-\t\tVM_WARN_ON_ONCE_FOLIO(!success, folio);\n-\t\tfolio_set_unevictable(folio);\n-\t\tlruvec_add_folio(lruvec, folio);\n-\t\t__count_vm_events(UNEVICTABLE_PGCULLED, delta);\n-\t\treturn true;\n-\t}\n-\n \t/* promoted */\n \tif (gen != lru_gen_from_seq(lrugen-\u003emin_seq[type])) {\n \t\tlist_move(\u0026folio-\u003elru, \u0026lrugen-\u003efolios[gen][type][zone]);\n"
}

best-expensive

null

{
  "EnableConfigs": [
    "LRU_GEN",
    "LRU_GEN_ENABLED"
  ],
  "FocusSymbols": [
    "try_to_free_pages",
    "shrink_all_memory",
    "try_to_free_mem_cgroup_pages"
  ],
  "Reasoning": "The patch modifies the core logic of the Multi-Gen LRU (MGLRU) page eviction by removing the special handling of unevictable folios in sort_folio(). This is a functional change in the memory management subsystem that affects how pages are reclaimed and should be fuzzed.",
  "WorthFuzzing": true
}

You are an expert Linux kernel maintainer.
Your job is to review a provided patch series and determine
if it makes functional changes to the kernel that should be fuzzed.

IMPORTANT: The changes have ALREADY been applied and committed as the HEAD commit in
your workspace. Do NOT rely on your internal knowledge of the kernel. You must actively
use your code access tools to examine the actual source code and confirm any assumptions.

Return WorthFuzzing=false if the patch only contains:
- Modifications to Documentation/, Kconfig files, or code comments.
- Purely decorative changes, such as logging (e.g., pr_err, printk) or tracepoints.
- Changes to numeric constants or macros that do not functionally alter execution flow.
- Code paths that are impossible to reach in virtualized environments like GCE or QEMU,
  even when utilizing software-emulated hardware (e.g., usb gadget, mac80211_hwsim).
- Code in vendor-specific PCIe switch, SmartNIC, or GPU drivers (e.g., mlxsw, pds_core, qed,
  ionic, amdgpu) that require physical PCIe hardware cards not emulated in standard QEMU.
- Driver .remove, .shutdown, or pci_unregister_driver teardown callbacks (e.g., igb_remove)
  that are executed only during PCI hot-unplug or sysfs driver unbind operations.

If it modifies reachable core kernel logic, drivers, or architectures, use your code search
tools to verify the code can be executed, then return WorthFuzzing=true.

When returning WorthFuzzing=true, you MUST ALSO:
1. Extract any specific kernel functions that should be heavily fuzzed into FocusSymbols.
   Avoid listing generic hot-path functions to prevent skewed test distributions.
   Prefer non-static, non-inlined API entrypoint functions over internal static helper functions
   (which are inlined by the compiler and do not have distinct symbol addresses).
2. Identify any specific CONFIG_ options required to properly test this new/modified feature.
   Go and look into the Kconfig files and check for ifdefs around the code, do not make assumptions.
   Also check "depends on" lines in Kconfig to include any non-standard parent subsystem configs
   needed for Kbuild to compile the code statically into vmlinux. List them in the EnableConfigs
   output array, and DO NOT add a '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.

For your convenience, here is the diff of the changes:
commit 1d940b4a5f7af25dd549b47c71c5a041b267129f
Author: syz-cluster <triage@syzkaller.com>
Date:   Tue Aug 11 09:46:11 2026 +0000

    syz-cluster: applied patch under review

diff --git a/mm/vmscan.c b/mm/vmscan.c
index 3194da7dcc795..eca5ff64238dd 100644
--- a/mm/vmscan.c
+++ b/mm/vmscan.c
@@ -4648,7 +4648,6 @@ void lru_gen_reparent_memcg(struct mem_cgroup *memcg, struct mem_cgroup *parent,
 static bool sort_folio(struct lruvec *lruvec, struct folio *folio, struct scan_control *sc,
 		       int tier_idx)
 {
-	bool success;
 	int gen = folio_lru_gen(folio);
 	int type = folio_is_file_lru(folio);
 	int zone = folio_zonenum(folio);
@@ -4660,16 +4659,6 @@ static bool sort_folio(struct lruvec *lruvec, struct folio *folio, struct scan_c
 
 	VM_WARN_ON_ONCE_FOLIO(gen >= MAX_NR_GENS, folio);
 
-	/* unevictable */
-	if (!folio_evictable(folio)) {
-		success = lru_gen_del_folio(lruvec, folio, true);
-		VM_WARN_ON_ONCE_FOLIO(!success, folio);
-		folio_set_unevictable(folio);
-		lruvec_add_folio(lruvec, folio);
-		__count_vm_events(UNEVICTABLE_PGCULLED, delta);
-		return true;
-	}
-
 	/* promoted */
 	if (gen != lru_gen_from_seq(lrugen->min_seq[type])) {
 		list_move(&folio->lru, &lrugen->folios[gen][type][zone]);

gemini-3.1-pro-preview

null

null

							input: 2246
							output: 29
							thoughts: 182
						

**Analyzing the Removal of Unevictable Folio Handling**

Okay, so I'm looking at this patch that's touched `mm/vmscan.c`. The core of it seems to be taking out a section of code within the `sort_folio` function. Specifically, it's removing the part that deals with unevictable folios. Let me quickly refresh my memory of what that block was actually doing. Ah, right. It was handling the scenario where a folio couldn't be evicted.

It looks like the original code would:

1.  Check if the folio *wasn't* evictable.
2.  Then, it'd try to remove the folio from the LRU list using `lru_gen_del_folio`. I'll want to double-check the implications of the `true` flag there, I seem to recall that one can cause some performance considerations.
3.  If that removal failed, it would trigger a warning, using `VM_WARN_ON_ONCE_FOLIO`. That's a good sanity check; it tells us something went wrong.
4.  Then, it would mark the folio as unevictable with `folio_set_unevictable`.
5.  After that, it would re-add the folio to the LRU using `lruvec_add_folio`.
6.  Finally, it would update the `UNEVICTABLE_PGCULLED` counter.

So, in essence, it's a critical path to manage unevictable folios. I need to understand what the motivation is for removing this. Is it a performance optimization? A bug fix? Or is the functionality being moved somewhere else?

{
  "Expression": "sort_folio",
  "PathPrefix": "mm/vmscan.c"
}

{
  "Output": "mm/vmscan.c=4619=void lru_gen_reparent_memcg(struct mem_cgroup *memcg, struct mem_cgroup *parent, int nid)\n--\nmm/vmscan.c-4647-\nmm/vmscan.c:4648:static bool sort_folio(struct lruvec *lruvec, struct folio *folio, struct scan_control *sc,\nmm/vmscan.c-4649-\t\t       int tier_idx)\n--\nmm/vmscan.c=4717=static int scan_folios(unsigned long nr_to_scan, struct lruvec *lruvec,\n--\nmm/vmscan.c-4755-\nmm/vmscan.c:4756:\t\t\tif (sort_folio(lruvec, folio, sc, tier))\nmm/vmscan.c-4757-\t\t\t\tsorted += delta;\n"
}

gemini-3.1-pro-preview

null

null

							input: 3057
							output: 29
							thoughts: 72
						

**Tracing the Folio Eviction Process**

Okay, so I'm digging into this folio management stuff, specifically the Multi-Gen LRU (MGLRU) implementation. It looks like the `evict_folios` function is at the heart of the eviction process, and this is part of the MGLRU. Now, `evict_folios` seems to be calling `scan_folios`, which makes sense; we need to scan something to decide what to evict. Then `scan_folios` itself calls `sort_folio`, a static function. 

This gives me the flow: `evict_folios` -> `scan_folios` -> `sort_folio`. Seems pretty straightforward, but I need to understand how things are configured. The most important thing here is to check whether MGLRU is even enabled by default or if there's some kind of configuration setting that controls whether it's active. I need to figure out what triggers `evict_folios`. I need to figure out how this is enabled, what the defaults are, and how that impacts the overall behavior of the system.

{
  "Expression": "scan_folios",
  "PathPrefix": "mm/vmscan.c"
}

{
  "Output": "mm/vmscan.c=4693=static bool isolate_folio(struct lruvec *lruvec, struct folio *folio, struct scan_control *sc)\n--\nmm/vmscan.c-4716-\nmm/vmscan.c:4717:static int scan_folios(unsigned long nr_to_scan, struct lruvec *lruvec,\nmm/vmscan.c-4718-\t\t       struct scan_control *sc, int type, int tier,\n--\nmm/vmscan.c=4831=static int isolate_folios(unsigned long nr_to_scan, struct lruvec *lruvec,\n--\nmm/vmscan.c-4843-\nmm/vmscan.c:4844:\t\tscanned = scan_folios(nr_to_scan, lruvec, sc,\nmm/vmscan.c-4845-\t\t\t\t      type, tier, list, isolated);\n"
}

gemini-3.1-pro-preview

null

null

							input: 3630
							output: 29
							thoughts: 16
						

Okay, here's my take on those thoughts, framed as an expert's internal monologue:

**Checking `evict_folios` and `isolate_folios`**

Alright, time to dig in. The system is showing some unusual behavior, and my first instinct, given my experience with memory management, is to revisit `evict_folios` and `isolate_folios`. These are critical functions, often the linchpins of efficient folio handling. I've seen enough performance bottlenecks traced back to inefficient folio eviction or improper isolation, which can cascade into significant issues. So, let's start there. I need to refresh my understanding of how they're currently implemented, how they interact, and whether there are any potential race conditions or resource contention issues I'm overlooking. I'll focus on any recent changes or commits that have touched these routines, to see if there's been any regression or introduced inefficiency. The goal is to quickly rule out these common suspects or identify the smoking gun. Time to pull up the code and get to work.

{
  "Expression": "isolate_folios",
  "PathPrefix": "mm/vmscan.c"
}

{
  "Output": "mm/vmscan.c=4812=static int get_type_to_scan(struct lruvec *lruvec, int swappiness)\n--\nmm/vmscan.c-4830-\nmm/vmscan.c:4831:static int isolate_folios(unsigned long nr_to_scan, struct lruvec *lruvec,\nmm/vmscan.c-4832-\t\t\t  struct scan_control *sc, int swappiness,\n--\nmm/vmscan.c=4865=static int evict_folios(unsigned long nr_to_scan, struct lruvec *lruvec,\n--\nmm/vmscan.c-4886-\nmm/vmscan.c:4887:\tscanned = isolate_folios(nr_to_scan, lruvec, sc, swappiness,\nmm/vmscan.c-4888-\t\t\t\t \u0026list, \u0026isolated, \u0026type, \u0026type_scanned);\n"
}

gemini-3.1-pro-preview

null

null

							input: 4140
							output: 30
							thoughts: 10
						

Okay, here's my attempt at summarizing that thought process, tailored for an expert audience:

**Checking `evict_folios`**

Alright, let's dive in. The code is probably in a state now that means we need to review how folio eviction is handled. I need to make sure this is efficient, given the recent changes. Specifically, I should be looking at `evict_folios` now. I need to understand whether we're getting the behavior we expect, and, more importantly, whether there are any regressions or inefficiencies introduced with the new implementation.

I'll be paying close attention to the conditions under which it's triggered, the eviction strategy itself (LRU, clock, etc.), and the potential for any unnecessary overhead. I'll mentally walk through a few common scenarios and edge cases to ensure the logic holds. I'll be particularly interested in identifying any potential hotspots or opportunities for optimization within `evict_folios`. I'll want to quickly consider if there's any obvious locking contention or redundant operations that jump out. It's time to put on my memory management hat and see what's going on under the hood!

{
  "Expression": "evict_folios",
  "PathPrefix": "mm/vmscan.c"
}

{
  "Output": "mm/vmscan.c=4831=static int isolate_folios(unsigned long nr_to_scan, struct lruvec *lruvec,\n--\nmm/vmscan.c-4864-\nmm/vmscan.c:4865:static int evict_folios(unsigned long nr_to_scan, struct lruvec *lruvec,\nmm/vmscan.c-4866-\t\t\tstruct scan_control *sc, int swappiness)\n--\nmm/vmscan.c=5044=static bool try_to_shrink_lruvec(struct lruvec *lruvec, struct scan_control *sc)\n--\nmm/vmscan.c-5067-\t\tnr_batch = min(nr_to_scan, MIN_LRU_BATCH);\nmm/vmscan.c:5068:\t\tdelta = evict_folios(nr_batch, lruvec, sc, swappiness);\nmm/vmscan.c-5069-\t\tif (!delta)\n--\nmm/vmscan.c=5671=static int run_eviction(struct lruvec *lruvec, unsigned long seq, struct scan_control *sc,\n--\nmm/vmscan.c-5691-\t\tnr_batch = min(nr_to_reclaim - sc-\u003enr_reclaimed, MAX_LRU_BATCH);\nmm/vmscan.c:5692:\t\tif (!evict_folios(nr_batch, lruvec, sc, swappiness))\nmm/vmscan.c-5693-\t\t\treturn 0;\n"
}

gemini-3.1-pro-preview

null

null

							input: 4818
							output: 35
							thoughts: 15
						

Okay, here's my take on those thoughts, tailored for an expert audience, and delivered as a first-person internal monologue:

**Checking `try_to_shrink_lruvec`**

Alright, time to dive into `try_to_shrink_lruvec`. I'm starting here because... well, *I* know the code. It feels like this is the likely culprit for the performance anomaly we're seeing. Specifically, I need to make sure that the shrinking logic within `try_to_shrink_lruvec` isn't overly aggressive, or isn't firing when we don't expect it to. We've optimized the LRU data structure, the allocation, the deallocation, and the hot paths and this seems like the remaining potential source of problems. I need to walk through the conditions that trigger the shrinkage and the actual shrinking process itself. I need to verify, *thoroughly*, that the internal data structures are being handled correctly during the resizing operation. Any off-by-one errors or unintended copies could be disastrous here. I’m thinking about edge cases – what happens when the LRU is nearly empty? When it's full? When there's high churn? And, more importantly, how are we handling concurrent accesses during these shrink operations? This is potentially a big bottleneck, and I need to confirm our synchronization is robust. It's time to get into the details – the nitty-gritty of the LRU vector's internal state. Let's see how well it holds up to scrutiny.

{
  "Expression": "try_to_shrink_lruvec",
  "PathPrefix": "mm/vmscan.c"
}

{
  "Output": "mm/vmscan.c=5009=static bool should_abort_scan(struct lruvec *lruvec, struct scan_control *sc)\n--\nmm/vmscan.c-5043- */\nmm/vmscan.c:5044:static bool try_to_shrink_lruvec(struct lruvec *lruvec, struct scan_control *sc)\nmm/vmscan.c-5045-{\n--\nmm/vmscan.c=5089=static int shrink_one(struct lruvec *lruvec, struct scan_control *sc)\n--\nmm/vmscan.c-5108-\nmm/vmscan.c:5109:\tneed_rotate = try_to_shrink_lruvec(lruvec, sc);\nmm/vmscan.c-5110-\n--\nmm/vmscan.c=5200=static void lru_gen_shrink_lruvec(struct lruvec *lruvec, struct scan_control *sc)\n--\nmm/vmscan.c-5212-\nmm/vmscan.c:5213:\tif (try_to_shrink_lruvec(lruvec, sc))\nmm/vmscan.c-5214-\t\tlru_gen_rotate_memcg(lruvec, MEMCG_LRU_YOUNG);\n"
}

gemini-3.1-pro-preview

null

null

							input: 5542
							output: 29
							thoughts: 37
						

Here's a summary of my mental process:

**Diving into the MGLRU Shrinking Logic**

Okay, so I'm looking at `lru_gen_shrink_lruvec`. This appears to be the core function responsible for the shrinking process within MGLRU, which is interesting. Before I get too deep, it's worth checking: is MGLRU even enabled by default? I need to know if I'm even dealing with a typical or an unusual system setup when analyzing this function. Knowing the default configuration will help me contextualize the behavior I see and focus my attention appropriately.

{
  "Expression": "config LRU_GEN",
  "PathPrefix": "mm/Kconfig"
}

{
  "Output": "mm/Kconfig=1392=config PTE_MARKER_UFFD_WP\n--\nmm/Kconfig-1402-# multi-gen LRU {\nmm/Kconfig:1403:config LRU_GEN\nmm/Kconfig-1404-\tbool \"Multi-Gen LRU\"\n--\nmm/Kconfig-1411-\nmm/Kconfig:1412:config LRU_GEN_ENABLED\nmm/Kconfig-1413-\tbool \"Enable by default\"\n--\nmm/Kconfig-1417-\nmm/Kconfig:1418:config LRU_GEN_STATS\nmm/Kconfig-1419-\tbool \"Full stats for debugging\"\n--\nmm/Kconfig-1426-\nmm/Kconfig:1427:config LRU_GEN_WALKS_MMU\nmm/Kconfig-1428-\tdef_bool y\n"
}

gemini-3.1-pro-preview

null

null

							input: 5975
							output: 33
							thoughts: 26
						

Here's my thought process, summarized as you requested:

**Kconfig Dive for LRU Generation Configuration**

Okay, so I need to get a handle on how `LRU_GEN` and `LRU_GEN_ENABLED` are defined in this project. My first instinct is always to check the `mm/Kconfig` file. That's the standard location for memory management related configuration options, and given what I know about LRU algorithms, it's the logical place to start. I'm expecting to find the definitions, dependencies, and help text there, which will give me the crucial context I need to understand how these options are used and controlled within the build system. Let's see what's in there. I'm looking for the Kconfig syntax: `config LRU_GEN` and `config LRU_GEN_ENABLED`, specifically.

{
  "File": "mm/Kconfig",
  "FirstLine": 1400,
  "LineCount": 30
}

{
  "Contents": "1400:\t\t  file-backed memory types like shmem and hugetlbfs.\n1401:\t\n1402:\t# multi-gen LRU {\n1403:\tconfig LRU_GEN\n1404:\t\tbool \"Multi-Gen LRU\"\n1405:\t\tdepends on MMU\n1406:\t\t# make sure folio-\u003eflags has enough spare bits\n1407:\t\tdepends on 64BIT || !SPARSEMEM || SPARSEMEM_VMEMMAP\n1408:\t\thelp\n1409:\t\t  A high performance LRU implementation to overcommit memory. See\n1410:\t\t  Documentation/admin-guide/mm/multigen_lru.rst for details.\n1411:\t\n1412:\tconfig LRU_GEN_ENABLED\n1413:\t\tbool \"Enable by default\"\n1414:\t\tdepends on LRU_GEN\n1415:\t\thelp\n1416:\t\t  This option enables the multi-gen LRU by default.\n1417:\t\n1418:\tconfig LRU_GEN_STATS\n1419:\t\tbool \"Full stats for debugging\"\n1420:\t\tdepends on LRU_GEN\n1421:\t\thelp\n1422:\t\t  Do not enable this option unless you plan to look at historical stats\n1423:\t\t  from evicted generations for debugging purpose.\n1424:\t\n1425:\t\t  This option has a per-memcg and per-node memory overhead.\n1426:\t\n1427:\tconfig LRU_GEN_WALKS_MMU\n1428:\t\tdef_bool y\n1429:\t\tdepends on LRU_GEN \u0026\u0026 ARCH_HAS_HW_PTE_YOUNG\n"
}

gemini-3.1-pro-preview

null

null

							input: 6667
							output: 36
							thoughts: 304
						

**Analyzing a Key Memory Management Modification**

Okay, so I'm looking at this patch that tweaks `sort_folio` within `mm/vmscan.c`. Immediately, I see that this is a change to how we handle unevictable folios. Specifically, that whole block of code dealing with them is gone. That's a pretty significant functional modification within the core LRU eviction logic – a pretty sensitive area, really. Definitely something that demands thorough fuzzing.

Given that this directly touches LRU eviction, I know the `LRU_GEN` and `LRU_GEN_ENABLED` configurations are going to be key to testing this effectively. Now, I need to figure out the best symbols to target with my fuzzing efforts. `lru_gen_shrink_lruvec` is a likely candidate, especially since `sort_folio`, while relevant, is static and may well be inlined by the compiler. We'll also consider `evict_folios` too as there is a possibility this is not inlined, although it's also static. `scan_folios` is definitely worth a look too.

My next step is to quickly check if `lru_gen_shrink_lruvec` is static, which will have implications for the fuzzing approach I take. Let's see...

{
  "Expression": "lru_gen_shrink_lruvec",
  "PathPrefix": "mm/vmscan.c"
}

{
  "Output": "mm/vmscan.c=5130=static void shrink_many(struct pglist_data *pgdat, struct scan_control *sc)\n--\nmm/vmscan.c-5199-\nmm/vmscan.c:5200:static void lru_gen_shrink_lruvec(struct lruvec *lruvec, struct scan_control *sc)\nmm/vmscan.c-5201-{\n--\nmm/vmscan.c=5944=static void lru_gen_age_node(struct pglist_data *pgdat, struct scan_control *sc)\n--\nmm/vmscan.c-5948-\nmm/vmscan.c:5949:static void lru_gen_shrink_lruvec(struct lruvec *lruvec, struct scan_control *sc)\nmm/vmscan.c-5950-{\n--\nmm/vmscan.c=5961=static void shrink_lruvec(struct lruvec *lruvec, struct scan_control *sc)\n--\nmm/vmscan.c-5972-\tif ((lru_gen_enabled() || lru_gen_switching()) \u0026\u0026 !root_reclaim(sc)) {\nmm/vmscan.c:5973:\t\tlru_gen_shrink_lruvec(lruvec, sc);\nmm/vmscan.c-5974-\n"
}

gemini-3.1-pro-preview

null

null

							input: 7641
							output: 31
							thoughts: 12
						

Okay, here's my attempt at summarizing the thought process, as if it were my own, assuming I'm an expert in this field.

**Deconstructing `shrink_lruvec`**

Alright, let's break down this `shrink_lruvec` function. I'm focusing on it because, based on the context, it seems to be the core operation here. My initial thought is to figure out the key mechanics, specifically how it manages shrinking an LRU vector. I immediately start running through the common optimization strategies in my head: identifying the most efficient methods for this task in the domain of LRU implementations. It must be about efficiently removing least recently used elements to free up memory. What are the key considerations? Is it about simply freeing memory, or is it more nuanced than that, taking into account the impact of the elements that are being evicted? What data structures are in play here? Are we talking about simply decreasing the size of a vector, or is there more complex re-arrangement?

{
  "Expression": "shrink_lruvec",
  "PathPrefix": "mm/vmscan.c"
}

{
  "Output": "mm/vmscan.c=5009=static bool should_abort_scan(struct lruvec *lruvec, struct scan_control *sc)\n--\nmm/vmscan.c-5043- */\nmm/vmscan.c:5044:static bool try_to_shrink_lruvec(struct lruvec *lruvec, struct scan_control *sc)\nmm/vmscan.c-5045-{\n--\nmm/vmscan.c=5089=static int shrink_one(struct lruvec *lruvec, struct scan_control *sc)\n--\nmm/vmscan.c-5108-\nmm/vmscan.c:5109:\tneed_rotate = try_to_shrink_lruvec(lruvec, sc);\nmm/vmscan.c-5110-\n--\nmm/vmscan.c=5130=static void shrink_many(struct pglist_data *pgdat, struct scan_control *sc)\n--\nmm/vmscan.c-5199-\nmm/vmscan.c:5200:static void lru_gen_shrink_lruvec(struct lruvec *lruvec, struct scan_control *sc)\nmm/vmscan.c-5201-{\n--\nmm/vmscan.c-5212-\nmm/vmscan.c:5213:\tif (try_to_shrink_lruvec(lruvec, sc))\nmm/vmscan.c-5214-\t\tlru_gen_rotate_memcg(lruvec, MEMCG_LRU_YOUNG);\n--\nmm/vmscan.c=5944=static void lru_gen_age_node(struct pglist_data *pgdat, struct scan_control *sc)\n--\nmm/vmscan.c-5948-\nmm/vmscan.c:5949:static void lru_gen_shrink_lruvec(struct lruvec *lruvec, struct scan_control *sc)\nmm/vmscan.c-5950-{\n--\nmm/vmscan.c=5954=static void lru_gen_shrink_node(struct pglist_data *pgdat, struct scan_control *sc)\n--\nmm/vmscan.c-5960-\nmm/vmscan.c:5961:static void shrink_lruvec(struct lruvec *lruvec, struct scan_control *sc)\nmm/vmscan.c-5962-{\n--\nmm/vmscan.c-5972-\tif ((lru_gen_enabled() || lru_gen_switching()) \u0026\u0026 !root_reclaim(sc)) {\nmm/vmscan.c:5973:\t\tlru_gen_shrink_lruvec(lruvec, sc);\nmm/vmscan.c-5974-\n--\nmm/vmscan.c=6152=static void shrink_node_memcgs(pg_data_t *pgdat, struct scan_control *sc)\n--\nmm/vmscan.c-6211-\nmm/vmscan.c:6212:\t\tshrink_lruvec(lruvec, sc);\nmm/vmscan.c-6213-\n--\nmm/vmscan.c=6807=unsigned long mem_cgroup_shrink_node(struct mem_cgroup *memcg,\n--\nmm/vmscan.c-6837-\t */\nmm/vmscan.c:6838:\tshrink_lruvec(lruvec, \u0026sc);\nmm/vmscan.c-6839-\n"
}

gemini-3.1-pro-preview

null

null

							input: 8797
							output: 34
							thoughts: 20
						

Here's my take on those thoughts:

**Analyzing Code Structure: Identifying Potential Scope for Optimization**

Okay, so `shrink_lruvec` is a static function. That immediately makes me think about scope and whether it's truly the best place for it within the broader system. Since it's static, it's limited in its accessibility. My primary thought is, let's cast a wider net and hunt for *non*-static functions, which suggests a potentially more flexible or globally relevant approach might be beneficial. Perhaps there are similar operations that could be generalized, or perhaps this function could benefit from broader visibility or even some form of modularity. This suggests I need to analyze how data flows in and out of that particular module.

{
  "Expression": "mem_cgroup_shrink_node",
  "PathPrefix": "mm/vmscan.c"
}

{
  "Output": "mm/vmscan.c=6761=unsigned long try_to_free_pages(struct zonelist *zonelist, int order,\n--\nmm/vmscan.c-6806-/* Only used by soft limit reclaim. Do not reuse for anything else. */\nmm/vmscan.c:6807:unsigned long mem_cgroup_shrink_node(struct mem_cgroup *memcg,\nmm/vmscan.c-6808-\t\t\t\t\t\tgfp_t gfp_mask, bool noswap,\n"
}

gemini-3.1-pro-preview

null

null

							input: 9141
							output: 33
							thoughts: 14
						

Here's a summary of my current thought process, expressed in the first person, assuming you, the user, are familiar with this level of detail:

**Thinking About `try_to_free_pages`**

Okay, so I'm thinking about `try_to_free_pages`. The key point here is that it's *not* a static function. That means it's not simply a utility function, operating independently of any specific object or module state. It suggests that `try_to_free_pages` relies on, or potentially modifies, data within a specific instance or object. Knowing this is the entry point to understanding how it functions within the larger system. I need to consider what object context it operates within. This could be crucial for things like concurrency, data integrity, and potential side effects within the memory management system.

{
  "Expression": "try_to_free_pages",
  "PathPrefix": "mm/vmscan.c"
}

{
  "Output": "mm/vmscan.c=6508=static void snapshot_refaults(struct mem_cgroup *target_memcg, pg_data_t *pgdat)\n--\nmm/vmscan.c-6538- */\nmm/vmscan.c:6539:static unsigned long do_try_to_free_pages(struct zonelist *zonelist,\nmm/vmscan.c-6540-\t\t\t\t\t  struct scan_control *sc)\n--\nmm/vmscan.c=6681=static bool throttle_direct_reclaim(gfp_t gfp_mask, struct zonelist *zonelist,\n--\nmm/vmscan.c-6760-\nmm/vmscan.c:6761:unsigned long try_to_free_pages(struct zonelist *zonelist, int order,\nmm/vmscan.c-6762-\t\t\t\tgfp_t gfp_mask, const nodemask_t *nodemask)\n--\nmm/vmscan.c-6795-\nmm/vmscan.c:6796:\tnr_reclaimed = do_try_to_free_pages(zonelist, \u0026sc);\nmm/vmscan.c-6797-\n--\nmm/vmscan.c=6847=unsigned long try_to_free_mem_cgroup_pages(struct mem_cgroup *memcg,\n--\nmm/vmscan.c-6878-\nmm/vmscan.c:6879:\tnr_reclaimed = do_try_to_free_pages(zonelist, \u0026sc);\nmm/vmscan.c-6880-\n--\nmm/vmscan.c=7645=unsigned long shrink_all_memory(unsigned long nr_to_reclaim)\n--\nmm/vmscan.c-7664-\nmm/vmscan.c:7665:\tnr_reclaimed = do_try_to_free_pages(zonelist, \u0026sc);\nmm/vmscan.c-7666-\n"
}

gemini-3.1-pro-preview

null

null

							input: 9871
							output: 29
							thoughts: 54
						

Okay, here's my take on those thoughts, framed as my own mental process:

**Focusing on Memory Reclamation Strategies**

Right, let's zero in on effective strategies for freeing up memory. My initial impression is that `try_to_free_pages` is a solid function to explore further. It seems to be a good high-level starting point. We should also investigate `shrink_all_memory`, that's another important one. And, specifically targeting memory pressure at the cgroup level, `try_to_free_mem_cgroup_pages` looks relevant too.

Now, let's shift gears slightly. I need to quickly determine the scope of `shrink_node`. I need to figure out if it's a non-static function. If it's static, it limits its utility for general analysis or potential modification, but if it's non-static, it opens up a number of interesting possibilities. Gotta check the definition to be sure.

{
  "Expression": "shrink_node",
  "PathPrefix": "mm/vmscan.c"
}

{
  "Output": "mm/vmscan.c=1940=static void handle_reclaim_writeback(unsigned long nr_taken,\n--\nmm/vmscan.c-1978-/*\nmm/vmscan.c:1979: * shrink_inactive_list() is a helper for shrink_node().  It returns the number\nmm/vmscan.c-1980- * of reclaimed pages\n--\nmm/vmscan.c=5200=static void lru_gen_shrink_lruvec(struct lruvec *lruvec, struct scan_control *sc)\n--\nmm/vmscan.c-5220-\nmm/vmscan.c:5221:static void lru_gen_shrink_node(struct pglist_data *pgdat, struct scan_control *sc)\nmm/vmscan.c-5222-{\n--\nmm/vmscan.c=5949=static void lru_gen_shrink_lruvec(struct lruvec *lruvec, struct scan_control *sc)\n--\nmm/vmscan.c-5953-\nmm/vmscan.c:5954:static void lru_gen_shrink_node(struct pglist_data *pgdat, struct scan_control *sc)\nmm/vmscan.c-5955-{\n--\nmm/vmscan.c=6100=static inline bool should_continue_reclaim(struct pglist_data *pgdat,\n--\nmm/vmscan.c-6151-\nmm/vmscan.c:6152:static void shrink_node_memcgs(pg_data_t *pgdat, struct scan_control *sc)\nmm/vmscan.c-6153-{\n--\nmm/vmscan.c-6230-\nmm/vmscan.c:6231:static void shrink_node(pg_data_t *pgdat, struct scan_control *sc)\nmm/vmscan.c-6232-{\n--\nmm/vmscan.c-6238-\t\tmemset(\u0026sc-\u003enr, 0, sizeof(sc-\u003enr));\nmm/vmscan.c:6239:\t\tlru_gen_shrink_node(pgdat, sc);\nmm/vmscan.c-6240-\n--\nmm/vmscan.c-6255-\nmm/vmscan.c:6256:\tshrink_node_memcgs(pgdat, sc);\nmm/vmscan.c-6257-\n--\nmm/vmscan.c=6416=static void shrink_zones(struct zonelist *zonelist, struct scan_control *sc)\n--\nmm/vmscan.c-6494-\t\tlast_pgdat = zone-\u003ezone_pgdat;\nmm/vmscan.c:6495:\t\tshrink_node(zone-\u003ezone_pgdat, sc);\nmm/vmscan.c-6496-\t}\n--\nmm/vmscan.c=6761=unsigned long try_to_free_pages(struct zonelist *zonelist, int order,\n--\nmm/vmscan.c-6806-/* Only used by soft limit reclaim. Do not reuse for anything else. */\nmm/vmscan.c:6807:unsigned long mem_cgroup_shrink_node(struct mem_cgroup *memcg,\nmm/vmscan.c-6808-\t\t\t\t\t\tgfp_t gfp_mask, bool noswap,\n--\nmm/vmscan.c-6833-\t * here is not a good idea, since it limits the pages we can scan.\nmm/vmscan.c:6834:\t * if we don't reclaim here, the shrink_node from balance_pgdat\nmm/vmscan.c-6835-\t * will pick up pages from other mem cgroup's as well. We hack\n--\nmm/vmscan.c=6955=static bool pgdat_balanced(pg_data_t *pgdat, int order, int highest_zoneidx)\n--\nmm/vmscan.c-6979-\t\t * its own and needs kcompactd support. Once it's\nmm/vmscan.c:6980:\t\t * reclaimed a compaction gap, and kswapd_shrink_node\nmm/vmscan.c-6981-\t\t * has dropped order, simply ensure there are enough\n--\nmm/vmscan.c=7037=static bool prepare_kswapd_sleep(pg_data_t *pgdat, int order,\n--\nmm/vmscan.c-7075- */\nmm/vmscan.c:7076:static bool kswapd_shrink_node(pg_data_t *pgdat,\nmm/vmscan.c-7077-\t\t\t       struct scan_control *sc)\n--\nmm/vmscan.c-7092-\t */\nmm/vmscan.c:7093:\tshrink_node(pgdat, sc);\nmm/vmscan.c-7094-\n--\nmm/vmscan.c=7149=static int balance_pgdat(pg_data_t *pgdat, int order, int highest_zoneidx)\n--\nmm/vmscan.c-7258-\nmm/vmscan.c:7259:\t\t/* Call soft limit reclaim before calling shrink_node. */\nmm/vmscan.c-7260-\t\tsc.nr_scanned = 0;\n--\nmm/vmscan.c-7270-\t\t */\nmm/vmscan.c:7271:\t\tif (kswapd_shrink_node(pgdat, \u0026sc))\nmm/vmscan.c-7272-\t\t\traise_priority = false;\n--\nmm/vmscan.c=7825=static unsigned long __node_reclaim(struct pglist_data *pgdat,\n--\nmm/vmscan.c-7852-\t\tdo {\nmm/vmscan.c:7853:\t\t\tshrink_node(pgdat, sc);\nmm/vmscan.c-7854-\t\t} while (sc-\u003enr_reclaimed \u003c nr_pages \u0026\u0026 --sc-\u003epriority \u003e= 0);\n"
}

gemini-3.1-pro-preview

null

null

							input: 11674
							output: 29
							thoughts: 76
						

Here's my summary, as I see it:

**Investigating Memory Management Function Visibility**

Okay, so I'm looking at some memory management functions: `try_to_free_pages`, `mem_cgroup_shrink_node`, `try_to_free_mem_cgroup_pages`, and `shrink_all_memory`. The key thing here is that they're *not* declared as `static`, which means they're either exported using `EXPORT_SYMBOL` or, at the very least, are being used by other parts of the kernel. I need to be sure.

My next move is to dive into `mm/vmscan.c`. I want to quickly scan that file and determine whether these functions are explicitly exported for external use. I'm also looking for anything else in that file that *isn't* `static` – anything that might be accessible outside its intended scope is a potential area of interest for whatever I'm currently working on. A quick `grep` for `EXPORT_SYMBOL` or a visual scan for non-static functions within that file should give me a solid answer. I'm trying to quickly establish the intended scope and visibility of these memory management primitives, in order to gain a clearer picture of their overall purpose and any implications they might have.

{
  "Expression": "EXPORT_SYMBOL",
  "PathPrefix": "mm/vmscan.c"
}

{
  "Output": "mm/vmscan.c=8065=void check_move_unevictable_folios(struct folio_batch *fbatch)\n--\nmm/vmscan.c-8099-}\nmm/vmscan.c:8100:EXPORT_SYMBOL_GPL(check_move_unevictable_folios);\nmm/vmscan.c-8101-\n"
}

gemini-3.1-pro-preview

null

null

							input: 12156
							output: 35
							thoughts: 22
						

Here's my attempt at summarizing the thought process, tailored for an expert audience:

**Diving into `try_to_free_pages`**

Okay, so we're looking at a page reclaim issue, and naturally, my first instinct is to zero in on `try_to_free_pages` in `mm/vmscan.c`. It's the core of the active scanning process. Let's see if there's anything immediately obvious jumping out. I'm hoping to quickly identify any potential bottlenecks or inefficiencies in how pages are being evaluated and reclaimed. Is it a matter of how aggressive the scanning is? Or perhaps some specific types of pages are causing trouble? Let's trace through the logic and check out what variables are being used. What conditions are failing? I'm expecting to refresh my memory on the interactions of this function with `shrink_slab`, `shrink_inactive_list`, and the overall LRU process. I'll be looking for clues in the return values and error handling as well. This should be interesting.

{
  "Expression": "unsigned long try_to_free_pages",
  "PathPrefix": "mm/vmscan.c"
}

{
  "Output": "mm/vmscan.c=6681=static bool throttle_direct_reclaim(gfp_t gfp_mask, struct zonelist *zonelist,\n--\nmm/vmscan.c-6760-\nmm/vmscan.c:6761:unsigned long try_to_free_pages(struct zonelist *zonelist, int order,\nmm/vmscan.c-6762-\t\t\t\tgfp_t gfp_mask, const nodemask_t *nodemask)\n"
}

gemini-3.1-pro-preview

null

null

							input: 12566
							output: 33
							thoughts: 48
						

Okay, here's my take on those thoughts, framed as my own mental process, given my expertise:

**Examining Memory Management Strategies**

Alright, my internal radar is picking up on a couple of interesting potential areas for memory reclamation. `try_to_free_pages` feels like a solid starting point – it's a direct, focused approach. But then again, `shrink_all_memory` is also intriguing. It sounds like a broader, more aggressive strategy, potentially encompassing more aspects of the memory system.

Let's dig into `shrink_all_memory`. Given my experience, the place to start is almost certainly `mm/vmscan.c`. It's the core of the virtual memory scanning and reclaiming logic in the kernel. I expect to find the implementation of `shrink_all_memory` there, along with the details of how it orchestrates the page scanning and eviction processes. I'll be looking for clues about how it prioritizes different types of memory, how it interacts with the page cache, and what criteria it uses to decide which pages are eligible for eviction. This could be where I find the root cause.

{
  "Expression": "unsigned long shrink_all_memory",
  "PathPrefix": "mm/vmscan.c"
}

{
  "Output": "mm/vmscan.c=7631=bool kswapd_test_hopeless(pg_data_t *pgdat)\n--\nmm/vmscan.c-7644- */\nmm/vmscan.c:7645:unsigned long shrink_all_memory(unsigned long nr_to_reclaim)\nmm/vmscan.c-7646-{\n"
}

gemini-3.1-pro-preview

null

null

							input: 12990
							output: 40
							thoughts: 27
						

Okay, let's dive into this. Here's my thought process on what we're looking at, summarized from that prompt:

**Investigating `try_to_free_mem_cgroup_pages`**

Right, so the first thing I'm doing is to locate `try_to_free_mem_cgroup_pages` within the `mm/vmscan.c` file. I need to understand how the memory cgroup page freeing is managed. From here, I need to see what logic is in this specific call, and its interactions with the rest of the VM system. This will offer insight into how the kernel handles memory reclaim specifically from within cgroups. I'm going to start with the function definition itself, then trace where it's called from. I'll need to pay attention to the conditions under which it's triggered, which should inform me about how proactive or reactive the memory cgroup's page freeing scheme is. I'll also be focusing on performance considerations. What are the potential bottlenecks? And how the policy decisions are made here. In essence, my goal is a deep understanding of the reclaim path for memory cgroups, as triggered by this function.

{
  "Expression": "unsigned long try_to_free_mem_cgroup_pages",
  "PathPrefix": "mm/vmscan.c"
}

{
  "Output": "mm/vmscan.c=6807=unsigned long mem_cgroup_shrink_node(struct mem_cgroup *memcg,\n--\nmm/vmscan.c-6846-\nmm/vmscan.c:6847:unsigned long try_to_free_mem_cgroup_pages(struct mem_cgroup *memcg,\nmm/vmscan.c-6848-\t\t\t\t\t   unsigned long nr_pages,\n--\nmm/vmscan.c-6887-#else\nmm/vmscan.c:6888:unsigned long try_to_free_mem_cgroup_pages(struct mem_cgroup *memcg,\nmm/vmscan.c-6889-\t\t\t\t\t   unsigned long nr_pages,\n"
}

gemini-3.1-pro-preview

null

null

							input: 13501
							output: 29
							thoughts: 52
						

**Analyzing the MGLRU Patch**

Okay, so this patch is touching `sort_folio`, which is a key function within the MGLRU implementation. My initial thought is to immediately zoom in on the configuration options involved. I see `LRU_GEN` and, consequently, `LRU_GEN_ENABLED` being relevant here. Given my expertise, I already know these are probably related to generational LRU behavior, but I need to be precise. My next step, as always, is to determine dependencies. I need to understand if `LRU_GEN` itself relies on any other configurations or features before I can fully assess the impact of this change. Let's see what the Kconfig files reveal.

{
  "Expression": "config LRU_GEN",
  "PathPrefix": "mm/Kconfig"
}

{
  "Output": "mm/Kconfig=1392=config PTE_MARKER_UFFD_WP\n--\nmm/Kconfig-1402-# multi-gen LRU {\nmm/Kconfig:1403:config LRU_GEN\nmm/Kconfig-1404-\tbool \"Multi-Gen LRU\"\n--\nmm/Kconfig-1411-\nmm/Kconfig:1412:config LRU_GEN_ENABLED\nmm/Kconfig-1413-\tbool \"Enable by default\"\n--\nmm/Kconfig-1417-\nmm/Kconfig:1418:config LRU_GEN_STATS\nmm/Kconfig-1419-\tbool \"Full stats for debugging\"\n--\nmm/Kconfig-1426-\nmm/Kconfig:1427:config LRU_GEN_WALKS_MMU\nmm/Kconfig-1428-\tdef_bool y\n"
}

gemini-3.1-pro-preview

null

null

							input: 13969
							output: 29
							thoughts: 147
						

**Analyzing Memory Management Configuration**

Okay, so I've just been reviewing lines 1400-1430 within `mm/Kconfig` – the section dealing with the Multi-Gen LRU feature. I see that `LRU_GEN` is the primary config option, along with a related `LRU_GEN_ENABLED`. This is tied to the presence of an MMU, which makes perfect sense. The dependency on `64BIT`, or the absence of `SPARSEMEM` or its use with `VMEMMAP`, is important, ensuring there are enough spare bits available in the `folio->flags` structure, as the comment suggests.

Now, my mind is already starting to piece together the implications. I'll need to keep an eye on key functions like `try_to_free_pages`, `shrink_all_memory`, and `try_to_free_mem_cgroup_pages` as I dig deeper into how this Multi-Gen LRU is actually implemented. And I can't forget `kswapd`, the kernel thread. I'm assuming its role will be key as well.

{
  "Expression": "kswapd",
  "PathPrefix": "mm/vmscan.c"
}

{
  "Output": "\nFull output is too long, showing 500 out of 524 lines.\nUse more precise expression if possible.\n\nmm/vmscan.c-5- *  Swap reorganised 29.12.95, Stephen Tweedie.\nmm/vmscan.c:6: *  kswapd added: 7.1.96  sct\nmm/vmscan.c:7: *  Removed kswapd_ctl limits, and swap out as many pages as needed\nmm/vmscan.c-8- *  to bring the system back to freepages.high: 2.4.97, Rik van Riel.\nmm/vmscan.c:9: *  Zone aware kswapd started 02/00, Kanoj Sarcar (kanoj@sgi.com).\nmm/vmscan.c-10- *  Multiqueue VM started 5.8.00, Rik van Riel.\n--\nmm/vmscan.c=446=static int reclaimer_offset(struct scan_control *sc)\n--\nmm/vmscan.c-451-\nmm/vmscan.c:452:\tif (current_is_kswapd())\nmm/vmscan.c-453-\t\treturn 0;\n--\nmm/vmscan.c=482=static bool skip_throttle_noprogress(pg_data_t *pgdat)\n--\nmm/vmscan.c-487-\t/*\nmm/vmscan.c:488:\t * If kswapd is disabled, reschedule if necessary but do not\nmm/vmscan.c-489-\t * throttle as the system is likely near OOM.\nmm/vmscan.c-490-\t */\nmm/vmscan.c:491:\tif (kswapd_test_hopeless(pgdat))\nmm/vmscan.c-492-\t\treturn true;\n--\nmm/vmscan.c=510=void reclaim_throttle(pg_data_t *pgdat, enum vmscan_throttle_state reason)\n--\nmm/vmscan.c-516-\t/*\nmm/vmscan.c:517:\t * Do not throttle user workers, kthreads other than kswapd or\nmm/vmscan.c-518-\t * workqueues. They may be required for reclaim to make\n--\nmm/vmscan.c-520-\t */\nmm/vmscan.c:521:\tif (!current_is_kswapd() \u0026\u0026\nmm/vmscan.c-522-\t    current-\u003eflags \u0026 (PF_USER_WORKER|PF_KTHREAD)) {\n--\nmm/vmscan.c=965=static struct folio *alloc_demote_folio(struct folio *src,\n--\nmm/vmscan.c-974-\t * make sure we allocate from the target node first also trying to\nmm/vmscan.c:975:\t * demote or reclaim pages from the target node via kswapd if we are\nmm/vmscan.c-976-\t * low on free memory on target node. If we don't do this and if\n--\nmm/vmscan.c=1057=static unsigned int shrink_folio_list(struct list_head *folio_list,\n--\nmm/vmscan.c-1120-\t\t * The number of dirty pages determines if a node is marked\nmm/vmscan.c:1121:\t\t * reclaim_congested. kswapd will stall and start writing\nmm/vmscan.c-1122-\t\t * folios if the tail of the LRU is all dirty unqueued folios.\n--\nmm/vmscan.c-1189-\t\t\t/* Case 1 above */\nmm/vmscan.c:1190:\t\t\tif (current_is_kswapd() \u0026\u0026\nmm/vmscan.c-1191-\t\t\t    folio_test_reclaim(folio) \u0026\u0026\n--\nmm/vmscan.c=1588=unsigned int reclaim_clean_pages_from_list(struct zone *zone,\n--\nmm/vmscan.c-1613-\t * We should be safe here since we are only dealing with file pages and\nmm/vmscan.c:1614:\t * we are not kswapd and therefore cannot write dirty file pages. But\nmm/vmscan.c-1615-\t * call memalloc_noreclaim_save() anyway, just in case these conditions\n--\nmm/vmscan.c=1821=static bool too_many_isolated(struct pglist_data *pgdat, int file,\n--\nmm/vmscan.c-1826-\nmm/vmscan.c:1827:\tif (current_is_kswapd())\nmm/vmscan.c-1828-\t\treturn false;\n--\nmm/vmscan.c=3866=static struct lru_gen_mm_walk *set_mm_walk(struct pglist_data *pgdat, bool force_alloc)\n--\nmm/vmscan.c-3869-\nmm/vmscan.c:3870:\tif (pgdat \u0026\u0026 current_is_kswapd()) {\nmm/vmscan.c-3871-\t\tVM_WARN_ON_ONCE(walk);\n--\nmm/vmscan.c-3874-\t} else if (!walk \u0026\u0026 force_alloc) {\nmm/vmscan.c:3875:\t\tVM_WARN_ON_ONCE(current_is_kswapd());\nmm/vmscan.c-3876-\n--\nmm/vmscan.c=3886=static void clear_mm_walk(void)\n--\nmm/vmscan.c-3894-\nmm/vmscan.c:3895:\tif (!current_is_kswapd())\nmm/vmscan.c-3896-\t\tkfree(walk);\n--\nmm/vmscan.c=4208=static void lru_gen_age_node(struct pglist_data *pgdat, struct scan_control *sc)\n--\nmm/vmscan.c-4213-\nmm/vmscan.c:4214:\tVM_WARN_ON_ONCE(!current_is_kswapd());\nmm/vmscan.c-4215-\n--\nmm/vmscan.c=5009=static bool should_abort_scan(struct lruvec *lruvec, struct scan_control *sc)\n--\nmm/vmscan.c-5020-\t/* check the order to exclude compaction-induced reclaim */\nmm/vmscan.c:5021:\tif (!current_is_kswapd() || sc-\u003eorder)\nmm/vmscan.c-5022-\t\treturn false;\n--\nmm/vmscan.c-5034-\nmm/vmscan.c:5035:\t/* kswapd should abort if all eligible zones are safe */\nmm/vmscan.c-5036-\treturn true;\n--\nmm/vmscan.c=5221=static void lru_gen_shrink_node(struct pglist_data *pgdat, struct scan_control *sc)\n--\nmm/vmscan.c-5243-\nmm/vmscan.c:5244:\tif (current_is_kswapd())\nmm/vmscan.c-5245-\t\tsc-\u003enr_reclaimed = 0;\n--\nmm/vmscan.c-5251-\nmm/vmscan.c:5252:\tif (current_is_kswapd())\nmm/vmscan.c-5253-\t\tsc-\u003enr_reclaimed += reclaimed;\n--\nmm/vmscan.c-5259-\tif (sc-\u003enr_reclaimed \u003e reclaimed)\nmm/vmscan.c:5260:\t\tkswapd_try_clear_hopeless(pgdat, sc-\u003eorder, sc-\u003ereclaim_idx);\nmm/vmscan.c-5261-}\n--\nmm/vmscan.c=5961=static void shrink_lruvec(struct lruvec *lruvec, struct scan_control *sc)\n--\nmm/vmscan.c-5990-\t * DEF_PRIORITY on the assumption that the fact we are direct\nmm/vmscan.c:5991:\t * reclaiming implies that kswapd is not keeping up and it is best to\nmm/vmscan.c-5992-\t * do a batch of work at once. For memcg reclaim one check is made to\n--\nmm/vmscan.c-5995-\t */\nmm/vmscan.c:5996:\tproportional_reclaim = (!cgroup_reclaim(sc) \u0026\u0026 !current_is_kswapd() \u0026\u0026\nmm/vmscan.c-5997-\t\t\t\tsc-\u003epriority == DEF_PRIORITY);\n--\nmm/vmscan.c-6020-\t\t/*\nmm/vmscan.c:6021:\t\t * For kswapd and memcg, reclaim at least the number of pages\nmm/vmscan.c-6022-\t\t * requested. Ensure that the anon and file LRUs are scanned\n--\nmm/vmscan.c=6152=static void shrink_node_memcgs(pg_data_t *pgdat, struct scan_control *sc)\n--\nmm/vmscan.c-6166-\t *\nmm/vmscan.c:6167:\t * For kswapd, reliable forward progress is more important\nmm/vmscan.c-6168-\t * than a quick return to idle. Always do full walks.\nmm/vmscan.c-6169-\t */\nmm/vmscan.c:6170:\tif (current_is_kswapd() || sc-\u003ememcg_full_walk)\nmm/vmscan.c-6171-\t\tpartial = NULL;\n--\nmm/vmscan.c=6231=static void shrink_node(pg_data_t *pgdat, struct scan_control *sc)\n--\nmm/vmscan.c-6269-\nmm/vmscan.c:6270:\tif (current_is_kswapd()) {\nmm/vmscan.c-6271-\t\t/*\n--\nmm/vmscan.c-6282-\t\t *\nmm/vmscan.c:6283:\t\t * Once a node is flagged PGDAT_WRITEBACK, kswapd will\nmm/vmscan.c-6284-\t\t * count the number of pages under pages flagged for\n--\nmm/vmscan.c-6291-\t\t/*\nmm/vmscan.c:6292:\t\t * If kswapd scans pages marked for immediate\nmm/vmscan.c-6293-\t\t * reclaim and under writeback (nr_immediate), it\n--\nmm/vmscan.c-6312-\nmm/vmscan.c:6313:\t\tif (current_is_kswapd())\nmm/vmscan.c-6314-\t\t\tset_bit(LRUVEC_NODE_CONGESTED, \u0026target_lruvec-\u003eflags);\n--\nmm/vmscan.c-6318-\t * Stall direct reclaim for IO completions if the lruvec is\nmm/vmscan.c:6319:\t * node is congested. Allow kswapd to continue until it\nmm/vmscan.c-6320-\t * starts encountering unqueued dirty pages or cycling through\n--\nmm/vmscan.c-6322-\t */\nmm/vmscan.c:6323:\tif (!current_is_kswapd() \u0026\u0026 current_may_throttle() \u0026\u0026\nmm/vmscan.c-6324-\t    !sc-\u003ehibernation_mode \u0026\u0026\n--\nmm/vmscan.c-6335-\t * sleep. On reclaim progress, reset the failure counter. A\nmm/vmscan.c:6336:\t * successful direct reclaim run will revive a dormant kswapd.\nmm/vmscan.c-6337-\t */\nmm/vmscan.c-6338-\tif (reclaimable)\nmm/vmscan.c:6339:\t\tkswapd_try_clear_hopeless(pgdat, sc-\u003eorder, sc-\u003ereclaim_idx);\nmm/vmscan.c-6340-\telse if (sc-\u003ecache_trim_mode)\n--\nmm/vmscan.c=6378=static void consider_reclaim_throttle(pg_data_t *pgdat, struct scan_control *sc)\n--\nmm/vmscan.c-6394-\t/*\nmm/vmscan.c:6395:\t * Do not throttle kswapd or cgroup reclaim on NOPROGRESS as it will\nmm/vmscan.c-6396-\t * throttle on VMSCAN_THROTTLE_WRITEBACK if there are too many pages\n--\nmm/vmscan.c-6399-\t */\nmm/vmscan.c:6400:\tif (current_is_kswapd() || cgroup_reclaim(sc))\nmm/vmscan.c-6401-\t\treturn;\n--\nmm/vmscan.c=6636=static bool allow_direct_reclaim(pg_data_t *pgdat)\n--\nmm/vmscan.c-6643-\nmm/vmscan.c:6644:\tif (kswapd_test_hopeless(pgdat))\nmm/vmscan.c-6645-\t\treturn true;\n--\nmm/vmscan.c-6660-\nmm/vmscan.c:6661:\t/* kswapd must be awake if processes are being throttled */\nmm/vmscan.c:6662:\tif (!wmark_ok \u0026\u0026 waitqueue_active(\u0026pgdat-\u003ekswapd_wait)) {\nmm/vmscan.c:6663:\t\tif (READ_ONCE(pgdat-\u003ekswapd_highest_zoneidx) \u003e ZONE_NORMAL)\nmm/vmscan.c:6664:\t\t\tWRITE_ONCE(pgdat-\u003ekswapd_highest_zoneidx, ZONE_NORMAL);\nmm/vmscan.c-6665-\nmm/vmscan.c:6666:\t\twake_up_interruptible(\u0026pgdat-\u003ekswapd_wait);\nmm/vmscan.c-6667-\t}\n--\nmm/vmscan.c-6674- * and the PFMEMALLOC reserve for the preferred node is getting dangerously\nmm/vmscan.c:6675: * depleted. kswapd will continue to make progress and wake the processes\nmm/vmscan.c-6676- * when the low watermark is reached.\n--\nmm/vmscan.c=6681=static bool throttle_direct_reclaim(gfp_t gfp_mask, struct zonelist *zonelist,\n--\nmm/vmscan.c-6711-\t * Throttling is based on the first usable node and throttled processes\nmm/vmscan.c:6712:\t * wait on a queue until kswapd makes progress and wakes them. There\nmm/vmscan.c-6713-\t * is an affinity then between processes waking up and where reclaim\n--\nmm/vmscan.c-6741-\t * transaction in the case of a filesystem like ext[3|4]. In this case,\nmm/vmscan.c:6742:\t * it is not safe to block on pfmemalloc_wait as kswapd could be\nmm/vmscan.c-6743-\t * blocked waiting on the same lock. Instead, throttle for up to a\n--\nmm/vmscan.c-6749-\telse\nmm/vmscan.c:6750:\t\t/* Throttle until kswapd wakes the process */\nmm/vmscan.c-6751-\t\twait_event_killable(zone-\u003ezone_pgdat-\u003epfmemalloc_wait,\n--\nmm/vmscan.c=6888=unsigned long try_to_free_mem_cgroup_pages(struct mem_cgroup *memcg,\n--\nmm/vmscan.c-6897-\nmm/vmscan.c:6898:static void kswapd_age_node(struct pglist_data *pgdat, struct scan_control *sc)\nmm/vmscan.c-6899-{\n--\nmm/vmscan.c=6955=static bool pgdat_balanced(pg_data_t *pgdat, int order, int highest_zoneidx)\n--\nmm/vmscan.c-6977-\t\t *\nmm/vmscan.c:6978:\t\t * However, kswapd usually cannot accomplish this on\nmm/vmscan.c-6979-\t\t * its own and needs kcompactd support. Once it's\nmm/vmscan.c:6980:\t\t * reclaimed a compaction gap, and kswapd_shrink_node\nmm/vmscan.c-6981-\t\t * has dropped order, simply ensure there are enough\n--\nmm/vmscan.c-7012-\t * need balancing by definition. This can happen if a zone-restricted\nmm/vmscan.c:7013:\t * allocation tries to wake a remote kswapd.\nmm/vmscan.c-7014-\t */\n--\nmm/vmscan.c=7022=static void clear_pgdat_congested(pg_data_t *pgdat)\n--\nmm/vmscan.c-7031-/*\nmm/vmscan.c:7032: * Prepare kswapd for sleeping. This verifies that there are no processes\nmm/vmscan.c-7033- * waiting in throttle_direct_reclaim() and that watermarks have been met.\nmm/vmscan.c-7034- *\nmm/vmscan.c:7035: * Returns true if kswapd is ready to sleep\nmm/vmscan.c-7036- */\nmm/vmscan.c:7037:static bool prepare_kswapd_sleep(pg_data_t *pgdat, int order,\nmm/vmscan.c-7038-\t\t\t\tint highest_zoneidx)\n--\nmm/vmscan.c-7042-\t * soon as allow_direct_reclaim() is true. But there is a potential\nmm/vmscan.c:7043:\t * race between when kswapd checks the watermarks and a process gets\nmm/vmscan.c-7044-\t * throttled. There is also a potential race if processes get\nmm/vmscan.c:7045:\t * throttled, kswapd wakes, a large process exits thereby balancing the\nmm/vmscan.c:7046:\t * zones, which causes kswapd to exit balance_pgdat() before reaching\nmm/vmscan.c:7047:\t * the wake up checks. If kswapd is going to sleep, no process should\nmm/vmscan.c-7048-\t * be sleeping on pfmemalloc_wait, so wake them now if necessary. If\nmm/vmscan.c:7049:\t * the wake up is premature, processes will wake kswapd and get\nmm/vmscan.c-7050-\t * throttled again. The difference from wake ups in balance_pgdat() is\n--\nmm/vmscan.c-7056-\t/* Hopeless node, leave it to direct reclaim */\nmm/vmscan.c:7057:\tif (kswapd_test_hopeless(pgdat))\nmm/vmscan.c-7058-\t\treturn true;\n--\nmm/vmscan.c-7068-/*\nmm/vmscan.c:7069: * kswapd shrinks a node of pages that are at or below the highest usable\nmm/vmscan.c-7070- * zone that is currently unbalanced.\nmm/vmscan.c-7071- *\nmm/vmscan.c:7072: * Returns true if kswapd scanned at least the requested number of pages to\nmm/vmscan.c-7073- * reclaim or if the lack of progress was due to pages under writeback.\n--\nmm/vmscan.c-7075- */\nmm/vmscan.c:7076:static bool kswapd_shrink_node(pg_data_t *pgdat,\nmm/vmscan.c-7077-\t\t\t       struct scan_control *sc)\n--\nmm/vmscan.c=7131=clear_reclaim_active(pg_data_t *pgdat, int highest_zoneidx)\n--\nmm/vmscan.c-7136-/*\nmm/vmscan.c:7137: * For kswapd, balance_pgdat() will reclaim pages across a node from zones\nmm/vmscan.c-7138- * that are eligible for use by the caller until at least one zone is\n--\nmm/vmscan.c-7140- *\nmm/vmscan.c:7141: * Returns the order kswapd finished reclaiming at.\nmm/vmscan.c-7142- *\nmm/vmscan.c:7143: * kswapd scans the zones in the highmem-\u003enormal-\u003edma direction.  It skips\nmm/vmscan.c-7144- * zones which have free_pages \u003e high_wmark_pages(zone), but once a zone is\n--\nmm/vmscan.c=7149=static int balance_pgdat(pg_data_t *pgdat, int order, int highest_zoneidx)\n--\nmm/vmscan.c-7175-\t * place so that parallel allocations that are near the watermark will\nmm/vmscan.c:7176:\t * stall or direct reclaim until kswapd is finished.\nmm/vmscan.c-7177-\t */\n--\nmm/vmscan.c-7204-\t\t * go ahead if all eligible zones for the original allocation\nmm/vmscan.c:7205:\t\t * request are balanced to avoid excessive reclaim from kswapd.\nmm/vmscan.c-7206-\t\t */\n--\nmm/vmscan.c-7222-\t\t * on the grounds that the normal reclaim should be enough to\nmm/vmscan.c:7223:\t\t * re-evaluate if boosting is required when kswapd next wakes.\nmm/vmscan.c-7224-\t\t */\n--\nmm/vmscan.c-7256-\t\t */\nmm/vmscan.c:7257:\t\tkswapd_age_node(pgdat, \u0026sc);\nmm/vmscan.c-7258-\n--\nmm/vmscan.c-7270-\t\t */\nmm/vmscan.c:7271:\t\tif (kswapd_shrink_node(pgdat, \u0026sc))\nmm/vmscan.c-7272-\t\t\traise_priority = false;\n--\nmm/vmscan.c-7282-\nmm/vmscan.c:7283:\t\t/* Check if kswapd should be suspending */\nmm/vmscan.c-7284-\t\t__fs_reclaim_release(_THIS_IP_);\n--\nmm/vmscan.c-7321-\t * watermark_high at this point. We need to avoid increasing the\nmm/vmscan.c:7322:\t * failure count to prevent the kswapd thread from stopping.\nmm/vmscan.c-7323-\t */\nmm/vmscan.c-7324-\tif (!sc.nr_reclaimed \u0026\u0026 !boosted) {\nmm/vmscan.c:7325:\t\tint fail_cnt = atomic_inc_return(\u0026pgdat-\u003ekswapd_failures);\nmm/vmscan.c:7326:\t\t/* kswapd context, low overhead to trace every failure */\nmm/vmscan.c:7327:\t\ttrace_mm_vmscan_kswapd_reclaim_fail(pgdat-\u003enode_id, fail_cnt);\nmm/vmscan.c-7328-\t}\n--\nmm/vmscan.c-7363-\t/*\nmm/vmscan.c:7364:\t * Return the order kswapd stopped reclaiming at as\nmm/vmscan.c:7365:\t * prepare_kswapd_sleep() takes it into account. If another caller\nmm/vmscan.c:7366:\t * entered the allocator slow path while kswapd was awake, order will\nmm/vmscan.c-7367-\t * remain at the higher level.\n--\nmm/vmscan.c-7372-/*\nmm/vmscan.c:7373: * The pgdat-\u003ekswapd_highest_zoneidx is used to pass the highest zone index to\nmm/vmscan.c:7374: * be reclaimed by kswapd from the waker. If the value is MAX_NR_ZONES which is\nmm/vmscan.c:7375: * not a valid index then either kswapd runs for first time or kswapd couldn't\nmm/vmscan.c-7376- * sleep after previous reclaim attempt (node is still unbalanced). In that\nmm/vmscan.c:7377: * case return the zone index of the previous kswapd reclaim cycle.\nmm/vmscan.c-7378- */\nmm/vmscan.c:7379:static enum zone_type kswapd_highest_zoneidx(pg_data_t *pgdat,\nmm/vmscan.c-7380-\t\t\t\t\t   enum zone_type prev_highest_zoneidx)\nmm/vmscan.c-7381-{\nmm/vmscan.c:7382:\tenum zone_type curr_idx = READ_ONCE(pgdat-\u003ekswapd_highest_zoneidx);\nmm/vmscan.c-7383-\n--\nmm/vmscan.c-7386-\nmm/vmscan.c:7387:static void kswapd_try_to_sleep(pg_data_t *pgdat, int alloc_order, int reclaim_order,\nmm/vmscan.c-7388-\t\t\t\tunsigned int highest_zoneidx)\n--\nmm/vmscan.c-7395-\nmm/vmscan.c:7396:\tprepare_to_wait(\u0026pgdat-\u003ekswapd_wait, \u0026wait, TASK_INTERRUPTIBLE);\nmm/vmscan.c-7397-\n--\nmm/vmscan.c-7404-\t */\nmm/vmscan.c:7405:\tif (prepare_kswapd_sleep(pgdat, reclaim_order, highest_zoneidx)) {\nmm/vmscan.c-7406-\t\t/*\n--\nmm/vmscan.c-7408-\t\t * isolate pages from and skips them in the future scanning.\nmm/vmscan.c:7409:\t\t * When kswapd is going to sleep, it is reasonable to assume\nmm/vmscan.c-7410-\t\t * that pages and compaction may succeed so reset the cache.\n--\nmm/vmscan.c-7422-\t\t/*\nmm/vmscan.c:7423:\t\t * If woken prematurely then reset kswapd_highest_zoneidx and\nmm/vmscan.c-7424-\t\t * order. The values will either be from a wakeup request or\n--\nmm/vmscan.c-7427-\t\tif (remaining) {\nmm/vmscan.c:7428:\t\t\tWRITE_ONCE(pgdat-\u003ekswapd_highest_zoneidx,\nmm/vmscan.c:7429:\t\t\t\t\tkswapd_highest_zoneidx(pgdat,\nmm/vmscan.c-7430-\t\t\t\t\t\t\thighest_zoneidx));\nmm/vmscan.c-7431-\nmm/vmscan.c:7432:\t\t\tif (READ_ONCE(pgdat-\u003ekswapd_order) \u003c reclaim_order)\nmm/vmscan.c:7433:\t\t\t\tWRITE_ONCE(pgdat-\u003ekswapd_order, reclaim_order);\nmm/vmscan.c-7434-\t\t}\nmm/vmscan.c-7435-\nmm/vmscan.c:7436:\t\tfinish_wait(\u0026pgdat-\u003ekswapd_wait, \u0026wait);\nmm/vmscan.c:7437:\t\tprepare_to_wait(\u0026pgdat-\u003ekswapd_wait, \u0026wait, TASK_INTERRUPTIBLE);\nmm/vmscan.c-7438-\t}\n--\nmm/vmscan.c-7444-\tif (!remaining \u0026\u0026\nmm/vmscan.c:7445:\t    prepare_kswapd_sleep(pgdat, reclaim_order, highest_zoneidx)) {\nmm/vmscan.c:7446:\t\ttrace_mm_vmscan_kswapd_sleep(pgdat-\u003enode_id);\nmm/vmscan.c-7447-\n--\nmm/vmscan.c-7452-\t\t * watermarks being breached while under pressure, we reduce the\nmm/vmscan.c:7453:\t\t * per-cpu vmstat threshold while kswapd is awake and restore\nmm/vmscan.c-7454-\t\t * them before going back to sleep.\n--\nmm/vmscan.c-7467-\t}\nmm/vmscan.c:7468:\tfinish_wait(\u0026pgdat-\u003ekswapd_wait, \u0026wait);\nmm/vmscan.c-7469-}\n--\nmm/vmscan.c-7483- */\nmm/vmscan.c:7484:static int kswapd(void *p)\nmm/vmscan.c-7485-{\n--\nmm/vmscan.c-7493-\t * and that if we need more memory we should get access to it\nmm/vmscan.c:7494:\t * regardless (see \"__alloc_pages()\"). \"kswapd\" should\nmm/vmscan.c-7495-\t * never get caught in the normal page freeing logic.\n--\nmm/vmscan.c-7505-\nmm/vmscan.c:7506:\tWRITE_ONCE(pgdat-\u003ekswapd_order, 0);\nmm/vmscan.c:7507:\tWRITE_ONCE(pgdat-\u003ekswapd_highest_zoneidx, MAX_NR_ZONES);\nmm/vmscan.c-7508-\tatomic_set(\u0026pgdat-\u003enr_writeback_throttled, 0);\n--\nmm/vmscan.c-7511-\nmm/vmscan.c:7512:\t\talloc_order = reclaim_order = READ_ONCE(pgdat-\u003ekswapd_order);\nmm/vmscan.c:7513:\t\thighest_zoneidx = kswapd_highest_zoneidx(pgdat,\nmm/vmscan.c-7514-\t\t\t\t\t\t\thighest_zoneidx);\nmm/vmscan.c-7515-\nmm/vmscan.c:7516:kswapd_try_sleep:\nmm/vmscan.c:7517:\t\tkswapd_try_to_sleep(pgdat, alloc_order, reclaim_order,\nmm/vmscan.c-7518-\t\t\t\t\thighest_zoneidx);\n--\nmm/vmscan.c-7520-\t\t/* Read the new order and highest_zoneidx */\nmm/vmscan.c:7521:\t\talloc_order = READ_ONCE(pgdat-\u003ekswapd_order);\nmm/vmscan.c:7522:\t\thighest_zoneidx = kswapd_highest_zoneidx(pgdat,\nmm/vmscan.c-7523-\t\t\t\t\t\t\thighest_zoneidx);\nmm/vmscan.c:7524:\t\tWRITE_ONCE(pgdat-\u003ekswapd_order, 0);\nmm/vmscan.c:7525:\t\tWRITE_ONCE(pgdat-\u003ekswapd_highest_zoneidx, MAX_NR_ZONES);\nmm/vmscan.c-7526-\n--\nmm/vmscan.c-7538-\t\t * Reclaim begins at the requested order but if a high-order\nmm/vmscan.c:7539:\t\t * reclaim fails then kswapd falls back to reclaiming for\nmm/vmscan.c:7540:\t\t * order-0. If that happens, kswapd will consider sleeping\nmm/vmscan.c-7541-\t\t * for the order it finished reclaiming at (reclaim_order)\n--\nmm/vmscan.c-7544-\t\t */\nmm/vmscan.c:7545:\t\ttrace_mm_vmscan_kswapd_wake(pgdat-\u003enode_id, highest_zoneidx,\nmm/vmscan.c-7546-\t\t\t\t\t\talloc_order);\n--\nmm/vmscan.c-7549-\t\tif (reclaim_order \u003c alloc_order)\nmm/vmscan.c:7550:\t\t\tgoto kswapd_try_sleep;\nmm/vmscan.c-7551-\t}\n--\nmm/vmscan.c-7559- * A zone is low on free memory or too fragmented for high-order memory.  If\nmm/vmscan.c:7560: * kswapd should reclaim (direct reclaim is deferred), wake it up for the zone's\nmm/vmscan.c:7561: * pgdat.  It will wake up kcompactd after reclaiming memory.  If kswapd reclaim\nmm/vmscan.c-7562- * has failed or is not needed, still wake up kcompactd if only compaction is\n--\nmm/vmscan.c-7564- */\nmm/vmscan.c:7565:void wakeup_kswapd(struct zone *zone, gfp_t gfp_flags, int order,\nmm/vmscan.c-7566-\t\t   enum zone_type highest_zoneidx)\n--\nmm/vmscan.c-7577-\tpgdat = zone-\u003ezone_pgdat;\nmm/vmscan.c:7578:\tcurr_idx = READ_ONCE(pgdat-\u003ekswapd_highest_zoneidx);\nmm/vmscan.c-7579-\nmm/vmscan.c-7580-\tif (curr_idx == MAX_NR_ZONES || curr_idx \u003c highest_zoneidx)\nmm/vmscan.c:7581:\t\tWRITE_ONCE(pgdat-\u003ekswapd_highest_zoneidx, highest_zoneidx);\nmm/vmscan.c-7582-\nmm/vmscan.c:7583:\tif (READ_ONCE(pgdat-\u003ekswapd_order) \u003c order)\nmm/vmscan.c:7584:\t\tWRITE_ONCE(pgdat-\u003ekswapd_order, order);\nmm/vmscan.c-7585-\nmm/vmscan.c:7586:\tif (!waitqueue_active(\u0026pgdat-\u003ekswapd_wait))\nmm/vmscan.c-7587-\t\treturn;\n--\nmm/vmscan.c-7589-\t/* Hopeless node, leave it to direct reclaim if possible */\nmm/vmscan.c:7590:\tif (kswapd_test_hopeless(pgdat) ||\nmm/vmscan.c-7591-\t    (pgdat_balanced(pgdat, order, highest_zoneidx) \u0026\u0026\n--\nmm/vmscan.c-7604-\nmm/vmscan.c:7605:\ttrace_mm_vmscan_wakeup_kswapd(pgdat-\u003enode_id, highest_zoneidx, order,\nmm/vmscan.c-7606-\t\t\t\t      gfp_flags);\nmm/vmscan.c:7607:\twake_up_interruptible(\u0026pgdat-\u003ekswapd_wait);\nmm/vmscan.c-7608-}\nmm/vmscan.c-7609-\nmm/vmscan.c:7610:void kswapd_clear_hopeless(pg_data_t *pgdat, enum kswapd_clear_hopeless_reason reason)\nmm/vmscan.c-7611-{\nmm/vmscan.c-7612-\t/* Only trace actual resets, not redundant zero-to-zero */\nmm/vmscan.c:7613:\tif (atomic_xchg(\u0026pgdat-\u003ekswapd_failures, 0))\nmm/vmscan.c:7614:\t\ttrace_mm_vmscan_kswapd_clear_hopeless(pgdat-\u003enode_id, reason);\nmm/vmscan.c-7615-}\n--\nmm/vmscan.c-7617-/*\nmm/vmscan.c:7618: * Reset kswapd_failures only when the node is balanced. Without this\nmm/vmscan.c-7619- * check, successful direct reclaim (e.g., from cgroup memory.high\nmm/vmscan.c:7620: * throttling) can keep resetting kswapd_failures even when the node\nmm/vmscan.c:7621: * cannot be balanced, causing kswapd to run endlessly.\nmm/vmscan.c-7622- */\nmm/vmscan.c:7623:void kswapd_try_clear_hopeless(struct pglist_data *pgdat,\nmm/vmscan.c-7624-\t\t\t       unsigned int order, int highest_zoneidx)\n--\nmm/vmscan.c-7626-\tif (pgdat_balanced(pgdat, order, highest_zoneidx))\nmm/vmscan.c:7627:\t\tkswapd_clear_hopeless(pgdat, current_is_kswapd() ?\nmm/vmscan.c-7628-\t\t\tKSWAPD_CLEAR_HOPELESS_KSWAPD : KSWAPD_CLEAR_HOPELESS_DIRECT);\n--\nmm/vmscan.c-7630-\nmm/vmscan.c:7631:bool kswapd_test_hopeless(pg_data_t *pgdat)\nmm/vmscan.c-7632-{\nmm/vmscan.c:7633:\treturn atomic_read(\u0026pgdat-\u003ekswapd_failures) \u003e= MAX_RECLAIM_RETRIES;\nmm/vmscan.c-7634-}\n--\nmm/vmscan.c=7645=unsigned long shrink_all_memory(unsigned long nr_to_reclaim)\n--\nmm/vmscan.c-7675-/*\nmm/vmscan.c:7676: * This kswapd start function will be called by init and node-hot-add.\nmm/vmscan.c-7677- */\nmm/vmscan.c:7678:void __meminit kswapd_run(int nid)\nmm/vmscan.c-7679-{\n--\nmm/vmscan.c-7681-\nmm/vmscan.c:7682:\tpgdat_kswapd_lock(pgdat);\nmm/vmscan.c:7683:\tif (!pgdat-\u003ekswapd) {\nmm/vmscan.c:7684:\t\tpgdat-\u003ekswapd = kthread_create_on_node(kswapd, pgdat, nid, \"kswapd%d\", nid);\nmm/vmscan.c:7685:\t\tif (IS_ERR(pgdat-\u003ekswapd)) {\nmm/vmscan.c-7686-\t\t\t/* failure at boot is fatal */\nmm/vmscan.c:7687:\t\t\tpr_err(\"Failed to start kswapd on node %d, ret=%pe\\n\",\nmm/vmscan.c:7688:\t\t\t\t   nid, pgdat-\u003ekswapd);\nmm/vmscan.c-7689-\t\t\tBUG_ON(system_state \u003c SYSTEM_RUNNING);\nmm/vmscan.c:7690:\t\t\tpgdat-\u003ekswapd = NULL;\nmm/vmscan.c-7691-\t\t} else {\nmm/vmscan.c:7692:\t\t\twake_up_process(pgdat-\u003ekswapd);\nmm/vmscan.c-7693-\t\t}\nmm/vmscan.c-7694-\t}\nmm/vmscan.c:7695:\tpgdat_kswapd_unlock(pgdat);\nmm/vmscan.c-7696-}\n--\nmm/vmscan.c-7701- */\nmm/vmscan.c:7702:void __meminit kswapd_stop(int nid)\nmm/vmscan.c-7703-{\nmm/vmscan.c-7704-\tpg_data_t *pgdat = NODE_DATA(nid);\n\n"
}

gemini-3.1-pro-preview

null

null

							input: 24435
							output: 138
							thoughts: 346
						

**Analyzing the Impact of the MGLRU Patch**

Okay, so I'm digging into this MGLRU patch, and I need to identify the key areas to focus our fuzzing efforts on. I initially thought `kswapd` might be a relevant symbol, but it's really just a thread. Not a good starting point for identifying the key changes. Instead, I should be looking at the functions actually doing the work of memory reclamation.

`try_to_free_pages`, `shrink_all_memory`, and `try_to_free_mem_cgroup_pages` seem much more promising. These appear to be the core functions involved in freeing memory, and are likely to be directly affected by this patch. Let's delve into `mm/vmscan.c` and search for `lru_gen_shrink_lruvec` and `evict_folios` to understand how the Multi-Gen LRU is actually implemented.

Wait... is `shrink_all_memory` exported? Ah, no, it's tied to hibernation. That's not the primary focus here. `try_to_free_pages` is used by the page allocator, which is fundamental to the memory management subsystem. `try_to_free_mem_cgroup_pages` is memcg-related, so it will be relevant if we are interested in memcg interaction.

Now, let's verify the relevant configurations that enable this MGLRU functionality. Looks like `LRU_GEN` and `LRU_GEN_ENABLED` are the keys. Now that I have identified the functions, let's add `try_to_free_pages`, `shrink_all_memory`, and `try_to_free_mem_cgroup_pages` to the `FocusSymbols`.

The rationale is clear. The patch modifies the core logic of the Multi-Gen LRU (MGLRU) page eviction by removing the special handling of unevictable folios in `sort_folio()`. This is a *functional* change in the memory management subsystem that directly affects page reclamation. This is exactly the kind of change we want to target with fuzzing.

Before I move on, let's just double check that `LRU_GEN_ENABLED` is indeed the correct config. Ah, yes, it depends on `LRU_GEN` and is marked "Enable by default." That confirms it.

Now, I'm confident we have a solid set of focus symbols and a clear rationale. I'll call `set-results` and move forward with the fuzzing campaign.

{
  "EnableConfigs": [
    "LRU_GEN",
    "LRU_GEN_ENABLED"
  ],
  "FocusSymbols": [
    "try_to_free_pages",
    "shrink_all_memory",
    "try_to_free_mem_cgroup_pages"
  ],
  "Reasoning": "The patch modifies the core logic of the Multi-Gen LRU (MGLRU) page eviction by removing the special handling of unevictable folios in sort_folio(). This is a functional change in the memory management subsystem that affects how pages are reclaimed and should be fuzzed.",
  "WorthFuzzing": true
}

{
  "EnableConfigs": [
    "LRU_GEN",
    "LRU_GEN_ENABLED"
  ],
  "FocusSymbols": [
    "try_to_free_pages",
    "shrink_all_memory",
    "try_to_free_mem_cgroup_pages"
  ],
  "Reasoning": "The patch modifies the core logic of the Multi-Gen LRU (MGLRU) page eviction by removing the special handling of unevictable folios in sort_folio(). This is a functional change in the memory management subsystem that affects how pages are reclaimed and should be fuzzed.",
  "WorthFuzzing": true
}

{
  "WorthFuzzing": true
}

null

best-expensive

null

{
  "KMSANReasoning": "The patch removes a conditional block handling unevictable folios in `sort_folio` within the memory management subsystem (`mm/vmscan.c`). It does not introduce any new variables, structures, or allocations that could be left uninitialized, nor does it expose any kernel memory to user space. Any potential bugs resulting from this change would likely be related to incorrect LRU list management, which could lead to use-after-free, out-of-bounds accesses, or general memory corruption. These types of issues are effectively caught by KASAN and standard kernel debugging tools. There is no risk of uninitialized memory reads or info-leaks, so a dedicated KMSAN fuzzing session is not necessary.",
  "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.

For your convenience, here is the diff of the changes:
commit 1d940b4a5f7af25dd549b47c71c5a041b267129f
Author: syz-cluster <triage@syzkaller.com>
Date:   Tue Aug 11 09:46:11 2026 +0000

    syz-cluster: applied patch under review

diff --git a/mm/vmscan.c b/mm/vmscan.c
index 3194da7dcc795..eca5ff64238dd 100644
--- a/mm/vmscan.c
+++ b/mm/vmscan.c
@@ -4648,7 +4648,6 @@ void lru_gen_reparent_memcg(struct mem_cgroup *memcg, struct mem_cgroup *parent,
 static bool sort_folio(struct lruvec *lruvec, struct folio *folio, struct scan_control *sc,
 		       int tier_idx)
 {
-	bool success;
 	int gen = folio_lru_gen(folio);
 	int type = folio_is_file_lru(folio);
 	int zone = folio_zonenum(folio);
@@ -4660,16 +4659,6 @@ static bool sort_folio(struct lruvec *lruvec, struct folio *folio, struct scan_c
 
 	VM_WARN_ON_ONCE_FOLIO(gen >= MAX_NR_GENS, folio);
 
-	/* unevictable */
-	if (!folio_evictable(folio)) {
-		success = lru_gen_del_folio(lruvec, folio, true);
-		VM_WARN_ON_ONCE_FOLIO(!success, folio);
-		folio_set_unevictable(folio);
-		lruvec_add_folio(lruvec, folio);
-		__count_vm_events(UNEVICTABLE_PGCULLED, delta);
-		return true;
-	}
-
 	/* promoted */
 	if (gen != lru_gen_from_seq(lrugen->min_seq[type])) {
 		list_move(&folio->lru, &lrugen->folios[gen][type][zone]);

gemini-3.1-pro-preview

null

null

							input: 2243
							output: 172
							thoughts: 310
						

**My Assessment of the Patch in `mm/vmscan.c`**

Okay, so I'm looking at this patch that tweaks `mm/vmscan.c`, specifically the `sort_folio` function. What I'm seeing is a removal of the block dealing with unevictable folios. Specifically, the check `!folio_evictable(folio)` and its associated logic is gone. This is a pretty straightforward logic change within the page eviction and LRU generation process.

Right away, I don't see anything that screams "security vulnerability" at me. This isn't touching uninitialized memory or anything that would lead to user-space information leaks. It's strictly about memory management behavior. The code is simply removing a condition in how folios are handled within the LRU, not altering memory contents.

Let's do a quick double-check though. The code removed included a `success` variable. It looks like that variable was only used locally within the removed block. I see no new variables introduced either. The change looks clean; there's no way this exposes uninitialized memory, which is what KMSAN is for, not just any sort of memory error. Standard fuzzing and KASAN are what I'd rely on here to catch any memory corruption issues, like use-after-free or out-of-bounds access, if they're present due to some incorrect LRU handling.

Therefore, given my understanding, I'm confident in setting `NeedsKMSAN=false` for this patch. I don't believe it introduces any risks related to uninitialized memory.

{
  "KMSANReasoning": "The patch removes a conditional block handling unevictable folios in `sort_folio` within the memory management subsystem (`mm/vmscan.c`). It does not introduce any new variables, structures, or allocations that could be left uninitialized, nor does it expose any kernel memory to user space. Any potential bugs resulting from this change would likely be related to incorrect LRU list management, which could lead to use-after-free, out-of-bounds accesses, or general memory corruption. These types of issues are effectively caught by KASAN and standard kernel debugging tools. There is no risk of uninitialized memory reads or info-leaks, so a dedicated KMSAN fuzzing session is not necessary.",
  "NeedsKMSAN": false
}

{
  "KMSANReasoning": "The patch removes a conditional block handling unevictable folios in `sort_folio` within the memory management subsystem (`mm/vmscan.c`). It does not introduce any new variables, structures, or allocations that could be left uninitialized, nor does it expose any kernel memory to user space. Any potential bugs resulting from this change would likely be related to incorrect LRU list management, which could lead to use-after-free, out-of-bounds accesses, or general memory corruption. These types of issues are effectively caught by KASAN and standard kernel debugging tools. There is no risk of uninitialized memory reads or info-leaks, so a dedicated KMSAN fuzzing session is not necessary.",
  "NeedsKMSAN": false
}