If the inode is on the LRU it has a full reference and thus no longer
needs to be pinned while it is being isolated.

Remove the I_LRU_ISOLATING flag and associated helper functions
(inode_pin_lru_isolating, inode_unpin_lru_isolating, and
inode_wait_for_lru_isolating) as they are no longer needed.

Signed-off-by: Josef Bacik <josef@toxicpanda.com>
---
 fs/inode.c                       | 46 --------------------------------
 include/linux/fs.h               | 39 ++++++++++++---------------
 include/trace/events/writeback.h |  1 -
 3 files changed, 17 insertions(+), 69 deletions(-)

diff --git a/fs/inode.c b/fs/inode.c
index 4f77db7aca75..77f009edd5df 100644
--- a/fs/inode.c
+++ b/fs/inode.c
@@ -656,49 +656,6 @@ void inode_lru_list_del(struct inode *inode)
 	}
 }
 
-static void inode_pin_lru_isolating(struct inode *inode)
-{
-	lockdep_assert_held(&inode->i_lock);
-	WARN_ON(inode->i_state & I_LRU_ISOLATING);
-	inode->i_state |= I_LRU_ISOLATING;
-}
-
-static void inode_unpin_lru_isolating(struct inode *inode)
-{
-	spin_lock(&inode->i_lock);
-	WARN_ON(!(inode->i_state & I_LRU_ISOLATING));
-	inode->i_state &= ~I_LRU_ISOLATING;
-	/* Called with inode->i_lock which ensures memory ordering. */
-	inode_wake_up_bit(inode, __I_LRU_ISOLATING);
-	spin_unlock(&inode->i_lock);
-}
-
-static void inode_wait_for_lru_isolating(struct inode *inode)
-{
-	struct wait_bit_queue_entry wqe;
-	struct wait_queue_head *wq_head;
-
-	lockdep_assert_held(&inode->i_lock);
-	if (!(inode->i_state & I_LRU_ISOLATING))
-		return;
-
-	wq_head = inode_bit_waitqueue(&wqe, inode, __I_LRU_ISOLATING);
-	for (;;) {
-		prepare_to_wait_event(wq_head, &wqe.wq_entry, TASK_UNINTERRUPTIBLE);
-		/*
-		 * Checking I_LRU_ISOLATING with inode->i_lock guarantees
-		 * memory ordering.
-		 */
-		if (!(inode->i_state & I_LRU_ISOLATING))
-			break;
-		spin_unlock(&inode->i_lock);
-		schedule();
-		spin_lock(&inode->i_lock);
-	}
-	finish_wait(wq_head, &wqe.wq_entry);
-	WARN_ON(inode->i_state & I_LRU_ISOLATING);
-}
-
 /**
  * inode_sb_list_add - add inode to the superblock list of inodes
  * @inode: inode to add
@@ -885,7 +842,6 @@ static void evict(struct inode *inode)
 	inode_sb_list_del(inode);
 
 	spin_lock(&inode->i_lock);
-	inode_wait_for_lru_isolating(inode);
 
 	/*
 	 * Wait for flusher thread to be done with the inode so that filesystem
@@ -1030,7 +986,6 @@ static enum lru_status inode_lru_isolate(struct list_head *item,
 	 * be under pressure before the cache inside the highmem zone.
 	 */
 	if (inode_has_buffers(inode) || !mapping_empty(&inode->i_data)) {
-		inode_pin_lru_isolating(inode);
 		spin_unlock(&inode->i_lock);
 		spin_unlock(&lru->lock);
 		if (remove_inode_buffers(inode)) {
@@ -1042,7 +997,6 @@ static enum lru_status inode_lru_isolate(struct list_head *item,
 				__count_vm_events(PGINODESTEAL, reap);
 			mm_account_reclaimed_pages(reap);
 		}
-		inode_unpin_lru_isolating(inode);
 		return LRU_RETRY;
 	}
 
diff --git a/include/linux/fs.h b/include/linux/fs.h
index 39cde53c1b3b..61113026efd5 100644
--- a/include/linux/fs.h
+++ b/include/linux/fs.h
@@ -734,9 +734,6 @@ is_uncached_acl(struct posix_acl *acl)
  *
  * I_PINNING_FSCACHE_WB	Inode is pinning an fscache object for writeback.
  *
- * I_LRU_ISOLATING	Inode is pinned being isolated from LRU without holding
- *			i_count.
- *
  * I_LRU		Inode is on the LRU list and has an associated LRU
  *			reference count. Used to distinguish inodes where
  *			->i_lru is on the LRU and those that are using ->i_lru
@@ -745,34 +742,32 @@ is_uncached_acl(struct posix_acl *acl)
  * I_CACHED_LRU		Inode is cached because it is dirty or isn't shrinkable,
  *			and thus is on the s_cached_inode_lru list.
  *
- * __I_{SYNC,NEW,LRU_ISOLATING} are used to derive unique addresses to wait
- * upon. There's one free address left.
+ * __I_{SYNC,NEW} are used to derive unique addresses to wait upon. There are
+ * two free address left.
  */
 
 enum inode_state_bits {
 	__I_NEW			= 0U,
-	__I_SYNC		= 1U,
-	__I_LRU_ISOLATING	= 2U
+	__I_SYNC		= 1U
 };
 
 enum inode_state_flags_t {
 	I_NEW			= (1U << __I_NEW),
 	I_SYNC			= (1U << __I_SYNC),
-	I_LRU_ISOLATING         = (1U << __I_LRU_ISOLATING),
-	I_DIRTY_SYNC		= (1U << 3),
-	I_DIRTY_DATASYNC	= (1U << 4),
-	I_DIRTY_PAGES		= (1U << 5),
-	I_CLEAR			= (1U << 6),
-	I_LINKABLE		= (1U << 7),
-	I_DIRTY_TIME		= (1U << 8),
-	I_WB_SWITCH		= (1U << 9),
-	I_OVL_INUSE		= (1U << 10),
-	I_CREATING		= (1U << 11),
-	I_DONTCACHE		= (1U << 12),
-	I_SYNC_QUEUED		= (1U << 13),
-	I_PINNING_NETFS_WB	= (1U << 14),
-	I_LRU			= (1U << 15),
-	I_CACHED_LRU		= (1U << 16)
+	I_DIRTY_SYNC		= (1U << 2),
+	I_DIRTY_DATASYNC	= (1U << 3),
+	I_DIRTY_PAGES		= (1U << 4),
+	I_CLEAR			= (1U << 5),
+	I_LINKABLE		= (1U << 6),
+	I_DIRTY_TIME		= (1U << 7),
+	I_WB_SWITCH		= (1U << 8),
+	I_OVL_INUSE		= (1U << 9),
+	I_CREATING		= (1U << 10),
+	I_DONTCACHE		= (1U << 11),
+	I_SYNC_QUEUED		= (1U << 12),
+	I_PINNING_NETFS_WB	= (1U << 13),
+	I_LRU			= (1U << 14),
+	I_CACHED_LRU		= (1U << 15)
 };
 
 #define I_DIRTY_INODE (I_DIRTY_SYNC | I_DIRTY_DATASYNC)
diff --git a/include/trace/events/writeback.h b/include/trace/events/writeback.h
index b419b8060dda..a5b73d25eda6 100644
--- a/include/trace/events/writeback.h
+++ b/include/trace/events/writeback.h
@@ -25,7 +25,6 @@
 		{I_DONTCACHE,		"I_DONTCACHE"},		\
 		{I_SYNC_QUEUED,		"I_SYNC_QUEUED"},	\
 		{I_PINNING_NETFS_WB,	"I_PINNING_NETFS_WB"},	\
-		{I_LRU_ISOLATING,	"I_LRU_ISOLATING"},	\
 		{I_LRU,			"I_LRU"},		\
 		{I_CACHED_LRU,		"I_CACHED_LRU"}		\
 	)
-- 
2.49.0