linux-ext4 - [PATCH 13/50] fs: add an I

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Message-ID: <16c9c4ffea05cdf819d002eb0f65a90a23cb019b.1755806649.git.josef@toxicpanda.com>
Date: Thu, 21 Aug 2025 16:18:24 -0400
From: Josef Bacik <josef@...icpanda.com>
To: linux-fsdevel@...r.kernel.org,
	linux-btrfs@...r.kernel.org,
	kernel-team@...com,
	linux-ext4@...r.kernel.org,
	linux-xfs@...r.kernel.org,
	brauner@...nel.org,
	viro@...IV.linux.org.uk
Subject: [PATCH 13/50] fs: add an I_LRU flag to the inode

We will be adding another list for the inode to keep track of inodes
that are being cached for other reasons. This is necessary to make sure
we know which list the inode is on, and to differentiate it from the
private dispose lists.

Signed-off-by: Josef Bacik <josef@...icpanda.com>
---
 fs/inode.c                       | 7 +++++++
 include/linux/fs.h               | 6 ++++++
 include/trace/events/writeback.h | 3 ++-
 3 files changed, 15 insertions(+), 1 deletion(-)

diff --git a/fs/inode.c b/fs/inode.c
index 814c03f5dbb1..94769b356224 100644
--- a/fs/inode.c
+++ b/fs/inode.c
@@ -545,6 +545,7 @@ static void __inode_add_lru(struct inode *inode, bool rotate)
 
 	if (list_lru_add_obj(&inode->i_sb->s_inode_lru, &inode->i_lru)) {
 		iobj_get(inode);
+		inode->i_state |= I_LRU;
 		this_cpu_inc(nr_unused);
 	} else if (rotate) {
 		inode->i_state |= I_REFERENCED;
@@ -574,7 +575,11 @@ void inode_add_lru(struct inode *inode)
 
 static void inode_lru_list_del(struct inode *inode)
 {
+	if (!(inode->i_state & I_LRU))
+		return;
+
 	if (list_lru_del_obj(&inode->i_sb->s_inode_lru, &inode->i_lru)) {
+		inode->i_state &= ~I_LRU;
 		iobj_put(inode);
 		this_cpu_dec(nr_unused);
 	}
@@ -955,6 +960,7 @@ static enum lru_status inode_lru_isolate(struct list_head *item,
 	    (inode->i_state & ~I_REFERENCED) ||
 	    !mapping_shrinkable(&inode->i_data)) {
 		list_lru_isolate(lru, &inode->i_lru);
+		inode->i_state &= ~I_LRU;
 		spin_unlock(&inode->i_lock);
 		this_cpu_dec(nr_unused);
 		return LRU_REMOVED;
@@ -991,6 +997,7 @@ static enum lru_status inode_lru_isolate(struct list_head *item,
 
 	WARN_ON(inode->i_state & I_NEW);
 	inode->i_state |= I_FREEING;
+	inode->i_state &= ~I_LRU;
 	list_lru_isolate_move(lru, &inode->i_lru, freeable);
 	spin_unlock(&inode->i_lock);
 
diff --git a/include/linux/fs.h b/include/linux/fs.h
index b2048fd9c300..509e696a4df0 100644
--- a/include/linux/fs.h
+++ b/include/linux/fs.h
@@ -744,6 +744,11 @@ is_uncached_acl(struct posix_acl *acl)
  * 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
+ *			for some other means.
+ *
  * Q: What is the difference between I_WILL_FREE and I_FREEING?
  *
  * __I_{SYNC,NEW,LRU_ISOLATING} are used to derive unique addresses to wait
@@ -780,6 +785,7 @@ enum inode_state_bits {
 	INODE_BIT(I_DONTCACHE),
 	INODE_BIT(I_SYNC_QUEUED),
 	INODE_BIT(I_PINNING_NETFS_WB),
+	INODE_BIT(I_LRU),
 };
 
 #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 1e23919c0da9..486f85aca84d 100644
--- a/include/trace/events/writeback.h
+++ b/include/trace/events/writeback.h
@@ -28,7 +28,8 @@
 		{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_ISOLATING,	"I_LRU_ISOLATING"},	\
+		{I_LRU,			"I_LRU"}		\
 	)
 
 /* enums need to be exported to user space */
-- 
2.49.0