linux-ext4 - [PATCH 12/50] fs: rework iput logic

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <51eb4b2eef8ee1f7bb4f0974b048dc85452d182d.1755806649.git.josef@toxicpanda.com>
Date: Thu, 21 Aug 2025 16:18:23 -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 12/50] fs: rework iput logic

Currently, if we are the last iput, and we have the I_DIRTY_TIME bit
set, we will grab a reference on the inode again and then mark it dirty
and then redo the put.  This is to make sure we delay the time update
for as long as possible.

We can rework this logic to simply dec i_count if it is not 1, and if it
is do the time update while still holding the i_count reference.

Then we can replace the atomic_dec_and_lock with locking the ->i_lock
and doing atomic_dec_and_test, since we did the atomic_add_unless above.

This is preparation for no longer allowing 0 i_count inodes to exist.

Signed-off-by: Josef Bacik <josef@...icpanda.com>
---
 fs/inode.c | 31 ++++++++++++++++---------------
 1 file changed, 16 insertions(+), 15 deletions(-)

diff --git a/fs/inode.c b/fs/inode.c
index 16acad5583fc..814c03f5dbb1 100644
--- a/fs/inode.c
+++ b/fs/inode.c
@@ -1928,22 +1928,23 @@ void iput(struct inode *inode)
 	if (!inode)
 		return;
 	BUG_ON(inode->i_state & I_CLEAR);
-retry:
-	if (atomic_dec_and_lock(&inode->i_count, &inode->i_lock)) {
-		if (inode->i_nlink && (inode->i_state & I_DIRTY_TIME)) {
-			/*
-			 * Increment i_count directly as we still have our
-			 * i_obj_count reference still. This is temporary and
-			 * will go away in a future patch.
-			 */
-			atomic_inc(&inode->i_count);
-			spin_unlock(&inode->i_lock);
-			trace_writeback_lazytime_iput(inode);
-			mark_inode_dirty_sync(inode);
-			goto retry;
-		}
-		iput_final(inode);
+
+	if (atomic_add_unless(&inode->i_count, -1, 1)) {
+		iobj_put(inode);
+		return;
 	}
+
+	if (inode->i_nlink && (inode->i_state & I_DIRTY_TIME)) {
+		trace_writeback_lazytime_iput(inode);
+		mark_inode_dirty_sync(inode);
+	}
+
+	spin_lock(&inode->i_lock);
+	if (atomic_dec_and_test(&inode->i_count))
+		iput_final(inode);
+	else
+		spin_unlock(&inode->i_lock);
+
 	iobj_put(inode);
 }
 EXPORT_SYMBOL(iput);
-- 
2.49.0