This is a note to let you know that I've just added the patch titled
nilfs2: fix deadlock warnings caused by lock dependency in init_nilfs()
to the 6.1-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary
The filename of the patch is:
nilfs2-fix-deadlock-warnings-caused-by-lock-dependency-in-init_nilfs.patch
and it can be found in the queue-6.1 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <[email protected]> know about it.
>From [email protected] Tue Oct 21 16:19:13
>2025
From: Mahmoud Adam <[email protected]>
Date: Tue, 21 Oct 2025 09:03:43 +0200
Subject: nilfs2: fix deadlock warnings caused by lock dependency in init_nilfs()
To: <[email protected]>
Cc: <[email protected]>, <[email protected]>, Ryusuke Konishi
<[email protected]>,
<[email protected]>,
<[email protected]>, Andrew Morton
<[email protected]>, Jens Axboe <[email protected]>, Xiubo Li
<[email protected]>, Ilya Dryomov <[email protected]>, Jeff Layton
<[email protected]>, Alexander Viro <[email protected]>, Theodore Ts'o
<[email protected]>, Andreas Dilger <[email protected]>, Jaegeuk Kim
<[email protected]>, Chao Yu <[email protected]>, Christoph Hellwig
<[email protected]>, "Darrick J. Wong" <[email protected]>, Trond Myklebust
<[email protected]>, Anna Schumaker <[email protected]>, "Matthew
Wilcox (Oracle)" <[email protected]>, Hannes Reinecke <[email protected]>, Damien
Le Moal <[email protected]>, Luis Chamberlain <[email protected]>,
<[email protected]>, <[email protected]>,
<[email protected]>, <linux-fsdevel@vger.
kernel.org>, <[email protected]>,
<[email protected]>, <[email protected]>,
<[email protected]>, <[email protected]>, <[email protected]>
Message-ID: <[email protected]>
From: Ryusuke Konishi <[email protected]>
commit fb881cd7604536b17a1927fb0533f9a6982ffcc5 upstream.
After commit c0e473a0d226 ("block: fix race between set_blocksize and read
paths") was merged, set_blocksize() called by sb_set_blocksize() now locks
the inode of the backing device file. As a result of this change, syzbot
started reporting deadlock warnings due to a circular dependency involving
the semaphore "ns_sem" of the nilfs object, the inode lock of the backing
device file, and the locks that this inode lock is transitively dependent
on.
This is caused by a new lock dependency added by the above change, since
init_nilfs() calls sb_set_blocksize() in the lock section of "ns_sem".
However, these warnings are false positives because init_nilfs() is called
in the early stage of the mount operation and the filesystem has not yet
started.
The reason why "ns_sem" is locked in init_nilfs() was to avoid a race
condition in nilfs_fill_super() caused by sharing a nilfs object among
multiple filesystem instances (super block structures) in the early
implementation. However, nilfs objects and super block structures have
long ago become one-to-one, and there is no longer any need to use the
semaphore there.
So, fix this issue by removing the use of the semaphore "ns_sem" in
init_nilfs().
Link: https://lkml.kernel.org/r/[email protected]
Fixes: c0e473a0d226 ("block: fix race between set_blocksize and read paths")
Signed-off-by: Ryusuke Konishi <[email protected]>
Reported-by: [email protected]
Closes: https://syzkaller.appspot.com/bug?extid=00f7f5b884b117ee6773
Tested-by: [email protected]
Reported-by: [email protected]
Closes: https://syzkaller.appspot.com/bug?extid=f30591e72bfc24d4715b
Tested-by: [email protected]>
Signed-off-by: Andrew Morton <[email protected]>
Signed-off-by: Mahmoud Adam <[email protected]>
Signed-off-by: Greg Kroah-Hartman <[email protected]>
---
fs/nilfs2/the_nilfs.c | 3 ---
1 file changed, 3 deletions(-)
--- a/fs/nilfs2/the_nilfs.c
+++ b/fs/nilfs2/the_nilfs.c
@@ -680,8 +680,6 @@ int init_nilfs(struct the_nilfs *nilfs,
int blocksize;
int err;
- down_write(&nilfs->ns_sem);
-
blocksize = sb_min_blocksize(sb, NILFS_MIN_BLOCK_SIZE);
if (!blocksize) {
nilfs_err(sb, "unable to set blocksize");
@@ -757,7 +755,6 @@ int init_nilfs(struct the_nilfs *nilfs,
set_nilfs_init(nilfs);
err = 0;
out:
- up_write(&nilfs->ns_sem);
return err;
failed_sbh:
Patches currently in stable-queue which might be from [email protected] are
queue-6.1/block-fix-race-between-set_blocksize-and-read-paths.patch
queue-6.1/filemap-add-a-kiocb_invalidate_pages-helper.patch
queue-6.1/fs-factor-out-a-direct_write_fallback-helper.patch
queue-6.1/direct_write_fallback-on-error-revert-the-ki_pos-update-from-buffered-write.patch
queue-6.1/filemap-update-ki_pos-in-generic_perform_write.patch
queue-6.1/filemap-add-a-kiocb_invalidate_post_direct_write-helper.patch
queue-6.1/nilfs2-fix-deadlock-warnings-caused-by-lock-dependency-in-init_nilfs.patch
queue-6.1/block-open-code-__generic_file_write_iter-for-blkdev-writes.patch
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