Patch "nilfs2: fix deadlock warnings caused by lock dependency in init_nilfs()" has been added to the 6.1-stable tree

[<gregkh@linuxfoundation.org>]

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 <stable@vger.kernel.org> know about it.


From stable+bounces-188303-greg=kroah.com@vger.kernel.org Tue Oct 21 16:19:13 2025
From: Mahmoud Adam <mngyadam@amazon.de>
Date: Tue, 21 Oct 2025 09:03:43 +0200
Subject: nilfs2: fix deadlock warnings caused by lock dependency in init_nilfs()
To: <stable@vger.kernel.org>
Cc: <gregkh@linuxfoundation.org>, <nagy@khwaternagy.com>, Ryusuke Konishi <konishi.ryusuke@gmail.com>, <syzbot+00f7f5b884b117ee6773@syzkaller.appspotmail.com>, <syzbot+f30591e72bfc24d4715b@syzkaller.appspotmail.com>, Andrew Morton <akpm@linux-foundation.org>, Jens Axboe <axboe@kernel.dk>, Xiubo Li <xiubli@redhat.com>, Ilya Dryomov <idryomov@gmail.com>, Jeff Layton <jlayton@kernel.org>, Alexander Viro <viro@zeniv.linux.org.uk>, Theodore Ts'o <tytso@mit.edu>, Andreas Dilger <adilger.kernel@dilger.ca>, Jaegeuk Kim <jaegeuk@kernel.org>, Chao Yu <chao@kernel.org>, Christoph Hellwig <hch@infradead.org>, "Darrick J. Wong" <djwong@kernel.org>, Trond Myklebust <trond.myklebust@hammerspace.com>, Anna Schumaker <anna@kernel.org>, "Matthew Wilcox (Oracle)" <willy@infradead.org>, Hannes Reinecke <hare@suse.de>, Damien Le Moal <dlemoal@kernel.org>, Luis Chamberlain <mcgrof@kernel.org>, <linux-block@vger.kernel.org>, <linux-kernel@vger.kernel.org>, <ceph-devel@vger.kernel.org>, <linux-fsdev
 el@vger.
 kernel.org>, <linux-ext4@vger.kernel.org>, <linux-f2fs-devel@lists.sourceforge.net>, <linux-xfs@vger.kernel.org>, <linux-nfs@vger.kernel.org>, <linux-nilfs@vger.kernel.org>, <linux-mm@kvack.org>
Message-ID: <20251021070353.96705-10-mngyadam@amazon.de>

From: Ryusuke Konishi <konishi.ryusuke@gmail.com>

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/20250503053327.12294-1-konishi.ryusuke@gmail.com
Fixes: c0e473a0d226 ("block: fix race between set_blocksize and read paths")
Signed-off-by: Ryusuke Konishi <konishi.ryusuke@gmail.com>
Reported-by: syzbot+00f7f5b884b117ee6773@syzkaller.appspotmail.com
Closes: https://syzkaller.appspot.com/bug?extid=00f7f5b884b117ee6773
Tested-by: syzbot+00f7f5b884b117ee6773@syzkaller.appspotmail.com
Reported-by: syzbot+f30591e72bfc24d4715b@syzkaller.appspotmail.com
Closes: https://syzkaller.appspot.com/bug?extid=f30591e72bfc24d4715b
Tested-by: syzbot+f30591e72bfc24d4715b@syzkaller.appspotmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Mahmoud Adam <mngyadam@amazon.de>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
 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 mngyadam@amazon.de 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