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 --- Follow up fix.
fs/nilfs2/the_nilfs.c | 3 --- 1 file changed, 3 deletions(-)
diff --git a/fs/nilfs2/the_nilfs.c b/fs/nilfs2/the_nilfs.c index be41e26b782469..05fdbbc63e1f5f 100644 --- a/fs/nilfs2/the_nilfs.c +++ b/fs/nilfs2/the_nilfs.c @@ -680,8 +680,6 @@ int init_nilfs(struct the_nilfs *nilfs, struct super_block *sb, char *data) 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, struct super_block *sb, char *data) set_nilfs_init(nilfs); err = 0; out: - up_write(&nilfs->ns_sem); return err;
failed_sbh: