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]>
---
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:
--
2.47.3
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