2020-07-24 12:46:01

by Pavel Machek

[permalink] [raw]

Subject: [PATCH] ocfs2: fix unbalanced locking

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Based on what fails, function can return with nfs_sync_rwlock either
locked or unlocked. That can not be right.

Always return with lock unlocked on error.

Signed-off-by: Pavel Machek (CIP) <[email protected]>

diff --git a/fs/ocfs2/dlmglue.c b/fs/ocfs2/dlmglue.c
index 751bc4dc7466..8e3a369086db 100644
--- a/fs/ocfs2/dlmglue.c
+++ b/fs/ocfs2/dlmglue.c
@@ -2871,9 +2871,15 @@ int ocfs2_nfs_sync_lock(struct ocfs2_super *osb, int ex)

status = ocfs2_cluster_lock(osb, lockres, ex ? LKM_EXMODE : LKM_PRMODE,
0, 0);
- if (status < 0)
+ if (status < 0) {
mlog(ML_ERROR, "lock on nfs sync lock failed %d\n", status);

+ if (ex)
+ up_write(&osb->nfs_sync_rwlock);
+ else
+ up_read(&osb->nfs_sync_rwlock);
+ }
+
return status;
}


--
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(cesky, pictures) http://atrey.karlin.mff.cuni.cz/~pavel/picture/horses/blog.html

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2020-07-27 07:16:44

by Joseph Qi

[permalink] [raw]

Subject: Re: [PATCH] ocfs2: fix unbalanced locking

---

On 2020/7/24 20:44, Pavel Machek wrote:
>
> Based on what fails, function can return with nfs_sync_rwlock either
> locked or unlocked. That can not be right.
>
> Always return with lock unlocked on error.
>
> Signed-off-by: Pavel Machek (CIP) <[email protected]>

Looks good.

Fixes: 4cd9973f9ff6 ("ocfs2: avoid inode removal while nfsd is accessing it")
Reviewed-by: Joseph Qi <[email protected]>

>
> diff --git a/fs/ocfs2/dlmglue.c b/fs/ocfs2/dlmglue.c
> index 751bc4dc7466..8e3a369086db 100644
> --- a/fs/ocfs2/dlmglue.c
> +++ b/fs/ocfs2/dlmglue.c
> @@ -2871,9 +2871,15 @@ int ocfs2_nfs_sync_lock(struct ocfs2_super *osb, int ex)
>
> status = ocfs2_cluster_lock(osb, lockres, ex ? LKM_EXMODE : LKM_PRMODE,
> 0, 0);
> - if (status < 0)
> + if (status < 0) {
> mlog(ML_ERROR, "lock on nfs sync lock failed %d\n", status);
>
> + if (ex)
> + up_write(&osb->nfs_sync_rwlock);
> + else
> + up_read(&osb->nfs_sync_rwlock);
> + }
> +
> return status;
> }
>
>