[Ocfs2-devel] [PATCH] ocfs2: __ocfs2_mknod_locked should return error when ocfs2_create_new_inode_locks() failed
Joel Becker
jlbec at evilplan.org
Wed Mar 26 21:28:28 PDT 2014
On Wed, Mar 26, 2014 at 03:23:13PM +0800, Xue jiufei wrote:
> When ocfs2_create_new_inode_locks() return error, inode open lock may
> not be obtainted for this inode. So other nodes can remove this file
> and free dinode when inode still remain in memory on this node,
> which is not correct and may trigger BUG. So __ocfs2_mknod_locked
> should return error when ocfs2_create_new_inode_locks() failed.
>
> Node_1 Node_2
> create fileA, call ocfs2_mknod()
> -> ocfs2_get_init_inode(), allocate inodeA
> -> ocfs2_claim_new_inode(), claim dinode(dinodeA)
> -> call ocfs2_create_new_inode_locks(),
> create open lock failed, return error
> -> __ocfs2_mknod_locked return success
>
> unlink fileA
> try open lock succeed,
> and free dinodeA
>
> create another file, call ocfs2_mknod()
> -> ocfs2_get_init_inode(), allocate inodeB
> -> ocfs2_claim_new_inode(), as Node_2 had freed dinodeA,
> so claim dinodeA and update generation for dinodeA
>
> call __ocfs2_drop_dl_inodes()->ocfs2_delete_inode()
> to free inodeA, and finally triggers BUG
> on(inode->i_generation != le32_to_cpu(fe->i_generation))
> in function ocfs2_inode_lock_update().
Wow, that's a deep race, and it's some salty old code. I think I buy
your description of the problem. I'm trying to figure out why we didn't
hit this before.
What workload or tests triggered this? Do you know why
ocfs2_create_new_inode_locks() failed in the first place? I suspect it
almost never fails, which is why we haven't seen this issue. Also,
which cluster stack was involved?
Finally, have you tested the result? I believe that the iput()
machinery will do the right thing, but tests are better than my
intuition.
Joel
>
> Signed-off-by: joyce.xue <xuejiufei at huawei.com>
> ---
> fs/ocfs2/namei.c | 3 ---
> 1 file changed, 3 deletions(-)
>
> diff --git a/fs/ocfs2/namei.c b/fs/ocfs2/namei.c
> index 3683643..63f9692 100644
> --- a/fs/ocfs2/namei.c
> +++ b/fs/ocfs2/namei.c
> @@ -576,9 +576,6 @@ static int __ocfs2_mknod_locked(struct inode *dir,
> mlog_errno(status);
> }
>
> - status = 0; /* error in ocfs2_create_new_inode_locks is not
> - * critical */
> -
> leave:
> if (status < 0) {
> if (*new_fe_bh) {
> --
> 1.8.4.3
>
>
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> Ocfs2-devel at oss.oracle.com
> https://oss.oracle.com/mailman/listinfo/ocfs2-devel
--
"Under capitalism, man exploits man. Under Communism, it's just
the opposite."
- John Kenneth Galbraith
http://www.jlbec.org/
jlbec at evilplan.org
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