[Ocfs2-devel] [PATCH] revert to using ocfs2_acl_chmod to avoid inode cluster lock hang

[Junxiao Bi]

Hi Tariq,

On 01/06/2016 10:27 AM, Tariq Saeed wrote:
> Orabug: 21793017
> 
> commit 743b5f1434f5 ("ocfs2: take inode lock in ocfs2_iop_set/get_acl()")
> introduced this issue.  ocfs2_setattr called by chmod command
> holds cluster wide inode lock (Orabug 21685187) when calling
> posix_acl_chmod. This latter function in turn calls ocfs2_iop_get_acl
> and ocfs2_iop_set_acl.  These two are also called directly from vfs
> layer for getfacl/setfacl commands and therefore acquire the cluster wide
> inode lock. If a remote conversion request comes after the first inode
> lock in ocfs2_setattr, OCFS2_LOCK_BLOCKED will be set in l_flags. This
> will cause the second call to inode lock from the  ocfs2_iop_get_acl()
> to block indefinetly.
This fixed part of the deadlock. There is another part.
ocfs2_mknod()->posix_acl_create()->ocfs2_iop_get_acl()

Thanks,
Junxiao.

> 
> To solve this, we need to use nolock version of getacl.  Since
> nolock version of posix_acl_chmod does not exist, we restore a slightly
> modified version of  ocfs2_acl_chmod, which was removed in
> commit 702e5bc68ad2 ("ocfs2: use generic posix ACL infrastructure")
> that uses nolock version of getacl.
> 
> Signed-off-by: Tariq Saeed <tariq.x.saeed at oracle.com>
> ---
>  fs/ocfs2/acl.c  |   25 +++++++++++++++++++++++++
>  fs/ocfs2/acl.h  |    1 +
>  fs/ocfs2/file.c |    4 ++--
>  3 files changed, 28 insertions(+), 2 deletions(-)
> 
> diff --git a/fs/ocfs2/acl.c b/fs/ocfs2/acl.c
> index 0cdf497..0fbd18c 100644
> --- a/fs/ocfs2/acl.c
> +++ b/fs/ocfs2/acl.c
> @@ -322,3 +322,28 @@ struct posix_acl *ocfs2_iop_get_acl(struct inode *inode, int type)
>  	brelse(di_bh);
>  	return acl;
>  }
> +
> +int ocfs2_acl_chmod(struct inode *inode, struct buffer_head *bh)
> +{
> +	struct ocfs2_super *osb = OCFS2_SB(inode->i_sb);
> +	struct posix_acl *acl;
> +	int ret;
> +
> +	if (S_ISLNK(inode->i_mode))
> +		return -EOPNOTSUPP;
> +
> +	if (!(osb->s_mount_opt & OCFS2_MOUNT_POSIX_ACL))
> +		return 0;
> +
> +	acl = ocfs2_get_acl_nolock(inode, ACL_TYPE_ACCESS, bh);
> +	if (IS_ERR(acl) || !acl)
> +		return PTR_ERR(acl);
> +	ret = __posix_acl_chmod(&acl, GFP_KERNEL, inode->i_mode);
> +	if (ret)
> +		return ret;
> +	ret = ocfs2_set_acl(NULL, inode, NULL, ACL_TYPE_ACCESS,
> +			    acl, NULL, NULL);
> +	posix_acl_release(acl);
> +	return ret;
> +}
> +
> diff --git a/fs/ocfs2/acl.h b/fs/ocfs2/acl.h
> index 3fce68d..035e587 100644
> --- a/fs/ocfs2/acl.h
> +++ b/fs/ocfs2/acl.h
> @@ -35,5 +35,6 @@ int ocfs2_set_acl(handle_t *handle,
>  			 struct posix_acl *acl,
>  			 struct ocfs2_alloc_context *meta_ac,
>  			 struct ocfs2_alloc_context *data_ac);
> +extern int ocfs2_acl_chmod(struct inode *, struct buffer_head *);
>  
>  #endif /* OCFS2_ACL_H */
> diff --git a/fs/ocfs2/file.c b/fs/ocfs2/file.c
> index 0e5b451..77d30cb 100644
> --- a/fs/ocfs2/file.c
> +++ b/fs/ocfs2/file.c
> @@ -1268,20 +1268,20 @@ bail_unlock_rw:
>  	if (size_change)
>  		ocfs2_rw_unlock(inode, 1);
>  bail:
> -	brelse(bh);
>  
>  	/* Release quota pointers in case we acquired them */
>  	for (qtype = 0; qtype < OCFS2_MAXQUOTAS; qtype++)
>  		dqput(transfer_to[qtype]);
>  
>  	if (!status && attr->ia_valid & ATTR_MODE) {
> -		status = posix_acl_chmod(inode, inode->i_mode);
> +		status = ocfs2_acl_chmod(inode, bh);
>  		if (status < 0)
>  			mlog_errno(status);
>  	}
>  	if (inode_locked)
>  		ocfs2_inode_unlock(inode, 1);
>  
> +	brelse(bh);
>  	return status;
>  }
>  
>