Date:   Thu, 22 Jun 2017 14:24:44 -0700
From:   Andrew Morton <akpm@...ux-foundation.org>
To:     Joseph Qi <jiangqi903@...il.com>
Cc:     Eric Ren <zren@...e.com>, ocfs2-devel@....oracle.com,
        mfasheh@...sity.com, jlbec@...lplan.org, tv@...96.de, ghe@...e.com,
        junxiao.bi@...cle.com, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2] ocfs2: fix deadlock caused by recursive locking in
 xattr

On Thu, 22 Jun 2017 14:10:38 +0800 Joseph Qi <jiangqi903@...il.com> wrote:

> Looks good.
> Reviewed-by: Joseph Qi <jiangqi903@...il.com>

Should this fix be backported into -stable kernels?

> On 17/6/22 09:47, Eric Ren wrote:
> > Another deadlock path caused by recursive locking is reported.
> > This kind of issue was introduced since commit 743b5f1434f5 ("ocfs2:
> > take inode lock in ocfs2_iop_set/get_acl()"). Two deadlock paths
> > have been fixed by commit b891fa5024a9 ("ocfs2: fix deadlock issue when
> > taking inode lock at vfs entry points"). Yes, we intend to fix this
> > kind of case in incremental way, because it's hard to find out all
> > possible paths at once.
> > 
> > This one can be reproduced like this. On node1, cp a large file from
> > home directory to ocfs2 mountpoint. While on node2, run setfacl/getfacl.
> > Both nodes will hang up there. The backtraces:
> > 
> > On node1:
> > [<ffffffffc06a1f67>] __ocfs2_cluster_lock.isra.39+0x357/0x740 [ocfs2]
> > [<ffffffffc06a2d3d>] ocfs2_inode_lock_full_nested+0x17d/0x840 [ocfs2]
> > [<ffffffffc0692043>] ocfs2_write_begin+0x43/0x1a0 [ocfs2]
> > [<ffffffffa21ac719>] generic_perform_write+0xa9/0x180
> > [<ffffffffa21aecda>] __generic_file_write_iter+0x1aa/0x1d0
> > [<ffffffffc06abc24>] ocfs2_file_write_iter+0x4f4/0xb40 [ocfs2]
> > [<ffffffffa223c3b3>] __vfs_write+0xc3/0x130
> > [<ffffffffa223cae1>] vfs_write+0xb1/0x1a0
> > [<ffffffffa223dfe6>] SyS_write+0x46/0xa0
> > 
> > On node2:
> > [<ffffffffc07b6f67>] __ocfs2_cluster_lock.isra.39+0x357/0x740 [ocfs2]
> > [<ffffffffc07b7d3d>] ocfs2_inode_lock_full_nested+0x17d/0x840 [ocfs2]
> > [<ffffffffc0815c1e>] ocfs2_xattr_set+0x12e/0xe80 [ocfs2]
> > [<ffffffffc081783d>] ocfs2_set_acl+0x22d/0x260 [ocfs2]
> > [<ffffffffc08178d5>] ocfs2_iop_set_acl+0x65/0xb0 [ocfs2]
> > [<ffffffffa62a43f5>] set_posix_acl+0x75/0xb0
> > [<ffffffffa62a4479>] posix_acl_xattr_set+0x49/0xa0
> > [<ffffffffa6265c69>] __vfs_setxattr+0x69/0x80
> > [<ffffffffa6266832>] __vfs_setxattr_noperm+0x72/0x1a0
> > [<ffffffffa6266a07>] vfs_setxattr+0xa7/0xb0
> > [<ffffffffa6266b3d>] setxattr+0x12d/0x190
> > [<ffffffffa6266c3f>] path_setxattr+0x9f/0xb0
> > [<ffffffffa6266d74>] SyS_setxattr+0x14/0x20
> > 
> > Fixes this one by using ocfs2_inode_{lock|unlock}_tracker, which is
> > exported by commit 439a36b8ef38 ("ocfs2/dlmglue: prepare tracking
> > logic to avoid recursive cluster lock").
> > 
> > Changes since v1:
> > - Revised git commit description style in commit log.
> > 
> > Reported-by: Thomas Voegtle <tv@...96.de>
> > Tested-by: Thomas Voegtle <tv@...96.de>
> > Signed-off-by: Eric Ren <zren@...e.com>
> > ---
> >  fs/ocfs2/dlmglue.c |  4 ++++
> >  fs/ocfs2/xattr.c   | 23 +++++++++++++----------
> >  2 files changed, 17 insertions(+), 10 deletions(-)
> > 
> > diff --git a/fs/ocfs2/dlmglue.c b/fs/ocfs2/dlmglue.c
> > index 3b7c937..4689940 100644
> > --- a/fs/ocfs2/dlmglue.c
> > +++ b/fs/ocfs2/dlmglue.c
> > @@ -2591,6 +2591,10 @@ void ocfs2_inode_unlock_tracker(struct inode *inode,
> >  	struct ocfs2_lock_res *lockres;
> >  
> >  	lockres = &OCFS2_I(inode)->ip_inode_lockres;
> > +	/* had_lock means that the currect process already takes the cluster
> > +	 * lock previously. If had_lock is 1, we have nothing to do here, and
> > +	 * it will get unlocked where we got the lock.
> > +	 */
> >  	if (!had_lock) {
> >  		ocfs2_remove_holder(lockres, oh);
> >  		ocfs2_inode_unlock(inode, ex);
> > diff --git a/fs/ocfs2/xattr.c b/fs/ocfs2/xattr.c
> > index 3c5384d..f70c377 100644
> > --- a/fs/ocfs2/xattr.c
> > +++ b/fs/ocfs2/xattr.c
> > @@ -1328,20 +1328,21 @@ static int ocfs2_xattr_get(struct inode *inode,
> >  			   void *buffer,
> >  			   size_t buffer_size)
> >  {
> > -	int ret;
> > +	int ret, had_lock;
> >  	struct buffer_head *di_bh = NULL;
> > +	struct ocfs2_lock_holder oh;
> >  
> > -	ret = ocfs2_inode_lock(inode, &di_bh, 0);
> > -	if (ret < 0) {
> > -		mlog_errno(ret);
> > -		return ret;
> > +	had_lock = ocfs2_inode_lock_tracker(inode, &di_bh, 0, &oh);
> > +	if (had_lock < 0) {
> > +		mlog_errno(had_lock);
> > +		return had_lock;
> >  	}
> >  	down_read(&OCFS2_I(inode)->ip_xattr_sem);
> >  	ret = ocfs2_xattr_get_nolock(inode, di_bh, name_index,
> >  				     name, buffer, buffer_size);
> >  	up_read(&OCFS2_I(inode)->ip_xattr_sem);
> >  
> > -	ocfs2_inode_unlock(inode, 0);
> > +	ocfs2_inode_unlock_tracker(inode, 0, &oh, had_lock);
> >  
> >  	brelse(di_bh);
> >  
> > @@ -3537,11 +3538,12 @@ int ocfs2_xattr_set(struct inode *inode,
> >  {
> >  	struct buffer_head *di_bh = NULL;
> >  	struct ocfs2_dinode *di;
> > -	int ret, credits, ref_meta = 0, ref_credits = 0;
> > +	int ret, credits, had_lock, ref_meta = 0, ref_credits = 0;
> >  	struct ocfs2_super *osb = OCFS2_SB(inode->i_sb);
> >  	struct inode *tl_inode = osb->osb_tl_inode;
> >  	struct ocfs2_xattr_set_ctxt ctxt = { NULL, NULL, NULL, };
> >  	struct ocfs2_refcount_tree *ref_tree = NULL;
> > +	struct ocfs2_lock_holder oh;
> >  
> >  	struct ocfs2_xattr_info xi = {
> >  		.xi_name_index = name_index,
> > @@ -3572,8 +3574,9 @@ int ocfs2_xattr_set(struct inode *inode,
> >  		return -ENOMEM;
> >  	}
> >  
> > -	ret = ocfs2_inode_lock(inode, &di_bh, 1);
> > -	if (ret < 0) {
> > +	had_lock = ocfs2_inode_lock_tracker(inode, &di_bh, 1, &oh);
> > +	if (had_lock < 0) {
> > +		ret = had_lock;
> >  		mlog_errno(ret);
> >  		goto cleanup_nolock;
> >  	}
> > @@ -3670,7 +3673,7 @@ int ocfs2_xattr_set(struct inode *inode,
> >  		if (ret)
> >  			mlog_errno(ret);
> >  	}
> > -	ocfs2_inode_unlock(inode, 1);
> > +	ocfs2_inode_unlock_tracker(inode, 1, &oh, had_lock);
> >  cleanup_nolock:
> >  	brelse(di_bh);
> >  	brelse(xbs.xattr_bh);
> > 

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