Re: [PATCH] xfs: bmap shouldn't barf on inline-format directories

From: "Darrick J. Wong" <darrick.wong@oracle.com>
To: Brian Foster <bfoster@redhat.com>
Cc: xfs <linux-xfs@vger.kernel.org>
Subject: Re: [PATCH] xfs: bmap shouldn't barf on inline-format directories
Date: Wed, 10 May 2017 11:17:52 -0700	[thread overview]
Message-ID: <20170510181752.GB5639@birch.djwong.org> (raw)
In-Reply-To: <20170510181032.GB10534@localhost.localdomain>

On Wed, May 10, 2017 at 02:10:32PM -0400, Brian Foster wrote:
> On Wed, May 10, 2017 at 09:03:29AM -0700, Darrick J. Wong wrote:
> > When we're fulfilling a BMAPX request, check that the fork is still in
> > extents or btree format just prior to calling bmapi.  This prevents us
> > from hitting a debugging check in bmapi_read and barfing errors back
> > to userspace.  The on-disk extent count check later isn't sufficient for
> > IF_DELALLOC mode because da extents are in memory and not on disk.
> > 
> > To reproduce, run "xfs_io -c 'bmap -e'" on any inline directory.
> > 
> > Signed-off-by: Darrick J. Wong <darrick.wong@oracle.com>
> > ---
> >  fs/xfs/xfs_bmap_util.c |    5 +++++
> >  1 file changed, 5 insertions(+)
> > 
> > diff --git a/fs/xfs/xfs_bmap_util.c b/fs/xfs/xfs_bmap_util.c
> > index 7ac80a1..378f142 100644
> > --- a/fs/xfs/xfs_bmap_util.c
> > +++ b/fs/xfs/xfs_bmap_util.c
> > @@ -614,6 +614,11 @@ xfs_getbmap(
> >  		return -EINVAL;
> >  	bmvend = bmv->bmv_offset + bmv->bmv_length;
> >  
> > +	/* Local format inodes don't have any extents to report. */
> > +	if (ip->i_d.di_format == XFS_DINODE_FMT_LOCAL) {
> > +		bmv->bmv_entries = 0;
> > +		return 0;
> > +	}
> 
> This means we'd return 0 extents for any inode where the data fork is in
> local format, even if the bmap query is of the attr fork. For example,
> consider something like an 'xfs_io -c "bmap -a" <dir>' where the attr
> fork of the directory is extent format and the data fork is local
> format.

D'oh. :/

> Could we be more explicit about the check here? Actually, is there any
> reason we couldn't pull this check up a bit earlier into the whichfork
> switch statement?

Probably not -- the only reason I could see is if some future XFS supports
inline data for regular files and we want to flush to see if that'll turn
the fork from inline format to extents format.  We can cross that bridge
when we get to it, however.

In the meantime, yes, we can check for local format up in the whichfork
switch statement.

--D

> Brian
> 
> >  
> >  	if (bmv->bmv_count > ULONG_MAX / sizeof(struct getbmapx))
> >  		return -ENOMEM;
> > --
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