Re: [PATCH v2] fs: clear writeback errors in inode_init_always

Darrick J. Wong
2018-05-22T14:38:41Z

On Tue, May 22, 2018 at 08:14:01AM -0400, Brian Foster wrote:
> On Mon, May 21, 2018 at 09:06:31PM -0700, Darrick J. Wong wrote:
> > From: Darrick J. Wong <darrick.wong@oracle.com>
> >
> > In inode_init_always(), we clear the inode mapping flags, which clears
> > any retained error (AS_EIO, AS_ENOSPC) bits. Unfortunately, we do not
> > also clear wb_err, which means that old mapping errors can leak through
> > to new inodes.
> >
> > This is crucial for the XFS inode allocation path because we recycle old
> > in-core inodes and we do not want error state from an old file to leak
> > into the new file. This bug was discovered by running generic/036 and
> > generic/047 in a loop and noticing that the EIOs generated by the
> > collision of direct and buffered writes in generic/036 would survive the
> > remount between 036 and 047, and get reported to the fsyncs (on
> > different files!) in generic/047.
> >
> > Since we're changing the semantics of inode_init_always, we must also
> > change xfs_reinit_inode to retain the writeback error state when we go
> > to recover an inode that has been torn down in the vfs but not yet
> > disposed of by XFS.
> >
> > Signed-off-by: Darrick J. Wong <darrick.wong@oracle.com>
> > ---
> > v2: retain AS_EIO/AS_ENOSPC across xfs inode reinit
> > ---
> > fs/inode.c | 1 +
> > fs/xfs/xfs_icache.c | 9 +++++++++
> > 2 files changed, 10 insertions(+)
> >
> ...
> > diff --git a/fs/xfs/xfs_icache.c b/fs/xfs/xfs_icache.c
> > index 164350d91efc..d01f9544ff01 100644
> > --- a/fs/xfs/xfs_icache.c
> > +++ b/fs/xfs/xfs_icache.c
> > @@ -298,6 +298,10 @@ xfs_reinit_inode(
> > uint64_t version = inode_peek_iversion(inode);
> > umode_t mode = inode->i_mode;
> > dev_t dev = inode->i_rdev;
> > + errseq_t old_err = inode->i_mapping->wb_err;
> > + bool as_eio = test_bit(AS_EIO, &inode->i_mapping->flags);
> > + bool as_enospc = test_bit(AS_ENOSPC,
> > + &inode->i_mapping->flags);
> >
> > error = inode_init_always(mp->m_super, inode);
> >
> > @@ -306,6 +310,11 @@ xfs_reinit_inode(
> > inode_set_iversion_queried(inode, version);
> > inode->i_mode = mode;
> > inode->i_rdev = dev;
> > + inode->i_mapping->wb_err = old_err;
> > + if (as_eio)
> > + set_bit(AS_EIO, &inode->i_mapping->flags);
> > + if (as_enospc)
> > + set_bit(AS_ENOSPC, &inode->i_mapping->flags);
>
> I'm wondering how safe this is. Can't the associated on-disk inode have
> been unlinked and reallocated anew across this kind of reinit of the
> in-core ip?

Oops, yeah, xfs_ialloc ought to clear those error states unconditionally
when allocating a new on-disk inode.

--D

> Brian
>
> > return error;
> > }
> >
> > --
> > To unsubscribe from this list: send the line "unsubscribe linux-xfs" in
> > the body of a message to majordomo@vger.kernel.org
> > More majordomo info at http://vger.kernel.org/majordomo-info.html
> --
> To unsubscribe from this list: send the line "unsubscribe fstests" in
> the body of a message to majordomo@vger.kernel.org
> More majordomo info at http://vger.kernel.org/majordomo-info.html