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

Darrick J. Wong
2018-05-21T17:55:23Z

On Sat, May 19, 2018 at 08:36:19AM -0700, Matthew Wilcox wrote:
> On Sat, May 19, 2018 at 08:27:00AM -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_ENOSC) bits. Unfortunately, we do not
>
> typo of ENOSPC in case you do a new version

Fixed, thanks.

> > 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 on a reformatted fs!) 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.
>
> Don't you also need to preserve inode->i_mapping->flags across the
> reinitialisation for the users which aren't yet using ->wb_err?

At first I thought (mistakenly) that xfs had been completely converted,
but digging further we still use the old filemap_check_errors. It seems
reasonable to me that if we're going to resurrect an incore inode then
we should try to hang on to AS_EIO/AS_ENOSPC for as long as we can.

--D

> > +++ b/fs/xfs/xfs_icache.c
> > @@ -298,6 +298,7 @@ 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;
> >
> > error = inode_init_always(mp->m_super, inode);
> >
> > @@ -306,6 +307,7 @@ xfs_reinit_inode(
> > inode_set_iversion_queried(inode, version);
> > inode->i_mode = mode;
> > inode->i_rdev = dev;
> > + inode->i_mapping->wb_err = old_err;
> > 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