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

["Theodore Y. Ts'o" <tytso@mit.edu>]

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
> 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.
> 
> Signed-off-by: Darrick J. Wong <darrick.wong@oracle.com>

This may fix the generic/047 failure, but alas, it does not address
the shared/298 failure.

Jeff's theory that we may need to clear the errseq_t information after
detaching the loop device makes sense to me; and in the case of the
loop device, we wouldn't be initializing the inode, so your patch
wouldn't do anything about that particular case.

						- Ted