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

Matthew Wilcox
2018-05-19T15:36:22Z

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

> 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?

> +++ 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;
> }
>