Re: [PATCH 2/2] xfs: flush both inodes in xfs_swap_extents

Brian Foster
2014-08-01T12:44:15Z

On Thu, Jul 31, 2014 at 04:12:08PM +1000, Dave Chinner wrote:
> From: Dave Chinner <dchinner@redhat.com>
>
> We need to treat both inodes identically from a page cache point of
> view when prepareing them for extent swapping. We don't do this
> right now - we assume that one of the inodes empty, because that's
> what xfs_fsr currently does. Remove this assumption from the code.
>
> While factoring out the flushing and related checks, move the
> transactions reservation to immeidately after the flushes so that we
> don't need to pick up and then drop the ilock to do the transaction
> reservation. There are no issues with aborting the transaction it if
> the checks fail before we join the inodes to the transaction and
> dirty them, so this is a safe change to make.
>
> Signed-off-by: Dave Chinner <dchinner@redhat.com>
> ---

Both of these looked fine to me, but I couldn't apply this one to
for-next or master...

Brian

> fs/xfs/xfs_bmap_util.c | 81 +++++++++++++++++++++++---------------------------
> 1 file changed, 37 insertions(+), 44 deletions(-)
>
> diff --git a/fs/xfs/xfs_bmap_util.c b/fs/xfs/xfs_bmap_util.c
> index 3c60c43..2f1e30d 100644
> --- a/fs/xfs/xfs_bmap_util.c
> +++ b/fs/xfs/xfs_bmap_util.c
> @@ -1619,6 +1619,30 @@ xfs_swap_extents_check_format(
> }
>
> int
> +xfs_swap_extent_flush(
> + struct xfs_inode *ip)
> +{
> + int error;
> +
> + error = filemap_write_and_wait(VFS_I(ip)->i_mapping);
> + if (error)
> + return error;
> + truncate_pagecache_range(VFS_I(ip), 0, -1);
> +
> + /* Verify O_DIRECT for ftmp */
> + if (VFS_I(ip)->i_mapping->nrpages)
> + return -EINVAL;
> +
> + /*
> + * Don't try to swap extents on mmap()d files because we can't lock
> + * out races against page faults safely.
> + */
> + if (mapping_mapped(VFS_I(ip)->i_mapping))
> + return -EBUSY;
> + return 0;
> +}
> +
> +int
> xfs_swap_extents(
> xfs_inode_t *ip, /* target inode */
> xfs_inode_t *tip, /* tmp inode */
> @@ -1662,26 +1686,28 @@ xfs_swap_extents(
> goto out_unlock;
> }
>
> - error = filemap_write_and_wait(VFS_I(tip)->i_mapping);
> + error = xfs_swap_extent_flush(ip);
> + if (error)
> + goto out_unlock;
> + error = xfs_swap_extent_flush(tip);
> if (error)
> goto out_unlock;
> - truncate_pagecache_range(VFS_I(tip), 0, -1);
> -
> - xfs_lock_two_inodes(ip, tip, XFS_ILOCK_EXCL);
> - lock_flags |= XFS_ILOCK_EXCL;
>
> - /* Verify O_DIRECT for ftmp */
> - if (VFS_I(tip)->i_mapping->nrpages) {
> - error = -EINVAL;
> + tp = xfs_trans_alloc(mp, XFS_TRANS_SWAPEXT);
> + error = xfs_trans_reserve(tp, &M_RES(mp)->tr_ichange, 0, 0);
> + if (error) {
> + xfs_trans_cancel(tp, 0);
> goto out_unlock;
> }
> + xfs_lock_two_inodes(ip, tip, XFS_ILOCK_EXCL);
> + lock_flags |= XFS_ILOCK_EXCL;
>
> /* Verify all data are being swapped */
> if (sxp->sx_offset != 0 ||
> sxp->sx_length != ip->i_d.di_size ||
> sxp->sx_length != tip->i_d.di_size) {
> error = -EFAULT;
> - goto out_unlock;
> + goto out_trans_cancel;
> }
>
> trace_xfs_swap_extent_before(ip, 0);
> @@ -1693,7 +1719,7 @@ xfs_swap_extents(
> xfs_notice(mp,
> "%s: inode 0x%llx format is incompatible for exchanging.",
> __func__, ip->i_ino);
> - goto out_unlock;
> + goto out_trans_cancel;
> }
>
> /*
> @@ -1708,41 +1734,8 @@ xfs_swap_extents(
> (sbp->bs_mtime.tv_sec != VFS_I(ip)->i_mtime.tv_sec) ||
> (sbp->bs_mtime.tv_nsec != VFS_I(ip)->i_mtime.tv_nsec)) {
> error = -EBUSY;
> - goto out_unlock;
> - }
> -
> - /* We need to fail if the file is memory mapped. Once we have tossed
> - * all existing pages, the page fault will have no option
> - * but to go to the filesystem for pages. By making the page fault call
> - * vop_read (or write in the case of autogrow) they block on the iolock
> - * until we have switched the extents.
> - */
> - if (mapping_mapped(VFS_I(ip)->i_mapping)) {
> - error = -EBUSY;
> - goto out_unlock;
> - }
> -
> - xfs_iunlock(ip, XFS_ILOCK_EXCL);
> - xfs_iunlock(tip, XFS_ILOCK_EXCL);
> - lock_flags &= ~XFS_ILOCK_EXCL;
> -
> - /*
> - * There is a race condition here since we gave up the
> - * ilock. However, the data fork will not change since
> - * we have the iolock (locked for truncation too) so we
> - * are safe. We don't really care if non-io related
> - * fields change.
> - */
> - truncate_pagecache_range(VFS_I(ip), 0, -1);
> -
> - tp = xfs_trans_alloc(mp, XFS_TRANS_SWAPEXT);
> - error = xfs_trans_reserve(tp, &M_RES(mp)->tr_ichange, 0, 0);
> - if (error)
> goto out_trans_cancel;
> -
> - xfs_lock_two_inodes(ip, tip, XFS_ILOCK_EXCL);
> - lock_flags |= XFS_ILOCK_EXCL;
> -
> + }
> /*
> * Count the number of extended attribute blocks
> */
> --
> 2.0.0
>
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