On Mon, Nov 28, 2016 at 02:09:38PM -0500, Brian Foster wrote:
> xfs_file_iomap_begin_delay() uses the got variable for the extent
> returned by the in-core extent list lookup, the allocated extent
> returned by xfs_bmapi_reserve_delalloc() and the extent mapped to the
> iomap data structure for the caller.
>
> This is fine for current usage, but doesn't work for COW fork
> reservation. In that case, the extent returned by
> xfs_bmapi_reserve_delalloc() is the COW reservation and not the extent
> to be mapped to the iomap. Instead, the shared data fork extent should
> be trimmed appropriately and mapped to the iomap.
>
> To prepare *_begin_delay() to support COW fork reservation, add a new
> imap variable to separately track the data fork extent (for iomap) from
> the extent returned from the lookup. The latter extent may refer to
> either the data or COW fork in the future.
>
> Signed-off-by: Brian Foster <bfoster@xxxxxxxxxx>
> ---
> fs/xfs/xfs_iomap.c | 33 +++++++++++++++++++++------------
> 1 file changed, 21 insertions(+), 12 deletions(-)
>
> diff --git a/fs/xfs/xfs_iomap.c b/fs/xfs/xfs_iomap.c
> index 0a4ef18..0dec431c 100644
> --- a/fs/xfs/xfs_iomap.c
> +++ b/fs/xfs/xfs_iomap.c
> @@ -536,6 +536,7 @@ xfs_iomap_search_extents(
> struct xfs_inode *ip,
> xfs_fileoff_t offset_fsb,
> xfs_fileoff_t end_fsb,
> + struct xfs_bmbt_irec *imap, /* for iomap mapping */
> int *eof,
> int *idx,
> struct xfs_bmbt_irec *got,
> @@ -546,15 +547,21 @@ xfs_iomap_search_extents(
>
> *found = false;
>
> - *eof = !xfs_iext_lookup_extent(ip, ifp, offset_fsb, idx, got);
> - if (*eof || got->br_startoff > offset_fsb)
> + /*
> + * Look up a preexisting extent directly into imap. Set got for the
> + * bmapi delalloc call if nothing is found.
> + */
> + *eof = !xfs_iext_lookup_extent(ip, ifp, offset_fsb, idx, imap);
> + if (*eof || imap->br_startoff > offset_fsb) {
> + *got = *imap;
> return 0;
> + }
>
> if (xfs_is_reflink_inode(ip)) {
> bool shared;
>
> - xfs_trim_extent(got, offset_fsb, end_fsb - offset_fsb);
> - error = xfs_reflink_reserve_cow(ip, got, &shared);
> + xfs_trim_extent(imap, offset_fsb, end_fsb - offset_fsb);
> + error = xfs_reflink_reserve_cow(ip, imap, &shared);
> if (error)
> return error;
> }
> @@ -580,6 +587,7 @@ xfs_file_iomap_begin_delay(
> xfs_fileoff_t maxbytes_fsb =
> XFS_B_TO_FSB(mp, mp->m_super->s_maxbytes);
> int error = 0, eof = 0;
> + struct xfs_bmbt_irec imap;
> struct xfs_bmbt_irec got;
> xfs_extnum_t idx;
> xfs_fsblock_t prealloc_blocks = 0;
> @@ -614,12 +622,12 @@ xfs_file_iomap_begin_delay(
> * Search for preexisting extents. If an existing data extent is shared,
> * this will perform COW fork reservation.
> */
> - error = xfs_iomap_search_extents(ip, offset_fsb, end_fsb, &eof, &idx,
> - &got, &found);
> + error = xfs_iomap_search_extents(ip, offset_fsb, end_fsb, &imap, &eof,
> + &idx, &got, &found);
> if (error)
> goto out_unlock;
> if (found) {
> - trace_xfs_iomap_found(ip, offset, count, 0, &got);
> + trace_xfs_iomap_found(ip, offset, count, 0, &imap);
> goto done;
> }
>
> @@ -680,17 +688,18 @@ xfs_file_iomap_begin_delay(
> }
>
> trace_xfs_iomap_alloc(ip, offset, count, 0, &got);
> + imap = got;
> done:
> - if (isnullstartblock(got.br_startblock))
> - got.br_startblock = DELAYSTARTBLOCK;
> + if (isnullstartblock(imap.br_startblock))
> + imap.br_startblock = DELAYSTARTBLOCK;
>
> - if (!got.br_startblock) {
> - error = xfs_alert_fsblock_zero(ip, &got);
> + if (!imap.br_startblock) {
> + error = xfs_alert_fsblock_zero(ip, &imap);
> if (error)
> goto out_unlock;
> }
>
> - xfs_bmbt_to_iomap(ip, iomap, &got);
> + xfs_bmbt_to_iomap(ip, iomap, &imap);
>
> out_unlock:
> xfs_iunlock(ip, XFS_ILOCK_EXCL);
Seems fine to me, so
Reviewed-by: Darrick J. Wong <darrick.wong@xxxxxxxxxx>
> --
> 2.7.4
>
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