On Mon, Nov 28, 2016 at 02:09:37PM -0500, Brian Foster wrote:
> In preparation for reuse of the existing delayed allocation code for COW
> reservation, factor out the part of xfs_file_iomap_begin_delay()
> responsible for existing extent lookup into a new helper. This patch
> does not change behavior.
>
> Signed-off-by: Brian Foster <bfoster@xxxxxxxxxx>
> ---
> fs/xfs/xfs_iomap.c | 72 ++++++++++++++++++++++++++++++++++++++++++------------
> 1 file changed, 57 insertions(+), 15 deletions(-)
>
> diff --git a/fs/xfs/xfs_iomap.c b/fs/xfs/xfs_iomap.c
> index 4f46f49..0a4ef18 100644
> --- a/fs/xfs/xfs_iomap.c
> +++ b/fs/xfs/xfs_iomap.c
> @@ -522,6 +522,48 @@ xfs_iomap_prealloc_size(
> return alloc_blocks;
> }
>
> +/*
> + * Prepare to handle delayed allocation based on whether extents exist in the
> + * inode data and COW forks. If an existing data extent is shared, determine
> + * whether COW fork reservation is necessary.
> + *
> + * The 'found' parameter indicates whether a writable mapping was found. If the
> + * mapping is shared, a COW reservation is performed for the corresponding
> + * range.
> + */
> +static int
> +xfs_iomap_search_extents(
> + struct xfs_inode *ip,
> + xfs_fileoff_t offset_fsb,
> + xfs_fileoff_t end_fsb,
> + int *eof,
> + int *idx,
> + struct xfs_bmbt_irec *got,
> + bool *found) /* found usable extent */
> +{
> + struct xfs_ifork *ifp = XFS_IFORK_PTR(ip, XFS_DATA_FORK);
> + int error = 0;
> +
> + *found = false;
> +
> + *eof = !xfs_iext_lookup_extent(ip, ifp, offset_fsb, idx, got);
> + if (*eof || got->br_startoff > offset_fsb)
> + 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);
> + if (error)
> + return error;
> + }
> +
> + *found = true;
> +
> + return error;
> +}
> +
> static int
> xfs_file_iomap_begin_delay(
> struct inode *inode,
> @@ -533,18 +575,22 @@ xfs_file_iomap_begin_delay(
> struct xfs_inode *ip = XFS_I(inode);
> struct xfs_mount *mp = ip->i_mount;
> struct xfs_ifork *ifp = XFS_IFORK_PTR(ip, XFS_DATA_FORK);
> - xfs_fileoff_t offset_fsb = XFS_B_TO_FSBT(mp, offset);
> + xfs_fileoff_t offset_fsb;
> + xfs_fileoff_t end_fsb;
> xfs_fileoff_t maxbytes_fsb =
> XFS_B_TO_FSB(mp, mp->m_super->s_maxbytes);
> - xfs_fileoff_t end_fsb;
> int error = 0, eof = 0;
> struct xfs_bmbt_irec got;
> xfs_extnum_t idx;
> xfs_fsblock_t prealloc_blocks = 0;
> + bool found;
>
> ASSERT(!XFS_IS_REALTIME_INODE(ip));
> ASSERT(!xfs_get_extsz_hint(ip));
>
> + offset_fsb = XFS_B_TO_FSBT(mp, offset);
> + end_fsb = min(XFS_B_TO_FSB(mp, offset + count), maxbytes_fsb);
> +
> xfs_ilock(ip, XFS_ILOCK_EXCL);
>
> if (unlikely(XFS_TEST_ERROR(
> @@ -564,19 +610,15 @@ xfs_file_iomap_begin_delay(
> goto out_unlock;
> }
>
> - eof = !xfs_iext_lookup_extent(ip, ifp, offset_fsb, &idx, &got);
> - if (!eof && got.br_startoff <= offset_fsb) {
> - if (xfs_is_reflink_inode(ip)) {
> - bool shared;
> -
> - end_fsb = min(XFS_B_TO_FSB(mp, offset + count),
> - maxbytes_fsb);
> - xfs_trim_extent(&got, offset_fsb, end_fsb - offset_fsb);
> - error = xfs_reflink_reserve_cow(ip, &got, &shared);
> - if (error)
> - goto out_unlock;
> - }
> -
> + /*
> + * 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);
> + if (error)
> + goto out_unlock;
> + if (found) {
Looks ok...
Reviewed-by: Darrick J. Wong <darrick.wong@xxxxxxxxxx>
--D
> trace_xfs_iomap_found(ip, offset, count, 0, &got);
> goto done;
> }
> --
> 2.7.4
>
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