On Tue, Jul 03, 2018 at 01:22:55PM -0400, Brian Foster wrote:
> xfs_bmapi_write() always expects a valid firstblock pointer. It
> immediately dereferences the pointer to help determine how to
> initialize the bma.minleft field. The remaining accesses are
> related to modifying btree format forks, which is only relevant for
> !COW fork callers.
>
> The reflink code passes a NULL transaction to xfs_bmapi_write() in a
> couple places that do COW fork unwritten conversion. The purpose of
> the firstblock field is to track the first block allocation in the
> current transaction, so technically firstblock should not be
> required for these callers either.
>
> Tweak xfs_bmapi_write() to initialize the bma correctly without
> accessing the firstblock pointer if no transaction is provided in
> the first place. Update the reflink callers to pass NULL instead of
> otherwise unused firstblock references.
>
> Signed-off-by: Brian Foster <bfoster@xxxxxxxxxx>
Looks ok,
Reviewed-by: Darrick J. Wong <darrick.wong@xxxxxxxxxx>
--D
> ---
> fs/xfs/libxfs/xfs_bmap.c | 2 +-
> fs/xfs/xfs_reflink.c | 9 +++------
> 2 files changed, 4 insertions(+), 7 deletions(-)
>
> diff --git a/fs/xfs/libxfs/xfs_bmap.c b/fs/xfs/libxfs/xfs_bmap.c
> index 2e2a9661600b..c6a5a957674d 100644
> --- a/fs/xfs/libxfs/xfs_bmap.c
> +++ b/fs/xfs/libxfs/xfs_bmap.c
> @@ -4304,7 +4304,7 @@ xfs_bmapi_write(
>
> XFS_STATS_INC(mp, xs_blk_mapw);
>
> - if (*firstblock == NULLFSBLOCK) {
> + if (!tp || *firstblock == NULLFSBLOCK) {
> if (XFS_IFORK_FORMAT(ip, whichfork) == XFS_DINODE_FMT_BTREE)
> bma.minleft = be16_to_cpu(ifp->if_broot->bb_level) + 1;
> else
> diff --git a/fs/xfs/xfs_reflink.c b/fs/xfs/xfs_reflink.c
> index 8496312dde6a..92b6e1b5d33c 100644
> --- a/fs/xfs/xfs_reflink.c
> +++ b/fs/xfs/xfs_reflink.c
> @@ -314,7 +314,6 @@ xfs_reflink_convert_cow_extent(
> xfs_fileoff_t offset_fsb,
> xfs_filblks_t count_fsb)
> {
> - xfs_fsblock_t first_block = NULLFSBLOCK;
> int nimaps = 1;
>
> if (imap->br_state == XFS_EXT_NORM)
> @@ -325,8 +324,8 @@ xfs_reflink_convert_cow_extent(
> if (imap->br_blockcount == 0)
> return 0;
> return xfs_bmapi_write(NULL, ip, imap->br_startoff, imap->br_blockcount,
> - XFS_BMAPI_COWFORK | XFS_BMAPI_CONVERT, &first_block,
> - 0, imap, &nimaps);
> + XFS_BMAPI_COWFORK | XFS_BMAPI_CONVERT, NULL, 0, imap,
> + &nimaps);
> }
>
> /* Convert all of the unwritten CoW extents in a file's range to real ones. */
> @@ -341,7 +340,6 @@ xfs_reflink_convert_cow(
> xfs_fileoff_t end_fsb = XFS_B_TO_FSB(mp, offset + count);
> xfs_filblks_t count_fsb = end_fsb - offset_fsb;
> struct xfs_bmbt_irec imap;
> - xfs_fsblock_t first_block = NULLFSBLOCK;
> int nimaps = 1, error = 0;
>
> ASSERT(count != 0);
> @@ -349,8 +347,7 @@ xfs_reflink_convert_cow(
> xfs_ilock(ip, XFS_ILOCK_EXCL);
> error = xfs_bmapi_write(NULL, ip, offset_fsb, count_fsb,
> XFS_BMAPI_COWFORK | XFS_BMAPI_CONVERT |
> - XFS_BMAPI_CONVERT_ONLY, &first_block, 0, &imap,
> - &nimaps);
> + XFS_BMAPI_CONVERT_ONLY, NULL, 0, &imap, &nimaps);
> xfs_iunlock(ip, XFS_ILOCK_EXCL);
> return error;
> }
> --
> 2.17.1
>
> --
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