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xfs: allow null firstblock in xfs_bmapi_write() when tp is null 

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@redhat.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Darrick J. Wong <darrick.wong@oracle.com>
Signed-off-by: Darrick J. Wong <darrick.wong@oracle.com>
This commit is contained in:
Brian Foster 2018-07-11 22:26:19 -07:00 committed by Darrick J. Wong
parent bcd2c9f335
commit 3ae2d89174
2 changed files with 4 additions and 7 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

2
fs/xfs/libxfs/xfs_bmap.c
View File

@ -4302,7 +4302,7 @@ 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

9
fs/xfs/xfs_reflink.c
View File

@ -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;
}