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xfs: rework breaking of shared extents in xfs_file_iomap_begin 

Rework the data flow in xfs_file_iomap_begin where we decide if we have
to break shared extents.

Signed-off-by: Darrick J. Wong <darrick.wong@oracle.com>
Reviewed-by: Brian Foster <bfoster@redhat.com>
This commit is contained in:
Darrick J. Wong 2019-02-21 16:36:17 -08:00
parent affe250a08
commit 4f29e10d68
1 changed files with 7 additions and 5 deletions
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12
fs/xfs/xfs_iomap.c
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@ -982,7 +982,7 @@ xfs_file_iomap_begin(
* been done up front, so we don't need to do them here.
*/
if (xfs_is_cow_inode(ip)) {
struct xfs_bmbt_irec orig = imap;
struct xfs_bmbt_irec cmap;
bool directio = (flags & IOMAP_DIRECT);
/* if zeroing doesn't need COW allocation, then we are done. */
@ -991,7 +991,8 @@ xfs_file_iomap_begin(
goto out_found;
/* may drop and re-acquire the ilock */
error = xfs_reflink_allocate_cow(ip, &imap, &shared, &lockmode,
cmap = imap;
error = xfs_reflink_allocate_cow(ip, &cmap, &shared, &lockmode,
directio);
if (error)
goto out_unlock;
@ -1002,10 +1003,11 @@ xfs_file_iomap_begin(
* write code can perform read-modify-write operations; we
* won't need the CoW fork mapping until writeback. For direct
* I/O, which must be block aligned, we need to report the
* newly allocated address.
* newly allocated address. If the data fork has a hole, copy
* the COW fork mapping to avoid allocating to the data fork.
*/
if (!directio && orig.br_startblock != HOLESTARTBLOCK)
imap = orig;
if (directio || imap.br_startblock == HOLESTARTBLOCK)
imap = cmap;
end_fsb = imap.br_startoff + imap.br_blockcount;
length = XFS_FSB_TO_B(mp, end_fsb) - offset;