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xfs: add xfs_trim_extent

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This helpers allows to trim an extent to a subset of it's original range
while making sure the block numbers in it remain valid,

In the future xfs_trim_extent and xfs_bmapi_trim_map should probably be
merged in some form.

Signed-off-by: Darrick J. Wong <darrick.wong@oracle.com>
[hch: split from a previous patch from Darrick, moved around and added
 support for "raw" delayed extents"]
Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Darrick J. Wong <darrick.wong@oracle.com>
Reviewed-by: Brian Foster <bfoster@redhat.com>
Signed-off-by: Dave Chinner <david@fromorbit.com>
This commit is contained in:
Darrick J. Wong 2016-10-20 15:51:50 +11:00 • committed by Dave Chinner
parent d33fd776f9
commit 0a0af28cad
2 changed files with 35 additions and 0 deletions
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33
fs/xfs/libxfs/xfs_bmap.c
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@ -3996,6 +3996,39 @@ xfs_bmap_alloc(
return xfs_bmap_btalloc(ap);
}
/* Trim extent to fit a logical block range. */
void
xfs_trim_extent(
struct xfs_bmbt_irec *irec,
xfs_fileoff_t bno,
xfs_filblks_t len)
{
xfs_fileoff_t distance;
xfs_fileoff_t end = bno + len;
if (irec->br_startoff + irec->br_blockcount <= bno ||
irec->br_startoff >= end) {
irec->br_blockcount = 0;
return;
}
if (irec->br_startoff < bno) {
distance = bno - irec->br_startoff;
if (isnullstartblock(irec->br_startblock))
irec->br_startblock = DELAYSTARTBLOCK;
if (irec->br_startblock != DELAYSTARTBLOCK &&
irec->br_startblock != HOLESTARTBLOCK)
irec->br_startblock += distance;
irec->br_startoff += distance;
irec->br_blockcount -= distance;
}
if (end < irec->br_startoff + irec->br_blockcount) {
distance = irec->br_startoff + irec->br_blockcount - end;
irec->br_blockcount -= distance;
}
}
/*
* Trim the returned map to the required bounds
*/