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xfs: introduce reflink utility functions

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These functions will be used by the other reflink functions to find
the maximum length of a range of shared blocks.

Signed-off-by: Darrick J. Wong <darrick.wong@oracle.coM>
Reviewed-by: Christoph Hellwig <hch@lst.de>
This commit is contained in:
Darrick J. Wong 2016-10-03 09:11:25 -07:00
parent d0e853f360
commit 350a27a6a6
2 changed files with 106 additions and 0 deletions
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102
fs/xfs/libxfs/xfs_refcount.c
View File

@ -1163,3 +1163,105 @@ xfs_refcount_decrease_extent(
return __xfs_refcount_add(mp, dfops, XFS_REFCOUNT_DECREASE,
PREV->br_startblock, PREV->br_blockcount);
}
/*
* Given an AG extent, find the lowest-numbered run of shared blocks
* within that range and return the range in fbno/flen. If
* find_end_of_shared is set, return the longest contiguous extent of
* shared blocks; if not, just return the first extent we find. If no
* shared blocks are found, fbno and flen will be set to NULLAGBLOCK
* and 0, respectively.
*/
int
xfs_refcount_find_shared(
struct xfs_btree_cur *cur,
xfs_agblock_t agbno,
xfs_extlen_t aglen,
xfs_agblock_t *fbno,
xfs_extlen_t *flen,
bool find_end_of_shared)
{
struct xfs_refcount_irec tmp;
int i;
int have;
int error;
trace_xfs_refcount_find_shared(cur->bc_mp, cur->bc_private.a.agno,
agbno, aglen);
/* By default, skip the whole range */
*fbno = NULLAGBLOCK;
*flen = 0;
/* Try to find a refcount extent that crosses the start */
error = xfs_refcount_lookup_le(cur, agbno, &have);
if (error)
goto out_error;
if (!have) {
/* No left extent, look at the next one */
error = xfs_btree_increment(cur, 0, &have);
if (error)
goto out_error;
if (!have)
goto done;
}
error = xfs_refcount_get_rec(cur, &tmp, &i);
if (error)
goto out_error;
XFS_WANT_CORRUPTED_GOTO(cur->bc_mp, i == 1, out_error);
/* If the extent ends before the start, look at the next one */
if (tmp.rc_startblock + tmp.rc_blockcount <= agbno) {
error = xfs_btree_increment(cur, 0, &have);
if (error)
goto out_error;
if (!have)
goto done;
error = xfs_refcount_get_rec(cur, &tmp, &i);
if (error)
goto out_error;
XFS_WANT_CORRUPTED_GOTO(cur->bc_mp, i == 1, out_error);
}
/* If the extent starts after the range we want, bail out */
if (tmp.rc_startblock >= agbno + aglen)
goto done;
/* We found the start of a shared extent! */
if (tmp.rc_startblock < agbno) {
tmp.rc_blockcount -= (agbno - tmp.rc_startblock);
tmp.rc_startblock = agbno;
}
*fbno = tmp.rc_startblock;
*flen = min(tmp.rc_blockcount, agbno + aglen - *fbno);
if (!find_end_of_shared)
goto done;
/* Otherwise, find the end of this shared extent */
while (*fbno + *flen < agbno + aglen) {
error = xfs_btree_increment(cur, 0, &have);
if (error)
goto out_error;
if (!have)
break;
error = xfs_refcount_get_rec(cur, &tmp, &i);
if (error)
goto out_error;
XFS_WANT_CORRUPTED_GOTO(cur->bc_mp, i == 1, out_error);
if (tmp.rc_startblock >= agbno + aglen ||
tmp.rc_startblock != *fbno + *flen)
break;
*flen = min(*flen + tmp.rc_blockcount, agbno + aglen - *fbno);
}
done:
trace_xfs_refcount_find_shared_result(cur->bc_mp,
cur->bc_private.a.agno, *fbno, *flen);
out_error:
if (error)
trace_xfs_refcount_find_shared_error(cur->bc_mp,
cur->bc_private.a.agno, error, _RET_IP_);
return error;
}

4
fs/xfs/libxfs/xfs_refcount.h
View File

@ -54,4 +54,8 @@ extern int xfs_refcount_finish_one(struct xfs_trans *tp,
xfs_fsblock_t *new_fsb, xfs_extlen_t *new_len,
struct xfs_btree_cur **pcur);
extern int xfs_refcount_find_shared(struct xfs_btree_cur *cur,
xfs_agblock_t agbno, xfs_extlen_t aglen, xfs_agblock_t *fbno,
xfs_extlen_t *flen, bool find_end_of_shared);
#endif /* __XFS_REFCOUNT_H__ */