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xfs: refactor delalloc indlen reservation split into helper 

The delayed allocation indirect reservation splitting code is not
sufficient in some cases where a delalloc extent is split in two. In
preparation for enhancements to this code, refactor the current indlen
distribution algorithm into a new helper function.

[dchinner: rename temp, temp2 variables]

Signed-off-by: Brian Foster <bfoster@redhat.com>
Reviewed-by: Dave Chinner <dchinner@redhat.com>
Signed-off-by: Dave Chinner <david@fromorbit.com>
This commit is contained in:
Brian Foster 2016-03-15 11:42:46 +11:00 committed by Dave Chinner
parent b2706a05ba
commit a9bd24ac2b
1 changed files with 55 additions and 20 deletions
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75
fs/xfs/libxfs/xfs_bmap.c
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@ -4720,6 +4720,47 @@ xfs_bmapi_write(
return error;
}
/*
* When a delalloc extent is split (e.g., due to a hole punch), the original
* indlen reservation must be shared across the two new extents that are left
* behind.
*
* Given the original reservation and the worst case indlen for the two new
* extents (as calculated by xfs_bmap_worst_indlen()), split the original
* reservation fairly across the two new extents.
*/
static void
xfs_bmap_split_indlen(
xfs_filblks_t ores, /* original res. */
xfs_filblks_t *indlen1, /* ext1 worst indlen */
xfs_filblks_t *indlen2) /* ext2 worst indlen */
{
xfs_filblks_t len1 = *indlen1;
xfs_filblks_t len2 = *indlen2;
xfs_filblks_t nres = len1 + len2; /* new total res. */
/*
* The only blocks available are those reserved for the original extent.
* Therefore, we have to skim blocks off each of the new reservations so
* long as the new total reservation is greater than the original.
*/
while (nres > ores) {
if (len1) {
len1--;
nres--;
}
if (nres == ores)
break;
if (len2) {
len2--;
nres--;
}
}
*indlen1 = len1;
*indlen2 = len2;
}
/*
* Called by xfs_bmapi to update file extent records and the btree
* after removing space (or undoing a delayed allocation).
@ -4985,27 +5026,21 @@ xfs_bmap_del_extent(
XFS_IFORK_NEXTENTS(ip, whichfork) + 1);
} else {
ASSERT(whichfork == XFS_DATA_FORK);
temp = xfs_bmap_worst_indlen(ip, temp);
xfs_bmbt_set_startblock(ep, nullstartblock((int)temp));
temp2 = xfs_bmap_worst_indlen(ip, temp2);
new.br_startblock = nullstartblock((int)temp2);
/*
* Distribute the original indlen reservation across the
* two new extents.
*/
temp = xfs_bmap_worst_indlen(ip, got.br_blockcount);
temp2 = xfs_bmap_worst_indlen(ip, new.br_blockcount);
xfs_bmap_split_indlen(da_old, &temp, &temp2);
da_new = temp + temp2;
while (da_new > da_old) {
if (temp) {
temp--;
da_new--;
xfs_bmbt_set_startblock(ep,
nullstartblock((int)temp));
}
if (da_new == da_old)
break;
if (temp2) {
temp2--;
da_new--;
new.br_startblock =
nullstartblock((int)temp2);
}
}
/*
* Set the reservation for each extent.
*/
xfs_bmbt_set_startblock(ep, nullstartblock((int)temp));
new.br_startblock = nullstartblock((int)temp2);
}
trace_xfs_bmap_post_update(ip, *idx, state, _THIS_IP_);
xfs_iext_insert(ip, *idx + 1, 1, &new, state);