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xfs: refactor the xrep_extent_list into xfs_bitmap
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As mentioned previously, the xrep_extent_list basically implements a
bitmap with two functions: set and disjoint union.  Rename all these
functions to xfs_bitmap to shorten the name and make it more obvious
what we're doing.

Signed-off-by: Darrick J. Wong <darrick.wong@oracle.com>
Reviewed-by: Brian Foster <bfoster@redhat.com>
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Darrick J. Wong committed Jul 31, 2018
1 parent 51d6269 commit 86d969b
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Showing 5 changed files with 149 additions and 163 deletions.
183 changes: 93 additions & 90 deletions fs/xfs/scrub/bitmap.c
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Original file line number Diff line number Diff line change
Expand Up @@ -16,183 +16,186 @@
#include "scrub/repair.h"
#include "scrub/bitmap.h"

/* Collect a dead btree extent for later disposal. */
/*
* Set a range of this bitmap. Caller must ensure the range is not set.
*
* This is the logical equivalent of bitmap |= mask(start, len).
*/
int
xrep_collect_btree_extent(
struct xfs_scrub *sc,
struct xrep_extent_list *exlist,
xfs_fsblock_t fsbno,
xfs_extlen_t len)
xfs_bitmap_set(
struct xfs_bitmap *bitmap,
uint64_t start,
uint64_t len)
{
struct xrep_extent *rex;
struct xfs_bitmap_range *bmr;

trace_xrep_collect_btree_extent(sc->mp,
XFS_FSB_TO_AGNO(sc->mp, fsbno),
XFS_FSB_TO_AGBNO(sc->mp, fsbno), len);

rex = kmem_alloc(sizeof(struct xrep_extent), KM_MAYFAIL);
if (!rex)
bmr = kmem_alloc(sizeof(struct xfs_bitmap_range), KM_MAYFAIL);
if (!bmr)
return -ENOMEM;

INIT_LIST_HEAD(&rex->list);
rex->fsbno = fsbno;
rex->len = len;
list_add_tail(&rex->list, &exlist->list);
INIT_LIST_HEAD(&bmr->list);
bmr->start = start;
bmr->len = len;
list_add_tail(&bmr->list, &bitmap->list);

return 0;
}

/*
* An error happened during the rebuild so the transaction will be cancelled.
* The fs will shut down, and the administrator has to unmount and run repair.
* Therefore, free all the memory associated with the list so we can die.
*/
/* Free everything related to this bitmap. */
void
xrep_cancel_btree_extents(
struct xfs_scrub *sc,
struct xrep_extent_list *exlist)
xfs_bitmap_destroy(
struct xfs_bitmap *bitmap)
{
struct xrep_extent *rex;
struct xrep_extent *n;
struct xfs_bitmap_range *bmr;
struct xfs_bitmap_range *n;

for_each_xrep_extent_safe(rex, n, exlist) {
list_del(&rex->list);
kmem_free(rex);
for_each_xfs_bitmap_extent(bmr, n, bitmap) {
list_del(&bmr->list);
kmem_free(bmr);
}
}

/* Set up a per-AG block bitmap. */
void
xfs_bitmap_init(
struct xfs_bitmap *bitmap)
{
INIT_LIST_HEAD(&bitmap->list);
}

/* Compare two btree extents. */
static int
xrep_btree_extent_cmp(
xfs_bitmap_range_cmp(
void *priv,
struct list_head *a,
struct list_head *b)
{
struct xrep_extent *ap;
struct xrep_extent *bp;
struct xfs_bitmap_range *ap;
struct xfs_bitmap_range *bp;

ap = container_of(a, struct xrep_extent, list);
bp = container_of(b, struct xrep_extent, list);
ap = container_of(a, struct xfs_bitmap_range, list);
bp = container_of(b, struct xfs_bitmap_range, list);

if (ap->fsbno > bp->fsbno)
if (ap->start > bp->start)
return 1;
if (ap->fsbno < bp->fsbno)
if (ap->start < bp->start)
return -1;
return 0;
}

/*
* Remove all the blocks mentioned in @sublist from the extents in @exlist.
* Remove all the blocks mentioned in @sub from the extents in @bitmap.
*
* The intent is that callers will iterate the rmapbt for all of its records
* for a given owner to generate @exlist; and iterate all the blocks of the
* for a given owner to generate @bitmap; and iterate all the blocks of the
* metadata structures that are not being rebuilt and have the same rmapbt
* owner to generate @sublist. This routine subtracts all the extents
* mentioned in sublist from all the extents linked in @exlist, which leaves
* @exlist as the list of blocks that are not accounted for, which we assume
* owner to generate @sub. This routine subtracts all the extents
* mentioned in sub from all the extents linked in @bitmap, which leaves
* @bitmap as the list of blocks that are not accounted for, which we assume
* are the dead blocks of the old metadata structure. The blocks mentioned in
* @exlist can be reaped.
* @bitmap can be reaped.
*
* This is the logical equivalent of bitmap &= ~sub.
*/
#define LEFT_ALIGNED (1 << 0)
#define RIGHT_ALIGNED (1 << 1)
int
xrep_subtract_extents(
struct xfs_scrub *sc,
struct xrep_extent_list *exlist,
struct xrep_extent_list *sublist)
xfs_bitmap_disunion(
struct xfs_bitmap *bitmap,
struct xfs_bitmap *sub)
{
struct list_head *lp;
struct xrep_extent *ex;
struct xrep_extent *newex;
struct xrep_extent *subex;
xfs_fsblock_t sub_fsb;
xfs_extlen_t sub_len;
struct xfs_bitmap_range *br;
struct xfs_bitmap_range *new_br;
struct xfs_bitmap_range *sub_br;
uint64_t sub_start;
uint64_t sub_len;
int state;
int error = 0;

if (list_empty(&exlist->list) || list_empty(&sublist->list))
if (list_empty(&bitmap->list) || list_empty(&sub->list))
return 0;
ASSERT(!list_empty(&sublist->list));
ASSERT(!list_empty(&sub->list));

list_sort(NULL, &exlist->list, xrep_btree_extent_cmp);
list_sort(NULL, &sublist->list, xrep_btree_extent_cmp);
list_sort(NULL, &bitmap->list, xfs_bitmap_range_cmp);
list_sort(NULL, &sub->list, xfs_bitmap_range_cmp);

/*
* Now that we've sorted both lists, we iterate exlist once, rolling
* forward through sublist and/or exlist as necessary until we find an
* Now that we've sorted both lists, we iterate bitmap once, rolling
* forward through sub and/or bitmap as necessary until we find an
* overlap or reach the end of either list. We do not reset lp to the
* head of exlist nor do we reset subex to the head of sublist. The
* head of bitmap nor do we reset sub_br to the head of sub. The
* list traversal is similar to merge sort, but we're deleting
* instead. In this manner we avoid O(n^2) operations.
*/
subex = list_first_entry(&sublist->list, struct xrep_extent,
sub_br = list_first_entry(&sub->list, struct xfs_bitmap_range,
list);
lp = exlist->list.next;
while (lp != &exlist->list) {
ex = list_entry(lp, struct xrep_extent, list);
lp = bitmap->list.next;
while (lp != &bitmap->list) {
br = list_entry(lp, struct xfs_bitmap_range, list);

/*
* Advance subex and/or ex until we find a pair that
* Advance sub_br and/or br until we find a pair that
* intersect or we run out of extents.
*/
while (subex->fsbno + subex->len <= ex->fsbno) {
if (list_is_last(&subex->list, &sublist->list))
while (sub_br->start + sub_br->len <= br->start) {
if (list_is_last(&sub_br->list, &sub->list))
goto out;
subex = list_next_entry(subex, list);
sub_br = list_next_entry(sub_br, list);
}
if (subex->fsbno >= ex->fsbno + ex->len) {
if (sub_br->start >= br->start + br->len) {
lp = lp->next;
continue;
}

/* trim subex to fit the extent we have */
sub_fsb = subex->fsbno;
sub_len = subex->len;
if (subex->fsbno < ex->fsbno) {
sub_len -= ex->fsbno - subex->fsbno;
sub_fsb = ex->fsbno;
/* trim sub_br to fit the extent we have */
sub_start = sub_br->start;
sub_len = sub_br->len;
if (sub_br->start < br->start) {
sub_len -= br->start - sub_br->start;
sub_start = br->start;
}
if (sub_len > ex->len)
sub_len = ex->len;
if (sub_len > br->len)
sub_len = br->len;

state = 0;
if (sub_fsb == ex->fsbno)
if (sub_start == br->start)
state |= LEFT_ALIGNED;
if (sub_fsb + sub_len == ex->fsbno + ex->len)
if (sub_start + sub_len == br->start + br->len)
state |= RIGHT_ALIGNED;
switch (state) {
case LEFT_ALIGNED:
/* Coincides with only the left. */
ex->fsbno += sub_len;
ex->len -= sub_len;
br->start += sub_len;
br->len -= sub_len;
break;
case RIGHT_ALIGNED:
/* Coincides with only the right. */
ex->len -= sub_len;
br->len -= sub_len;
lp = lp->next;
break;
case LEFT_ALIGNED | RIGHT_ALIGNED:
/* Total overlap, just delete ex. */
lp = lp->next;
list_del(&ex->list);
kmem_free(ex);
list_del(&br->list);
kmem_free(br);
break;
case 0:
/*
* Deleting from the middle: add the new right extent
* and then shrink the left extent.
*/
newex = kmem_alloc(sizeof(struct xrep_extent),
new_br = kmem_alloc(sizeof(struct xfs_bitmap_range),
KM_MAYFAIL);
if (!newex) {
if (!new_br) {
error = -ENOMEM;
goto out;
}
INIT_LIST_HEAD(&newex->list);
newex->fsbno = sub_fsb + sub_len;
newex->len = ex->fsbno + ex->len - newex->fsbno;
list_add(&newex->list, &ex->list);
ex->len = sub_fsb - ex->fsbno;
INIT_LIST_HEAD(&new_br->list);
new_br->start = sub_start + sub_len;
new_br->len = br->start + br->len - new_br->start;
list_add(&new_br->list, &br->list);
br->len = sub_start - br->start;
lp = lp->next;
break;
default:
Expand Down
35 changes: 15 additions & 20 deletions fs/xfs/scrub/bitmap.h
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Original file line number Diff line number Diff line change
Expand Up @@ -6,32 +6,27 @@
#ifndef __XFS_SCRUB_BITMAP_H__
#define __XFS_SCRUB_BITMAP_H__

struct xrep_extent {
struct xfs_bitmap_range {
struct list_head list;
xfs_fsblock_t fsbno;
xfs_extlen_t len;
uint64_t start;
uint64_t len;
};

struct xrep_extent_list {
struct xfs_bitmap {
struct list_head list;
};

static inline void
xrep_init_extent_list(
struct xrep_extent_list *exlist)
{
INIT_LIST_HEAD(&exlist->list);
}
void xfs_bitmap_init(struct xfs_bitmap *bitmap);
void xfs_bitmap_destroy(struct xfs_bitmap *bitmap);

#define for_each_xrep_extent_safe(rbe, n, exlist) \
list_for_each_entry_safe((rbe), (n), &(exlist)->list, list)
int xrep_collect_btree_extent(struct xfs_scrub *sc,
struct xrep_extent_list *btlist, xfs_fsblock_t fsbno,
xfs_extlen_t len);
void xrep_cancel_btree_extents(struct xfs_scrub *sc,
struct xrep_extent_list *btlist);
int xrep_subtract_extents(struct xfs_scrub *sc,
struct xrep_extent_list *exlist,
struct xrep_extent_list *sublist);
#define for_each_xfs_bitmap_extent(bex, n, bitmap) \
list_for_each_entry_safe((bex), (n), &(bitmap)->list, list)

#define for_each_xfs_bitmap_block(b, bex, n, bitmap) \
list_for_each_entry_safe((bex), (n), &(bitmap)->list, list) \
for ((b) = bex->start; (b) < bex->start + bex->len; (b)++)

int xfs_bitmap_set(struct xfs_bitmap *bitmap, uint64_t start, uint64_t len);
int xfs_bitmap_disunion(struct xfs_bitmap *bitmap, struct xfs_bitmap *sub);

#endif /* __XFS_SCRUB_BITMAP_H__ */
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