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hbitmap: improve dirty iter 

Make dirty iter resistant to resetting bits in corresponding HBitmap.

Signed-off-by: Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>
Reviewed-by: Max Reitz <mreitz@redhat.com>
Reviewed-by: John Snow <jsnow@redhat.com>
Message-id: 20170628120530.31251-4-vsementsov@virtuozzo.com
Signed-off-by: Max Reitz <mreitz@redhat.com>
This commit is contained in:
Vladimir Sementsov-Ogievskiy 2017-06-28 15:05:03 +03:00 committed by Max Reitz
parent b348c262cc
commit f63ea4e92b
2 changed files with 26 additions and 23 deletions
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26
include/qemu/hbitmap.h
View File

@ -256,10 +256,9 @@ void hbitmap_free(HBitmap *hb);
* the lowest-numbered bit that is set in @hb, starting at @first.
*
* Concurrent setting of bits is acceptable, and will at worst cause the
* iteration to miss some of those bits. Resetting bits before the current
* position of the iterator is also okay. However, concurrent resetting of
* bits can lead to unexpected behavior if the iterator has not yet reached
* those bits.
* iteration to miss some of those bits.
*
* The concurrent resetting of bits is OK.
*/
void hbitmap_iter_init(HBitmapIter *hbi, const HBitmap *hb, uint64_t first);
@ -298,24 +297,7 @@ void hbitmap_free_meta(HBitmap *hb);
* Return the next bit that is set in @hbi's associated HBitmap,
* or -1 if all remaining bits are zero.
*/
static inline int64_t hbitmap_iter_next(HBitmapIter *hbi)
{
unsigned long cur = hbi->cur[HBITMAP_LEVELS - 1];
int64_t item;
if (cur == 0) {
cur = hbitmap_iter_skip_words(hbi);
if (cur == 0) {
return -1;
}
}
/* The next call will resume work from the next bit. */
hbi->cur[HBITMAP_LEVELS - 1] = cur & (cur - 1);
item = ((uint64_t)hbi->pos << BITS_PER_LEVEL) + ctzl(cur);
return item << hbi->granularity;
}
int64_t hbitmap_iter_next(HBitmapIter *hbi);
/**
* hbitmap_iter_next_word:

23
util/hbitmap.c
View File

@ -106,8 +106,9 @@ unsigned long hbitmap_iter_skip_words(HBitmapIter *hbi)
unsigned long cur;
do {
cur = hbi->cur[--i];
i--;
pos >>= BITS_PER_LEVEL;
cur = hbi->cur[i] & hb->levels[i][pos];
} while (cur == 0);
/* Check for end of iteration. We always use fewer than BITS_PER_LONG
@ -139,6 +140,26 @@ unsigned long hbitmap_iter_skip_words(HBitmapIter *hbi)
return cur;
}
int64_t hbitmap_iter_next(HBitmapIter *hbi)
{
unsigned long cur = hbi->cur[HBITMAP_LEVELS - 1] &
hbi->hb->levels[HBITMAP_LEVELS - 1][hbi->pos];
int64_t item;
if (cur == 0) {
cur = hbitmap_iter_skip_words(hbi);
if (cur == 0) {
return -1;
}
}
/* The next call will resume work from the next bit. */
hbi->cur[HBITMAP_LEVELS - 1] = cur & (cur - 1);
item = ((uint64_t)hbi->pos << BITS_PER_LEVEL) + ctzl(cur);
return item << hbi->granularity;
}
void hbitmap_iter_init(HBitmapIter *hbi, const HBitmap *hb, uint64_t first)
{
unsigned i, bit;