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block: introduce new dirty bitmap functionality

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Assert that write_compressed is never used with the dirty bitmap.
Setting the bits early is wrong, because a coroutine might concurrently
examine them and copy incomplete data from the source.

Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Signed-off-by: Kevin Wolf <kwolf@redhat.com>
This commit is contained in:
Paolo Bonzini 2012-10-18 16:49:18 +02:00 committed by Kevin Wolf
parent 9156df12a4
commit 1755da16e3
2 changed files with 48 additions and 8 deletions
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51
block.c
View File

@ -2391,7 +2391,7 @@ static int coroutine_fn bdrv_co_do_writev(BlockDriverState *bs,
} }
if (bs->dirty_bitmap) { if (bs->dirty_bitmap) {
set_dirty_bitmap(bs, sector_num, nb_sectors, 1); bdrv_set_dirty(bs, sector_num, nb_sectors);
} }
if (bs->wr_highest_sector < sector_num + nb_sectors - 1) { if (bs->wr_highest_sector < sector_num + nb_sectors - 1) {
@ -2960,9 +2960,7 @@ int bdrv_write_compressed(BlockDriverState *bs, int64_t sector_num,
if (bdrv_check_request(bs, sector_num, nb_sectors)) if (bdrv_check_request(bs, sector_num, nb_sectors))
return -EIO; return -EIO;
if (bs->dirty_bitmap) { assert(!bs->dirty_bitmap);
set_dirty_bitmap(bs, sector_num, nb_sectors, 1);
}
return drv->bdrv_write_compressed(bs, sector_num, buf, nb_sectors); return drv->bdrv_write_compressed(bs, sector_num, buf, nb_sectors);
} }
@ -4269,13 +4267,54 @@ int bdrv_get_dirty(BlockDriverState *bs, int64_t sector)
if (bs->dirty_bitmap && if (bs->dirty_bitmap &&
(sector << BDRV_SECTOR_BITS) < bdrv_getlength(bs)) { (sector << BDRV_SECTOR_BITS) < bdrv_getlength(bs)) {
return !!(bs->dirty_bitmap[chunk / (sizeof(unsigned long) * 8)] & return !!(bs->dirty_bitmap[chunk / BITS_PER_LONG] &
(1UL << (chunk % (sizeof(unsigned long) * 8)))); (1UL << (chunk % BITS_PER_LONG)));
} else { } else {
return 0; return 0;
} }
} }
int64_t bdrv_get_next_dirty(BlockDriverState *bs, int64_t sector)
{
int64_t chunk;
int bit, elem;
/* Avoid an infinite loop. */
assert(bs->dirty_count > 0);
sector = (sector | (BDRV_SECTORS_PER_DIRTY_CHUNK - 1)) + 1;
chunk = sector / (int64_t)BDRV_SECTORS_PER_DIRTY_CHUNK;
QEMU_BUILD_BUG_ON(sizeof(bs->dirty_bitmap[0]) * 8 != BITS_PER_LONG);
elem = chunk / BITS_PER_LONG;
bit = chunk % BITS_PER_LONG;
for (;;) {
if (sector >= bs->total_sectors) {
sector = 0;
bit = elem = 0;
}
if (bit == 0 && bs->dirty_bitmap[elem] == 0) {
sector += BDRV_SECTORS_PER_DIRTY_CHUNK * BITS_PER_LONG;
elem++;
} else {
if (bs->dirty_bitmap[elem] & (1UL << bit)) {
return sector;
}
sector += BDRV_SECTORS_PER_DIRTY_CHUNK;
if (++bit == BITS_PER_LONG) {
bit = 0;
elem++;
}
}
}
}
void bdrv_set_dirty(BlockDriverState *bs, int64_t cur_sector,
int nr_sectors)
{
set_dirty_bitmap(bs, cur_sector, nr_sectors, 1);
}
void bdrv_reset_dirty(BlockDriverState *bs, int64_t cur_sector, void bdrv_reset_dirty(BlockDriverState *bs, int64_t cur_sector,
int nr_sectors) int nr_sectors)
{ {

5
block.h
View File

@ -353,8 +353,9 @@ void *qemu_blockalign(BlockDriverState *bs, size_t size);
void bdrv_set_dirty_tracking(BlockDriverState *bs, int enable); void bdrv_set_dirty_tracking(BlockDriverState *bs, int enable);
int bdrv_get_dirty(BlockDriverState *bs, int64_t sector); int bdrv_get_dirty(BlockDriverState *bs, int64_t sector);
void bdrv_reset_dirty(BlockDriverState *bs, int64_t cur_sector, void bdrv_set_dirty(BlockDriverState *bs, int64_t cur_sector, int nr_sectors);
int nr_sectors); void bdrv_reset_dirty(BlockDriverState *bs, int64_t cur_sector, int nr_sectors);
int64_t bdrv_get_next_dirty(BlockDriverState *bs, int64_t sector);
int64_t bdrv_get_dirty_count(BlockDriverState *bs); int64_t bdrv_get_dirty_count(BlockDriverState *bs);
void bdrv_enable_copy_on_read(BlockDriverState *bs); void bdrv_enable_copy_on_read(BlockDriverState *bs);