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block migration: Cleanup dirty tracking code 

This switches the dirty bitmap to a true bitmap, reducing its footprint
(specifically in caches). It moreover fixes off-by-one bugs in
set_dirty_bitmap (nb_sectors+1 were marked) and bdrv_get_dirty (limit
check allowed one sector behind end of drive). And is drops redundant
dirty_tracking field from BlockDriverState.

Signed-off-by: Jan Kiszka <jan.kiszka@siemens.com>
Signed-off-by: Anthony Liguori <aliguori@us.ibm.com>
This commit is contained in:
Jan Kiszka 2009-11-30 18:21:20 +01:00 committed by Anthony Liguori
parent 6ea44308b0
commit c6d2283068
2 changed files with 25 additions and 22 deletions
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44
block.c
View File

@ -642,12 +642,21 @@ static void set_dirty_bitmap(BlockDriverState *bs, int64_t sector_num,
int nb_sectors, int dirty)
{
int64_t start, end;
unsigned long val, idx, bit;
start = sector_num / BDRV_SECTORS_PER_DIRTY_CHUNK;
end = (sector_num + nb_sectors) / BDRV_SECTORS_PER_DIRTY_CHUNK;
end = (sector_num + nb_sectors - 1) / BDRV_SECTORS_PER_DIRTY_CHUNK;
for (; start <= end; start++) {
bs->dirty_bitmap[start] = dirty;
idx = start / (sizeof(unsigned long) * 8);
bit = start % (sizeof(unsigned long) * 8);
val = bs->dirty_bitmap[idx];
if (dirty) {
val |= 1 << bit;
} else {
val &= ~(1 << bit);
}
bs->dirty_bitmap[idx] = val;
}
}
@ -668,7 +677,7 @@ int bdrv_write(BlockDriverState *bs, int64_t sector_num,
if (bdrv_check_request(bs, sector_num, nb_sectors))
return -EIO;
if (bs->dirty_tracking) {
if (bs->dirty_bitmap) {
set_dirty_bitmap(bs, sector_num, nb_sectors, 1);
}
@ -1218,7 +1227,7 @@ int bdrv_write_compressed(BlockDriverState *bs, int64_t sector_num,
if (bdrv_check_request(bs, sector_num, nb_sectors))
return -EIO;
if (bs->dirty_tracking) {
if (bs->dirty_bitmap) {
set_dirty_bitmap(bs, sector_num, nb_sectors, 1);
}
@ -1419,7 +1428,7 @@ BlockDriverAIOCB *bdrv_aio_writev(BlockDriverState *bs, int64_t sector_num,
if (bdrv_check_request(bs, sector_num, nb_sectors))
return NULL;
if (bs->dirty_tracking) {
if (bs->dirty_bitmap) {
set_dirty_bitmap(bs, sector_num, nb_sectors, 1);
}
@ -1965,23 +1974,17 @@ void bdrv_set_dirty_tracking(BlockDriverState *bs, int enable)
int64_t bitmap_size;
if (enable) {
if (bs->dirty_tracking == 0) {
int64_t i;
uint8_t test;
bitmap_size = (bdrv_getlength(bs) >> BDRV_SECTOR_BITS);
bitmap_size /= BDRV_SECTORS_PER_DIRTY_CHUNK;
bitmap_size++;
if (!bs->dirty_bitmap) {
bitmap_size = (bdrv_getlength(bs) >> BDRV_SECTOR_BITS) +
BDRV_SECTORS_PER_DIRTY_CHUNK * 8 - 1;
bitmap_size /= BDRV_SECTORS_PER_DIRTY_CHUNK * 8;
bs->dirty_bitmap = qemu_mallocz(bitmap_size);
bs->dirty_tracking = enable;
for(i = 0; i < bitmap_size; i++) test = bs->dirty_bitmap[i];
}
} else {
if (bs->dirty_tracking != 0) {
if (bs->dirty_bitmap) {
qemu_free(bs->dirty_bitmap);
bs->dirty_tracking = enable;
bs->dirty_bitmap = NULL;
}
}
}
@ -1990,9 +1993,10 @@ int bdrv_get_dirty(BlockDriverState *bs, int64_t sector)
{
int64_t chunk = sector / (int64_t)BDRV_SECTORS_PER_DIRTY_CHUNK;
if (bs->dirty_bitmap != NULL &&
(sector << BDRV_SECTOR_BITS) <= bdrv_getlength(bs)) {
return bs->dirty_bitmap[chunk];
if (bs->dirty_bitmap &&
(sector << BDRV_SECTOR_BITS) < bdrv_getlength(bs)) {
return bs->dirty_bitmap[chunk / (sizeof(unsigned long) * 8)] &
(1 << (chunk % (sizeof(unsigned long) * 8)));
} else {
return 0;
}

3
block_int.h
View File

@ -168,8 +168,7 @@ struct BlockDriverState {
int cyls, heads, secs, translation;
int type;
char device_name[32];
int dirty_tracking;
uint8_t *dirty_bitmap;
unsigned long *dirty_bitmap;
BlockDriverState *next;
void *private;
};