Commit 33656af7 authored by Marcelo Tosatti's avatar Marcelo Tosatti Committed by Anthony Liguori

block migration: do not submit multiple AIOs for same sector

Block migration can submit multiple AIO reads for the same sector/chunk, but
completion of such reads can happen out of order:

migration               guest
- get_dirty(N)
- aio_read(N)
- clear_dirty(N)
                        write(N)
                        set_dirty(N)
- get_dirty(N)
- aio_read(N)

If the first aio_read completes after the second, stale data will be
migrated to the destination.

Fix by not allowing multiple AIOs inflight for the same sector.
Signed-off-by: default avatarMarcelo Tosatti <mtosatti@redhat.com>
Signed-off-by: default avatarAnthony Liguori <aliguori@us.ibm.com>
parent 4dcafbb1
......@@ -49,12 +49,14 @@ typedef struct BlkMigDevState {
int64_t total_sectors;
int64_t dirty;
QSIMPLEQ_ENTRY(BlkMigDevState) entry;
unsigned long *aio_bitmap;
} BlkMigDevState;
typedef struct BlkMigBlock {
uint8_t *buf;
BlkMigDevState *bmds;
int64_t sector;
int nr_sectors;
struct iovec iov;
QEMUIOVector qiov;
BlockDriverAIOCB *aiocb;
......@@ -140,6 +142,57 @@ static inline long double compute_read_bwidth(void)
return (block_mig_state.reads * BLOCK_SIZE)/ block_mig_state.total_time;
}
static int bmds_aio_inflight(BlkMigDevState *bmds, int64_t sector)
{
int64_t chunk = sector / (int64_t)BDRV_SECTORS_PER_DIRTY_CHUNK;
if (bmds->aio_bitmap &&
(sector << BDRV_SECTOR_BITS) < bdrv_getlength(bmds->bs)) {
return !!(bmds->aio_bitmap[chunk / (sizeof(unsigned long) * 8)] &
(1UL << (chunk % (sizeof(unsigned long) * 8))));
} else {
return 0;
}
}
static void bmds_set_aio_inflight(BlkMigDevState *bmds, int64_t sector_num,
int nb_sectors, int set)
{
int64_t start, end;
unsigned long val, idx, bit;
start = sector_num / BDRV_SECTORS_PER_DIRTY_CHUNK;
end = (sector_num + nb_sectors - 1) / BDRV_SECTORS_PER_DIRTY_CHUNK;
for (; start <= end; start++) {
idx = start / (sizeof(unsigned long) * 8);
bit = start % (sizeof(unsigned long) * 8);
val = bmds->aio_bitmap[idx];
if (set) {
if (!(val & (1UL << bit))) {
val |= 1UL << bit;
}
} else {
if (val & (1UL << bit)) {
val &= ~(1UL << bit);
}
}
bmds->aio_bitmap[idx] = val;
}
}
static void alloc_aio_bitmap(BlkMigDevState *bmds)
{
BlockDriverState *bs = bmds->bs;
int64_t bitmap_size;
bitmap_size = (bdrv_getlength(bs) >> BDRV_SECTOR_BITS) +
BDRV_SECTORS_PER_DIRTY_CHUNK * 8 - 1;
bitmap_size /= BDRV_SECTORS_PER_DIRTY_CHUNK * 8;
bmds->aio_bitmap = qemu_mallocz(bitmap_size);
}
static void blk_mig_read_cb(void *opaque, int ret)
{
BlkMigBlock *blk = opaque;
......@@ -151,6 +204,7 @@ static void blk_mig_read_cb(void *opaque, int ret)
add_avg_read_time(blk->time);
QSIMPLEQ_INSERT_TAIL(&block_mig_state.blk_list, blk, entry);
bmds_set_aio_inflight(blk->bmds, blk->sector, blk->nr_sectors, 0);
block_mig_state.submitted--;
block_mig_state.read_done++;
......@@ -194,6 +248,7 @@ static int mig_save_device_bulk(Monitor *mon, QEMUFile *f,
blk->buf = qemu_malloc(BLOCK_SIZE);
blk->bmds = bmds;
blk->sector = cur_sector;
blk->nr_sectors = nr_sectors;
blk->iov.iov_base = blk->buf;
blk->iov.iov_len = nr_sectors * BDRV_SECTOR_SIZE;
......@@ -248,6 +303,7 @@ static void init_blk_migration_it(void *opaque, BlockDriverState *bs)
bmds->total_sectors = sectors;
bmds->completed_sectors = 0;
bmds->shared_base = block_mig_state.shared_base;
alloc_aio_bitmap(bmds);
block_mig_state.total_sector_sum += sectors;
......@@ -329,6 +385,8 @@ static int mig_save_device_dirty(Monitor *mon, QEMUFile *f,
int nr_sectors;
for (sector = bmds->cur_dirty; sector < bmds->total_sectors;) {
if (bmds_aio_inflight(bmds, sector))
qemu_aio_flush();
if (bdrv_get_dirty(bmds->bs, sector)) {
if (total_sectors - sector < BDRV_SECTORS_PER_DIRTY_CHUNK) {
......@@ -340,6 +398,7 @@ static int mig_save_device_dirty(Monitor *mon, QEMUFile *f,
blk->buf = qemu_malloc(BLOCK_SIZE);
blk->bmds = bmds;
blk->sector = sector;
blk->nr_sectors = nr_sectors;
if (is_async) {
blk->iov.iov_base = blk->buf;
......@@ -354,6 +413,7 @@ static int mig_save_device_dirty(Monitor *mon, QEMUFile *f,
goto error;
}
block_mig_state.submitted++;
bmds_set_aio_inflight(bmds, sector, nr_sectors, 1);
} else {
if (bdrv_read(bmds->bs, sector, blk->buf,
nr_sectors) < 0) {
......@@ -474,6 +534,7 @@ static void blk_mig_cleanup(Monitor *mon)
while ((bmds = QSIMPLEQ_FIRST(&block_mig_state.bmds_list)) != NULL) {
QSIMPLEQ_REMOVE_HEAD(&block_mig_state.bmds_list, entry);
qemu_free(bmds->aio_bitmap);
qemu_free(bmds);
}
......
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