block: per caller dirty bitmap

Previously a BlockDriverState has only one dirty bitmap, so only one
caller (e.g. a block job) can keep track of writing. This changes the
dirty bitmap to a list and creates a BdrvDirtyBitmap for each caller, the
lifecycle is managed with these new functions:

    bdrv_create_dirty_bitmap
    bdrv_release_dirty_bitmap

Where BdrvDirtyBitmap is a linked list wrapper structure of HBitmap.

In place of bdrv_set_dirty_tracking, a BdrvDirtyBitmap pointer argument
is added to these functions, since each caller has its own dirty bitmap:

    bdrv_get_dirty
    bdrv_dirty_iter_init
    bdrv_get_dirty_count

bdrv_set_dirty and bdrv_reset_dirty prototypes are unchanged but will
internally walk the list of all dirty bitmaps and set them one by one.

Signed-off-by: Fam Zheng <famz@redhat.com>
Reviewed-by: Stefan Hajnoczi <stefanha@redhat.com>
Signed-off-by: Kevin Wolf <kwolf@redhat.com>

block-migration.c

@@ -58,6 +58,7 @@ typedef struct BlkMigDevState {
     /* Protected by block migration lock.  */
     unsigned long *aio_bitmap;
     int64_t completed_sectors;
+    BdrvDirtyBitmap *dirty_bitmap;
 } BlkMigDevState;
 
 typedef struct BlkMigBlock {
@@ -309,12 +310,21 @@ static int mig_save_device_bulk(QEMUFile *f, BlkMigDevState *bmds)
 
 /* Called with iothread lock taken.  */
 
-static void set_dirty_tracking(int enable)
+static void set_dirty_tracking(void)
 {
     BlkMigDevState *bmds;
 
     QSIMPLEQ_FOREACH(bmds, &block_mig_state.bmds_list, entry) {
-        bdrv_set_dirty_tracking(bmds->bs, enable ? BLOCK_SIZE : 0);
+        bmds->dirty_bitmap = bdrv_create_dirty_bitmap(bmds->bs, BLOCK_SIZE);
+    }
+}
+
+static void unset_dirty_tracking(void)
+{
+    BlkMigDevState *bmds;
+
+    QSIMPLEQ_FOREACH(bmds, &block_mig_state.bmds_list, entry) {
+        bdrv_release_dirty_bitmap(bmds->bs, bmds->dirty_bitmap);
     }
 }
 
@@ -432,7 +442,7 @@ static int mig_save_device_dirty(QEMUFile *f, BlkMigDevState *bmds,
         } else {
             blk_mig_unlock();
         }
-        if (bdrv_get_dirty(bmds->bs, sector)) {
+        if (bdrv_get_dirty(bmds->bs, bmds->dirty_bitmap, sector)) {
 
             if (total_sectors - sector < BDRV_SECTORS_PER_DIRTY_CHUNK) {
                 nr_sectors = total_sectors - sector;
@@ -554,7 +564,7 @@ static int64_t get_remaining_dirty(void)
     int64_t dirty = 0;
 
     QSIMPLEQ_FOREACH(bmds, &block_mig_state.bmds_list, entry) {
-        dirty += bdrv_get_dirty_count(bmds->bs);
+        dirty += bdrv_get_dirty_count(bmds->bs, bmds->dirty_bitmap);
     }
 
     return dirty << BDRV_SECTOR_BITS;
@@ -569,7 +579,7 @@ static void blk_mig_cleanup(void)
 
     bdrv_drain_all();
 
-    set_dirty_tracking(0);
+    unset_dirty_tracking();
 
     blk_mig_lock();
     while ((bmds = QSIMPLEQ_FIRST(&block_mig_state.bmds_list)) != NULL) {
@@ -604,7 +614,7 @@ static int block_save_setup(QEMUFile *f, void *opaque)
     init_blk_migration(f);
 
     /* start track dirty blocks */
-    set_dirty_tracking(1);
+    set_dirty_tracking();
     qemu_mutex_unlock_iothread();
 
     ret = flush_blks(f);

block.c

@@ -49,6 +49,11 @@
 #include <windows.h>
 #endif
 
+struct BdrvDirtyBitmap {
+    HBitmap *bitmap;
+    QLIST_ENTRY(BdrvDirtyBitmap) list;
+};
+
 #define NOT_DONE 0x7fffffff /* used while emulated sync operation in progress */
 
 static void bdrv_dev_change_media_cb(BlockDriverState *bs, bool load);
@@ -318,6 +323,7 @@ BlockDriverState *bdrv_new(const char *device_name)
     BlockDriverState *bs;
 
     bs = g_malloc0(sizeof(BlockDriverState));
+    QLIST_INIT(&bs->dirty_bitmaps);
     pstrcpy(bs->device_name, sizeof(bs->device_name), device_name);
     if (device_name[0] != '\0') {
         QTAILQ_INSERT_TAIL(&bdrv_states, bs, list);
@@ -1617,7 +1623,7 @@ static void bdrv_move_feature_fields(BlockDriverState *bs_dest,
     bs_dest->iostatus           = bs_src->iostatus;
 
     /* dirty bitmap */
-    bs_dest->dirty_bitmap       = bs_src->dirty_bitmap;
+    bs_dest->dirty_bitmaps      = bs_src->dirty_bitmaps;
 
     /* reference count */
     bs_dest->refcnt             = bs_src->refcnt;
@@ -1650,7 +1656,7 @@ void bdrv_swap(BlockDriverState *bs_new, BlockDriverState *bs_old)
 
     /* bs_new must be anonymous and shouldn't have anything fancy enabled */
     assert(bs_new->device_name[0] == '\0');
-    assert(bs_new->dirty_bitmap == NULL);
+    assert(QLIST_EMPTY(&bs_new->dirty_bitmaps));
     assert(bs_new->job == NULL);
     assert(bs_new->dev == NULL);
     assert(bs_new->in_use == 0);
@@ -1711,6 +1717,7 @@ static void bdrv_delete(BlockDriverState *bs)
     assert(!bs->job);
     assert(!bs->in_use);
     assert(!bs->refcnt);
+    assert(QLIST_EMPTY(&bs->dirty_bitmaps));
 
     bdrv_close(bs);
 
@@ -2858,9 +2865,7 @@ static int coroutine_fn bdrv_co_do_writev(BlockDriverState *bs,
         ret = bdrv_co_flush(bs);
     }
 
-    if (bs->dirty_bitmap) {
-        bdrv_set_dirty(bs, sector_num, nb_sectors);
-    }
+    bdrv_set_dirty(bs, sector_num, nb_sectors);
 
     if (bs->wr_highest_sector < sector_num + nb_sectors - 1) {
         bs->wr_highest_sector = sector_num + nb_sectors - 1;
@@ -3431,7 +3436,7 @@ int bdrv_write_compressed(BlockDriverState *bs, int64_t sector_num,
     if (bdrv_check_request(bs, sector_num, nb_sectors))
         return -EIO;
 
-    assert(!bs->dirty_bitmap);
+    assert(QLIST_EMPTY(&bs->dirty_bitmaps));
 
     return drv->bdrv_write_compressed(bs, sector_num, buf, nb_sectors);
 }
@@ -4296,9 +4301,7 @@ int coroutine_fn bdrv_co_discard(BlockDriverState *bs, int64_t sector_num,
         return -EROFS;
     }
 
-    if (bs->dirty_bitmap) {
-        bdrv_reset_dirty(bs, sector_num, nb_sectors);
-    }
+    bdrv_reset_dirty(bs, sector_num, nb_sectors);
 
     /* Do nothing if disabled.  */
     if (!(bs->open_flags & BDRV_O_UNMAP)) {
@@ -4490,58 +4493,70 @@ bool bdrv_qiov_is_aligned(BlockDriverState *bs, QEMUIOVector *qiov)
     return true;
 }
 
-void bdrv_set_dirty_tracking(BlockDriverState *bs, int granularity)
+BdrvDirtyBitmap *bdrv_create_dirty_bitmap(BlockDriverState *bs, int granularity)
 {
     int64_t bitmap_size;
+    BdrvDirtyBitmap *bitmap;
 
     assert((granularity & (granularity - 1)) == 0);
 
-    if (granularity) {
-        granularity >>= BDRV_SECTOR_BITS;
-        assert(!bs->dirty_bitmap);
-        bitmap_size = (bdrv_getlength(bs) >> BDRV_SECTOR_BITS);
-        bs->dirty_bitmap = hbitmap_alloc(bitmap_size, ffs(granularity) - 1);
-    } else {
-        if (bs->dirty_bitmap) {
-            hbitmap_free(bs->dirty_bitmap);
-            bs->dirty_bitmap = NULL;
+    granularity >>= BDRV_SECTOR_BITS;
+    assert(granularity);
+    bitmap_size = (bdrv_getlength(bs) >> BDRV_SECTOR_BITS);
+    bitmap = g_malloc0(sizeof(BdrvDirtyBitmap));
+    bitmap->bitmap = hbitmap_alloc(bitmap_size, ffs(granularity) - 1);
+    QLIST_INSERT_HEAD(&bs->dirty_bitmaps, bitmap, list);
+    return bitmap;
+}
+
+void bdrv_release_dirty_bitmap(BlockDriverState *bs, BdrvDirtyBitmap *bitmap)
+{
+    BdrvDirtyBitmap *bm, *next;
+    QLIST_FOREACH_SAFE(bm, &bs->dirty_bitmaps, list, next) {
+        if (bm == bitmap) {
+            QLIST_REMOVE(bitmap, list);
+            hbitmap_free(bitmap->bitmap);
+            g_free(bitmap);
+            return;
         }
     }
 }
 
-int bdrv_get_dirty(BlockDriverState *bs, int64_t sector)
+int bdrv_get_dirty(BlockDriverState *bs, BdrvDirtyBitmap *bitmap, int64_t sector)
 {
-    if (bs->dirty_bitmap) {
-        return hbitmap_get(bs->dirty_bitmap, sector);
+    if (bitmap) {
+        return hbitmap_get(bitmap->bitmap, sector);
     } else {
         return 0;
     }
 }
 
-void bdrv_dirty_iter_init(BlockDriverState *bs, HBitmapIter *hbi)
+void bdrv_dirty_iter_init(BlockDriverState *bs,
+                          BdrvDirtyBitmap *bitmap, HBitmapIter *hbi)
 {
-    hbitmap_iter_init(hbi, bs->dirty_bitmap, 0);
+    hbitmap_iter_init(hbi, bitmap->bitmap, 0);
 }
 
 void bdrv_set_dirty(BlockDriverState *bs, int64_t cur_sector,
                     int nr_sectors)
 {
-    hbitmap_set(bs->dirty_bitmap, cur_sector, nr_sectors);
+    BdrvDirtyBitmap *bitmap;
+    QLIST_FOREACH(bitmap, &bs->dirty_bitmaps, list) {
+        hbitmap_set(bitmap->bitmap, cur_sector, nr_sectors);
+    }
 }
 
-void bdrv_reset_dirty(BlockDriverState *bs, int64_t cur_sector,
-                      int nr_sectors)
+void bdrv_reset_dirty(BlockDriverState *bs, int64_t cur_sector, int nr_sectors)
 {
-    hbitmap_reset(bs->dirty_bitmap, cur_sector, nr_sectors);
+    BdrvDirtyBitmap *bitmap;
+    QLIST_FOREACH(bitmap, &bs->dirty_bitmaps, list) {
+        hbitmap_reset(bitmap->bitmap, cur_sector, nr_sectors);
+    }
 }
 
-int64_t bdrv_get_dirty_count(BlockDriverState *bs)
+int64_t bdrv_get_dirty_count(BlockDriverState *bs, BdrvDirtyBitmap *bitmap)
 {
-    if (bs->dirty_bitmap) {
-        return hbitmap_count(bs->dirty_bitmap);
-    } else {
-        return 0;
-    }
+    return hbitmap_count(bitmap->bitmap);
 }
 
 /* Get a reference to bs */

block/mirror.c

@@ -39,6 +39,7 @@ typedef struct MirrorBlockJob {
     int64_t granularity;
     size_t buf_size;
     unsigned long *cow_bitmap;
+    BdrvDirtyBitmap *dirty_bitmap;
     HBitmapIter hbi;
     uint8_t *buf;
     QSIMPLEQ_HEAD(, MirrorBuffer) buf_free;
@@ -145,9 +146,10 @@ static void coroutine_fn mirror_iteration(MirrorBlockJob *s)
 
     s->sector_num = hbitmap_iter_next(&s->hbi);
     if (s->sector_num < 0) {
-        bdrv_dirty_iter_init(source, &s->hbi);
+        bdrv_dirty_iter_init(source, s->dirty_bitmap, &s->hbi);
         s->sector_num = hbitmap_iter_next(&s->hbi);
-        trace_mirror_restart_iter(s, bdrv_get_dirty_count(source));
+        trace_mirror_restart_iter(s,
+                                  bdrv_get_dirty_count(source, s->dirty_bitmap));
         assert(s->sector_num >= 0);
     }
 
@@ -183,7 +185,7 @@ static void coroutine_fn mirror_iteration(MirrorBlockJob *s)
     do {
         int added_sectors, added_chunks;
 
-        if (!bdrv_get_dirty(source, next_sector) ||
+        if (!bdrv_get_dirty(source, s->dirty_bitmap, next_sector) ||
             test_bit(next_chunk, s->in_flight_bitmap)) {
             assert(nb_sectors > 0);
             break;
@@ -249,7 +251,8 @@ static void coroutine_fn mirror_iteration(MirrorBlockJob *s)
         /* Advance the HBitmapIter in parallel, so that we do not examine
          * the same sector twice.
          */
-        if (next_sector > hbitmap_next_sector && bdrv_get_dirty(source, next_sector)) {
+        if (next_sector > hbitmap_next_sector
+            && bdrv_get_dirty(source, s->dirty_bitmap, next_sector)) {
             hbitmap_next_sector = hbitmap_iter_next(&s->hbi);
         }
 
@@ -355,7 +358,7 @@ static void coroutine_fn mirror_run(void *opaque)
         }
     }
 
-    bdrv_dirty_iter_init(bs, &s->hbi);
+    bdrv_dirty_iter_init(bs, s->dirty_bitmap, &s->hbi);
     last_pause_ns = qemu_clock_get_ns(QEMU_CLOCK_REALTIME);
     for (;;) {
         uint64_t delay_ns;
@@ -367,7 +370,7 @@ static void coroutine_fn mirror_run(void *opaque)
             goto immediate_exit;
         }
 
-        cnt = bdrv_get_dirty_count(bs);
+        cnt = bdrv_get_dirty_count(bs, s->dirty_bitmap);
 
         /* Note that even when no rate limit is applied we need to yield
          * periodically with no pending I/O so that qemu_aio_flush() returns.
@@ -409,7 +412,7 @@ static void coroutine_fn mirror_run(void *opaque)
 
                 should_complete = s->should_complete ||
                     block_job_is_cancelled(&s->common);
-                cnt = bdrv_get_dirty_count(bs);
+                cnt = bdrv_get_dirty_count(bs, s->dirty_bitmap);
             }
         }
 
@@ -424,7 +427,7 @@ static void coroutine_fn mirror_run(void *opaque)
              */
             trace_mirror_before_drain(s, cnt);
             bdrv_drain_all();
-            cnt = bdrv_get_dirty_count(bs);
+            cnt = bdrv_get_dirty_count(bs, s->dirty_bitmap);
         }
 
         ret = 0;
@@ -471,7 +474,7 @@ immediate_exit:
     qemu_vfree(s->buf);
     g_free(s->cow_bitmap);
     g_free(s->in_flight_bitmap);
-    bdrv_set_dirty_tracking(bs, 0);
+    bdrv_release_dirty_bitmap(bs, s->dirty_bitmap);
     bdrv_iostatus_disable(s->target);
     if (s->should_complete && ret == 0) {
         if (bdrv_get_flags(s->target) != bdrv_get_flags(s->common.bs)) {
@@ -575,7 +578,7 @@ void mirror_start(BlockDriverState *bs, BlockDriverState *target,
     s->granularity = granularity;
     s->buf_size = MAX(buf_size, granularity);
 
-    bdrv_set_dirty_tracking(bs, granularity);
+    s->dirty_bitmap = bdrv_create_dirty_bitmap(bs, granularity);
     bdrv_set_enable_write_cache(s->target, true);
     bdrv_set_on_error(s->target, on_target_error, on_target_error);
     bdrv_iostatus_enable(s->target);

block/qapi.c

@@ -204,14 +204,6 @@ void bdrv_query_info(BlockDriverState *bs,
         info->io_status = bs->iostatus;
     }
 
-    if (bs->dirty_bitmap) {
-        info->has_dirty = true;
-        info->dirty = g_malloc0(sizeof(*info->dirty));
-        info->dirty->count = bdrv_get_dirty_count(bs) * BDRV_SECTOR_SIZE;
-        info->dirty->granularity =
-         ((int64_t) BDRV_SECTOR_SIZE << hbitmap_granularity(bs->dirty_bitmap));
-    }
-
     if (bs->drv) {
         info->has_inserted = true;
         info->inserted = g_malloc0(sizeof(*info->inserted));

include/block/block.h

@@ -419,12 +419,15 @@ void *qemu_blockalign(BlockDriverState *bs, size_t size);
 bool bdrv_qiov_is_aligned(BlockDriverState *bs, QEMUIOVector *qiov);
 
 struct HBitmapIter;
-void bdrv_set_dirty_tracking(BlockDriverState *bs, int granularity);
-int bdrv_get_dirty(BlockDriverState *bs, int64_t sector);
+typedef struct BdrvDirtyBitmap BdrvDirtyBitmap;
+BdrvDirtyBitmap *bdrv_create_dirty_bitmap(BlockDriverState *bs, int granularity);
+void bdrv_release_dirty_bitmap(BlockDriverState *bs, BdrvDirtyBitmap *bitmap);
+int bdrv_get_dirty(BlockDriverState *bs, BdrvDirtyBitmap *bitmap, int64_t sector);
 void bdrv_set_dirty(BlockDriverState *bs, int64_t cur_sector, int nr_sectors);
 void bdrv_reset_dirty(BlockDriverState *bs, int64_t cur_sector, int nr_sectors);
-void bdrv_dirty_iter_init(BlockDriverState *bs, struct HBitmapIter *hbi);
-int64_t bdrv_get_dirty_count(BlockDriverState *bs);
+void bdrv_dirty_iter_init(BlockDriverState *bs,
+                          BdrvDirtyBitmap *bitmap, struct HBitmapIter *hbi);
+int64_t bdrv_get_dirty_count(BlockDriverState *bs, BdrvDirtyBitmap *bitmap);
 
 void bdrv_enable_copy_on_read(BlockDriverState *bs);
 void bdrv_disable_copy_on_read(BlockDriverState *bs);

include/block/block_int.h

@@ -318,7 +318,7 @@ struct BlockDriverState {
     bool iostatus_enabled;
     BlockDeviceIoStatus iostatus;
     char device_name[32];
-    HBitmap *dirty_bitmap;
+    QLIST_HEAD(, BdrvDirtyBitmap) dirty_bitmaps;
     int refcnt;
     int in_use; /* users other than guest access, eg. block migration */
     QTAILQ_ENTRY(BlockDriverState) list;