[Qemu-devel] [PATCH 16/17] block: protect modification of dirty bitmaps with a mutex

[Paolo Bonzini <pbonzini@redhat.com>]

Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
---
 block/dirty-bitmap.c         | 74 +++++++++++++++++++++++++++++++++++++++++---
 block/mirror.c               | 11 +++++--
 include/block/block_int.h    |  4 +--
 include/block/dirty-bitmap.h | 23 +++++++++++---
 4 files changed, 97 insertions(+), 15 deletions(-)

diff --git a/block/dirty-bitmap.c b/block/dirty-bitmap.c
index e13718e..b854077 100644
--- a/block/dirty-bitmap.c
+++ b/block/dirty-bitmap.c
@@ -37,6 +37,7 @@
  *     or enabled. A frozen bitmap can only abdicate() or reclaim().
  */
 struct BdrvDirtyBitmap {
+    QemuMutex *mutex;
     HBitmap *bitmap;            /* Dirty sector bitmap implementation */
     HBitmap *meta;              /* Meta dirty bitmap */
     BdrvDirtyBitmap *successor; /* Anonymous child; implies frozen status */
@@ -69,6 +70,16 @@ static inline void bdrv_dirty_bitmaps_unlock(BlockDriverState *bs)
     qemu_mutex_unlock(&dirty_bitmap_mutex);
 }
 
+void bdrv_dirty_bitmap_lock(BdrvDirtyBitmap *bitmap)
+{
+    qemu_mutex_lock(bitmap->mutex);
+}
+
+void bdrv_dirty_bitmap_unlock(BdrvDirtyBitmap *bitmap)
+{
+    qemu_mutex_unlock(bitmap->mutex);
+}
+
 /* Called with BQL or dirty_bitmap lock taken.  */
 BdrvDirtyBitmap *bdrv_find_dirty_bitmap(BlockDriverState *bs, const char *name)
 {
@@ -116,6 +127,7 @@ BdrvDirtyBitmap *bdrv_create_dirty_bitmap(BlockDriverState *bs,
         return NULL;
     }
     bitmap = g_new0(BdrvDirtyBitmap, 1);
+    bitmap->mutex = &bs->dirty_bitmap_mutex;
     bitmap->bitmap = hbitmap_alloc(bitmap_size, ctz32(sector_granularity));
     bitmap->size = bitmap_size;
     bitmap->name = g_strdup(name);
@@ -141,18 +153,22 @@ void bdrv_create_meta_dirty_bitmap(BdrvDirtyBitmap *bitmap,
                                    int chunk_size)
 {
     assert(!bitmap->meta);
+    qemu_mutex_lock(bitmap->mutex);
     bitmap->meta = hbitmap_create_meta(bitmap->bitmap,
                                        chunk_size * BITS_PER_BYTE);
+    qemu_mutex_unlock(bitmap->mutex);
 }
 
 void bdrv_release_meta_dirty_bitmap(BdrvDirtyBitmap *bitmap)
 {
     assert(bitmap->meta);
+    qemu_mutex_lock(bitmap->mutex);
     hbitmap_free_meta(bitmap->bitmap);
     bitmap->meta = NULL;
+    qemu_mutex_unlock(bitmap->mutex);
 }
 
-int bdrv_dirty_bitmap_get_meta(BlockDriverState *bs,
+int bdrv_dirty_bitmap_get_meta_locked(BlockDriverState *bs,
                                BdrvDirtyBitmap *bitmap, int64_t sector,
                                int nb_sectors)
 {
@@ -169,11 +185,26 @@ int bdrv_dirty_bitmap_get_meta(BlockDriverState *bs,
     return false;
 }
 
+int bdrv_dirty_bitmap_get_meta(BlockDriverState *bs,
+                               BdrvDirtyBitmap *bitmap, int64_t sector,
+                               int nb_sectors)
+{
+    bool dirty;
+
+    qemu_mutex_lock(bitmap->mutex);
+    dirty = bdrv_dirty_bitmap_get_meta_locked(bs, bitmap, sector, nb_sectors);
+    qemu_mutex_unlock(bitmap->mutex);
+
+    return dirty;
+}
+
 void bdrv_dirty_bitmap_reset_meta(BlockDriverState *bs,
                                   BdrvDirtyBitmap *bitmap, int64_t sector,
                                   int nb_sectors)
 {
+    qemu_mutex_lock(bitmap->mutex);
     hbitmap_reset(bitmap->meta, sector, nb_sectors);
+    qemu_mutex_unlock(bitmap->mutex);
 }
 
 int64_t bdrv_dirty_bitmap_size(const BdrvDirtyBitmap *bitmap)
@@ -400,7 +431,8 @@ BlockDirtyInfoList *bdrv_query_dirty_bitmaps(BlockDriverState *bs)
     return list;
 }
 
-int bdrv_get_dirty(BlockDriverState *bs, BdrvDirtyBitmap *bitmap,
+/* Called within bdrv_dirty_bitmap_lock..unlock */
+int bdrv_get_dirty_locked(BlockDriverState *bs, BdrvDirtyBitmap *bitmap,
                    int64_t sector)
 {
     if (bitmap) {
@@ -410,6 +442,18 @@ int bdrv_get_dirty(BlockDriverState *bs, BdrvDirtyBitmap *bitmap,
     }
 }
 
+int bdrv_get_dirty(BlockDriverState *bs, BdrvDirtyBitmap *bitmap,
+                   int64_t sector)
+{
+    bool dirty;
+
+    bdrv_dirty_bitmap_lock(bitmap);
+    dirty = bdrv_get_dirty_locked(bs, bitmap, sector);
+    bdrv_dirty_bitmap_unlock(bitmap);
+
+    return dirty;
+}
+
 /**
  * Chooses a default granularity based on the existing cluster size,
  * but clamped between [4K, 64K]. Defaults to 64K in the case that there
@@ -474,23 +518,42 @@ int64_t bdrv_dirty_iter_next(BdrvDirtyBitmapIter *iter)
     return hbitmap_iter_next(&iter->hbi);
 }
 
+/* Called within bdrv_dirty_bitmap_lock..unlock */
+void bdrv_set_dirty_bitmap_locked(BdrvDirtyBitmap *bitmap,
+                                  int64_t cur_sector, int64_t nr_sectors)
+{
+    assert(bdrv_dirty_bitmap_enabled(bitmap));
+    hbitmap_set(bitmap->bitmap, cur_sector, nr_sectors);
+}
+
 void bdrv_set_dirty_bitmap(BdrvDirtyBitmap *bitmap,
                            int64_t cur_sector, int64_t nr_sectors)
 {
+    bdrv_dirty_bitmap_lock(bitmap);
+    bdrv_set_dirty_bitmap_locked(bitmap, cur_sector, nr_sectors);
+    bdrv_dirty_bitmap_unlock(bitmap);
+}
+
+/* Called within bdrv_dirty_bitmap_lock..unlock */
+void bdrv_reset_dirty_bitmap_locked(BdrvDirtyBitmap *bitmap,
+                                    int64_t cur_sector, int64_t nr_sectors)
+{
     assert(bdrv_dirty_bitmap_enabled(bitmap));
-    hbitmap_set(bitmap->bitmap, cur_sector, nr_sectors);
+    hbitmap_reset(bitmap->bitmap, cur_sector, nr_sectors);
 }
 
 void bdrv_reset_dirty_bitmap(BdrvDirtyBitmap *bitmap,
                              int64_t cur_sector, int64_t nr_sectors)
 {
-    assert(bdrv_dirty_bitmap_enabled(bitmap));
-    hbitmap_reset(bitmap->bitmap, cur_sector, nr_sectors);
+    bdrv_dirty_bitmap_lock(bitmap);
+    bdrv_reset_dirty_bitmap_locked(bitmap, cur_sector, nr_sectors);
+    bdrv_dirty_bitmap_unlock(bitmap);
 }
 
 void bdrv_clear_dirty_bitmap(BdrvDirtyBitmap *bitmap, HBitmap **out)
 {
     assert(bdrv_dirty_bitmap_enabled(bitmap));
+    bdrv_dirty_bitmap_lock(bitmap);
     if (!out) {
         hbitmap_reset_all(bitmap->bitmap);
     } else {
@@ -499,6 +562,7 @@ void bdrv_clear_dirty_bitmap(BdrvDirtyBitmap *bitmap, HBitmap **out)
                                        hbitmap_granularity(backup));
         *out = backup;
     }
+    bdrv_dirty_bitmap_unlock(bitmap);
 }
 
 void bdrv_undo_clear_dirty_bitmap(BdrvDirtyBitmap *bitmap, HBitmap *in)
diff --git a/block/mirror.c b/block/mirror.c
index dc227a2..6a5b0f8 100644
--- a/block/mirror.c
+++ b/block/mirror.c
@@ -344,10 +344,12 @@ static uint64_t coroutine_fn mirror_iteration(MirrorBlockJob *s)
 
     sector_num = bdrv_dirty_iter_next(s->dbi);
     if (sector_num < 0) {
+        bdrv_dirty_bitmap_lock(s->dirty_bitmap);
         bdrv_set_dirty_iter(s->dbi, 0);
         sector_num = bdrv_dirty_iter_next(s->dbi);
         trace_mirror_restart_iter(s, bdrv_get_dirty_count(s->dirty_bitmap));
         assert(sector_num >= 0);
+        bdrv_dirty_bitmap_unlock(s->dirty_bitmap);
     }
 
     first_chunk = sector_num / sectors_per_chunk;
@@ -360,12 +362,13 @@ static uint64_t coroutine_fn mirror_iteration(MirrorBlockJob *s)
 
     /* Find the number of consective dirty chunks following the first dirty
      * one, and wait for in flight requests in them. */
+    bdrv_dirty_bitmap_lock(s->dirty_bitmap);
     while (nb_chunks * sectors_per_chunk < (s->buf_size >> BDRV_SECTOR_BITS)) {
         int64_t next_dirty;
         int64_t next_sector = sector_num + nb_chunks * sectors_per_chunk;
         int64_t next_chunk = next_sector / sectors_per_chunk;
         if (next_sector >= end ||
-            !bdrv_get_dirty(source, s->dirty_bitmap, next_sector)) {
+            !bdrv_get_dirty_locked(source, s->dirty_bitmap, next_sector)) {
             break;
         }
         if (test_bit(next_chunk, s->in_flight_bitmap)) {
@@ -386,8 +389,10 @@ static uint64_t coroutine_fn mirror_iteration(MirrorBlockJob *s)
      * calling bdrv_get_block_status_above could yield - if some blocks are
      * marked dirty in this window, we need to know.
      */
-    bdrv_reset_dirty_bitmap(s->dirty_bitmap, sector_num,
-                            nb_chunks * sectors_per_chunk);
+    bdrv_reset_dirty_bitmap_locked(s->dirty_bitmap, sector_num,
+                                  nb_chunks * sectors_per_chunk);
+    bdrv_dirty_bitmap_unlock(s->dirty_bitmap);
+
     bitmap_set(s->in_flight_bitmap, sector_num / sectors_per_chunk, nb_chunks);
     while (nb_chunks > 0 && sector_num < end) {
         int64_t ret;
diff --git a/include/block/block_int.h b/include/block/block_int.h
index 03db2cf..c264ead 100644
--- a/include/block/block_int.h
+++ b/include/block/block_int.h
@@ -598,8 +598,8 @@ struct BlockDriverState {
 
     /* Writing to the list requires the BQL _and_ the dirty_bitmap_mutex.
      * Reading from the list can be done with either the BQL or the
-     * dirty_bitmap_mutex.  Modifying a bitmap requires the AioContext
-     * lock.  */
+     * dirty_bitmap_mutex.  Modifying a bitmap only requires
+     * dirty_bitmap_mutex.  */
     QemuMutex dirty_bitmap_mutex;
     QLIST_HEAD(, BdrvDirtyBitmap) dirty_bitmaps;
 
diff --git a/include/block/dirty-bitmap.h b/include/block/dirty-bitmap.h
index 9dea14b..b6fc35b 100644
--- a/include/block/dirty-bitmap.h
+++ b/include/block/dirty-bitmap.h
@@ -45,6 +45,9 @@ void bdrv_reset_dirty_bitmap(BdrvDirtyBitmap *bitmap,
 int bdrv_dirty_bitmap_get_meta(BlockDriverState *bs,
                                BdrvDirtyBitmap *bitmap, int64_t sector,
                                int nb_sectors);
+int bdrv_dirty_bitmap_get_meta_locked(BlockDriverState *bs,
+                                      BdrvDirtyBitmap *bitmap, int64_t sector,
+                                      int nb_sectors);
 void bdrv_dirty_bitmap_reset_meta(BlockDriverState *bs,
                                   BdrvDirtyBitmap *bitmap, int64_t sector,
                                   int nb_sectors);
@@ -52,11 +55,6 @@ BdrvDirtyBitmapIter *bdrv_dirty_meta_iter_new(BdrvDirtyBitmap *bitmap);
 BdrvDirtyBitmapIter *bdrv_dirty_iter_new(BdrvDirtyBitmap *bitmap,
                                          uint64_t first_sector);
 void bdrv_dirty_iter_free(BdrvDirtyBitmapIter *iter);
-int64_t bdrv_dirty_iter_next(BdrvDirtyBitmapIter *iter);
-void bdrv_set_dirty_iter(BdrvDirtyBitmapIter *hbi, int64_t sector_num);
-int64_t bdrv_get_dirty_count(BdrvDirtyBitmap *bitmap);
-int64_t bdrv_get_meta_dirty_count(BdrvDirtyBitmap *bitmap);
-void bdrv_dirty_bitmap_truncate(BlockDriverState *bs);
 
 uint64_t bdrv_dirty_bitmap_serialization_size(const BdrvDirtyBitmap *bitmap,
                                               uint64_t start, uint64_t count);
@@ -72,4 +70,19 @@ void bdrv_dirty_bitmap_deserialize_zeroes(BdrvDirtyBitmap *bitmap,
                                           bool finish);
 void bdrv_dirty_bitmap_deserialize_finish(BdrvDirtyBitmap *bitmap);
 
+/* Functions that require manual locking.  */
+void bdrv_dirty_bitmap_lock(BdrvDirtyBitmap *bitmap);
+void bdrv_dirty_bitmap_unlock(BdrvDirtyBitmap *bitmap);
+int bdrv_get_dirty_locked(BlockDriverState *bs, BdrvDirtyBitmap *bitmap,
+                          int64_t sector);
+void bdrv_set_dirty_bitmap_locked(BdrvDirtyBitmap *bitmap,
+                                  int64_t cur_sector, int64_t nr_sectors);
+void bdrv_reset_dirty_bitmap_locked(BdrvDirtyBitmap *bitmap,
+                                    int64_t cur_sector, int64_t nr_sectors);
+int64_t bdrv_dirty_iter_next(BdrvDirtyBitmapIter *iter);
+void bdrv_set_dirty_iter(BdrvDirtyBitmapIter *hbi, int64_t sector_num);
+int64_t bdrv_get_dirty_count(BdrvDirtyBitmap *bitmap);
+int64_t bdrv_get_meta_dirty_count(BdrvDirtyBitmap *bitmap);
+void bdrv_dirty_bitmap_truncate(BlockDriverState *bs);
+
 #endif
-- 
2.9.3