[PATCH v3 0/3] proper locking on bitmap add/remove paths

[PATCH v3 0/3] proper locking on bitmap add/remove paths

[Vladimir Sementsov-Ogievskiy]

Hi all!

We need to lock qcow2 mutex on accessing in-image metadata, especially
on updating this metadata. Let's implement it.

v3:
01: add John's r-b
02: - fix bdrv_remove_persistent_dirty_bitmap return value
    - drop extra zeroing of ret in qcow2_remove_persistent_dirty_bitmap
03: add John's r-b

Vladimir Sementsov-Ogievskiy (3):
  block: move bdrv_can_store_new_dirty_bitmap to block/dirty-bitmap.c
  block/dirty-bitmap: return int from
    bdrv_remove_persistent_dirty_bitmap
  block/qcow2: proper locking on bitmap add/remove paths

 block/qcow2.h                |  14 ++---
 include/block/block_int.h    |  14 ++---
 include/block/dirty-bitmap.h |   5 +-
 block.c                      |  22 -------
 block/dirty-bitmap.c         | 119 +++++++++++++++++++++++++++++++++--
 block/qcow2-bitmap.c         |  36 +++++++----
 block/qcow2.c                |   5 +-
 blockdev.c                   |  28 +++------
 8 files changed, 163 insertions(+), 80 deletions(-)

-- 
2.21.0

[PATCH v3 1/3] block: move bdrv_can_store_new_dirty_bitmap to block/dirty-bitmap.c

[Vladimir Sementsov-Ogievskiy]

block/dirty-bitmap.c seems to be more appropriate for it and
bdrv_remove_persistent_dirty_bitmap already in it.

Signed-off-by: Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>
Reviewed-by: John Snow <jsnow@redhat.com>
---
 block.c              | 22 ----------------------
 block/dirty-bitmap.c | 22 ++++++++++++++++++++++
 2 files changed, 22 insertions(+), 22 deletions(-)

diff --git a/block.c b/block.c
index 5944124845..bea03cfcc9 100644
--- a/block.c
+++ b/block.c
@@ -6555,25 +6555,3 @@ void bdrv_del_child(BlockDriverState *parent_bs, BdrvChild *child, Error **errp)
 
     parent_bs->drv->bdrv_del_child(parent_bs, child, errp);
 }
-
-bool bdrv_can_store_new_dirty_bitmap(BlockDriverState *bs, const char *name,
-                                     uint32_t granularity, Error **errp)
-{
-    BlockDriver *drv = bs->drv;
-
-    if (!drv) {
-        error_setg_errno(errp, ENOMEDIUM,
-                         "Can't store persistent bitmaps to %s",
-                         bdrv_get_device_or_node_name(bs));
-        return false;
-    }
-
-    if (!drv->bdrv_can_store_new_dirty_bitmap) {
-        error_setg_errno(errp, ENOTSUP,
-                         "Can't store persistent bitmaps to %s",
-                         bdrv_get_device_or_node_name(bs));
-        return false;
-    }
-
-    return drv->bdrv_can_store_new_dirty_bitmap(bs, name, granularity, errp);
-}
diff --git a/block/dirty-bitmap.c b/block/dirty-bitmap.c
index 134e0c9a0c..8f42015db9 100644
--- a/block/dirty-bitmap.c
+++ b/block/dirty-bitmap.c
@@ -464,6 +464,28 @@ void bdrv_remove_persistent_dirty_bitmap(BlockDriverState *bs,
     }
 }
 
+bool bdrv_can_store_new_dirty_bitmap(BlockDriverState *bs, const char *name,
+                                     uint32_t granularity, Error **errp)
+{
+    BlockDriver *drv = bs->drv;
+
+    if (!drv) {
+        error_setg_errno(errp, ENOMEDIUM,
+                         "Can't store persistent bitmaps to %s",
+                         bdrv_get_device_or_node_name(bs));
+        return false;
+    }
+
+    if (!drv->bdrv_can_store_new_dirty_bitmap) {
+        error_setg_errno(errp, ENOTSUP,
+                         "Can't store persistent bitmaps to %s",
+                         bdrv_get_device_or_node_name(bs));
+        return false;
+    }
+
+    return drv->bdrv_can_store_new_dirty_bitmap(bs, name, granularity, errp);
+}
+
 void bdrv_disable_dirty_bitmap(BdrvDirtyBitmap *bitmap)
 {
     bdrv_dirty_bitmap_lock(bitmap);
-- 
2.21.0

[PATCH v3 2/3] block/dirty-bitmap: return int from bdrv_remove_persistent_dirty_bitmap

[Vladimir Sementsov-Ogievskiy]

It's more comfortable to not deal with local_err.

Signed-off-by: Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>
---
 block/qcow2.h                |  5 ++---
 include/block/block_int.h    |  6 +++---
 include/block/dirty-bitmap.h |  5 ++---
 block/dirty-bitmap.c         |  9 +++++----
 block/qcow2-bitmap.c         | 18 ++++++++++--------
 blockdev.c                   |  7 +++----
 6 files changed, 25 insertions(+), 25 deletions(-)

diff --git a/block/qcow2.h b/block/qcow2.h
index a488d761ff..2ed5482163 100644
--- a/block/qcow2.h
+++ b/block/qcow2.h
@@ -747,9 +747,8 @@ bool qcow2_can_store_new_dirty_bitmap(BlockDriverState *bs,
                                       const char *name,
                                       uint32_t granularity,
                                       Error **errp);
-void qcow2_remove_persistent_dirty_bitmap(BlockDriverState *bs,
-                                          const char *name,
-                                          Error **errp);
+int qcow2_remove_persistent_dirty_bitmap(BlockDriverState *bs, const char *name,
+                                         Error **errp);
 
 ssize_t coroutine_fn
 qcow2_co_compress(BlockDriverState *bs, void *dest, size_t dest_size,
diff --git a/include/block/block_int.h b/include/block/block_int.h
index 0422acdf1c..503ac9e3cd 100644
--- a/include/block/block_int.h
+++ b/include/block/block_int.h
@@ -556,9 +556,9 @@ struct BlockDriver {
                                             const char *name,
                                             uint32_t granularity,
                                             Error **errp);
-    void (*bdrv_remove_persistent_dirty_bitmap)(BlockDriverState *bs,
-                                                const char *name,
-                                                Error **errp);
+    int (*bdrv_remove_persistent_dirty_bitmap)(BlockDriverState *bs,
+                                               const char *name,
+                                               Error **errp);
 
     /**
      * Register/unregister a buffer for I/O. For example, when the driver is
diff --git a/include/block/dirty-bitmap.h b/include/block/dirty-bitmap.h
index 4b4b731b46..07503b03b5 100644
--- a/include/block/dirty-bitmap.h
+++ b/include/block/dirty-bitmap.h
@@ -37,9 +37,8 @@ int bdrv_dirty_bitmap_check(const BdrvDirtyBitmap *bitmap, uint32_t flags,
                             Error **errp);
 void bdrv_release_dirty_bitmap(BlockDriverState *bs, BdrvDirtyBitmap *bitmap);
 void bdrv_release_named_dirty_bitmaps(BlockDriverState *bs);
-void bdrv_remove_persistent_dirty_bitmap(BlockDriverState *bs,
-                                         const char *name,
-                                         Error **errp);
+int bdrv_remove_persistent_dirty_bitmap(BlockDriverState *bs, const char *name,
+                                        Error **errp);
 void bdrv_disable_dirty_bitmap(BdrvDirtyBitmap *bitmap);
 void bdrv_enable_dirty_bitmap(BdrvDirtyBitmap *bitmap);
 void bdrv_enable_dirty_bitmap_locked(BdrvDirtyBitmap *bitmap);
diff --git a/block/dirty-bitmap.c b/block/dirty-bitmap.c
index 8f42015db9..d1ae2e1922 100644
--- a/block/dirty-bitmap.c
+++ b/block/dirty-bitmap.c
@@ -455,13 +455,14 @@ void bdrv_release_named_dirty_bitmaps(BlockDriverState *bs)
  * not fail.
  * This function doesn't release corresponding BdrvDirtyBitmap.
  */
-void bdrv_remove_persistent_dirty_bitmap(BlockDriverState *bs,
-                                         const char *name,
-                                         Error **errp)
+int bdrv_remove_persistent_dirty_bitmap(BlockDriverState *bs, const char *name,
+                                        Error **errp)
 {
     if (bs->drv && bs->drv->bdrv_remove_persistent_dirty_bitmap) {
-        bs->drv->bdrv_remove_persistent_dirty_bitmap(bs, name, errp);
+        return bs->drv->bdrv_remove_persistent_dirty_bitmap(bs, name, errp);
     }
+
+    return 0;
 }
 
 bool bdrv_can_store_new_dirty_bitmap(BlockDriverState *bs, const char *name,
diff --git a/block/qcow2-bitmap.c b/block/qcow2-bitmap.c
index b2487101ed..9821c1628f 100644
--- a/block/qcow2-bitmap.c
+++ b/block/qcow2-bitmap.c
@@ -1404,9 +1404,8 @@ static Qcow2Bitmap *find_bitmap_by_name(Qcow2BitmapList *bm_list,
     return NULL;
 }
 
-void qcow2_remove_persistent_dirty_bitmap(BlockDriverState *bs,
-                                          const char *name,
-                                          Error **errp)
+int qcow2_remove_persistent_dirty_bitmap(BlockDriverState *bs, const char *name,
+                                         Error **errp)
 {
     int ret;
     BDRVQcow2State *s = bs->opaque;
@@ -1416,18 +1415,19 @@ void qcow2_remove_persistent_dirty_bitmap(BlockDriverState *bs,
     if (s->nb_bitmaps == 0) {
         /* Absence of the bitmap is not an error: see explanation above
          * bdrv_remove_persistent_dirty_bitmap() definition. */
-        return;
+        return 0;
     }
 
     bm_list = bitmap_list_load(bs, s->bitmap_directory_offset,
                                s->bitmap_directory_size, errp);
     if (bm_list == NULL) {
-        return;
+        return -EIO;
     }
 
     bm = find_bitmap_by_name(bm_list, name);
     if (bm == NULL) {
-        goto fail;
+        ret = -EINVAL;
+        goto out;
     }
 
     QSIMPLEQ_REMOVE(bm_list, bm, Qcow2Bitmap, entry);
@@ -1435,14 +1435,16 @@ void qcow2_remove_persistent_dirty_bitmap(BlockDriverState *bs,
     ret = update_ext_header_and_dir(bs, bm_list);
     if (ret < 0) {
         error_setg_errno(errp, -ret, "Failed to update bitmap extension");
-        goto fail;
+        goto out;
     }
 
     free_bitmap_clusters(bs, &bm->table);
 
-fail:
+out:
     bitmap_free(bm);
     bitmap_list_free(bm_list);
+
+    return ret;
 }
 
 void qcow2_store_persistent_dirty_bitmaps(BlockDriverState *bs, Error **errp)
diff --git a/blockdev.c b/blockdev.c
index fbef6845c8..0813adfb2b 100644
--- a/blockdev.c
+++ b/blockdev.c
@@ -2940,15 +2940,14 @@ static BdrvDirtyBitmap *do_block_dirty_bitmap_remove(
     }
 
     if (bdrv_dirty_bitmap_get_persistence(bitmap)) {
+        int ret;
         AioContext *aio_context = bdrv_get_aio_context(bs);
-        Error *local_err = NULL;
 
         aio_context_acquire(aio_context);
-        bdrv_remove_persistent_dirty_bitmap(bs, name, &local_err);
+        ret = bdrv_remove_persistent_dirty_bitmap(bs, name, errp);
         aio_context_release(aio_context);
 
-        if (local_err != NULL) {
-            error_propagate(errp, local_err);
+        if (ret < 0) {
             return NULL;
         }
     }
-- 
2.21.0

[PATCH v3 3/3] block/qcow2: proper locking on bitmap add/remove paths

[Vladimir Sementsov-Ogievskiy]

qmp_block_dirty_bitmap_add and do_block_dirty_bitmap_remove do acquire
aio context since 0a6c86d024c52b. But this is not enough: we also must
lock qcow2 mutex when access in-image metadata. Especially it concerns
freeing qcow2 clusters.

To achieve this, move qcow2_can_store_new_dirty_bitmap and
qcow2_remove_persistent_dirty_bitmap to coroutine context.

Since we work in coroutines in correct aio context, we don't need
context acquiring in blockdev.c anymore, drop it.

Signed-off-by: Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>
Reviewed-by: John Snow <jsnow@redhat.com>
---
 block/qcow2.h             |  11 ++--
 include/block/block_int.h |  10 ++--
 block/dirty-bitmap.c      | 102 +++++++++++++++++++++++++++++++++++---
 block/qcow2-bitmap.c      |  24 ++++++---
 block/qcow2.c             |   5 +-
 blockdev.c                |  27 +++-------
 6 files changed, 131 insertions(+), 48 deletions(-)

diff --git a/block/qcow2.h b/block/qcow2.h
index 2ed5482163..113d99bf52 100644
--- a/block/qcow2.h
+++ b/block/qcow2.h
@@ -743,12 +743,13 @@ int qcow2_reopen_bitmaps_rw(BlockDriverState *bs, Error **errp);
 int qcow2_truncate_bitmaps_check(BlockDriverState *bs, Error **errp);
 void qcow2_store_persistent_dirty_bitmaps(BlockDriverState *bs, Error **errp);
 int qcow2_reopen_bitmaps_ro(BlockDriverState *bs, Error **errp);
-bool qcow2_can_store_new_dirty_bitmap(BlockDriverState *bs,
-                                      const char *name,
-                                      uint32_t granularity,
-                                      Error **errp);
-int qcow2_remove_persistent_dirty_bitmap(BlockDriverState *bs, const char *name,
+bool qcow2_co_can_store_new_dirty_bitmap(BlockDriverState *bs,
+                                         const char *name,
+                                         uint32_t granularity,
                                          Error **errp);
+int qcow2_co_remove_persistent_dirty_bitmap(BlockDriverState *bs,
+                                            const char *name,
+                                            Error **errp);
 
 ssize_t coroutine_fn
 qcow2_co_compress(BlockDriverState *bs, void *dest, size_t dest_size,
diff --git a/include/block/block_int.h b/include/block/block_int.h
index 503ac9e3cd..1e54486ad1 100644
--- a/include/block/block_int.h
+++ b/include/block/block_int.h
@@ -552,13 +552,13 @@ struct BlockDriver {
      * field of BlockDirtyBitmap's in case of success.
      */
     int (*bdrv_reopen_bitmaps_rw)(BlockDriverState *bs, Error **errp);
-    bool (*bdrv_can_store_new_dirty_bitmap)(BlockDriverState *bs,
-                                            const char *name,
-                                            uint32_t granularity,
-                                            Error **errp);
-    int (*bdrv_remove_persistent_dirty_bitmap)(BlockDriverState *bs,
+    bool (*bdrv_co_can_store_new_dirty_bitmap)(BlockDriverState *bs,
                                                const char *name,
+                                               uint32_t granularity,
                                                Error **errp);
+    int (*bdrv_co_remove_persistent_dirty_bitmap)(BlockDriverState *bs,
+                                                  const char *name,
+                                                  Error **errp);
 
     /**
      * Register/unregister a buffer for I/O. For example, when the driver is
diff --git a/block/dirty-bitmap.c b/block/dirty-bitmap.c
index d1ae2e1922..03e0872b97 100644
--- a/block/dirty-bitmap.c
+++ b/block/dirty-bitmap.c
@@ -26,6 +26,7 @@
 #include "trace.h"
 #include "block/block_int.h"
 #include "block/blockjob.h"
+#include "qemu/main-loop.h"
 
 struct BdrvDirtyBitmap {
     QemuMutex *mutex;
@@ -455,18 +456,59 @@ void bdrv_release_named_dirty_bitmaps(BlockDriverState *bs)
  * not fail.
  * This function doesn't release corresponding BdrvDirtyBitmap.
  */
-int bdrv_remove_persistent_dirty_bitmap(BlockDriverState *bs, const char *name,
-                                        Error **errp)
+static int coroutine_fn
+bdrv_co_remove_persistent_dirty_bitmap(BlockDriverState *bs, const char *name,
+                                       Error **errp)
 {
-    if (bs->drv && bs->drv->bdrv_remove_persistent_dirty_bitmap) {
-        return bs->drv->bdrv_remove_persistent_dirty_bitmap(bs, name, errp);
+    if (bs->drv && bs->drv->bdrv_co_remove_persistent_dirty_bitmap) {
+        return bs->drv->bdrv_co_remove_persistent_dirty_bitmap(bs, name, errp);
     }
 
     return 0;
 }
 
-bool bdrv_can_store_new_dirty_bitmap(BlockDriverState *bs, const char *name,
-                                     uint32_t granularity, Error **errp)
+typedef struct BdrvRemovePersistentDirtyBitmapCo {
+    BlockDriverState *bs;
+    const char *name;
+    Error **errp;
+    int ret;
+} BdrvRemovePersistentDirtyBitmapCo;
+
+static void coroutine_fn
+bdrv_co_remove_persistent_dirty_bitmap_entry(void *opaque)
+{
+    BdrvRemovePersistentDirtyBitmapCo *s = opaque;
+
+    s->ret = bdrv_co_remove_persistent_dirty_bitmap(s->bs, s->name, s->errp);
+    aio_wait_kick();
+}
+
+int bdrv_remove_persistent_dirty_bitmap(BlockDriverState *bs, const char *name,
+                                        Error **errp)
+{
+    if (qemu_in_coroutine()) {
+        return bdrv_co_remove_persistent_dirty_bitmap(bs, name, errp);
+    } else {
+        Coroutine *co;
+        BdrvRemovePersistentDirtyBitmapCo s = {
+            .bs = bs,
+            .name = name,
+            .errp = errp,
+            .ret = -EINPROGRESS,
+        };
+
+        co = qemu_coroutine_create(bdrv_co_remove_persistent_dirty_bitmap_entry,
+                                   &s);
+        bdrv_coroutine_enter(bs, co);
+        BDRV_POLL_WHILE(bs, s.ret == -EINPROGRESS);
+
+        return s.ret;
+    }
+}
+
+static bool coroutine_fn
+bdrv_co_can_store_new_dirty_bitmap(BlockDriverState *bs, const char *name,
+                                   uint32_t granularity, Error **errp)
 {
     BlockDriver *drv = bs->drv;
 
@@ -477,14 +519,58 @@ bool bdrv_can_store_new_dirty_bitmap(BlockDriverState *bs, const char *name,
         return false;
     }
 
-    if (!drv->bdrv_can_store_new_dirty_bitmap) {
+    if (!drv->bdrv_co_can_store_new_dirty_bitmap) {
         error_setg_errno(errp, ENOTSUP,
                          "Can't store persistent bitmaps to %s",
                          bdrv_get_device_or_node_name(bs));
         return false;
     }
 
-    return drv->bdrv_can_store_new_dirty_bitmap(bs, name, granularity, errp);
+    return drv->bdrv_co_can_store_new_dirty_bitmap(bs, name, granularity, errp);
+}
+
+typedef struct BdrvCanStoreNewDirtyBitmapCo {
+    BlockDriverState *bs;
+    const char *name;
+    uint32_t granularity;
+    Error **errp;
+    bool ret;
+
+    bool in_progress;
+} BdrvCanStoreNewDirtyBitmapCo;
+
+static void coroutine_fn bdrv_co_can_store_new_dirty_bitmap_entry(void *opaque)
+{
+    BdrvCanStoreNewDirtyBitmapCo *s = opaque;
+
+    s->ret = bdrv_co_can_store_new_dirty_bitmap(s->bs, s->name, s->granularity,
+                                                s->errp);
+    s->in_progress = false;
+    aio_wait_kick();
+}
+
+bool bdrv_can_store_new_dirty_bitmap(BlockDriverState *bs, const char *name,
+                                     uint32_t granularity, Error **errp)
+{
+    if (qemu_in_coroutine()) {
+        return bdrv_co_can_store_new_dirty_bitmap(bs, name, granularity, errp);
+    } else {
+        Coroutine *co;
+        BdrvCanStoreNewDirtyBitmapCo s = {
+            .bs = bs,
+            .name = name,
+            .granularity = granularity,
+            .errp = errp,
+            .in_progress = true,
+        };
+
+        co = qemu_coroutine_create(bdrv_co_can_store_new_dirty_bitmap_entry,
+                                   &s);
+        bdrv_coroutine_enter(bs, co);
+        BDRV_POLL_WHILE(bs, s.in_progress);
+
+        return s.ret;
+    }
 }
 
 void bdrv_disable_dirty_bitmap(BdrvDirtyBitmap *bitmap)
diff --git a/block/qcow2-bitmap.c b/block/qcow2-bitmap.c
index 9821c1628f..644837eb03 100644
--- a/block/qcow2-bitmap.c
+++ b/block/qcow2-bitmap.c
@@ -1404,12 +1404,13 @@ static Qcow2Bitmap *find_bitmap_by_name(Qcow2BitmapList *bm_list,
     return NULL;
 }
 
-int qcow2_remove_persistent_dirty_bitmap(BlockDriverState *bs, const char *name,
-                                         Error **errp)
+int coroutine_fn qcow2_co_remove_persistent_dirty_bitmap(BlockDriverState *bs,
+                                                         const char *name,
+                                                         Error **errp)
 {
     int ret;
     BDRVQcow2State *s = bs->opaque;
-    Qcow2Bitmap *bm;
+    Qcow2Bitmap *bm = NULL;
     Qcow2BitmapList *bm_list;
 
     if (s->nb_bitmaps == 0) {
@@ -1418,10 +1419,13 @@ int qcow2_remove_persistent_dirty_bitmap(BlockDriverState *bs, const char *name,
         return 0;
     }
 
+    qemu_co_mutex_lock(&s->lock);
+
     bm_list = bitmap_list_load(bs, s->bitmap_directory_offset,
                                s->bitmap_directory_size, errp);
     if (bm_list == NULL) {
-        return -EIO;
+        ret = -EIO;
+        goto out;
     }
 
     bm = find_bitmap_by_name(bm_list, name);
@@ -1441,6 +1445,8 @@ int qcow2_remove_persistent_dirty_bitmap(BlockDriverState *bs, const char *name,
     free_bitmap_clusters(bs, &bm->table);
 
 out:
+    qemu_co_mutex_unlock(&s->lock);
+
     bitmap_free(bm);
     bitmap_list_free(bm_list);
 
@@ -1615,10 +1621,10 @@ int qcow2_reopen_bitmaps_ro(BlockDriverState *bs, Error **errp)
     return 0;
 }
 
-bool qcow2_can_store_new_dirty_bitmap(BlockDriverState *bs,
-                                      const char *name,
-                                      uint32_t granularity,
-                                      Error **errp)
+bool coroutine_fn qcow2_co_can_store_new_dirty_bitmap(BlockDriverState *bs,
+                                                      const char *name,
+                                                      uint32_t granularity,
+                                                      Error **errp)
 {
     BDRVQcow2State *s = bs->opaque;
     bool found;
@@ -1655,8 +1661,10 @@ bool qcow2_can_store_new_dirty_bitmap(BlockDriverState *bs,
         goto fail;
     }
 
+    qemu_co_mutex_lock(&s->lock);
     bm_list = bitmap_list_load(bs, s->bitmap_directory_offset,
                                s->bitmap_directory_size, errp);
+    qemu_co_mutex_unlock(&s->lock);
     if (bm_list == NULL) {
         goto fail;
     }
diff --git a/block/qcow2.c b/block/qcow2.c
index 4d16393e61..43a6cc423d 100644
--- a/block/qcow2.c
+++ b/block/qcow2.c
@@ -5263,8 +5263,9 @@ BlockDriver bdrv_qcow2 = {
     .bdrv_attach_aio_context  = qcow2_attach_aio_context,
 
     .bdrv_reopen_bitmaps_rw = qcow2_reopen_bitmaps_rw,
-    .bdrv_can_store_new_dirty_bitmap = qcow2_can_store_new_dirty_bitmap,
-    .bdrv_remove_persistent_dirty_bitmap = qcow2_remove_persistent_dirty_bitmap,
+    .bdrv_co_can_store_new_dirty_bitmap = qcow2_co_can_store_new_dirty_bitmap,
+    .bdrv_co_remove_persistent_dirty_bitmap =
+            qcow2_co_remove_persistent_dirty_bitmap,
 };
 
 static void bdrv_qcow2_init(void)
diff --git a/blockdev.c b/blockdev.c
index 0813adfb2b..228ce94a88 100644
--- a/blockdev.c
+++ b/blockdev.c
@@ -2898,16 +2898,10 @@ void qmp_block_dirty_bitmap_add(const char *node, const char *name,
         disabled = false;
     }
 
-    if (persistent) {
-        AioContext *aio_context = bdrv_get_aio_context(bs);
-        bool ok;
-
-        aio_context_acquire(aio_context);
-        ok = bdrv_can_store_new_dirty_bitmap(bs, name, granularity, errp);
-        aio_context_release(aio_context);
-        if (!ok) {
-            return;
-        }
+    if (persistent &&
+        !bdrv_can_store_new_dirty_bitmap(bs, name, granularity, errp))
+    {
+        return;
     }
 
     bitmap = bdrv_create_dirty_bitmap(bs, granularity, name, errp);
@@ -2939,17 +2933,10 @@ static BdrvDirtyBitmap *do_block_dirty_bitmap_remove(
         return NULL;
     }
 
-    if (bdrv_dirty_bitmap_get_persistence(bitmap)) {
-        int ret;
-        AioContext *aio_context = bdrv_get_aio_context(bs);
-
-        aio_context_acquire(aio_context);
-        ret = bdrv_remove_persistent_dirty_bitmap(bs, name, errp);
-        aio_context_release(aio_context);
-
-        if (ret < 0) {
+    if (bdrv_dirty_bitmap_get_persistence(bitmap) &&
+        bdrv_remove_persistent_dirty_bitmap(bs, name, errp) < 0)
+    {
             return NULL;
-        }
     }
 
     if (release) {
-- 
2.21.0

Re: [PATCH v3 0/3] proper locking on bitmap add/remove paths

[John Snow]

On 9/20/19 4:25 AM, Vladimir Sementsov-Ogievskiy wrote:
> Hi all!
> 
> We need to lock qcow2 mutex on accessing in-image metadata, especially
> on updating this metadata. Let's implement it.
> 
> v3:
> 01: add John's r-b
> 02: - fix bdrv_remove_persistent_dirty_bitmap return value
>     - drop extra zeroing of ret in qcow2_remove_persistent_dirty_bitmap
> 03: add John's r-b
> 
> Vladimir Sementsov-Ogievskiy (3):
>   block: move bdrv_can_store_new_dirty_bitmap to block/dirty-bitmap.c
>   block/dirty-bitmap: return int from
>     bdrv_remove_persistent_dirty_bitmap
>   block/qcow2: proper locking on bitmap add/remove paths
> 
>  block/qcow2.h                |  14 ++---
>  include/block/block_int.h    |  14 ++---
>  include/block/dirty-bitmap.h |   5 +-
>  block.c                      |  22 -------
>  block/dirty-bitmap.c         | 119 +++++++++++++++++++++++++++++++++--
>  block/qcow2-bitmap.c         |  36 +++++++----
>  block/qcow2.c                |   5 +-
>  blockdev.c                   |  28 +++------
>  8 files changed, 163 insertions(+), 80 deletions(-)
> 

I'll take this; I imagine the return signatures are going to change
again with your error propagation series, though ...?

Re: [PATCH v3 2/3] block/dirty-bitmap: return int from bdrv_remove_persistent_dirty_bitmap

[John Snow]

On 9/20/19 4:25 AM, Vladimir Sementsov-Ogievskiy wrote:
> It's more comfortable to not deal with local_err.
> 
> Signed-off-by: Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>

Reviewed-by: John Snow <jsnow@redhat.com>

Re: [PATCH v3 0/3] proper locking on bitmap add/remove paths

[John Snow]

On 9/20/19 4:25 AM, Vladimir Sementsov-Ogievskiy wrote:
> Hi all!
> 
> We need to lock qcow2 mutex on accessing in-image metadata, especially
> on updating this metadata. Let's implement it.
> 
> v3:
> 01: add John's r-b
> 02: - fix bdrv_remove_persistent_dirty_bitmap return value
>     - drop extra zeroing of ret in qcow2_remove_persistent_dirty_bitmap
> 03: add John's r-b
> 
> Vladimir Sementsov-Ogievskiy (3):
>   block: move bdrv_can_store_new_dirty_bitmap to block/dirty-bitmap.c
>   block/dirty-bitmap: return int from
>     bdrv_remove_persistent_dirty_bitmap
>   block/qcow2: proper locking on bitmap add/remove paths
> 
>  block/qcow2.h                |  14 ++---
>  include/block/block_int.h    |  14 ++---
>  include/block/dirty-bitmap.h |   5 +-
>  block.c                      |  22 -------
>  block/dirty-bitmap.c         | 119 +++++++++++++++++++++++++++++++++--
>  block/qcow2-bitmap.c         |  36 +++++++----
>  block/qcow2.c                |   5 +-
>  blockdev.c                   |  28 +++------
>  8 files changed, 163 insertions(+), 80 deletions(-)
> 

Thanks, applied to my bitmaps tree:

https://github.com/jnsnow/qemu/commits/bitmaps
https://github.com/jnsnow/qemu.git

--js

Re: [PATCH v3 0/3] proper locking on bitmap add/remove paths

[Vladimir Sementsov-Ogievskiy]

26.09.2019 22:01, John Snow wrote:
> 
> 
> On 9/20/19 4:25 AM, Vladimir Sementsov-Ogievskiy wrote:
>> Hi all!
>>
>> We need to lock qcow2 mutex on accessing in-image metadata, especially
>> on updating this metadata. Let's implement it.
>>
>> v3:
>> 01: add John's r-b
>> 02: - fix bdrv_remove_persistent_dirty_bitmap return value
>>      - drop extra zeroing of ret in qcow2_remove_persistent_dirty_bitmap
>> 03: add John's r-b
>>
>> Vladimir Sementsov-Ogievskiy (3):
>>    block: move bdrv_can_store_new_dirty_bitmap to block/dirty-bitmap.c
>>    block/dirty-bitmap: return int from
>>      bdrv_remove_persistent_dirty_bitmap
>>    block/qcow2: proper locking on bitmap add/remove paths
>>
>>   block/qcow2.h                |  14 ++---
>>   include/block/block_int.h    |  14 ++---
>>   include/block/dirty-bitmap.h |   5 +-
>>   block.c                      |  22 -------
>>   block/dirty-bitmap.c         | 119 +++++++++++++++++++++++++++++++++--
>>   block/qcow2-bitmap.c         |  36 +++++++----
>>   block/qcow2.c                |   5 +-
>>   blockdev.c                   |  28 +++------
>>   8 files changed, 163 insertions(+), 80 deletions(-)
>>
> 
> I'll take this; I imagine the return signatures are going to change
> again with your error propagation series, though ...?
> 

Thanks a lot!

Hmm, I don't think so, as I used to think that returning int for errp-functions
is better anyway..

ret = f(..., errp);
if (ret < 0) {

}

vs

f(..., errp);
if (*errp) {

}

Hmmm... The latter just looks unfamiliar in comparison with "if (ret < 0)".. But
if we anyway going to convert a lot of "if (*local_err)" to "if (*errp)", it will
become familiar.. And the latter may save 6 characters in a line with function call,
which may save the whole line in some places.

So I don't know.

returning two errors is not very good, we don't have convention for it actually.

if I have int ret = f(..., errp), what should I report?

error_report_err_errno(ret, errp), or just error_report_err(errp), assuming errp
contains the whole information?

Still, sometimes we need to distinguish one error code from another, and we can't
check errp for such thing..

-- 
Best regards,
Vladimir

Re: [PATCH v3 0/3] proper locking on bitmap add/remove paths

[John Snow]

On 9/27/19 4:37 AM, Vladimir Sementsov-Ogievskiy wrote:
> 26.09.2019 22:01, John Snow wrote:
>>
>>
>> On 9/20/19 4:25 AM, Vladimir Sementsov-Ogievskiy wrote:
>>> Hi all!
>>>
>>> We need to lock qcow2 mutex on accessing in-image metadata, especially
>>> on updating this metadata. Let's implement it.
>>>
>>> v3:
>>> 01: add John's r-b
>>> 02: - fix bdrv_remove_persistent_dirty_bitmap return value
>>>      - drop extra zeroing of ret in qcow2_remove_persistent_dirty_bitmap
>>> 03: add John's r-b
>>>
>>> Vladimir Sementsov-Ogievskiy (3):
>>>    block: move bdrv_can_store_new_dirty_bitmap to block/dirty-bitmap.c
>>>    block/dirty-bitmap: return int from
>>>      bdrv_remove_persistent_dirty_bitmap
>>>    block/qcow2: proper locking on bitmap add/remove paths
>>>
>>>   block/qcow2.h                |  14 ++---
>>>   include/block/block_int.h    |  14 ++---
>>>   include/block/dirty-bitmap.h |   5 +-
>>>   block.c                      |  22 -------
>>>   block/dirty-bitmap.c         | 119 +++++++++++++++++++++++++++++++++--
>>>   block/qcow2-bitmap.c         |  36 +++++++----
>>>   block/qcow2.c                |   5 +-
>>>   blockdev.c                   |  28 +++------
>>>   8 files changed, 163 insertions(+), 80 deletions(-)
>>>
>>
>> I'll take this; I imagine the return signatures are going to change
>> again with your error propagation series, though ...?
>>
> 
> Thanks a lot!
> 
> Hmm, I don't think so, as I used to think that returning int for errp-functions
> is better anyway..
> 

OK, well, no problem. I'm not very picky about the error propagation
paradigm; since you are investing your effort in it lately I'm just
going to trust your judgment here.

> ret = f(..., errp);
> if (ret < 0) {
> 
> }
> 
> vs
> 
> f(..., errp);
> if (*errp) {
> 
> }
> 
> Hmmm... The latter just looks unfamiliar in comparison with "if (ret < 0)".. But
> if we anyway going to convert a lot of "if (*local_err)" to "if (*errp)", it will
> become familiar.. And the latter may save 6 characters in a line with function call,
> which may save the whole line in some places.
> 
> So I don't know.
> 
> returning two errors is not very good, we don't have convention for it actually.
> 
> if I have int ret = f(..., errp), what should I report?
> 
> error_report_err_errno(ret, errp), or just error_report_err(errp), assuming errp
> contains the whole information?
> 
> Still, sometimes we need to distinguish one error code from another, and we can't
> check errp for such thing..
> 

OK, I just wasn't sure the details of your series, actually -- I just
wanted to know if we'd need to make changes, but if not, that's easier :)

--js