Patchwork [2/5] block/dirty-bitmaps: rename frozen predicate helper

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Submitter John Snow
Date Feb. 12, 2019, 1:02 a.m.
Message ID <20190212010248.11056-3-jsnow@redhat.com>
Download mbox | patch
Permalink /patch/723463/
State New
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Comments

John Snow - Feb. 12, 2019, 1:02 a.m.
"Frozen" was a good description a long time ago, but it isn't adequate now.
Rename the frozen predicate to has_successor to make the semantics of the
predicate more clear to outside callers.

In the process, remove some calls to frozen() that no longer semantically
make sense. For enabled and disabled in particular, it's actually okay for
the internals to do this but only forbidden for users to invoke them, and
all of the QMP entry uses already check against qmp_locked.

Several other assertions really want to check that the bitmap isn't in-use
by another operation -- use the qmp_locked function for this instead, which
presently also checks for has_successor.
---
 block/dirty-bitmap.c           | 32 +++++++++++++++++---------------
 include/block/dirty-bitmap.h   |  2 +-
 migration/block-dirty-bitmap.c |  2 +-
 3 files changed, 19 insertions(+), 17 deletions(-)
Eric Blake - Feb. 12, 2019, 6:26 p.m.
On 2/11/19 7:02 PM, John Snow wrote:
> "Frozen" was a good description a long time ago, but it isn't adequate now.
> Rename the frozen predicate to has_successor to make the semantics of the
> predicate more clear to outside callers.
> 
> In the process, remove some calls to frozen() that no longer semantically
> make sense. For enabled and disabled in particular, it's actually okay for
> the internals to do this but only forbidden for users to invoke them, and
> all of the QMP entry uses already check against qmp_locked.
> 
> Several other assertions really want to check that the bitmap isn't in-use
> by another operation -- use the qmp_locked function for this instead, which
> presently also checks for has_successor.
> ---

Missing S-o-b on entire series, so you have to send v2 anyway :)

> @@ -244,12 +244,16 @@ int bdrv_dirty_bitmap_create_successor(BlockDriverState *bs,
>      uint64_t granularity;
>      BdrvDirtyBitmap *child;
>  
> -    if (bdrv_dirty_bitmap_frozen(bitmap)) {
> -        error_setg(errp, "Cannot create a successor for a bitmap that is "
> -                   "currently frozen");
> +    if (bdrv_dirty_bitmap_has_successor(bitmap)) {
> +        error_setg(errp, "Cannot create a successor for a bitmap that already "
> +                   "has one");
> +        return -1;
> +    }
> +    if (bdrv_dirty_bitmap_user_locked(bitmap)) {
> +        error_setg(errp, "Cannot create a successor for a bitmap that is in-use "
> +                   "by an operation.");
>          return -1;

No trailing dot in error_setg().

Should these two errors be swapped (check for locked before
has_successor)?  After all, having a successor is an internal detail,
whereas being in use by something I already triggered is fairly
straightforward to understand.


> @@ -325,7 +328,7 @@ BdrvDirtyBitmap *bdrv_dirty_bitmap_abdicate(BlockDriverState *bs,
>  /**
>   * In cases of failure where we can no longer safely delete the parent,
>   * we may wish to re-join the parent and child/successor.
> - * The merged parent will be un-frozen, but not explicitly re-enabled.
> + * The merged parent will not be user_locked, but not explicitly re-enabled.

s/but not/nor/
John Snow - Feb. 12, 2019, 6:30 p.m.
On 2/12/19 1:26 PM, Eric Blake wrote:
> On 2/11/19 7:02 PM, John Snow wrote:
>> "Frozen" was a good description a long time ago, but it isn't adequate now.
>> Rename the frozen predicate to has_successor to make the semantics of the
>> predicate more clear to outside callers.
>>
>> In the process, remove some calls to frozen() that no longer semantically
>> make sense. For enabled and disabled in particular, it's actually okay for
>> the internals to do this but only forbidden for users to invoke them, and
>> all of the QMP entry uses already check against qmp_locked.
>>
>> Several other assertions really want to check that the bitmap isn't in-use
>> by another operation -- use the qmp_locked function for this instead, which
>> presently also checks for has_successor.
>> ---
> 
> Missing S-o-b on entire series, so you have to send v2 anyway :)
> 
>> @@ -244,12 +244,16 @@ int bdrv_dirty_bitmap_create_successor(BlockDriverState *bs,
>>      uint64_t granularity;
>>      BdrvDirtyBitmap *child;
>>  
>> -    if (bdrv_dirty_bitmap_frozen(bitmap)) {
>> -        error_setg(errp, "Cannot create a successor for a bitmap that is "
>> -                   "currently frozen");
>> +    if (bdrv_dirty_bitmap_has_successor(bitmap)) {
>> +        error_setg(errp, "Cannot create a successor for a bitmap that already "
>> +                   "has one");
>> +        return -1;
>> +    }
>> +    if (bdrv_dirty_bitmap_user_locked(bitmap)) {
>> +        error_setg(errp, "Cannot create a successor for a bitmap that is in-use "
>> +                   "by an operation.");
>>          return -1;
> 
> No trailing dot in error_setg().
> 

D'oh. I need to re-enable checkpatch, obviously.

> Should these two errors be swapped (check for locked before
> has_successor)?  After all, having a successor is an internal detail,
> whereas being in use by something I already triggered is fairly
> straightforward to understand.
> 

Good point. Will do.

> 
>> @@ -325,7 +328,7 @@ BdrvDirtyBitmap *bdrv_dirty_bitmap_abdicate(BlockDriverState *bs,
>>  /**
>>   * In cases of failure where we can no longer safely delete the parent,
>>   * we may wish to re-join the parent and child/successor.
>> - * The merged parent will be un-frozen, but not explicitly re-enabled.
>> + * The merged parent will not be user_locked, but not explicitly re-enabled.
> 
> s/but not/nor/
> 

I was trying to draw a contrast between "We will forcibly set locked =
false, but make no guaranteed about enable/disable."

I guess nor still works in that case.

Patch

diff --git a/block/dirty-bitmap.c b/block/dirty-bitmap.c
index 101383b3af..dbe2d97d3f 100644
--- a/block/dirty-bitmap.c
+++ b/block/dirty-bitmap.c
@@ -50,7 +50,7 @@  struct BdrvDirtyBitmap {
     HBitmap *meta;              /* Meta dirty bitmap */
     bool qmp_locked;            /* Bitmap is locked, it can't be modified
                                    through QMP */
-    BdrvDirtyBitmap *successor; /* Anonymous child; implies frozen status */
+    BdrvDirtyBitmap *successor; /* Anonymous child; implies user_locked state */
     char *name;                 /* Optional non-empty unique ID */
     int64_t size;               /* Size of the bitmap, in bytes */
     bool disabled;              /* Bitmap is disabled. It ignores all writes to
@@ -183,14 +183,14 @@  const char *bdrv_dirty_bitmap_name(const BdrvDirtyBitmap *bitmap)
 }
 
 /* Called with BQL taken.  */
-bool bdrv_dirty_bitmap_frozen(BdrvDirtyBitmap *bitmap)
+bool bdrv_dirty_bitmap_has_successor(BdrvDirtyBitmap *bitmap)
 {
     return bitmap->successor;
 }
 
 /* Both conditions disallow user-modification via QMP. */
 bool bdrv_dirty_bitmap_user_locked(BdrvDirtyBitmap *bitmap) {
-    return bdrv_dirty_bitmap_frozen(bitmap) ||
+    return bdrv_dirty_bitmap_has_successor(bitmap) ||
            bdrv_dirty_bitmap_qmp_locked(bitmap);
 }
 
@@ -215,7 +215,7 @@  bool bdrv_dirty_bitmap_enabled(BdrvDirtyBitmap *bitmap)
 /* Called with BQL taken.  */
 DirtyBitmapStatus bdrv_dirty_bitmap_status(BdrvDirtyBitmap *bitmap)
 {
-    if (bdrv_dirty_bitmap_frozen(bitmap)) {
+    if (bdrv_dirty_bitmap_has_successor(bitmap)) {
         return DIRTY_BITMAP_STATUS_FROZEN;
     } else if (bdrv_dirty_bitmap_qmp_locked(bitmap)) {
         return DIRTY_BITMAP_STATUS_LOCKED;
@@ -235,7 +235,7 @@  static bool bdrv_dirty_bitmap_recording(BdrvDirtyBitmap *bitmap)
 
 /**
  * Create a successor bitmap destined to replace this bitmap after an operation.
- * Requires that the bitmap is not frozen and has no successor.
+ * Requires that the bitmap is not locked and has no successor.
  * Called with BQL taken.
  */
 int bdrv_dirty_bitmap_create_successor(BlockDriverState *bs,
@@ -244,12 +244,16 @@  int bdrv_dirty_bitmap_create_successor(BlockDriverState *bs,
     uint64_t granularity;
     BdrvDirtyBitmap *child;
 
-    if (bdrv_dirty_bitmap_frozen(bitmap)) {
-        error_setg(errp, "Cannot create a successor for a bitmap that is "
-                   "currently frozen");
+    if (bdrv_dirty_bitmap_has_successor(bitmap)) {
+        error_setg(errp, "Cannot create a successor for a bitmap that already "
+                   "has one");
+        return -1;
+    }
+    if (bdrv_dirty_bitmap_user_locked(bitmap)) {
+        error_setg(errp, "Cannot create a successor for a bitmap that is in-use "
+                   "by an operation.");
         return -1;
     }
-    assert(!bitmap->successor);
 
     /* Create an anonymous successor */
     granularity = bdrv_dirty_bitmap_granularity(bitmap);
@@ -268,7 +272,6 @@  int bdrv_dirty_bitmap_create_successor(BlockDriverState *bs,
 
 void bdrv_enable_dirty_bitmap_locked(BdrvDirtyBitmap *bitmap)
 {
-    assert(!bdrv_dirty_bitmap_frozen(bitmap));
     bitmap->disabled = false;
 }
 
@@ -285,7 +288,7 @@  void bdrv_dirty_bitmap_enable_successor(BdrvDirtyBitmap *bitmap)
 static void bdrv_release_dirty_bitmap_locked(BdrvDirtyBitmap *bitmap)
 {
     assert(!bitmap->active_iterators);
-    assert(!bdrv_dirty_bitmap_frozen(bitmap));
+    assert(!bdrv_dirty_bitmap_user_locked(bitmap));
     assert(!bitmap->meta);
     QLIST_REMOVE(bitmap, list);
     hbitmap_free(bitmap->bitmap);
@@ -325,7 +328,7 @@  BdrvDirtyBitmap *bdrv_dirty_bitmap_abdicate(BlockDriverState *bs,
 /**
  * In cases of failure where we can no longer safely delete the parent,
  * we may wish to re-join the parent and child/successor.
- * The merged parent will be un-frozen, but not explicitly re-enabled.
+ * The merged parent will not be user_locked, but not explicitly re-enabled.
  * Called within bdrv_dirty_bitmap_lock..unlock and with BQL taken.
  */
 BdrvDirtyBitmap *bdrv_reclaim_dirty_bitmap_locked(BlockDriverState *bs,
@@ -373,7 +376,7 @@  void bdrv_dirty_bitmap_truncate(BlockDriverState *bs, int64_t bytes)
 
     bdrv_dirty_bitmaps_lock(bs);
     QLIST_FOREACH(bitmap, &bs->dirty_bitmaps, list) {
-        assert(!bdrv_dirty_bitmap_frozen(bitmap));
+        assert(!bdrv_dirty_bitmap_user_locked(bitmap));
         assert(!bitmap->active_iterators);
         hbitmap_truncate(bitmap->bitmap, bytes);
         bitmap->size = bytes;
@@ -391,7 +394,7 @@  void bdrv_release_dirty_bitmap(BlockDriverState *bs, BdrvDirtyBitmap *bitmap)
 
 /**
  * Release all named dirty bitmaps attached to a BDS (for use in bdrv_close()).
- * There must not be any frozen bitmaps attached.
+ * There must not be any user_locked bitmaps attached.
  * This function does not remove persistent bitmaps from the storage.
  * Called with BQL taken.
  */
@@ -428,7 +431,6 @@  void bdrv_remove_persistent_dirty_bitmap(BlockDriverState *bs,
 void bdrv_disable_dirty_bitmap(BdrvDirtyBitmap *bitmap)
 {
     bdrv_dirty_bitmap_lock(bitmap);
-    assert(!bdrv_dirty_bitmap_frozen(bitmap));
     bitmap->disabled = true;
     bdrv_dirty_bitmap_unlock(bitmap);
 }
diff --git a/include/block/dirty-bitmap.h b/include/block/dirty-bitmap.h
index 04a117fc81..cdbb4dfefd 100644
--- a/include/block/dirty-bitmap.h
+++ b/include/block/dirty-bitmap.h
@@ -36,7 +36,7 @@  BlockDirtyInfoList *bdrv_query_dirty_bitmaps(BlockDriverState *bs);
 uint32_t bdrv_get_default_bitmap_granularity(BlockDriverState *bs);
 uint32_t bdrv_dirty_bitmap_granularity(const BdrvDirtyBitmap *bitmap);
 bool bdrv_dirty_bitmap_enabled(BdrvDirtyBitmap *bitmap);
-bool bdrv_dirty_bitmap_frozen(BdrvDirtyBitmap *bitmap);
+bool bdrv_dirty_bitmap_has_successor(BdrvDirtyBitmap *bitmap);
 const char *bdrv_dirty_bitmap_name(const BdrvDirtyBitmap *bitmap);
 int64_t bdrv_dirty_bitmap_size(const BdrvDirtyBitmap *bitmap);
 DirtyBitmapStatus bdrv_dirty_bitmap_status(BdrvDirtyBitmap *bitmap);
diff --git a/migration/block-dirty-bitmap.c b/migration/block-dirty-bitmap.c
index 6426151e4f..ac6954142f 100644
--- a/migration/block-dirty-bitmap.c
+++ b/migration/block-dirty-bitmap.c
@@ -542,7 +542,7 @@  static void dirty_bitmap_load_complete(QEMUFile *f, DirtyBitmapLoadState *s)
         }
     }
 
-    if (bdrv_dirty_bitmap_frozen(s->bitmap)) {
+    if (bdrv_dirty_bitmap_has_successor(s->bitmap)) {
         bdrv_dirty_bitmap_lock(s->bitmap);
         if (enabled_bitmaps == NULL) {
             /* in postcopy */