This patch is used in the 'block/stream: introduce a bottom node'
that is following. Instead of the base node, the caller may pass
the node that has the base as its backing image to the new function
bdrv_is_allocated_above_inclusive() and get rid of the dependency
on the base that may change during commit/stream parallel jobs.
If the specified base is not found in the backing image chain, the
function fails.

Suggested-by: Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>
Signed-off-by: Andrey Shinkevich <andrey.shinkevich@virtuozzo.com>
---
 block/io.c            | 32 +++++++++++++++++++++++++++-----
 include/block/block.h |  5 ++++-
 2 files changed, 31 insertions(+), 6 deletions(-)

diff --git a/block/io.c b/block/io.c
index dfc153b..7edeeb2 100644
--- a/block/io.c
+++ b/block/io.c
@@ -2317,7 +2317,8 @@ int coroutine_fn bdrv_is_allocated(BlockDriverState *bs, int64_t offset,
  * Given an image chain: ... -> [BASE] -> [INTER1] -> [INTER2] -> [TOP]
  *
  * Return true if (a prefix of) the given range is allocated in any image
- * between BASE and TOP (inclusive).  BASE can be NULL to check if the given
+ * between BASE and TOP (TOP included). To check the BASE image, set the
+ * 'base_included' to 'true'. The BASE can be NULL to check if the given
  * offset is allocated in any image of the chain.  Return false otherwise,
  * or negative errno on failure.
  *
@@ -2329,16 +2330,18 @@ int coroutine_fn bdrv_is_allocated(BlockDriverState *bs, int64_t offset,
  * but 'pnum' will only be 0 when end of file is reached.
  *
  */
-int bdrv_is_allocated_above(BlockDriverState *top,
-                            BlockDriverState *base,
-                            int64_t offset, int64_t bytes, int64_t *pnum)
+static int bdrv_do_is_allocated_above(BlockDriverState *top,
+                                      BlockDriverState *base,
+                                      bool base_included, int64_t offset,
+                                      int64_t bytes, int64_t *pnum)
 {
     BlockDriverState *intermediate;
     int ret;
     int64_t n = bytes;
+    assert(base || !base_included);
 
     intermediate = top;
-    while (intermediate && intermediate != base) {
+    while (base_included || intermediate != base) {
         int64_t pnum_inter;
         int64_t size_inter;
 
@@ -2360,6 +2363,10 @@ int bdrv_is_allocated_above(BlockDriverState *top,
             n = pnum_inter;
         }
 
+        if (intermediate == base) {
+            break;
+        }
+
         intermediate = backing_bs(intermediate);
     }
 
@@ -2367,6 +2374,21 @@ int bdrv_is_allocated_above(BlockDriverState *top,
     return 0;
 }
 
+int bdrv_is_allocated_above(BlockDriverState *top,
+                            BlockDriverState *base,
+                            int64_t offset, int64_t bytes, int64_t *pnum)
+{
+    return bdrv_do_is_allocated_above(top, base, false, offset, bytes, pnum);
+}
+
+int bdrv_is_allocated_above_inclusive(BlockDriverState *top,
+                                      BlockDriverState *base,
+                                      int64_t offset, int64_t bytes,
+                                      int64_t *pnum)
+{
+    return bdrv_do_is_allocated_above(top, base, true, offset, bytes, pnum);
+}
+
 typedef struct BdrvVmstateCo {
     BlockDriverState    *bs;
     QEMUIOVector        *qiov;
diff --git a/include/block/block.h b/include/block/block.h
index c7a2619..a7846d9 100644
--- a/include/block/block.h
+++ b/include/block/block.h
@@ -448,7 +448,10 @@ int bdrv_is_allocated(BlockDriverState *bs, int64_t offset, int64_t bytes,
                       int64_t *pnum);
 int bdrv_is_allocated_above(BlockDriverState *top, BlockDriverState *base,
                             int64_t offset, int64_t bytes, int64_t *pnum);
-
+int bdrv_is_allocated_above_inclusive(BlockDriverState *top,
+                                      BlockDriverState *base,
+                                      int64_t offset, int64_t bytes,
+                                      int64_t *pnum);
 bool bdrv_is_read_only(BlockDriverState *bs);
 int bdrv_can_set_read_only(BlockDriverState *bs, bool read_only,
                            bool ignore_allow_rdw, Error **errp);
-- 
1.8.3.1

01.04.2019 15:06, Andrey Shinkevich wrote:
> This patch is used in the 'block/stream: introduce a bottom node'
> that is following. Instead of the base node, the caller may pass
> the node that has the base as its backing image to the new function
> bdrv_is_allocated_above_inclusive() and get rid of the dependency
> on the base that may change during commit/stream parallel jobs.
> If the specified base is not found in the backing image chain, the
> function fails.

More honest: s/fail/now crashes/

And I think it's correct. But it would be good to check all callers.. Do we
freeze backing chain in all cases before calling this function?

> 
> Suggested-by: Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>
> Signed-off-by: Andrey Shinkevich <andrey.shinkevich@virtuozzo.com>
> ---
>   block/io.c            | 32 +++++++++++++++++++++++++++-----
>   include/block/block.h |  5 ++++-
>   2 files changed, 31 insertions(+), 6 deletions(-)
> 
> diff --git a/block/io.c b/block/io.c
> index dfc153b..7edeeb2 100644
> --- a/block/io.c
> +++ b/block/io.c
> @@ -2317,7 +2317,8 @@ int coroutine_fn bdrv_is_allocated(BlockDriverState *bs, int64_t offset,
>    * Given an image chain: ... -> [BASE] -> [INTER1] -> [INTER2] -> [TOP]
>    *
>    * Return true if (a prefix of) the given range is allocated in any image
> - * between BASE and TOP (inclusive).  BASE can be NULL to check if the given
> + * between BASE and TOP (TOP included). To check the BASE image, set the
> + * 'base_included' to 'true'. The BASE can be NULL to check if the given
>    * offset is allocated in any image of the chain.  Return false otherwise,
>    * or negative errno on failure.
>    *
> @@ -2329,16 +2330,18 @@ int coroutine_fn bdrv_is_allocated(BlockDriverState *bs, int64_t offset,
>    * but 'pnum' will only be 0 when end of file is reached.
>    *
>    */
> -int bdrv_is_allocated_above(BlockDriverState *top,
> -                            BlockDriverState *base,
> -                            int64_t offset, int64_t bytes, int64_t *pnum)
> +static int bdrv_do_is_allocated_above(BlockDriverState *top,
> +                                      BlockDriverState *base,
> +                                      bool base_included, int64_t offset,
> +                                      int64_t bytes, int64_t *pnum)
>   {
>       BlockDriverState *intermediate;
>       int ret;
>       int64_t n = bytes;

empty line after variable definitions

> +    assert(base || !base_included);
>   
>       intermediate = top;
> -    while (intermediate && intermediate != base) {
> +    while (base_included || intermediate != base) {
>           int64_t pnum_inter;
>           int64_t size_inter;
>   
> @@ -2360,6 +2363,10 @@ int bdrv_is_allocated_above(BlockDriverState *top,
>               n = pnum_inter;
>           }
>   
> +        if (intermediate == base) {
> +            break;
> +        }
> +
>           intermediate = backing_bs(intermediate);
>       }
>   
> @@ -2367,6 +2374,21 @@ int bdrv_is_allocated_above(BlockDriverState *top,
>       return 0;
>   }
>   
> +int bdrv_is_allocated_above(BlockDriverState *top,
> +                            BlockDriverState *base,
> +                            int64_t offset, int64_t bytes, int64_t *pnum)
> +{
> +    return bdrv_do_is_allocated_above(top, base, false, offset, bytes, pnum);
> +}
> +
> +int bdrv_is_allocated_above_inclusive(BlockDriverState *top,
> +                                      BlockDriverState *base,
> +                                      int64_t offset, int64_t bytes,
> +                                      int64_t *pnum)
> +{
> +    return bdrv_do_is_allocated_above(top, base, true, offset, bytes, pnum);
> +}
> +
>   typedef struct BdrvVmstateCo {
>       BlockDriverState    *bs;
>       QEMUIOVector        *qiov;
> diff --git a/include/block/block.h b/include/block/block.h
> index c7a2619..a7846d9 100644
> --- a/include/block/block.h
> +++ b/include/block/block.h
> @@ -448,7 +448,10 @@ int bdrv_is_allocated(BlockDriverState *bs, int64_t offset, int64_t bytes,
>                         int64_t *pnum);
>   int bdrv_is_allocated_above(BlockDriverState *top, BlockDriverState *base,
>                               int64_t offset, int64_t bytes, int64_t *pnum);
> -
> +int bdrv_is_allocated_above_inclusive(BlockDriverState *top,
> +                                      BlockDriverState *base,
> +                                      int64_t offset, int64_t bytes,
> +                                      int64_t *pnum);

dropped empty line better stay here.

>   bool bdrv_is_read_only(BlockDriverState *bs);
>   int bdrv_can_set_read_only(BlockDriverState *bs, bool read_only,
>                              bool ignore_allow_rdw, Error **errp);
> 


Reviewed-by: Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>

-- 
Best regards,
Vladimir