[Qemu-devel] [PATCH 1/3] block: include base when checking image chain for block allocation

[Andrey Shinkevich]

A caller of the function bdrv_is_allocated_above() may want to
include the base node in the search. It is useful when we have
parallel commit/stream jobs on the same backing image chain. The
base node may be a top one of a parallel job at the same time
and go away before the first job completed. Instead of base, pass
the node that has the base as its backing one to the new function
bdrv_is_allocated_above_inclusive() to manage the issue.

Suggested-by: Vladimir Sementsov-Ogievskiy <address@hidden>
Signed-off-by: Andrey Shinkevich <address@hidden>
---
 block/io.c            | 39 ++++++++++++++++++++++++++++++++++-----
 include/block/block.h |  5 ++++-
 2 files changed, 38 insertions(+), 6 deletions(-)

diff --git a/block/io.c b/block/io.c
index dfc153b..8b273e5 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 +2330,21 @@ 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;
+    bool exit_loop = top == base ? true : false;
+    /* Sanity check */
+    base_included = base ? base_included : false;
+    bool include_node = top == base ? base_included : true;
 
     intermediate = top;
-    while (intermediate && intermediate != base) {
+    while (intermediate && include_node) {
         int64_t pnum_inter;
         int64_t size_inter;
 
@@ -2361,12 +2367,35 @@ int bdrv_is_allocated_above(BlockDriverState *top,
         }
 
         intermediate = backing_bs(intermediate);
+        include_node = intermediate != base;
+        if (exit_loop) {
+            include_node = false;
+        } else if (!include_node && base_included) {
+            /* Iterate once more */
+            include_node = true;
+            exit_loop = true;
+        }
     }
 
     *pnum = n;
     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