block: expect errors from bdrv_co_is_allocated

Some bdrv_is_allocated callers do not expect errors, but the fallback
in qcow2.c might make other callers trip on assertion failures or
infinite loops.

Fix the callers to always look for errors.

Cc: qemu-stable@nongnu.org
Reviewed-by: Eric Blake <eblake@redhat.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>

6 files changed, 30 insertions, 9 deletions

diff --git a/block.c b/block.c
index c6404eb..5df17de 100644
--- a/block.c
+++ b/block.c
@@ -1857,8 +1857,11 @@ int bdrv_commit(BlockDriverState *bs)
     buf = g_malloc(COMMIT_BUF_SECTORS * BDRV_SECTOR_SIZE);
 
     for (sector = 0; sector < total_sectors; sector += n) {
-        if (bdrv_is_allocated(bs, sector, COMMIT_BUF_SECTORS, &n)) {
-
+        ret = bdrv_is_allocated(bs, sector, COMMIT_BUF_SECTORS, &n);
+        if (ret < 0) {
+            goto ro_cleanup;
+        }
+        if (ret) {
             if (bdrv_read(bs, sector, buf, n) != 0) {
                 ret = -EIO;
                 goto ro_cleanup;
diff --git a/block/cow.c b/block/cow.c
index f4eca10..7450801 100644
--- a/block/cow.c
+++ b/block/cow.c
@@ -212,7 +212,11 @@ static int coroutine_fn cow_read(BlockDriverState *bs, int64_t sector_num,
     int ret, n;
 
     while (nb_sectors > 0) {
-        if (cow_co_is_allocated(bs, sector_num, nb_sectors, &n)) {
+        ret = cow_co_is_allocated(bs, sector_num, nb_sectors, &n);
+        if (ret < 0) {
+            return ret;
+        }
+        if (ret) {
             ret = bdrv_pread(bs->file,
                         s->cow_sectors_offset + sector_num * 512,
                         buf, n * 512);
diff --git a/block/qcow2.c b/block/qcow2.c
index 4d7bd78..cf03a14 100644
--- a/block/qcow2.c
+++ b/block/qcow2.c
@@ -696,13 +696,11 @@ static int coroutine_fn qcow2_co_is_allocated(BlockDriverState *bs,
     int ret;
 
     *pnum = nb_sectors;
-    /* FIXME We can get errors here, but the bdrv_co_is_allocated interface
-     * can't pass them on today */
     qemu_co_mutex_lock(&s->lock);
     ret = qcow2_get_cluster_offset(bs, sector_num << 9, pnum, &cluster_offset);
     qemu_co_mutex_unlock(&s->lock);
     if (ret < 0) {
-        *pnum = 0;
+        return ret;
     }
 
     return (cluster_offset != 0) || (ret == QCOW2_CLUSTER_ZERO);
diff --git a/block/stream.c b/block/stream.c
index e640bc5..078ce4a 100644
--- a/block/stream.c
+++ b/block/stream.c
@@ -124,7 +124,7 @@ wait:
         if (ret == 1) {
             /* Allocated in the top, no need to copy.  */
             copy = false;
-        } else {
+        } else if (ret >= 0) {
             /* Copy if allocated in the intermediate images.  Limit to the
              * known-unallocated area [sector_num, sector_num+n).  */
             ret = bdrv_is_allocated_above(bs->backing_hd, base,
diff --git a/qemu-img.c b/qemu-img.c
index 744c0d9..27cc006 100644
--- a/qemu-img.c
+++ b/qemu-img.c
@@ -1508,8 +1508,15 @@ static int img_convert(int argc, char **argv)
                    are present in both the output's and input's base images (no
                    need to copy them). */
                 if (out_baseimg) {
-                    if (!bdrv_is_allocated(bs[bs_i], sector_num - bs_offset,
-                                           n, &n1)) {
+                    ret = bdrv_is_allocated(bs[bs_i], sector_num - bs_offset,
+                                            n, &n1);
+                    if (ret < 0) {
+                        error_report("error while reading metadata for sector "
+                                     "%" PRId64 ": %s",
+                                     sector_num - bs_offset, strerror(-ret));
+                        goto out;
+                    }
+                    if (!ret) {
                         sector_num += n1;
                         continue;
                     }
@@ -2099,6 +2106,11 @@ static int img_rebase(int argc, char **argv)
 
             /* If the cluster is allocated, we don't need to take action */
             ret = bdrv_is_allocated(bs, sector, n, &n);
+            if (ret < 0) {
+                error_report("error while reading image metadata: %s",
+                             strerror(-ret));
+                goto out;
+            }
             if (ret) {
                 continue;
             }
diff --git a/qemu-io-cmds.c b/qemu-io-cmds.c
index f91b6c4..8565d49 100644
--- a/qemu-io-cmds.c
+++ b/qemu-io-cmds.c
@@ -1830,6 +1830,10 @@ static int alloc_f(BlockDriverState *bs, int argc, char **argv)
     sector_num = offset >> 9;
     while (remaining) {
         ret = bdrv_is_allocated(bs, sector_num, remaining, &num);
+        if (ret < 0) {
+            printf("is_allocated failed: %s\n", strerror(-ret));
+            return 0;
+        }
         sector_num += num;
         remaining -= num;
         if (ret) {