[Qemu-devel] [PATCH 25/25] qcow2-bitmap: improve check_constraints_on_bitmap

[Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>]

Add detailed error messages.

Signed-off-by: Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>
---
 block/qcow2-bitmap.c | 63 ++++++++++++++++++++++++++++++++++------------------
 1 file changed, 41 insertions(+), 22 deletions(-)

diff --git a/block/qcow2-bitmap.c b/block/qcow2-bitmap.c
index 7ad1f7c..113d48c 100644
--- a/block/qcow2-bitmap.c
+++ b/block/qcow2-bitmap.c
@@ -160,28 +160,49 @@ static int check_table_entry(uint64_t entry, int cluster_size)
 
 static int check_constraints_on_bitmap(BlockDriverState *bs,
                                        const char *name,
-                                       uint32_t granularity)
+                                       uint32_t granularity,
+                                       Error **errp)
 {
     BDRVQcow2State *s = bs->opaque;
     int granularity_bits = ctz32(granularity);
     int64_t len = bdrv_getlength(bs);
-    bool fail;
 
     assert(granularity > 0);
     assert((granularity & (granularity - 1)) == 0);
 
     if (len < 0) {
+        error_setg_errno(errp, -len, "Failed to get size of '%s'",
+                         bdrv_get_device_or_node_name(bs));
         return len;
     }
 
-    fail = (granularity_bits > BME_MAX_GRANULARITY_BITS) ||
-           (granularity_bits < BME_MIN_GRANULARITY_BITS) ||
-           (len > (uint64_t)BME_MAX_PHYS_SIZE << granularity_bits) ||
-           (len > (uint64_t)BME_MAX_TABLE_SIZE * s->cluster_size <<
-                  granularity_bits) ||
-           (strlen(name) > BME_MAX_NAME_SIZE);
+    if (granularity_bits > BME_MAX_GRANULARITY_BITS) {
+        error_setg(errp, "Granularity exceeds maximum (%u bytes)",
+                   1 << BME_MAX_GRANULARITY_BITS);
+        return -EINVAL;
+    }
+    if (granularity_bits < BME_MIN_GRANULARITY_BITS) {
+        error_setg(errp, "Granularity is under minimum (%u bytes)",
+                   1 << BME_MIN_GRANULARITY_BITS);
+        return -EINVAL;
+    }
 
-    return fail ? -EINVAL : 0;
+    if ((len > (uint64_t)BME_MAX_PHYS_SIZE << granularity_bits) ||
+        (len > (uint64_t)BME_MAX_TABLE_SIZE * s->cluster_size <<
+               granularity_bits))
+    {
+        error_setg(errp, "Too much space will be occupied by the bitmap. "
+                   "Use larger granularity");
+        return -EINVAL;
+    }
+
+    if (strlen(name) > BME_MAX_NAME_SIZE) {
+        error_setg(errp, "Name length exceeds maximum (%u characters)",
+                   BME_MAX_NAME_SIZE);
+        return -EINVAL;
+    }
+
+    return 0;
 }
 
 static void clear_bitmap_table(BlockDriverState *bs, uint64_t *bitmap_table,
@@ -1142,9 +1163,9 @@ void qcow2_store_persistent_dirty_bitmaps(BlockDriverState *bs, Error **errp)
             continue;
         }
 
-        if (check_constraints_on_bitmap(bs, name, granularity) < 0) {
-            error_setg(errp, "Bitmap '%s' doesn't satisfy the constraints",
-                       name);
+        if (check_constraints_on_bitmap(bs, name, granularity, errp) < 0) {
+            error_prepend(errp, "Bitmap '%s' doesn't satisfy the constraints: ",
+                          name);
             goto fail;
         }
 
@@ -1230,13 +1251,11 @@ bool qcow2_can_store_new_dirty_bitmap(BlockDriverState *bs,
                                       Error **errp)
 {
     BDRVQcow2State *s = bs->opaque;
-    const char *reason = NULL;
     bool found;
     Qcow2BitmapList *bm_list;
 
-    if (check_constraints_on_bitmap(bs, name, granularity) != 0) {
-        reason = "it doesn't satisfy the constraints";
-        goto common_errp;
+    if (check_constraints_on_bitmap(bs, name, granularity, errp) != 0) {
+        goto fail;
     }
 
     if (s->nb_bitmaps == 0) {
@@ -1246,21 +1265,21 @@ bool qcow2_can_store_new_dirty_bitmap(BlockDriverState *bs,
     bm_list = bitmap_list_load(bs, s->bitmap_directory_offset,
                                s->bitmap_directory_size, errp);
     if (bm_list == NULL) {
-        return false;
+        goto fail;
     }
 
     found = find_bitmap_by_name(bm_list, name);
     bitmap_list_free(bm_list);
     if (found) {
-        reason = "bitmap with the same name is already stored";
-        goto common_errp;
+        error_setg(errp, "Bitmap with the same name is already stored");
+        goto fail;
     }
 
     return true;
 
-common_errp:
-    error_setg(errp, "Can't make bitmap '%s' persistent in '%s', as %s.",
-               name, bdrv_get_device_or_node_name(bs), reason);
+fail:
+    error_prepend(errp, "Can't make bitmap '%s' persistent in '%s': ",
+                  name, bdrv_get_device_or_node_name(bs));
     return false;
 }
 
-- 
1.8.3.1