qemu-img info: Optionally show block limits

Add a new --limits option to 'qemu-img info' that displays the block
limits for the image and all of its children, making the information
more accessible for human users than in QMP. This option is not enabled
by default because it can be a lot of output that isn't usually relevant
if you're not specifically trying to diagnose some I/O problem.

This makes the same information automatically also available in HMP
'info block -v'.

Signed-off-by: Kevin Wolf <kwolf@redhat.com>
Reviewed-by: Eric Blake <eblake@redhat.com>
Reviewed-by: Hanna Czenczek <hreitz@redhat.com>
Message-ID: <20251024123041.51254-4-kwolf@redhat.com>
Signed-off-by: Kevin Wolf <kwolf@redhat.com>

diff --git a/block/qapi.c b/block/qapi.c
index 54521d0a68b94462f7260bc0fd6896ddd458a8fe..9f5771e019539d6b27b0e20f68ea6c94c331b1f4 100644 (file)
--- a/block/qapi.c
+++ b/block/qapi.c
@@ -417,6 +417,7 @@ fail:
  */
 void bdrv_query_block_graph_info(BlockDriverState *bs,
                                  BlockGraphInfo **p_info,
+                                 bool limits,
                                  Error **errp)
 {
     ERRP_GUARD();
@@ -425,7 +426,7 @@ void bdrv_query_block_graph_info(BlockDriverState *bs,
     BdrvChild *c;
 
     info = g_new0(BlockGraphInfo, 1);
-    bdrv_do_query_node_info(bs, qapi_BlockGraphInfo_base(info), false, errp);
+    bdrv_do_query_node_info(bs, qapi_BlockGraphInfo_base(info), limits, errp);
     if (*errp) {
         goto fail;
     }
@@ -439,7 +440,7 @@ void bdrv_query_block_graph_info(BlockDriverState *bs,
         QAPI_LIST_APPEND(children_list_tail, c_info);
 
         c_info->name = g_strdup(c->name);
-        bdrv_query_block_graph_info(c->bs, &c_info->info, errp);
+        bdrv_query_block_graph_info(c->bs, &c_info->info, limits, errp);
         if (*errp) {
             goto fail;
         }
@@ -936,6 +937,29 @@ void bdrv_image_info_specific_dump(ImageInfoSpecific *info_spec,
     visit_free(v);
 }
 
+/**
+ * Dumps the given BlockLimitsInfo object in a human-readable form,
+ * prepending an optional prefix if the dump is not empty.
+ */
+static void bdrv_image_info_limits_dump(BlockLimitsInfo *limits,
+                                        const char *prefix,
+                                        int indentation)
+{
+    QObject *obj;
+    Visitor *v = qobject_output_visitor_new(&obj);
+
+    visit_type_BlockLimitsInfo(v, NULL, &limits, &error_abort);
+    visit_complete(v, &obj);
+    if (!qobject_is_empty_dump(obj)) {
+        if (prefix) {
+            qemu_printf("%*s%s", indentation * 4, "", prefix);
+        }
+        dump_qobject(indentation + 1, obj);
+    }
+    qobject_unref(obj);
+    visit_free(v);
+}
+
 /**
  * Print the given @info object in human-readable form.  Every field is indented
  * using the given @indentation (four spaces per indentation level).
@@ -1011,6 +1035,12 @@ void bdrv_node_info_dump(BlockNodeInfo *info, int indentation, bool protocol)
         }
     }
 
+    if (info->limits) {
+        bdrv_image_info_limits_dump(info->limits,
+                                    "Block limits:\n",
+                                    indentation);
+    }
+
     if (info->has_snapshots) {
         SnapshotInfoList *elem;
 

diff --git a/docs/tools/qemu-img.rst b/docs/tools/qemu-img.rst
index 5e7b85079d9cf5c66370312aa77d65dd5fc6976d..fdc9ea9cf2717e46cf286413d6f4e9f3dd882a66 100644 (file)
--- a/docs/tools/qemu-img.rst
+++ b/docs/tools/qemu-img.rst
@@ -503,7 +503,7 @@ Command description:
 
   The size syntax is similar to :manpage:`dd(1)`'s size syntax.
 
-.. option:: info [--object OBJECTDEF] [--image-opts] [-f FMT] [--output=OFMT] [--backing-chain] [-U] FILENAME
+.. option:: info [--object OBJECTDEF] [--image-opts] [-f FMT] [--output=OFMT] [--backing-chain] [--limits] [-U] FILENAME
 
   Give information about the disk image *FILENAME*. Use it in
   particular to know the size reserved on disk which can be different
@@ -571,6 +571,10 @@ Command description:
     ``ImageInfoSpecific*`` QAPI object (e.g. ``ImageInfoSpecificQCow2``
     for qcow2 images).
 
+  *Block limits*
+    The block limits for I/O that QEMU detected for the image.
+    This information is only shown if the ``--limits`` option was specified.
+
 .. option:: map [--object OBJECTDEF] [--image-opts] [-f FMT] [--start-offset=OFFSET] [--max-length=LEN] [--output=OFMT] [-U] FILENAME
 
   Dump the metadata of image *FILENAME* and its backing file chain.

diff --git a/include/block/qapi.h b/include/block/qapi.h
index 54c48de26a386442ec06fd5f5d523c6f1bb56684..be554e53dcaedc6266833176c36d40929bb181b9 100644 (file)
--- a/include/block/qapi.h
+++ b/include/block/qapi.h
@@ -42,7 +42,7 @@ bdrv_query_image_info(BlockDriverState *bs, ImageInfo **p_info, bool flat,
                       bool skip_implicit_filters, Error **errp);
 void GRAPH_RDLOCK
 bdrv_query_block_graph_info(BlockDriverState *bs, BlockGraphInfo **p_info,
-                            Error **errp);
+                            bool limits, Error **errp);
 
 void bdrv_snapshot_dump(QEMUSnapshotInfo *sn);
 void bdrv_image_info_specific_dump(ImageInfoSpecific *info_spec,

diff --git a/qemu-img-cmds.hx b/qemu-img-cmds.hx
index 2c5a8a28f9d12f5b6f0d09a489c001d1bb62ff3d..74b66f9d423ba5198e8f2b54ca9654082a673511 100644 (file)
--- a/qemu-img-cmds.hx
+++ b/qemu-img-cmds.hx
@@ -66,9 +66,9 @@ SRST
 ERST
 
 DEF("info", img_info,
-    "info [--object objectdef] [--image-opts] [-f fmt] [--output=ofmt] [--backing-chain] [-U] filename")
+    "info [--object objectdef] [--image-opts] [-f fmt] [--output=ofmt] [--backing-chain] [--limits] [-U] filename")
 SRST
-.. option:: info [--object OBJECTDEF] [--image-opts] [-f FMT] [--output=OFMT] [--backing-chain] [-U] FILENAME
+.. option:: info [--object OBJECTDEF] [--image-opts] [-f FMT] [--output=OFMT] [--backing-chain] [--limits] [-U] FILENAME
 ERST
 
 DEF("map", img_map,

diff --git a/qemu-img.c b/qemu-img.c
index 7a162fdc08d35d71013ae3a9d9f44e1fc6a10cf7..5cdbeda9699bf1fad8e8db5d2a717111dcb01f93 100644 (file)
--- a/qemu-img.c
+++ b/qemu-img.c
@@ -86,6 +86,7 @@ enum {
     OPTION_BITMAPS = 275,
     OPTION_FORCE = 276,
     OPTION_SKIP_BROKEN = 277,
+    OPTION_LIMITS = 278,
 };
 
 typedef enum OutputFormat {
@@ -3002,7 +3003,8 @@ static gboolean str_equal_func(gconstpointer a, gconstpointer b)
 static BlockGraphInfoList *collect_image_info_list(bool image_opts,
                                                    const char *filename,
                                                    const char *fmt,
-                                                   bool chain, bool force_share)
+                                                   bool chain, bool limits,
+                                                   bool force_share)
 {
     BlockGraphInfoList *head = NULL;
     BlockGraphInfoList **tail = &head;
@@ -3039,7 +3041,7 @@ static BlockGraphInfoList *collect_image_info_list(bool image_opts,
          * the chain manually here.
          */
         bdrv_graph_rdlock_main_loop();
-        bdrv_query_block_graph_info(bs, &info, &err);
+        bdrv_query_block_graph_info(bs, &info, limits, &err);
         bdrv_graph_rdunlock_main_loop();
 
         if (err) {
@@ -3088,6 +3090,7 @@ static int img_info(const img_cmd_t *ccmd, int argc, char **argv)
     BlockGraphInfoList *list;
     bool image_opts = false;
     bool force_share = false;
+    bool limits = false;
 
     fmt = NULL;
     for(;;) {
@@ -3097,6 +3100,7 @@ static int img_info(const img_cmd_t *ccmd, int argc, char **argv)
             {"image-opts", no_argument, 0, OPTION_IMAGE_OPTS},
             {"backing-chain", no_argument, 0, OPTION_BACKING_CHAIN},
             {"force-share", no_argument, 0, 'U'},
+            {"limits", no_argument, 0, OPTION_LIMITS},
             {"output", required_argument, 0, OPTION_OUTPUT},
             {"object", required_argument, 0, OPTION_OBJECT},
             {0, 0, 0, 0}
@@ -3119,6 +3123,8 @@ static int img_info(const img_cmd_t *ccmd, int argc, char **argv)
 "     display information about the backing chain for copy-on-write overlays\n"
 "  -U, --force-share\n"
 "     open image in shared mode for concurrent access\n"
+"  --limits\n"
+"     show detected block limits (may depend on options, e.g. cache mode)\n"
 "  --output human|json\n"
 "     specify output format (default: human)\n"
 "  --object OBJDEF\n"
@@ -3140,6 +3146,9 @@ static int img_info(const img_cmd_t *ccmd, int argc, char **argv)
         case 'U':
             force_share = true;
             break;
+        case OPTION_LIMITS:
+            limits = true;
+            break;
         case OPTION_OUTPUT:
             output_format = parse_output_format(argv[0], optarg);
             break;
@@ -3156,7 +3165,7 @@ static int img_info(const img_cmd_t *ccmd, int argc, char **argv)
     filename = argv[optind++];
 
     list = collect_image_info_list(image_opts, filename, fmt, chain,
-                                   force_share);
+                                   limits, force_share);
     if (!list) {
         return 1;
     }