hw/block/block.c: improve confusing blk_check_size_and_read_all() error

In cases where a device tries to read more bytes than the block device
contains, the error is vague: "device requires X bytes, block backend
provides Y bytes".

This patch changes the errors of this function to include the block
backend name, the device id and device type name where appropriate.

Reviewed-by: Philippe Mathieu-Daudé <philmd@linaro.org>
Signed-off-by: Manos Pitsidianakis <manos.pitsidianakis@linaro.org>
Message-id: 7260eadff22c08457740117c1bb7bd2b4353acb9.1706598705.git.manos.pitsidianakis@linaro.org
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>

hw/block/block.c

@@ -54,29 +54,30 @@ static int blk_pread_nonzeroes(BlockBackend *blk, hwaddr size, void *buf)
  * BDRV_REQUEST_MAX_BYTES.
  * On success, return true.
  * On failure, store an error through @errp and return false.
- * Note that the error messages do not identify the block backend.
+ *
- * TODO Since callers don't either, this can result in confusing
- * errors.
  * This function not intended for actual block devices, which read on
  * demand.  It's for things like memory devices that (ab)use a block
  * backend to provide persistence.
  */
-bool blk_check_size_and_read_all(BlockBackend *blk, void *buf, hwaddr size,
+bool blk_check_size_and_read_all(BlockBackend *blk, DeviceState *dev,
-                                 Error **errp)
+                                 void *buf, hwaddr size, Error **errp)
 {
     int64_t blk_len;
     int ret;
+    g_autofree char *dev_id = NULL;
 
     blk_len = blk_getlength(blk);
     if (blk_len < 0) {
         error_setg_errno(errp, -blk_len,
-                         "can't get size of block backend");
+                         "can't get size of %s block backend", blk_name(blk));
         return false;
     }
     if (blk_len != size) {
-        error_setg(errp, "device requires %" HWADDR_PRIu " bytes, "
+        dev_id = qdev_get_human_name(dev);
-                   "block backend provides %" PRIu64 " bytes",
+        error_setg(errp, "%s device '%s' requires %" HWADDR_PRIu
-                   size, blk_len);
+                   " bytes, %s block backend provides %" PRIu64 " bytes",
+                   object_get_typename(OBJECT(dev)), dev_id, size,
+                   blk_name(blk), blk_len);
         return false;
     }
 
@@ -89,7 +90,11 @@ bool blk_check_size_and_read_all(BlockBackend *blk, void *buf, hwaddr size,
     assert(size <= BDRV_REQUEST_MAX_BYTES);
     ret = blk_pread_nonzeroes(blk, size, buf);
     if (ret < 0) {
-        error_setg_errno(errp, -ret, "can't read block backend");
+        dev_id = qdev_get_human_name(dev);
+        error_setg_errno(errp, -ret, "can't read %s block backend"
+                         " for %s device '%s'",
+                         blk_name(blk), object_get_typename(OBJECT(dev)),
+                         dev_id);
         return false;
     }
     return true;

hw/block/m25p80.c

@@ -1617,7 +1617,8 @@ static void m25p80_realize(SSIPeripheral *ss, Error **errp)
         trace_m25p80_binding(s);
         s->storage = blk_blockalign(s->blk, s->size);
 
-        if (!blk_check_size_and_read_all(s->blk, s->storage, s->size, errp)) {
+        if (!blk_check_size_and_read_all(s->blk, DEVICE(s),
+                                         s->storage, s->size, errp)) {
             return;
         }
     } else {

hw/block/pflash_cfi01.c

@@ -848,8 +848,8 @@ static void pflash_cfi01_realize(DeviceState *dev, Error **errp)
     }
 
     if (pfl->blk) {
-        if (!blk_check_size_and_read_all(pfl->blk, pfl->storage, total_len,
+        if (!blk_check_size_and_read_all(pfl->blk, dev, pfl->storage,
-                                         errp)) {
+                                         total_len, errp)) {
             vmstate_unregister_ram(&pfl->mem, DEVICE(pfl));
             return;
         }

hw/block/pflash_cfi02.c

@@ -902,7 +902,7 @@ static void pflash_cfi02_realize(DeviceState *dev, Error **errp)
     }
 
     if (pfl->blk) {
-        if (!blk_check_size_and_read_all(pfl->blk, pfl->storage,
+        if (!blk_check_size_and_read_all(pfl->blk, dev, pfl->storage,
                                          pfl->chip_len, errp)) {
             vmstate_unregister_ram(&pfl->orig_mem, DEVICE(pfl));
             return;

include/hw/block/block.h

@@ -88,8 +88,8 @@ static inline unsigned int get_physical_block_exp(BlockConf *conf)
 
 /* Backend access helpers */
 
-bool blk_check_size_and_read_all(BlockBackend *blk, void *buf, hwaddr size,
+bool blk_check_size_and_read_all(BlockBackend *blk, DeviceState *dev,
-                                 Error **errp);
+                                 void *buf, hwaddr size, Error **errp);
 
 /* Configuration helpers */