[v2,2/2] hw/block/block.c: improve confusing blk_check_size_and_read_all() error

Commit Message

Manos Pitsidianakis Jan. 23, 2024, 3:35 p.m. UTC

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 <[e-mail]>
Signed-off-by: Manos Pitsidianakis <[e-mail]>
---
 hw/block/block.c         | 25 +++++++++++++++----------
 hw/block/m25p80.c        |  3 ++-
 hw/block/pflash_cfi01.c  |  4 ++--
 hw/block/pflash_cfi02.c  |  2 +-
 include/hw/block/block.h |  4 ++--
 5 files changed, 22 insertions(+), 16 deletions(-)

Comments

Stefan Hajnoczi Jan. 29, 2024, 11:58 p.m. UTC | #1

On Tue, Jan 23, 2024 at 05:35:31PM +0200, Manos Pitsidianakis wrote:
>      if (blk_len != size) {
> -        error_setg(errp, "device requires %" HWADDR_PRIu " bytes, "
> -                   "block backend provides %" PRIu64 " bytes",
> -                   size, blk_len);
> +        dev_id = qdev_get_human_name(dev);
> +        error_setg(errp, "%s device with id='%s' requires %" HWADDR_PRIu

Since qdev_get_human_name() falls back to returning the path instead of
the id, this error message could be confusing. Perhaps avoid saying what
dev_id is and let the user interpret it:

  %s device '%s'

> +                   " 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 with id='%s'",

Same here.

Patch

diff --git a/hw/block/block.c b/hw/block/block.c
index 9f52ee6e72..624389d62d 100644
--- a/hw/block/block.c
+++ b/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,
-                                 Error **errp)
+bool blk_check_size_and_read_all(BlockBackend *blk, DeviceState *dev,
+                                 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, "
-                   "block backend provides %" PRIu64 " bytes",
-                   size, blk_len);
+        dev_id = qdev_get_human_name(dev);
+        error_setg(errp, "%s device with id='%s' requires %" HWADDR_PRIu
+                   " 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 with id='%s'",
+                         blk_name(blk), object_get_typename(OBJECT(dev)),
+                         dev_id);
         return false;
     }
     return true;
diff --git a/hw/block/m25p80.c b/hw/block/m25p80.c
index 26ce895628..0a12030a3a 100644
--- a/hw/block/m25p80.c
+++ b/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 {
diff --git a/hw/block/pflash_cfi01.c b/hw/block/pflash_cfi01.c
index f956f8bcf7..1bda8424b9 100644
--- a/hw/block/pflash_cfi01.c
+++ b/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,
-                                         errp)) {
+        if (!blk_check_size_and_read_all(pfl->blk, dev, pfl->storage,
+                                         total_len, errp)) {
             vmstate_unregister_ram(&pfl->mem, DEVICE(pfl));
             return;
         }
diff --git a/hw/block/pflash_cfi02.c b/hw/block/pflash_cfi02.c
index 6fa56f14c0..2314142373 100644
--- a/hw/block/pflash_cfi02.c
+++ b/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;
diff --git a/include/hw/block/block.h b/include/hw/block/block.h
index 15fff66435..de3946a5f1 100644
--- a/include/hw/block/block.h
+++ b/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,
-                                 Error **errp);
+bool blk_check_size_and_read_all(BlockBackend *blk, DeviceState *dev,
+                                 void *buf, hwaddr size, Error **errp);
 
 /* Configuration helpers */