block: push error reporting into bdrv_all_*_snapshot functions

The bdrv_all_*_snapshot functions return a BlockDriverState pointer
for the invalid backend, which the callers then use to report an
error message. In some cases multiple callers are reporting the
same error message, but with slightly different text. In the future
there will be more error scenarios for some of these methods, which
will benefit from fine grained error message reporting. So it is
helpful to push error reporting down a level.

Reviewed-by: Eric Blake <eblake@redhat.com>
Signed-off-by: Daniel P. Berrangé <berrange@redhat.com>
[PMD: Initialize variables]
Signed-off-by: Philippe Mathieu-Daudé <philmd@redhat.com>
Message-Id: <20210204124834.774401-2-berrange@redhat.com>
Signed-off-by: Dr. David Alan Gilbert <dgilbert@redhat.com>

diff --git a/block/monitor/block-hmp-cmds.c b/block/monitor/block-hmp-cmds.c
index afd75ab628dd435e0cc810f177c4c2fbed1d7169..9532d085eac3065869762918ea709c2defcf57dd 100644 (file)
--- a/block/monitor/block-hmp-cmds.c
+++ b/block/monitor/block-hmp-cmds.c
@@ -900,10 +900,11 @@ void hmp_info_snapshots(Monitor *mon, const QDict *qdict)
 
     ImageEntry *image_entry, *next_ie;
     SnapshotEntry *snapshot_entry;
+    Error *err = NULL;
 
-    bs = bdrv_all_find_vmstate_bs();
+    bs = bdrv_all_find_vmstate_bs(&err);
     if (!bs) {
-        monitor_printf(mon, "No available block device supports snapshots\n");
+        error_report_err(err);
         return;
     }
     aio_context = bdrv_get_aio_context(bs);
@@ -953,7 +954,7 @@ void hmp_info_snapshots(Monitor *mon, const QDict *qdict)
     total = 0;
     for (i = 0; i < nb_sns; i++) {
         SnapshotEntry *next_sn;
-        if (bdrv_all_find_snapshot(sn_tab[i].name, &bs1) == 0) {
+        if (bdrv_all_find_snapshot(sn_tab[i].name, NULL) == 0) {
             global_snapshots[total] = i;
             total++;
             QTAILQ_FOREACH(image_entry, &image_list, next) {

diff --git a/block/snapshot.c b/block/snapshot.c
index a2bf3a54eb08f09e2c0fa837b1282906bae410d2..482e3fc7b72d6c8adf0b1692ce7fd6863c19cbfd 100644 (file)
--- a/block/snapshot.c
+++ b/block/snapshot.c
@@ -462,14 +462,14 @@ static bool bdrv_all_snapshots_includes_bs(BlockDriverState *bs)
  * These functions will properly handle dataplane (take aio_context_acquire
  * when appropriate for appropriate block drivers) */
 
-bool bdrv_all_can_snapshot(BlockDriverState **first_bad_bs)
+bool bdrv_all_can_snapshot(Error **errp)
 {
-    bool ok = true;
     BlockDriverState *bs;
     BdrvNextIterator it;
 
     for (bs = bdrv_first(&it); bs; bs = bdrv_next(&it)) {
         AioContext *ctx = bdrv_get_aio_context(bs);
+        bool ok = true;
 
         aio_context_acquire(ctx);
         if (bdrv_all_snapshots_includes_bs(bs)) {
@@ -477,26 +477,25 @@ bool bdrv_all_can_snapshot(BlockDriverState **first_bad_bs)
         }
         aio_context_release(ctx);
         if (!ok) {
+            error_setg(errp, "Device '%s' is writable but does not support "
+                       "snapshots", bdrv_get_device_or_node_name(bs));
             bdrv_next_cleanup(&it);
-            goto fail;
+            return false;
         }
     }
 
-fail:
-    *first_bad_bs = bs;
-    return ok;
+    return true;
 }
 
-int bdrv_all_delete_snapshot(const char *name, BlockDriverState **first_bad_bs,
-                             Error **errp)
+int bdrv_all_delete_snapshot(const char *name, Error **errp)
 {
-    int ret = 0;
     BlockDriverState *bs;
     BdrvNextIterator it;
     QEMUSnapshotInfo sn1, *snapshot = &sn1;
 
     for (bs = bdrv_first(&it); bs; bs = bdrv_next(&it)) {
         AioContext *ctx = bdrv_get_aio_context(bs);
+        int ret = 0;
 
         aio_context_acquire(ctx);
         if (bdrv_all_snapshots_includes_bs(bs) &&
@@ -507,26 +506,25 @@ int bdrv_all_delete_snapshot(const char *name, BlockDriverState **first_bad_bs,
         }
         aio_context_release(ctx);
         if (ret < 0) {
+            error_prepend(errp, "Could not delete snapshot '%s' on '%s': ",
+                          name, bdrv_get_device_or_node_name(bs));
             bdrv_next_cleanup(&it);
-            goto fail;
+            return -1;
         }
     }
 
-fail:
-    *first_bad_bs = bs;
-    return ret;
+    return 0;
 }
 
 
-int bdrv_all_goto_snapshot(const char *name, BlockDriverState **first_bad_bs,
-                           Error **errp)
+int bdrv_all_goto_snapshot(const char *name, Error **errp)
 {
-    int ret = 0;
     BlockDriverState *bs;
     BdrvNextIterator it;
 
     for (bs = bdrv_first(&it); bs; bs = bdrv_next(&it)) {
         AioContext *ctx = bdrv_get_aio_context(bs);
+        int ret = 0;
 
         aio_context_acquire(ctx);
         if (bdrv_all_snapshots_includes_bs(bs)) {
@@ -534,75 +532,75 @@ int bdrv_all_goto_snapshot(const char *name, BlockDriverState **first_bad_bs,
         }
         aio_context_release(ctx);
         if (ret < 0) {
+            error_prepend(errp, "Could not load snapshot '%s' on '%s': ",
+                          name, bdrv_get_device_or_node_name(bs));
             bdrv_next_cleanup(&it);
-            goto fail;
+            return -1;
         }
     }
 
-fail:
-    *first_bad_bs = bs;
-    return ret;
+    return 0;
 }
 
-int bdrv_all_find_snapshot(const char *name, BlockDriverState **first_bad_bs)
+int bdrv_all_find_snapshot(const char *name, Error **errp)
 {
     QEMUSnapshotInfo sn;
-    int err = 0;
     BlockDriverState *bs;
     BdrvNextIterator it;
 
     for (bs = bdrv_first(&it); bs; bs = bdrv_next(&it)) {
         AioContext *ctx = bdrv_get_aio_context(bs);
+        int ret = 0;
 
         aio_context_acquire(ctx);
         if (bdrv_all_snapshots_includes_bs(bs)) {
-            err = bdrv_snapshot_find(bs, &sn, name);
+            ret = bdrv_snapshot_find(bs, &sn, name);
         }
         aio_context_release(ctx);
-        if (err < 0) {
+        if (ret < 0) {
+            error_setg(errp, "Could not find snapshot '%s' on '%s'",
+                       name, bdrv_get_device_or_node_name(bs));
             bdrv_next_cleanup(&it);
-            goto fail;
+            return -1;
         }
     }
 
-fail:
-    *first_bad_bs = bs;
-    return err;
+    return 0;
 }
 
 int bdrv_all_create_snapshot(QEMUSnapshotInfo *sn,
                              BlockDriverState *vm_state_bs,
                              uint64_t vm_state_size,
-                             BlockDriverState **first_bad_bs)
+                             Error **errp)
 {
-    int err = 0;
     BlockDriverState *bs;
     BdrvNextIterator it;
 
     for (bs = bdrv_first(&it); bs; bs = bdrv_next(&it)) {
         AioContext *ctx = bdrv_get_aio_context(bs);
+        int ret = 0;
 
         aio_context_acquire(ctx);
         if (bs == vm_state_bs) {
             sn->vm_state_size = vm_state_size;
-            err = bdrv_snapshot_create(bs, sn);
+            ret = bdrv_snapshot_create(bs, sn);
         } else if (bdrv_all_snapshots_includes_bs(bs)) {
             sn->vm_state_size = 0;
-            err = bdrv_snapshot_create(bs, sn);
+            ret = bdrv_snapshot_create(bs, sn);
         }
         aio_context_release(ctx);
-        if (err < 0) {
+        if (ret < 0) {
+            error_setg(errp, "Could not create snapshot '%s' on '%s'",
+                       sn->name, bdrv_get_device_or_node_name(bs));
             bdrv_next_cleanup(&it);
-            goto fail;
+            return -1;
         }
     }
 
-fail:
-    *first_bad_bs = bs;
-    return err;
+    return 0;
 }
 
-BlockDriverState *bdrv_all_find_vmstate_bs(void)
+BlockDriverState *bdrv_all_find_vmstate_bs(Error **errp)
 {
     BlockDriverState *bs;
     BdrvNextIterator it;
@@ -620,5 +618,8 @@ BlockDriverState *bdrv_all_find_vmstate_bs(void)
             break;
         }
     }
+    if (!bs) {
+        error_setg(errp, "No block device supports snapshots");
+    }
     return bs;
 }

diff --git a/include/block/snapshot.h b/include/block/snapshot.h
index b0fe42993dccf8d587159cbd6c9824faea6c071e..5cb2b696ad09feda934f512a26eea52156821f8b 100644 (file)
--- a/include/block/snapshot.h
+++ b/include/block/snapshot.h
@@ -77,17 +77,15 @@ int bdrv_snapshot_load_tmp_by_id_or_name(BlockDriverState *bs,
  * These functions will properly handle dataplane (take aio_context_acquire
  * when appropriate for appropriate block drivers */
 
-bool bdrv_all_can_snapshot(BlockDriverState **first_bad_bs);
-int bdrv_all_delete_snapshot(const char *name, BlockDriverState **first_bsd_bs,
-                             Error **errp);
-int bdrv_all_goto_snapshot(const char *name, BlockDriverState **first_bad_bs,
-                           Error **errp);
-int bdrv_all_find_snapshot(const char *name, BlockDriverState **first_bad_bs);
+bool bdrv_all_can_snapshot(Error **errp);
+int bdrv_all_delete_snapshot(const char *name, Error **errp);
+int bdrv_all_goto_snapshot(const char *name, Error **errp);
+int bdrv_all_find_snapshot(const char *name, Error **errp);
 int bdrv_all_create_snapshot(QEMUSnapshotInfo *sn,
                              BlockDriverState *vm_state_bs,
                              uint64_t vm_state_size,
-                             BlockDriverState **first_bad_bs);
+                             Error **errp);
 
-BlockDriverState *bdrv_all_find_vmstate_bs(void);
+BlockDriverState *bdrv_all_find_vmstate_bs(Error **errp);
 
 #endif

diff --git a/migration/savevm.c b/migration/savevm.c
index 1178c6ca90b41a7a5f7a08516d008d07983b4485..948e82c9edc76b9f91b2cbb26c2773772664a77e 100644 (file)
--- a/migration/savevm.c
+++ b/migration/savevm.c
@@ -2766,7 +2766,7 @@ int qemu_load_device_state(QEMUFile *f)
 
 int save_snapshot(const char *name, Error **errp)
 {
-    BlockDriverState *bs, *bs1;
+    BlockDriverState *bs;
     QEMUSnapshotInfo sn1, *sn = &sn1;
     int ret = -1, ret2;
     QEMUFile *f;
@@ -2786,25 +2786,19 @@ int save_snapshot(const char *name, Error **errp)
         return ret;
     }
 
-    if (!bdrv_all_can_snapshot(&bs)) {
-        error_setg(errp, "Device '%s' is writable but does not support "
-                   "snapshots", bdrv_get_device_or_node_name(bs));
+    if (!bdrv_all_can_snapshot(errp)) {
         return ret;
     }
 
     /* Delete old snapshots of the same name */
     if (name) {
-        ret = bdrv_all_delete_snapshot(name, &bs1, errp);
-        if (ret < 0) {
-            error_prepend(errp, "Error while deleting snapshot on device "
-                          "'%s': ", bdrv_get_device_or_node_name(bs1));
+        if (bdrv_all_delete_snapshot(name, errp) < 0) {
             return ret;
         }
     }
 
-    bs = bdrv_all_find_vmstate_bs();
+    bs = bdrv_all_find_vmstate_bs(errp);
     if (bs == NULL) {
-        error_setg(errp, "No block device can accept snapshots");
         return ret;
     }
     aio_context = bdrv_get_aio_context(bs);
@@ -2868,11 +2862,9 @@ int save_snapshot(const char *name, Error **errp)
     aio_context_release(aio_context);
     aio_context = NULL;
 
-    ret = bdrv_all_create_snapshot(sn, bs, vm_state_size, &bs);
+    ret = bdrv_all_create_snapshot(sn, bs, vm_state_size, errp);
     if (ret < 0) {
-        error_setg(errp, "Error while creating snapshot on '%s'",
-                   bdrv_get_device_or_node_name(bs));
-        bdrv_all_delete_snapshot(sn->name, &bs, NULL);
+        bdrv_all_delete_snapshot(sn->name, NULL);
         goto the_end;
     }
 
@@ -2975,30 +2967,23 @@ void qmp_xen_load_devices_state(const char *filename, Error **errp)
 
 int load_snapshot(const char *name, Error **errp)
 {
-    BlockDriverState *bs, *bs_vm_state;
+    BlockDriverState *bs_vm_state;
     QEMUSnapshotInfo sn;
     QEMUFile *f;
     int ret;
     AioContext *aio_context;
     MigrationIncomingState *mis = migration_incoming_get_current();
 
-    if (!bdrv_all_can_snapshot(&bs)) {
-        error_setg(errp,
-                   "Device '%s' is writable but does not support snapshots",
-                   bdrv_get_device_or_node_name(bs));
+    if (!bdrv_all_can_snapshot(errp)) {
         return -ENOTSUP;
     }
-    ret = bdrv_all_find_snapshot(name, &bs);
+    ret = bdrv_all_find_snapshot(name, errp);
     if (ret < 0) {
-        error_setg(errp,
-                   "Device '%s' does not have the requested snapshot '%s'",
-                   bdrv_get_device_or_node_name(bs), name);
         return ret;
     }
 
-    bs_vm_state = bdrv_all_find_vmstate_bs();
+    bs_vm_state = bdrv_all_find_vmstate_bs(errp);
     if (!bs_vm_state) {
-        error_setg(errp, "No block device supports snapshots");
         return -ENOTSUP;
     }
     aio_context = bdrv_get_aio_context(bs_vm_state);
@@ -3024,10 +3009,8 @@ int load_snapshot(const char *name, Error **errp)
     /* Flush all IO requests so they don't interfere with the new state.  */
     bdrv_drain_all_begin();
 
-    ret = bdrv_all_goto_snapshot(name, &bs, errp);
+    ret = bdrv_all_goto_snapshot(name, errp);
     if (ret < 0) {
-        error_prepend(errp, "Could not load snapshot '%s' on '%s': ",
-                      name, bdrv_get_device_or_node_name(bs));
         goto err_drain;
     }
 

diff --git a/monitor/hmp-cmds.c b/monitor/hmp-cmds.c
index 992ecf6f047a053abee6bb54cba582204c8678da..2b954763e484134c847ca881ca762d073ceefdce 100644 (file)
--- a/monitor/hmp-cmds.c
+++ b/monitor/hmp-cmds.c
@@ -1155,15 +1155,10 @@ void hmp_savevm(Monitor *mon, const QDict *qdict)
 
 void hmp_delvm(Monitor *mon, const QDict *qdict)
 {
-    BlockDriverState *bs;
     Error *err = NULL;
     const char *name = qdict_get_str(qdict, "name");
 
-    if (bdrv_all_delete_snapshot(name, &bs, &err) < 0) {
-        error_prepend(&err,
-                      "deleting snapshot on device '%s': ",
-                      bdrv_get_device_name(bs));
-    }
+    bdrv_all_delete_snapshot(name, &err);
     hmp_handle_error(mon, err);
 }
 

diff --git a/replay/replay-debugging.c b/replay/replay-debugging.c
index 5ec574724a2505d44d14714e9b40136c9e5bec09..3a9b609e629aea9216aa8dd417d6e3543d6453d0 100644 (file)
--- a/replay/replay-debugging.c
+++ b/replay/replay-debugging.c
@@ -148,7 +148,7 @@ static char *replay_find_nearest_snapshot(int64_t icount,
 
     *snapshot_icount = -1;
 
-    bs = bdrv_all_find_vmstate_bs();
+    bs = bdrv_all_find_vmstate_bs(NULL);
     if (!bs) {
         goto fail;
     }
@@ -159,7 +159,7 @@ static char *replay_find_nearest_snapshot(int64_t icount,
     aio_context_release(aio_context);
 
     for (i = 0; i < nb_sns; i++) {
-        if (bdrv_all_find_snapshot(sn_tab[i].name, &bs) == 0) {
+        if (bdrv_all_find_snapshot(sn_tab[i].name, NULL) == 0) {
             if (sn_tab[i].icount != -1ULL
                 && sn_tab[i].icount <= icount
                 && (!nearest || nearest->icount < sn_tab[i].icount)) {

diff --git a/tests/qemu-iotests/267.out b/tests/qemu-iotests/267.out
index 27471ffae833ed5c4b98ff8df520a43971f4de76..6149029b25d9257c59dc822e86d7fa1af4ba6180 100644 (file)
--- a/tests/qemu-iotests/267.out
+++ b/tests/qemu-iotests/267.out
@@ -6,9 +6,9 @@ Formatting 'TEST_DIR/t.IMGFMT', fmt=IMGFMT size=134217728
 Testing:
 QEMU X.Y.Z monitor - type 'help' for more information
 (qemu) savevm snap0
-Error: No block device can accept snapshots
+Error: No block device supports snapshots
 (qemu) info snapshots
-No available block device supports snapshots
+No block device supports snapshots
 (qemu) loadvm snap0
 Error: No block device supports snapshots
 (qemu) quit
@@ -22,7 +22,7 @@ QEMU X.Y.Z monitor - type 'help' for more information
 (qemu) savevm snap0
 Error: Device 'none0' is writable but does not support snapshots
 (qemu) info snapshots
-No available block device supports snapshots
+No block device supports snapshots
 (qemu) loadvm snap0
 Error: Device 'none0' is writable but does not support snapshots
 (qemu) quit
@@ -58,7 +58,7 @@ QEMU X.Y.Z monitor - type 'help' for more information
 (qemu) savevm snap0
 Error: Device 'virtio0' is writable but does not support snapshots
 (qemu) info snapshots
-No available block device supports snapshots
+No block device supports snapshots
 (qemu) loadvm snap0
 Error: Device 'virtio0' is writable but does not support snapshots
 (qemu) quit
@@ -83,7 +83,7 @@ QEMU X.Y.Z monitor - type 'help' for more information
 (qemu) savevm snap0
 Error: Device 'file' is writable but does not support snapshots
 (qemu) info snapshots
-No available block device supports snapshots
+No block device supports snapshots
 (qemu) loadvm snap0
 Error: Device 'file' is writable but does not support snapshots
 (qemu) quit