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blockdev: Clean up fragile use of error_is_set()

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Using error_is_set(ERRP) to find out whether a function failed is
either wrong, fragile, or unnecessarily opaque.  It's wrong when ERRP
may be null, because errors go undetected when it is.  It's fragile
when proving ERRP non-null involves a non-local argument.  Else, it's
unnecessarily opaque (see commit 84d18f0).

The error_is_set(errp) in internal_snapshot_prepare() is merely
fragile, because the caller never passes a null errp argument.

Make the code more robust and more obviously correct: receive the
error in a local variable, then propagate it through the parameter.

Signed-off-by: Markus Armbruster <armbru@redhat.com>
Reviewed-by: Kevin Wolf <kwolf@redhat.com>
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
This commit is contained in:
Markus Armbruster 2014-04-25 16:50:34 +02:00 committed by Stefan Hajnoczi
parent 92de901290
commit f70edf9948
1 changed files with 5 additions and 2 deletions
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7
blockdev.c
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@ -1115,6 +1115,7 @@ typedef struct InternalSnapshotState {
static void internal_snapshot_prepare(BlkTransactionState *common, static void internal_snapshot_prepare(BlkTransactionState *common,
Error **errp) Error **errp)
{ {
Error *local_err = NULL;
const char *device; const char *device;
const char *name; const char *name;
BlockDriverState *bs; BlockDriverState *bs;
@ -1163,8 +1164,10 @@ static void internal_snapshot_prepare(BlkTransactionState *common,
} }
/* check whether a snapshot with name exist */ /* check whether a snapshot with name exist */
ret = bdrv_snapshot_find_by_id_and_name(bs, NULL, name, &old_sn, errp); ret = bdrv_snapshot_find_by_id_and_name(bs, NULL, name, &old_sn,
if (error_is_set(errp)) { &local_err);
if (local_err) {
error_propagate(errp, local_err);
return; return;
} else if (ret) { } else if (ret) {
error_setg(errp, error_setg(errp,