[Qemu-devel] [PATCH] qemu-io: Fix handling of bdrv_is_allocated() return value

[Qemu-devel] [PATCH] qemu-io: Fix handling of bdrv_is_allocated() return value

[Kevin Wolf]

bdrv_is_allocated() returns a boolean which indicates if the offset is
allocated, not 0 on success and everything else is an error.

Signed-off-by: Kevin Wolf <kwolf@redhat.com>
---
 qemu-io.c |   12 +++++-------
 1 files changed, 5 insertions(+), 7 deletions(-)

diff --git a/qemu-io.c b/qemu-io.c
index 466d22c..3e5c444 100644
--- a/qemu-io.c
+++ b/qemu-io.c
@@ -794,6 +794,7 @@ alloc_f(int argc, char **argv)
 	char s1[64];
 	int num;
 	int ret;
+	const char *retstr;
 
 	offset = cvtnum(argv[1]);
 	if (offset & 0x1ff) {
@@ -808,18 +809,15 @@ alloc_f(int argc, char **argv)
 		nb_sectors = 1;
 
 	ret = bdrv_is_allocated(bs, offset >> 9, nb_sectors, &num);
-	if (ret) {
-		printf("is_allocated: %s", strerror(ret));
-		return 0;
-	}
 
 	cvtstr(offset, s1, sizeof(s1));
 
+	retstr = ret ? "allocated" : "not allocated";
 	if (nb_sectors == 1)
-		printf("sector allocated at offset %s\n", s1);
+		printf("sector %s at offset %s\n", retstr, s1);
 	else
-		printf("%d/%d sectors allocated at offset %s\n",
-			num, nb_sectors, s1);
+		printf("%d/%d sectors %s at offset %s\n",
+			num, nb_sectors, retstr, s1);
 	return 0;
 }
 
-- 
1.6.0.6

Re: [Qemu-devel] [PATCH] qemu-io: Fix handling of bdrv_is_allocated() return value

[Christoph Hellwig]

On Thu, Apr 09, 2009 at 03:05:27PM +0200, Kevin Wolf wrote:
> bdrv_is_allocated() returns a boolean which indicates if the offset is
> allocated, not 0 on success and everything else is an error.

Yeah, the handling wa wrong before.  But a return value of 0 and *pnum =
0 seems to be a special error-ish value still which we might want to
handle.

Re: [Qemu-devel] [PATCH] qemu-io: Fix handling of bdrv_is_allocated() return value

[Kevin Wolf]

Christoph Hellwig schrieb:
> On Thu, Apr 09, 2009 at 03:05:27PM +0200, Kevin Wolf wrote:
>> bdrv_is_allocated() returns a boolean which indicates if the offset is
>> allocated, not 0 on success and everything else is an error.
> 
> Yeah, the handling wa wrong before.  But a return value of 0 and *pnum =
> 0 seems to be a special error-ish value still which we might want to
> handle.

The header comment of bdrv_is_allocated() doesn't specify error 
conditions. ;-)

You seem to be right that there is one place in block.c where *pnum = 0 
is used as something like an error return value. This isn't consistent 
though, qcow and vmdk return non-zero values in *pnum under the same 
conditions.

Maybe another patch to change that and bring the error message back 
again on *pnum == 0?

Kevin

Re: [Qemu-devel] [PATCH] qemu-io: Fix handling of bdrv_is_allocated() return value

[Christoph Hellwig]

On Thu, Apr 09, 2009 at 03:42:22PM +0200, Kevin Wolf wrote:
> Maybe another patch to change that and bring the error message back 
> again on *pnum == 0?

Ok, let's put this one in first.

As for dealing with errors, maybe we should change it to allow it to
return a negative error message for errors?