The unspoken premise of qemu_madvise() is that errno is set on
error. And it is mostly the case except for posix_madvise() which
is documented to return either zero (on success) or a positive
error number. This means, we must set errno ourselves. And while
at it, make the function return a negative value on error, just
like other error paths do.

Signed-off-by: Michal Privoznik <mprivozn@redhat.com>
---
 util/osdep.c | 7 ++++++-
 1 file changed, 6 insertions(+), 1 deletion(-)

diff --git a/util/osdep.c b/util/osdep.c
index e996c4744a..e42f4e8121 100644
--- a/util/osdep.c
+++ b/util/osdep.c
@@ -57,7 +57,12 @@ int qemu_madvise(void *addr, size_t len, int advice)
 #if defined(CONFIG_MADVISE)
     return madvise(addr, len, advice);
 #elif defined(CONFIG_POSIX_MADVISE)
-    return posix_madvise(addr, len, advice);
+    int rc = posix_madvise(addr, len, advice);
+    if (rc) {
+        errno = rc;
+        return -1;
+    }
+    return 0;
 #else
     errno = EINVAL;
     return -1;
-- 
2.44.1

Am 28.05.24 um 18:15 schrieb Michal Privoznik:
> The unspoken premise of qemu_madvise() is that errno is set on
> error. And it is mostly the case except for posix_madvise() which
> is documented to return either zero (on success) or a positive
> error number. This means, we must set errno ourselves. And while
> at it, make the function return a negative value on error, just
> like other error paths do.
> 
> Signed-off-by: Michal Privoznik <mprivozn@redhat.com>
> ---
>   util/osdep.c | 7 ++++++-
>   1 file changed, 6 insertions(+), 1 deletion(-)
> 
> diff --git a/util/osdep.c b/util/osdep.c
> index e996c4744a..e42f4e8121 100644
> --- a/util/osdep.c
> +++ b/util/osdep.c
> @@ -57,7 +57,12 @@ int qemu_madvise(void *addr, size_t len, int advice)
>   #if defined(CONFIG_MADVISE)
>       return madvise(addr, len, advice);
>   #elif defined(CONFIG_POSIX_MADVISE)
> -    return posix_madvise(addr, len, advice);
> +    int rc = posix_madvise(addr, len, advice);
> +    if (rc) {
> +        errno = rc;
> +        return -1;
> +    }
> +    return 0;
>   #else
>       errno = EINVAL;
>       return -1;

Interesting, seems to be correct

Reviewed-by: David Hildenbrand <david@redhat.com>

-- 
Thanks,

David / dhildenb