[PATCH v2] block/file-posix: Fix return value translation for AIO discards.

[Ari Sundholm]

AIO discards regressed as a result of the following commit:
        0dfc7af2 block/file-posix: Optimize for macOS

When trying to run blkdiscard within a Linux guest, the request would
fail, with some errors in dmesg:

---- [ snip ] ----
[    4.010070] sd 2:0:0:0: [sda] tag#0 FAILED Result: hostbyte=DID_OK
driverbyte=DRIVER_SENSE
[    4.011061] sd 2:0:0:0: [sda] tag#0 Sense Key : Aborted Command
[current]
[    4.011061] sd 2:0:0:0: [sda] tag#0 Add. Sense: I/O process
terminated
[    4.011061] sd 2:0:0:0: [sda] tag#0 CDB: Unmap/Read sub-channel 42
00 00 00 00 00 00 00 18 00
[    4.011061] blk_update_request: I/O error, dev sda, sector 0
---- [ snip ] ----

This turns out to be a result of a flaw in changes to the error value
translation logic in handle_aiocb_discard(). The default return value
may be left untranslated in some configurations, and the wrong variable
is used in one translation.

Fix both issues.

Signed-off-by: Ari Sundholm <ari@tuxera.com>
Signed-off-by: Emil Karlson <jkarlson@tuxera.com>
Reviewed-by: Akihiko Odaki <akihiko.odaki@gmail.com>
Reviewed-by: Stefan Hajnoczi <stefanha@redhat.com>

Cc: qemu-stable@nongnu.org
Fixes: 0dfc7af2b28 ("block/file-posix: Optimize for macOS")
---

v1 -> v2:
* Add Reviewed-by, Cc to qemu-stable and Fixes lines

 block/file-posix.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/block/file-posix.c b/block/file-posix.c
index 53be0bdc1b..6def2a4cba 100644
--- a/block/file-posix.c
+++ b/block/file-posix.c
@@ -1807,7 +1807,7 @@ static int handle_aiocb_copy_range(void *opaque)
 static int handle_aiocb_discard(void *opaque)
 {
     RawPosixAIOData *aiocb = opaque;
-    int ret = -EOPNOTSUPP;
+    int ret = -ENOTSUP;
     BDRVRawState *s = aiocb->bs->opaque;
 
     if (!s->has_discard) {
@@ -1829,7 +1829,7 @@ static int handle_aiocb_discard(void *opaque)
 #ifdef CONFIG_FALLOCATE_PUNCH_HOLE
         ret = do_fallocate(s->fd, FALLOC_FL_PUNCH_HOLE | FALLOC_FL_KEEP_SIZE,
                            aiocb->aio_offset, aiocb->aio_nbytes);
-        ret = translate_err(-errno);
+        ret = translate_err(ret);
 #elif defined(__APPLE__) && (__MACH__)
         fpunchhole_t fpunchhole;
         fpunchhole.fp_flags = 0;
-- 
2.31.1