From c85191e5c9e14d65cc4281ef3b31f480227aa6dd Mon Sep 17 00:00:00 2001
From: Paolo Bonzini <pbonzini@redhat.com>
Date: Mon, 14 Jan 2013 16:26:53 +0100
Subject: [PATCH] raw-posix: remember whether discard failed

Avoid sending system calls repeatedly if they shall fail.  This
does not apply to XFS: if the filesystem-specific ioctl fails,
something weird is happening.

Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
---
 block/raw-posix.c | 9 ++++++---
 1 file changed, 6 insertions(+), 3 deletions(-)

diff --git a/block/raw-posix.c b/block/raw-posix.c
index e8d79afe5f..b647cfbb2f 100644
--- a/block/raw-posix.c
+++ b/block/raw-posix.c
@@ -141,6 +141,7 @@ typedef struct BDRVRawState {
 #ifdef CONFIG_XFS
     bool is_xfs : 1;
 #endif
+    bool has_discard : 1;
 } BDRVRawState;
 
 typedef struct BDRVRawReopenState {
@@ -292,6 +293,7 @@ static int raw_open_common(BlockDriverState *bs, const char *filename,
     }
 #endif
 
+    s->has_discard = 1;
 #ifdef CONFIG_XFS
     if (platform_test_xfs_fd(s->fd)) {
         s->is_xfs = 1;
@@ -1078,10 +1080,12 @@ static coroutine_fn int raw_co_discard(BlockDriverState *bs,
     int64_t sector_num, int nb_sectors)
 {
     int ret = -EOPNOTSUPP;
-
-#if defined(CONFIG_FALLOCATE_PUNCH_HOLE) || defined(CONFIG_XFS)
     BDRVRawState *s = bs->opaque;
 
+    if (!s->has_discard) {
+        return 0;
+    }
+
 #ifdef CONFIG_XFS
     if (s->is_xfs) {
         return xfs_discard(s, sector_num, nb_sectors);
@@ -1098,7 +1102,6 @@ static coroutine_fn int raw_co_discard(BlockDriverState *bs,
     } while (errno == EINTR);
 
     ret = -errno;
-#endif
 #endif
 
     if (ret == -EOPNOTSUPP) {