[Qemu-devel] [RFC PATCH 14/17] block: support FALLOC_FL_PUNCH_HOLE trimming

[Paolo Bonzini <pbonzini@redhat.com>]

This will enable discard on more filesystems, including ext4.

Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
---
 block/raw-posix.c |   29 ++++++++++++++++++++++++-----
 1 files changed, 24 insertions(+), 5 deletions(-)

diff --git a/block/raw-posix.c b/block/raw-posix.c
index 2d1bc13..f23d92b 100644
--- a/block/raw-posix.c
+++ b/block/raw-posix.c
@@ -52,6 +52,7 @@
 #include <sys/param.h>
 #include <linux/cdrom.h>
 #include <linux/fd.h>
+#include <linux/falloc.h>
 #endif
 #if defined (__FreeBSD__) || defined(__FreeBSD_kernel__)
 #include <sys/disk.h>
@@ -131,6 +132,7 @@ typedef struct BDRVRawState {
 #endif
     uint8_t *aligned_buf;
     unsigned aligned_buf_size;
+    bool has_discard : 1;
 #ifdef CONFIG_XFS
     bool is_xfs : 1;
 #endif
@@ -257,11 +259,9 @@ static int raw_open_common(BlockDriverState *bs, const char *filename,
     }
 
 #ifdef CONFIG_XFS
-    if (platform_test_xfs_fd(s->fd)) {
-        s->is_xfs = 1;
-    }
+    s->is_xfs = platform_test_xfs_fd(s->fd);
 #endif
-
+    s->has_discard = 1;
     return 0;
 
 out_free_buf:
@@ -605,15 +605,34 @@ static int xfs_discard(BDRVRawState *s, int64_t sector_num, int nb_sectors)
 static coroutine_fn int raw_co_discard(BlockDriverState *bs,
     int64_t sector_num, int nb_sectors)
 {
-#ifdef CONFIG_XFS
     BDRVRawState *s = bs->opaque;
+    int retval;
 
+    if (s->has_discard == 0) {
+        return -ENOTSUP;
+    }
+#ifdef CONFIG_XFS
     if (s->is_xfs) {
         return xfs_discard(s, sector_num, nb_sectors);
     }
 #endif
 
+#ifdef FALLOC_FL_PUNCH_HOLE
+    retval = fallocate(s->fd, FALLOC_FL_PUNCH_HOLE|FALLOC_FL_KEEP_SIZE,
+                       sector_num << 9, (int64_t)nb_sectors << 9);
+    if (retval == -1) {
+        if (errno == ENODEV || errno == ENOSYS || errno == EOPNOTSUPP) {
+            s->has_discard = 0;
+            return -ENOTSUP;
+        } else {
+            return -errno;
+        }
+    }
     return 0;
+#else
+    s->has_discard = 0;
+    return -ENOTSUP;
+#endif
 }
 
 static QEMUOptionParameter raw_create_options[] = {
-- 
1.7.7.6