[Qemu-devel] [PATCH for-2.7 v2 05/17] raw-posix: Implement .bdrv_lockf

[Fam Zheng]

virtlockd in libvirt locks the first byte, we lock byte 1 to avoid
the intervene.

Suggested-by: "Daniel P. Berrange" <address@hidden>
Signed-off-by: Fam Zheng <address@hidden>
---
 block/raw-posix.c | 35 +++++++++++++++++++++++++++++++++++
 1 file changed, 35 insertions(+)

diff --git a/block/raw-posix.c b/block/raw-posix.c
index 906d5c9..3a2c17f 100644
--- a/block/raw-posix.c
+++ b/block/raw-posix.c
@@ -35,6 +35,7 @@
 #include "raw-aio.h"
 #include "qapi/util.h"
 #include "qapi/qmp/qstring.h"
+#include "glib.h"
 
 #if defined(__APPLE__) && (__MACH__)
 #include <paths.h>
@@ -397,6 +398,38 @@ static void raw_attach_aio_context(BlockDriverState *bs,
 #endif
 }
 
+static int raw_lockf(BlockDriverState *bs, BdrvLockfCmd cmd)
+{
+
+    BDRVRawState *s = bs->opaque;
+    int ret;
+    struct flock fl = (struct flock) {
+        .l_whence  = SEEK_SET,
+        /* Locking byte 1 avoids interfereing with virtlockd. */
+        .l_start = 1,
+        .l_len = 1,
+    };
+
+    switch (cmd) {
+    case BDRV_LOCKF_RWLOCK:
+        fl.l_type = F_WRLCK;
+        break;
+    case BDRV_LOCKF_ROLOCK:
+        fl.l_type = F_RDLCK;
+        break;
+    case BDRV_LOCKF_UNLOCK:
+        fl.l_type = F_UNLCK;
+        break;
+    default:
+        abort();
+    }
+    ret = fcntl(s->fd, F_SETLK, &fl);
+    if (ret) {
+        ret = -errno;
+    }
+    return ret;
+}
+
 #ifdef CONFIG_LINUX_AIO
 static int raw_set_aio(void **aio_ctx, int *use_aio, int bdrv_flags)
 {
@@ -1960,6 +1993,8 @@ BlockDriver bdrv_file = {
     .bdrv_detach_aio_context = raw_detach_aio_context,
     .bdrv_attach_aio_context = raw_attach_aio_context,
 
+    .bdrv_lockf = raw_lockf,
+
     .create_opts = &raw_create_opts,
 };
 
-- 
2.8.0