glusterfs: discard (hole punch) support

Add support for the DISCARD file operation. Discard punches a hole
in a file in the provided range. Block de-allocation is implemented
via fallocate() (as requested via fuse and passed on to the brick
fs) but a separate fop is created within gluster to emphasize the
fact that discard changes file data (the discarded region is
replaced with zeroes) and must invalidate caches where appropriate.

BUG: 963678
Change-Id: I34633a0bfff2187afeab4292a15f3cc9adf261af
Signed-off-by: Brian Foster <bfoster@redhat.com>
Reviewed-on: http://review.gluster.org/5090
Tested-by: Gluster Build System <jenkins@build.gluster.com>
Reviewed-by: Anand Avati <avati@redhat.com>

1 files changed, 30 insertions, 0 deletions

diff --git a/libglusterfs/src/syncop.c b/libglusterfs/src/syncop.c
index f57e8da5a72..9cceaf55c5c 100644
--- a/libglusterfs/src/syncop.c
+++ b/libglusterfs/src/syncop.c
@@ -1948,6 +1948,36 @@ syncop_fallocate(xlator_t *subvol, fd_t *fd, int32_t keep_size, off_t offset,
 
 
 int
+syncop_discard_cbk (call_frame_t *frame, void *cookie, xlator_t *this,
+                    int op_ret, int op_errno, struct iatt *prebuf,
+                    struct iatt *postbuf, dict_t *xdata)
+{
+	struct syncargs *args = NULL;
+
+        args = cookie;
+
+        args->op_ret   = op_ret;
+        args->op_errno = op_errno;
+
+        __wake (args);
+
+	return 0;
+}
+
+int
+syncop_discard(xlator_t *subvol, fd_t *fd, off_t offset, size_t len)
+{
+        struct syncargs args = {0, };
+
+        SYNCOP (subvol, (&args), syncop_discard_cbk, subvol->fops->discard,
+                fd, offset, len, NULL);
+
+        errno = args.op_errno;
+        return args.op_ret;
+}
+
+
+int
 syncop_lk_cbk (call_frame_t *frame, void *cookie, xlator_t *this,
 	       int op_ret, int op_errno, struct gf_flock *flock,
 	       dict_t *xdata)