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, 52 insertions, 0 deletions

diff --git a/xlators/performance/io-threads/src/io-threads.c b/xlators/performance/io-threads/src/io-threads.c
index 33642bffb25..c6bdc375439 100644
--- a/xlators/performance/io-threads/src/io-threads.c
+++ b/xlators/performance/io-threads/src/io-threads.c
@@ -308,6 +308,7 @@ iot_schedule (call_frame_t *frame, xlator_t *this, call_stub_t *stub)
         case GF_FOP_FXATTROP:
         case GF_FOP_RCHECKSUM:
 	case GF_FOP_FALLOCATE:
+	case GF_FOP_DISCARD:
                 pri = IOT_PRI_LO;
                 break;
 
@@ -2459,6 +2460,56 @@ out:
 }
 
 int
+iot_discard_cbk(call_frame_t *frame, void *cookie, xlator_t *this,
+                  int32_t op_ret, int32_t op_errno,
+                  struct iatt *preop, struct iatt *postop, dict_t *xdata)
+{
+        STACK_UNWIND_STRICT (discard, frame, op_ret, op_errno, preop, postop,
+                             xdata);
+        return 0;
+}
+
+
+int
+iot_discard_wrapper(call_frame_t *frame, xlator_t *this, fd_t *fd, off_t offset,
+		    size_t len, dict_t *xdata)
+{
+        STACK_WIND (frame, iot_discard_cbk, FIRST_CHILD (this),
+                    FIRST_CHILD (this)->fops->discard, fd, offset, len, xdata);
+        return 0;
+}
+
+
+int
+iot_discard(call_frame_t *frame, xlator_t *this, fd_t *fd, off_t offset,
+	    size_t len, dict_t *xdata)
+{
+        call_stub_t     *stub = NULL;
+        int              ret = -1;
+
+        stub = fop_discard_stub(frame, iot_discard_wrapper, fd, offset, len,
+				xdata);
+        if (!stub) {
+                gf_log (this->name, GF_LOG_ERROR, "cannot create discard stub"
+                        "(out of memory)");
+                ret = -ENOMEM;
+                goto out;
+        }
+
+        ret = iot_schedule (frame, this, stub);
+
+out:
+        if (ret < 0) {
+                STACK_UNWIND_STRICT (discard, frame, -1, -ret, NULL, NULL,
+                                     NULL);
+                if (stub != NULL) {
+                        call_stub_destroy (stub);
+                }
+        }
+        return 0;
+}
+
+int
 __iot_workers_scale (iot_conf_t *conf)
 {
         int       scale = 0;
@@ -2788,6 +2839,7 @@ struct xlator_fops fops = {
 	.fxattrop    = iot_fxattrop,
         .rchecksum   = iot_rchecksum,
 	.fallocate   = iot_fallocate,
+	.discard     = iot_discard,
 };
 
 struct xlator_cbks cbks;