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, 50 insertions, 0 deletions

diff --git a/xlators/performance/read-ahead/src/read-ahead.c b/xlators/performance/read-ahead/src/read-ahead.c
index 522fa52b8e9..241fa477fda 100644
--- a/xlators/performance/read-ahead/src/read-ahead.c
+++ b/xlators/performance/read-ahead/src/read-ahead.c
@@ -942,6 +942,55 @@ unwind:
         return 0;
 }
 
+int
+ra_discard_cbk(call_frame_t *frame, void *cookie, xlator_t *this,
+               int32_t op_ret, int32_t op_errno, struct iatt *prebuf,
+               struct iatt *postbuf, dict_t *xdata)
+{
+        GF_ASSERT (frame);
+
+        STACK_UNWIND_STRICT (discard, frame, op_ret, op_errno, prebuf,
+                             postbuf, xdata);
+        return 0;
+}
+
+static int
+ra_discard(call_frame_t *frame, xlator_t *this, fd_t *fd, off_t offset,
+	     size_t len, dict_t *xdata)
+{
+        ra_file_t *file    = NULL;
+        fd_t      *iter_fd = NULL;
+        inode_t   *inode   = NULL;
+        uint64_t  tmp_file = 0;
+        int32_t   op_errno = EINVAL;
+
+        GF_ASSERT (frame);
+        GF_VALIDATE_OR_GOTO (frame->this->name, this, unwind);
+        GF_VALIDATE_OR_GOTO (frame->this->name, fd, unwind);
+
+        inode = fd->inode;
+
+        LOCK (&inode->lock);
+        {
+                list_for_each_entry (iter_fd, &inode->fd_list, inode_list) {
+                        fd_ctx_get (iter_fd, this, &tmp_file);
+                        file = (ra_file_t *)(long)tmp_file;
+                        if (!file)
+                                continue;
+
+                        flush_region(frame, file, offset, len, 1);
+                }
+        }
+        UNLOCK (&inode->lock);
+
+        STACK_WIND (frame, ra_discard_cbk, FIRST_CHILD (this),
+                    FIRST_CHILD (this)->fops->discard, fd, offset, len, xdata);
+        return 0;
+
+unwind:
+        STACK_UNWIND_STRICT (discard, frame, -1, op_errno, NULL, NULL, NULL);
+        return 0;
+}
 
 int
 ra_priv_dump (xlator_t *this)
@@ -1123,6 +1172,7 @@ struct xlator_fops fops = {
         .truncate    = ra_truncate,
         .ftruncate   = ra_ftruncate,
         .fstat       = ra_fstat,
+	.discard     = ra_discard,
 };
 
 struct xlator_cbks cbks = {