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>

3 files changed, 43 insertions, 2 deletions

diff --git a/api/examples/gfapi.py b/api/examples/gfapi.py
index 8dfe2791d0c..8d9ed732947 100755
--- a/api/examples/gfapi.py
+++ b/api/examples/gfapi.py
@@ -100,6 +100,8 @@ class File(object):
 
 	def fallocate (self, mode, offset, len):
 		return api.glfs_fallocate(self.fd, mode, offset, len)
+	def discard (self, offset, len):
+		return api.glfs_discard(self.fd, offset, len)
 
 class Dir(object):
 
@@ -357,10 +359,13 @@ if __name__ == "__main__":
                 fd = vol.creat(mypath,os.O_WRONLY|os.O_EXCL,0644)
                 if not fd:
                         return False, "creat error"
-		rc = fd.fallocate(0, 0, 1024)
+		rc = fd.fallocate(0, 0, 1024*1024)
                 if rc != 0:
                         return False, "fallocate error"
-                return True, "fallocate worked"
+		rc = fd.discard(4096, 4096)
+		if rc != 0:
+			return False, "discard error"
+                return True, "fallocate/discard worked"
 
         test_list = (
                 test_create_write,
diff --git a/api/src/glfs-fops.c b/api/src/glfs-fops.c
index 4bc0bb1b6d3..fbc9f4b49e4 100644
--- a/api/src/glfs-fops.c
+++ b/api/src/glfs-fops.c
@@ -2666,6 +2666,40 @@ out:
 
 
 int
+glfs_discard (struct glfs_fd *glfd, off_t offset, size_t len)
+{
+	int              ret = -1;
+	xlator_t        *subvol = NULL;
+	fd_t		*fd = NULL;
+
+	__glfs_entry_fd (glfd);
+
+	subvol = glfs_active_subvol (glfd->fs);
+	if (!subvol) {
+		ret = -1;
+		errno = EIO;
+		goto out;
+	}
+
+	fd = glfs_resolve_fd (glfd->fs, subvol, glfd);
+	if (!fd) {
+		ret = -1;
+		errno = EBADFD;
+		goto out;
+	}
+
+	ret = syncop_discard (subvol, fd, offset, len);
+out:
+	if (fd)
+		fd_unref(fd);
+
+	glfs_subvol_done (glfd->fs, subvol);
+
+	return ret;
+}
+
+
+int
 glfs_chdir (struct glfs *fs, const char *path)
 {
 	int              ret = -1;
diff --git a/api/src/glfs.h b/api/src/glfs.h
index 3888a103eb9..700e10f17c9 100644
--- a/api/src/glfs.h
+++ b/api/src/glfs.h
@@ -450,6 +450,8 @@ int glfs_fremovexattr (glfs_fd_t *fd, const char *name);
 
 int glfs_fallocate(glfs_fd_t *fd, int keep_size, off_t offset, size_t len);
 
+int glfs_discard(glfs_fd_t *fd, off_t offset, size_t len);
+
 char *glfs_getcwd (glfs_t *fs, char *buf, size_t size);
 
 int glfs_chdir (glfs_t *fs, const char *path);