[PATCH 3/9] spaceman/defrag: defrag segments

[Wengang Wang <wen.gang.wang@oracle.com>]

For each segment, the following steps are done trying to defrag it:

1. share the segment with a temporary file
2. unshare the segment in the target file. kernel simulates Cow on the whole
   segment complete the unshare (defrag).
3. release blocks from the tempoary file.

Signed-off-by: Wengang Wang <wen.gang.wang@oracle.com>
---
 spaceman/defrag.c | 114 ++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 114 insertions(+)

diff --git a/spaceman/defrag.c b/spaceman/defrag.c
index 175cf461..9f11e36b 100644
--- a/spaceman/defrag.c
+++ b/spaceman/defrag.c
@@ -263,6 +263,40 @@ add_ext:
 	return ret;
 }
 
+/*
+ * check if the segment exceeds EoF.
+ * fix up the clone range and return true if EoF happens,
+ * return false otherwise.
+ */
+static bool
+defrag_clone_eof(struct file_clone_range *clone)
+{
+	off_t delta;
+
+	delta = clone->src_offset + clone->src_length - g_defrag_file_size;
+	if (delta > 0) {
+		clone->src_length = 0; // to the end
+		return true;
+	}
+	return false;
+}
+
+/*
+ * get the time delta since pre_time in ms.
+ * pre_time should contains values fetched by gettimeofday()
+ * cur_time is used to store current time by gettimeofday()
+ */
+static long long
+get_time_delta_us(struct timeval *pre_time, struct timeval *cur_time)
+{
+	long long us;
+
+	gettimeofday(cur_time, NULL);
+	us = (cur_time->tv_sec - pre_time->tv_sec) * 1000000;
+	us += (cur_time->tv_usec - pre_time->tv_usec);
+	return us;
+}
+
 /*
  * defragment a file
  * return 0 if successfully done, 1 otherwise
@@ -273,6 +307,7 @@ defrag_xfs_defrag(char *file_path) {
 	long	nr_seg_defrag = 0, nr_ext_defrag = 0;
 	int	scratch_fd = -1, defrag_fd = -1;
 	char	tmp_file_path[PATH_MAX+1];
+	struct file_clone_range clone;
 	char	*defrag_dir;
 	struct fsxattr	fsx;
 	int	ret = 0;
@@ -296,6 +331,8 @@ defrag_xfs_defrag(char *file_path) {
 		goto out;
 	}
 
+	clone.src_fd = defrag_fd;
+
 	defrag_dir = dirname(file_path);
 	snprintf(tmp_file_path, PATH_MAX, "%s/.xfsdefrag_%d", defrag_dir,
 		getpid());
@@ -309,7 +346,11 @@ defrag_xfs_defrag(char *file_path) {
 	}
 
 	do {
+		struct timeval t_clone, t_unshare, t_punch_hole;
 		struct defrag_segment segment;
+		long long seg_size, seg_off;
+		int time_delta;
+		bool stop;
 
 		ret = defrag_get_next_segment(defrag_fd, &segment);
 		/* no more segments, we are done */
@@ -322,6 +363,79 @@ defrag_xfs_defrag(char *file_path) {
 			ret = 1;
 			break;
 		}
+
+		/* we are done if the segment contains only 1 extent */
+		if (segment.ds_nr < 2)
+			continue;
+
+		/* to bytes */
+		seg_off = segment.ds_offset * 512;
+		seg_size = segment.ds_length * 512;
+
+		clone.src_offset = seg_off;
+		clone.src_length = seg_size;
+		clone.dest_offset = seg_off;
+
+		/* checks for EoF and fix up clone */
+		stop = defrag_clone_eof(&clone);
+		gettimeofday(&t_clone, NULL);
+		ret = ioctl(scratch_fd, FICLONERANGE, &clone);
+		if (ret != 0) {
+			fprintf(stderr, "FICLONERANGE failed %s\n",
+				strerror(errno));
+			break;
+		}
+
+		/* for time stats */
+		time_delta = get_time_delta_us(&t_clone, &t_unshare);
+		if (time_delta > max_clone_us)
+			max_clone_us = time_delta;
+
+		/* for defrag stats */
+		nr_ext_defrag += segment.ds_nr;
+
+		/*
+		 * For the shared range to be unshared via a copy-on-write
+		 * operation in the file to be defragged. This causes the
+		 * file needing to be defragged to have new extents allocated
+		 * and the data to be copied over and written out.
+		 */
+		ret = fallocate(defrag_fd, FALLOC_FL_UNSHARE_RANGE, seg_off,
+				seg_size);
+		if (ret != 0) {
+			fprintf(stderr, "UNSHARE_RANGE failed %s\n",
+				strerror(errno));
+			break;
+		}
+
+		/* for time stats */
+		time_delta = get_time_delta_us(&t_unshare, &t_punch_hole);
+		if (time_delta > max_unshare_us)
+			max_unshare_us = time_delta;
+
+		/*
+		 * Punch out the original extents we shared to the
+		 * scratch file so they are returned to free space.
+		 */
+		ret = fallocate(scratch_fd,
+			FALLOC_FL_PUNCH_HOLE|FALLOC_FL_KEEP_SIZE, seg_off,
+			seg_size);
+		if (ret != 0) {
+			fprintf(stderr, "PUNCH_HOLE failed %s\n",
+				strerror(errno));
+			break;
+		}
+
+		/* for defrag stats */
+		nr_seg_defrag += 1;
+
+		/* for time stats */
+		time_delta = get_time_delta_us(&t_punch_hole, &t_clone);
+		if (time_delta > max_punch_us)
+			max_punch_us = time_delta;
+
+		if (stop)
+			break;
 	} while (true);
 out:
 	if (scratch_fd != -1) {
-- 
2.39.3 (Apple Git-146)