[Ocfs2-tools-devel] [PATCH] discard unused blocks before mkfs

[Larry Chen]

From: Larry <lchen at suse.com>

When using a SSD as a block device, if unused SSD blocks could
be discarded in advance, performance will be improved.

This patch uses ioctl interface to release unused blocks on SSD
layer.

Signed-off-by: Larry Chen <lchen at suse.com>
---
 mkfs.ocfs2/mkfs.c | 51 +++++++++++++++++++++++++++++++++++++++++++++++++++
 mkfs.ocfs2/mkfs.h | 10 ++++++++++
 2 files changed, 61 insertions(+)

diff --git a/mkfs.ocfs2/mkfs.c b/mkfs.ocfs2/mkfs.c
index 354b2ee5..2aff6973 100644
--- a/mkfs.ocfs2/mkfs.c
+++ b/mkfs.ocfs2/mkfs.c
@@ -543,6 +543,46 @@ static void finish_normal_format(State *s)
 	ocfs2_close(fs);
 }
 
+static inline errcode_t discard_blocks(State *s, uint64_t block,
+		uint64_t count)
+{
+	int ret;
+	uint64_t range[2];
+
+	range[0] = (uint64_t)(block) << s->blocksize_bits;
+	range[1] = (uint64_t)(count) << s->blocksize_bits;
+
+	ret = ioctl(s->fd, BLKDISCARD, &range);
+	return ret;
+}
+
+static int discard_device_blocks(State *s)
+{
+	uint64_t blocks = s->volume_size_in_blocks;
+	uint64_t count = DISCARD_STEP_MB;
+	uint64_t cur = 0;
+	int retval = 0;
+
+	count *= (1024 * 1024);
+	count >>= s->blocksize_bits;
+
+	while (cur < blocks) {
+		if (cur + count > blocks)
+			count = blocks - cur;
+
+		retval = discard_blocks(s, cur, count);
+		if (retval) {
+			if (!s->quiet && errno != EOPNOTSUPP)
+				com_err(s->progname, errno,
+					"While discarding unused blocks...skip\n");
+			break;
+		}
+		cur += count;
+	}
+
+	return retval;
+}
+
 int
 main(int argc, char **argv)
 {
@@ -615,6 +655,10 @@ main(int argc, char **argv)
 		return 0;
 	}
 
+	if (s->discard_blocks) {
+		discard_device_blocks(s);
+	}
+
 	clear_both_ends(s);
 
 	init_record(s, &superblock_rec, SFI_OTHER, S_IFREG | 0644);
@@ -889,6 +933,7 @@ get_state(int argc, char **argv)
 	int no_backup_super = -1;
 	enum ocfs2_feature_levels level = OCFS2_FEATURE_LEVEL_DEFAULT;
 	ocfs2_fs_options feature_flags = {0,0,0}, reverse_flags = {0,0,0};
+	int discard_blocks = 1;
 
 	static struct option long_options[] = {
 		{ "block-size", 1, 0, 'b' },
@@ -903,6 +948,7 @@ get_state(int argc, char **argv)
 		{ "force", 0, 0, 'F'},
 		{ "mount", 1, 0, 'M'},
 		{ "dry-run", 0, 0, 'n' },
+		{ "no-discard", 0, 0, 'o'},
 		{ "no-backup-super", 0, 0, BACKUP_SUPER_OPTION },
 		{ "fs-feature-level=", 1, 0, FEATURE_LEVEL },
 		{ "fs-features=", 1, 0, FEATURES_OPTION },
@@ -1103,6 +1149,10 @@ get_state(int argc, char **argv)
 			globalhb = 1;
 			break;
 
+		case 'o':
+			discard_blocks = 0;
+			break;
+
 		default:
 			usage(progname);
 			break;
@@ -1148,6 +1198,7 @@ get_state(int argc, char **argv)
 	s->quiet         = quiet;
 	s->force         = force;
 	s->dry_run       = dry_run;
+	s->discard_blocks = discard_blocks;
 
 	s->prompt        = xtool ? 0 : 1;
 
diff --git a/mkfs.ocfs2/mkfs.h b/mkfs.ocfs2/mkfs.h
index f9ba4dcf..b144341f 100644
--- a/mkfs.ocfs2/mkfs.h
+++ b/mkfs.ocfs2/mkfs.h
@@ -41,6 +41,7 @@
 #include <inttypes.h>
 #include <ctype.h>
 #include <assert.h>
+#include <sys/ioctl.h>
 
 #include <uuid/uuid.h>
 
@@ -92,6 +93,14 @@
 
 #define MAX_EXTALLOC_RESERVE_PERCENT	5
 
+#define DISCARD_STEP_MB         2048
+
+#if defined(__linux__) && !defined(BLKDISCARD)
+#define BLKDISCARD		_IO(0x12,119)
+#endif
+
+
+
 enum {
 	SFI_JOURNAL,
 	SFI_CLUSTER,
@@ -193,6 +202,7 @@ struct _State {
 	int inline_data;
 	int dx_dirs;
 	int dry_run;
+	int discard_blocks;
 
 	uint32_t blocksize;
 	uint32_t blocksize_bits;
-- 
2.16.2