nilfs2: issue discard request after cleaning segments

This adds a function to send discard requests for given array of
segment numbers, and calls the function when garbage collection
succeeded.
Signed-off-by: NJiro SEKIBA <jir@unicus.jp>
Signed-off-by: NRyusuke Konishi <konishi.ryusuke@lab.ntt.co.jp>

Documentation/filesystems/nilfs2.txt

@@ -74,6 +74,9 @@ norecovery		Disable recovery of the filesystem on mount.
 			This disables every write access on the device for
 			read-only mounts or snapshots.  This option will fail
 			for r/w mounts on an unclean volume.
+discard			Issue discard/TRIM commands to the underlying block
+			device when blocks are freed.  This is useful for SSD
+			devices and sparse/thinly-provisioned LUNs.
 
 NILFS2 usage
 ============

fs/nilfs2/segment.c

@@ -2560,6 +2560,16 @@ int nilfs_clean_segments(struct super_block *sb, struct nilfs_argv *argv,
 		set_current_state(TASK_INTERRUPTIBLE);
 		schedule_timeout(sci->sc_interval);
 	}
+	if (nilfs_test_opt(sbi, DISCARD)) {
+		int ret = nilfs_discard_segments(nilfs, sci->sc_freesegs,
+						 sci->sc_nfreesegs);
+		if (ret) {
+			printk(KERN_WARNING
+			       "NILFS warning: error %d on discard request, "
+			       "turning discards off for the device\n", ret);
+			nilfs_clear_opt(sbi, DISCARD);
+		}
+	}
 
  out_unlock:
 	sci->sc_freesegs = NULL;

fs/nilfs2/super.c

@@ -481,6 +481,8 @@ static int nilfs_show_options(struct seq_file *seq, struct vfsmount *vfs)
 		seq_printf(seq, ",order=strict");
 	if (nilfs_test_opt(sbi, NORECOVERY))
 		seq_printf(seq, ",norecovery");
+	if (nilfs_test_opt(sbi, DISCARD))
+		seq_printf(seq, ",discard");
 
 	return 0;
 }
@@ -550,7 +552,7 @@ static const struct export_operations nilfs_export_ops = {
 enum {
 	Opt_err_cont, Opt_err_panic, Opt_err_ro,
 	Opt_nobarrier, Opt_snapshot, Opt_order, Opt_norecovery,
-	Opt_err,
+	Opt_discard, Opt_err,
 };
 
 static match_table_t tokens = {
@@ -561,6 +563,7 @@ static match_table_t tokens = {
 	{Opt_snapshot, "cp=%u"},
 	{Opt_order, "order=%s"},
 	{Opt_norecovery, "norecovery"},
+	{Opt_discard, "discard"},
 	{Opt_err, NULL}
 };
 
@@ -614,6 +617,9 @@ static int parse_options(char *options, struct super_block *sb)
 		case Opt_norecovery:
 			nilfs_set_opt(sbi, NORECOVERY);
 			break;
+		case Opt_discard:
+			nilfs_set_opt(sbi, DISCARD);
+			break;
 		default:
 			printk(KERN_ERR
 			       "NILFS: Unrecognized mount option \"%s\"\n", p);

fs/nilfs2/the_nilfs.c

@@ -646,6 +646,44 @@ int init_nilfs(struct the_nilfs *nilfs, struct nilfs_sb_info *sbi, char *data)
 	goto out;
 }
 
+int nilfs_discard_segments(struct the_nilfs *nilfs, __u64 *segnump,
+			    size_t nsegs)
+{
+	sector_t seg_start, seg_end;
+	sector_t start = 0, nblocks = 0;
+	unsigned int sects_per_block;
+	__u64 *sn;
+	int ret = 0;
+
+	sects_per_block = (1 << nilfs->ns_blocksize_bits) /
+		bdev_logical_block_size(nilfs->ns_bdev);
+	for (sn = segnump; sn < segnump + nsegs; sn++) {
+		nilfs_get_segment_range(nilfs, *sn, &seg_start, &seg_end);
+
+		if (!nblocks) {
+			start = seg_start;
+			nblocks = seg_end - seg_start + 1;
+		} else if (start + nblocks == seg_start) {
+			nblocks += seg_end - seg_start + 1;
+		} else {
+			ret = blkdev_issue_discard(nilfs->ns_bdev,
+						   start * sects_per_block,
+						   nblocks * sects_per_block,
+						   GFP_NOFS,
+						   DISCARD_FL_BARRIER);
+			if (ret < 0)
+				return ret;
+			nblocks = 0;
+		}
+	}
+	if (nblocks)
+		ret = blkdev_issue_discard(nilfs->ns_bdev,
+					   start * sects_per_block,
+					   nblocks * sects_per_block,
+					   GFP_NOFS, DISCARD_FL_BARRIER);
+	return ret;
+}
+
 int nilfs_count_free_blocks(struct the_nilfs *nilfs, sector_t *nblocks)
 {
 	struct inode *dat = nilfs_dat_inode(nilfs);

fs/nilfs2/the_nilfs.h

@@ -221,6 +221,7 @@ struct the_nilfs *find_or_create_nilfs(struct block_device *);
 void put_nilfs(struct the_nilfs *);
 int init_nilfs(struct the_nilfs *, struct nilfs_sb_info *, char *);
 int load_nilfs(struct the_nilfs *, struct nilfs_sb_info *);
+int nilfs_discard_segments(struct the_nilfs *, __u64 *, size_t);
 int nilfs_count_free_blocks(struct the_nilfs *, sector_t *);
 struct nilfs_sb_info *nilfs_find_sbinfo(struct the_nilfs *, int, __u64);
 int nilfs_checkpoint_is_mounted(struct the_nilfs *, __u64, int);

include/linux/nilfs2_fs.h

@@ -153,6 +153,7 @@ struct nilfs_super_root {
 						   semantics also for data */
 #define NILFS_MOUNT_NORECOVERY		0x4000  /* Disable write access during
 						   mount-time recovery */
+#define NILFS_MOUNT_DISCARD		0x8000  /* Issue DISCARD requests */
 
 
 /**