f2fs: don't split checkpoint in fstrim

Now, we issue discard asynchronously in separated thread instead of in
checkpoint, after that, we won't encounter long latency in checkpoint
due to huge number of synchronous discard command handling, so, we don't
need to split checkpoint to do trim in batch, merge it and obsolete
related sysfs entry.
Signed-off-by: Chao Yu <yuchao0@huawei.com>
Signed-off-by: Jaegeuk Kim <jaegeuk@kernel.org>

Documentation/ABI/testing/sysfs-fs-f2fs

@@ -101,6 +101,7 @@ Date:		February 2015
 Contact:	"Jaegeuk Kim" <jaegeuk@kernel.org>
 Description:
 		 Controls the trimming rate in batch mode.
+		 <deprecated>
 
 What:		/sys/fs/f2fs/<disk>/cp_interval
 Date:		October 2015

fs/f2fs/f2fs.h

@@ -176,11 +176,6 @@ enum {
 #define	CP_DISCARD	0x00000010
 #define CP_TRIMMED	0x00000020
 
-#define DEF_BATCHED_TRIM_SECTIONS	2048
-#define BATCHED_TRIM_SEGMENTS(sbi)	\
-		(GET_SEG_FROM_SEC(sbi, SM_I(sbi)->trim_sections))
-#define BATCHED_TRIM_BLOCKS(sbi)	\
-		(BATCHED_TRIM_SEGMENTS(sbi) << (sbi)->log_blocks_per_seg)
 #define MAX_DISCARD_BLOCKS(sbi)		BLKS_PER_SEC(sbi)
 #define DEF_MAX_DISCARD_REQUEST		8	/* issue 8 discards per round */
 #define DEF_MAX_DISCARD_LEN		512	/* Max. 2MB per discard */

fs/f2fs/segment.c

@@ -2395,7 +2395,7 @@ int f2fs_trim_fs(struct f2fs_sb_info *sbi, struct fstrim_range *range)
 {
 	__u64 start = F2FS_BYTES_TO_BLK(range->start);
 	__u64 end = start + F2FS_BYTES_TO_BLK(range->len) - 1;
-	unsigned int start_segno, end_segno, cur_segno;
+	unsigned int start_segno, end_segno;
 	block_t start_block, end_block;
 	struct cp_control cpc;
 	struct discard_policy dpolicy;
@@ -2421,40 +2421,27 @@ int f2fs_trim_fs(struct f2fs_sb_info *sbi, struct fstrim_range *range)
 
 	cpc.reason = CP_DISCARD;
 	cpc.trim_minlen = max_t(__u64, 1, F2FS_BYTES_TO_BLK(range->minlen));
+	cpc.trim_start = start_segno;
+	cpc.trim_end = end_segno;
 
-	/* do checkpoint to issue discard commands safely */
-	for (cur_segno = start_segno; cur_segno <= end_segno;
-					cur_segno = cpc.trim_end + 1) {
-		cpc.trim_start = cur_segno;
-
-		if (sbi->discard_blks == 0)
-			break;
-		else if (sbi->discard_blks < BATCHED_TRIM_BLOCKS(sbi))
-			cpc.trim_end = end_segno;
-		else
-			cpc.trim_end = min_t(unsigned int,
-				rounddown(cur_segno +
-				BATCHED_TRIM_SEGMENTS(sbi),
-				sbi->segs_per_sec) - 1, end_segno);
-
-		mutex_lock(&sbi->gc_mutex);
-		err = write_checkpoint(sbi, &cpc);
-		mutex_unlock(&sbi->gc_mutex);
-		if (err)
-			break;
+	if (sbi->discard_blks == 0)
+		goto out;
 
-		schedule();
-	}
+	mutex_lock(&sbi->gc_mutex);
+	err = write_checkpoint(sbi, &cpc);
+	mutex_unlock(&sbi->gc_mutex);
+	if (err)
+		goto out;
 
 	start_block = START_BLOCK(sbi, start_segno);
-	end_block = START_BLOCK(sbi, min(cur_segno, end_segno) + 1);
+	end_block = START_BLOCK(sbi, end_segno + 1);
 
 	__init_discard_policy(sbi, &dpolicy, DPOLICY_FSTRIM, cpc.trim_minlen);
 	__issue_discard_cmd_range(sbi, &dpolicy, start_block, end_block);
 	trimmed = __wait_discard_cmd_range(sbi, &dpolicy,
 					start_block, end_block);
-out:
 	range->len = F2FS_BLK_TO_BYTES(trimmed);
+out:
 	return err;
 }
 
@@ -3841,8 +3828,6 @@ int build_segment_manager(struct f2fs_sb_info *sbi)
 	sm_info->min_hot_blocks = DEF_MIN_HOT_BLOCKS;
 	sm_info->min_ssr_sections = reserved_sections(sbi);
 
-	sm_info->trim_sections = DEF_BATCHED_TRIM_SECTIONS;
-
 	INIT_LIST_HEAD(&sm_info->sit_entry_set);
 
 	init_rwsem(&sm_info->curseg_lock);

fs/f2fs/sysfs.c

@@ -245,6 +245,9 @@ static ssize_t f2fs_sbi_store(struct f2fs_attr *a,
 		return count;
 	}
 
+	if (!strcmp(a->attr.name, "trim_sections"))
+		return -EINVAL;
+
 	*ui = t;
 
 	if (!strcmp(a->attr.name, "iostat_enable") && *ui == 0)