f2fs: remove batched discard in f2fs_trim_fs

We don't need to do multiple checkpoints, since we don't actually wait for
completion of discard commands during checkpoint.
Instead, we still need to avoid very big discard commands, since that large
discard can interfere block allocation.

Signed-off-by: Jaegeuk Kim <jaegeuk@kernel.org>

Documentation/ABI/testing/sysfs-fs-f2fs

@@ -75,12 +75,6 @@ Contact:	"Jaegeuk Kim" <jaegeuk.kim@samsung.com>
 Description:
 		 Controls the memory footprint used by f2fs.
 
-What:		/sys/fs/f2fs/<disk>/trim_sections
-Date:		February 2015
-Contact:	"Jaegeuk Kim" <jaegeuk@kernel.org>
-Description:
-		 Controls the trimming rate in batch mode.
-
 What:		/sys/fs/f2fs/<disk>/cp_interval
 Date:		October 2015
 Contact:	"Jaegeuk Kim" <jaegeuk@kernel.org>

fs/f2fs/f2fs.h

@@ -195,11 +195,7 @@ enum {
 	CP_DISCARD,
 };
 
-#define DEF_BATCHED_TRIM_SECTIONS	2
+#define MAX_DISCARD_BLOCKS(sbi) (1 << (sbi)->log_blocks_per_seg)
-#define BATCHED_TRIM_SEGMENTS(sbi)	\
-		(SM_I(sbi)->trim_sections * (sbi)->segs_per_sec)
-#define BATCHED_TRIM_BLOCKS(sbi)	\
-		(BATCHED_TRIM_SEGMENTS(sbi) << (sbi)->log_blocks_per_seg)
 #define DEF_CP_INTERVAL			60	/* 60 secs */
 #define DEF_IDLE_INTERVAL		5	/* 5 secs */
 
@@ -705,9 +701,6 @@ struct f2fs_sm_info {
 	int nr_discards;			/* # of discards in the list */
 	int max_discards;			/* max. discards to be issued */
 
-	/* for batched trimming */
-	unsigned int trim_sections;		/* # of sections to trim */
-
 	struct list_head sit_entry_set;	/* sit entry set list */
 
 	unsigned int ipu_policy;	/* in-place-update policy */

fs/f2fs/segment.c

@@ -903,7 +903,8 @@ static void __add_discard_entry(struct f2fs_sb_info *sbi,
 	if (!list_empty(head)) {
 		last = list_last_entry(head, struct discard_entry, list);
 		if (START_BLOCK(sbi, cpc->trim_start) + start ==
-						last->blkaddr + last->len) {
+				last->blkaddr + last->len &&
+				last->len <= MAX_DISCARD_BLOCKS(sbi)) {
 			last->len += end - start;
 			goto done;
 		}
@@ -1593,36 +1594,25 @@ int f2fs_trim_fs(struct f2fs_sb_info *sbi, struct fstrim_range *range)
 			"Found FS corruption, run fsck to fix.");
 		goto out;
 	}
+	if (sbi->discard_blks == 0)
+		goto out;
 
 	/* start/end segment number in main_area */
 	start_segno = (start <= MAIN_BLKADDR(sbi)) ? 0 : GET_SEGNO(sbi, start);
 	end_segno = (end >= MAX_BLKADDR(sbi)) ? MAIN_SEGS(sbi) - 1 :
 						GET_SEGNO(sbi, end);
+	/*
+	 * do checkpoint to issue discard commands safely since we now can
+	 * use async discard.
+	 */
 	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 */
+	mutex_lock(&sbi->gc_mutex);
-	for (; start_segno <= end_segno; start_segno = cpc.trim_end + 1) {
+	err = write_checkpoint(sbi, &cpc);
-		cpc.trim_start = start_segno;
+	mutex_unlock(&sbi->gc_mutex);
-
-		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(start_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;
-
-		schedule();
-	}
 out:
 	range->len = F2FS_BLK_TO_BYTES(cpc.trimmed);
 	return err;
@@ -2788,8 +2778,6 @@ int build_segment_manager(struct f2fs_sb_info *sbi)
 	sm_info->nr_discards = 0;
 	sm_info->max_discards = 0;
 
-	sm_info->trim_sections = DEF_BATCHED_TRIM_SECTIONS;
-
 	INIT_LIST_HEAD(&sm_info->sit_entry_set);
 
 	if (test_opt(sbi, FLUSH_MERGE) && !f2fs_readonly(sbi->sb)) {

fs/f2fs/super.c

@@ -284,7 +284,6 @@ F2FS_RW_ATTR(GC_THREAD, f2fs_gc_kthread, gc_no_gc_sleep_time, no_gc_sleep_time);
 F2FS_RW_ATTR(GC_THREAD, f2fs_gc_kthread, gc_idle, gc_idle);
 F2FS_RW_ATTR(SM_INFO, f2fs_sm_info, reclaim_segments, rec_prefree_segments);
 F2FS_RW_ATTR(SM_INFO, f2fs_sm_info, max_small_discards, max_discards);
-F2FS_RW_ATTR(SM_INFO, f2fs_sm_info, batched_trim_sections, trim_sections);
 F2FS_RW_ATTR(SM_INFO, f2fs_sm_info, ipu_policy, ipu_policy);
 F2FS_RW_ATTR(SM_INFO, f2fs_sm_info, min_ipu_util, min_ipu_util);
 F2FS_RW_ATTR(SM_INFO, f2fs_sm_info, min_fsync_blocks, min_fsync_blocks);
@@ -309,7 +308,6 @@ static struct attribute *f2fs_attrs[] = {
 	ATTR_LIST(gc_idle),
 	ATTR_LIST(reclaim_segments),
 	ATTR_LIST(max_small_discards),
-	ATTR_LIST(batched_trim_sections),
 	ATTR_LIST(ipu_policy),
 	ATTR_LIST(min_ipu_util),
 	ATTR_LIST(min_fsync_blocks),