[PATCH 10/10] f2fs: return fs_trim if there is no candidate

[Jaegeuk Kim]

If there is no candidate to submit discard command during f2sf_trim_fs, let's
return without checkpoint.

Signed-off-by: Jaegeuk Kim <jaegeuk@xxxxxxxxxx>
---
 fs/f2fs/checkpoint.c |  5 +++++
 fs/f2fs/f2fs.h       |  1 +
 fs/f2fs/segment.c    | 28 +++++++++++++++++++++++-----
 3 files changed, 29 insertions(+), 5 deletions(-)

diff --git a/fs/f2fs/checkpoint.c b/fs/f2fs/checkpoint.c
index 917b5c5053ae..ccea40763d9d 100644
--- a/fs/f2fs/checkpoint.c
+++ b/fs/f2fs/checkpoint.c
@@ -1249,6 +1249,11 @@ int write_checkpoint(struct f2fs_sb_info *sbi, struct cp_control *cpc)
 
 	/* this is the case of multiple fstrims without any changes */
 	if (cpc->reason == CP_DISCARD) {
+		if (!exist_trim_candidates(sbi, cpc)) {
+			unblock_operations(sbi);
+			goto out;
+		}
+
 		if (NM_I(sbi)->dirty_nat_cnt == 0 &&
 				SIT_I(sbi)->dirty_sentries == 0 &&
 				prefree_segments(sbi) == 0) {
diff --git a/fs/f2fs/f2fs.h b/fs/f2fs/f2fs.h
index f2f40fce9d31..04d113f0d6bf 100644
--- a/fs/f2fs/f2fs.h
+++ b/fs/f2fs/f2fs.h
@@ -2119,6 +2119,7 @@ void release_discard_addrs(struct f2fs_sb_info *);
 int npages_for_summary_flush(struct f2fs_sb_info *, bool);
 void allocate_new_segments(struct f2fs_sb_info *);
 int f2fs_trim_fs(struct f2fs_sb_info *, struct fstrim_range *);
+bool exist_trim_candidates(struct f2fs_sb_info *, struct cp_control *);
 struct page *get_sum_page(struct f2fs_sb_info *, unsigned int);
 void update_meta_page(struct f2fs_sb_info *, void *, block_t);
 void write_meta_page(struct f2fs_sb_info *, struct page *);
diff --git a/fs/f2fs/segment.c b/fs/f2fs/segment.c
index 9a38424c3c1f..82078734f379 100644
--- a/fs/f2fs/segment.c
+++ b/fs/f2fs/segment.c
@@ -836,7 +836,8 @@ static void __add_discard_entry(struct f2fs_sb_info *sbi,
 	SM_I(sbi)->nr_discards += end - start;
 }
 
-static void add_discard_addrs(struct f2fs_sb_info *sbi, struct cp_control *cpc)
+static bool add_discard_addrs(struct f2fs_sb_info *sbi, struct cp_control *cpc,
+							bool check_only)
 {
 	int entries = SIT_VBLOCK_MAP_SIZE / sizeof(unsigned long);
 	int max_blocks = sbi->blocks_per_seg;
@@ -850,12 +851,12 @@ static void add_discard_addrs(struct f2fs_sb_info *sbi, struct cp_control *cpc)
 	int i;
 
 	if (se->valid_blocks == max_blocks || !f2fs_discard_en(sbi))
-		return;
+		return false;
 
 	if (!force) {
 		if (!test_opt(sbi, DISCARD) || !se->valid_blocks ||
 		    SM_I(sbi)->nr_discards >= SM_I(sbi)->max_discards)
-			return;
+			return false;
 	}
 
 	/* SIT_VBLOCK_MAP_SIZE should be multiple of sizeof(unsigned long) */
@@ -873,8 +874,12 @@ static void add_discard_addrs(struct f2fs_sb_info *sbi, struct cp_control *cpc)
 					&& (end - start) < cpc->trim_minlen)
 			continue;
 
+		if (check_only)
+			return true;
+
 		__add_discard_entry(sbi, cpc, se, start, end);
 	}
+	return false;
 }
 
 void release_discard_addrs(struct f2fs_sb_info *sbi)
@@ -1455,6 +1460,19 @@ static const struct segment_allocation default_salloc_ops = {
 	.allocate_segment = allocate_segment_by_default,
 };
 
+bool exist_trim_candidates(struct f2fs_sb_info *sbi, struct cp_control *cpc)
+{
+	__u64 trim_start = cpc->trim_start;
+
+	mutex_lock(&SIT_I(sbi)->sentry_lock);
+	for (; trim_start <= cpc->trim_end; trim_start++)
+		if (add_discard_addrs(sbi, cpc, true))
+			break;
+	mutex_unlock(&SIT_I(sbi)->sentry_lock);
+
+	return trim_start <= cpc->trim_end;
+}
+
 int f2fs_trim_fs(struct f2fs_sb_info *sbi, struct fstrim_range *range)
 {
 	__u64 start = F2FS_BYTES_TO_BLK(range->start);
@@ -2251,7 +2269,7 @@ void flush_sit_entries(struct f2fs_sb_info *sbi, struct cp_control *cpc)
 			/* add discard candidates */
 			if (cpc->reason != CP_DISCARD) {
 				cpc->trim_start = segno;
-				add_discard_addrs(sbi, cpc);
+				add_discard_addrs(sbi, cpc, false);
 			}
 
 			if (to_journal) {
@@ -2289,7 +2307,7 @@ void flush_sit_entries(struct f2fs_sb_info *sbi, struct cp_control *cpc)
 		__u64 trim_start = cpc->trim_start;
 
 		for (; cpc->trim_start <= cpc->trim_end; cpc->trim_start++)
-			add_discard_addrs(sbi, cpc);
+			add_discard_addrs(sbi, cpc, false);
 
 		cpc->trim_start = trim_start;
 	}
-- 
2.11.0