Re: [f2fs-dev] [PATCH 1/3 v2] f2fs-tools: give less overprovisioning space

[Jaegeuk Kim <jaegeuk@kernel.org>]

As f2fs becomes more resilient for GCs, let's give the marginal overprovision
space back to user.

Fix an issue where reserved_space > ovp_space, reported by Shinichiro.

Signed-off-by: Shinichiro Kawasaki <shinichiro.kawasaki@wdc.com>
Signed-off-by: Jaegeuk Kim <jaegeuk@kernel.org>
---

 Change log from v1:
  - adjust ovp should be larger than reserved to kick f2fs runtime GCs

 fsck/resize.c      | 12 +++++++++---
 include/f2fs_fs.h  |  7 +++++--
 mkfs/f2fs_format.c |  8 ++++++--
 3 files changed, 20 insertions(+), 7 deletions(-)

diff --git a/fsck/resize.c b/fsck/resize.c
index 3d8ea466dacd..c545dd950743 100644
--- a/fsck/resize.c
+++ b/fsck/resize.c
@@ -150,7 +150,7 @@ safe_resize:
 		c.new_overprovision = get_best_overprovision(sb);
 
 	c.new_reserved_segments =
-		(2 * (100 / c.new_overprovision + 1) + 6) *
+		(100 / c.new_overprovision + 1 + NR_CURSEG_TYPE) *
 						get_sb(segs_per_sec);
 
 	if ((get_sb(segment_count_main) - 2) < c.new_reserved_segments ||
@@ -475,8 +475,13 @@ static void rebuild_checkpoint(struct f2fs_sb_info *sbi,
 	set_cp(overprov_segment_count, (get_newsb(segment_count_main) -
 			get_cp(rsvd_segment_count)) *
 			c.new_overprovision / 100);
+
+	/* give 2 sections (DATA and NODE) to trigger GC in advance */
+	if (get_cp(overprov_segment_count) < get_cp(rsvd_segment_count))
+		set_cp(overprov_segment_count, get_cp(rsvd_segment_count));
+
 	set_cp(overprov_segment_count, get_cp(overprov_segment_count) +
-						get_cp(rsvd_segment_count));
+						2 * get_sb(segs_per_sec));
 
 	DBG(0, "Info: Overprovision ratio = %.3lf%%\n", c.new_overprovision);
 	DBG(0, "Info: Overprovision segments = %u (GC reserved = %u)\n",
@@ -607,7 +612,8 @@ static int f2fs_resize_check(struct f2fs_sb_info *sbi, struct f2fs_super_block *
 	overprov_segment_count = (get_newsb(segment_count_main) -
 			c.new_reserved_segments) *
 			c.new_overprovision / 100;
-	overprov_segment_count += c.new_reserved_segments;
+
+	overprov_segment_count += 2 * get_newsb(segs_per_sec);
 
 	user_block_count = (get_newsb(segment_count_main) -
 			overprov_segment_count) * c.blks_per_seg;
diff --git a/include/f2fs_fs.h b/include/f2fs_fs.h
index 5fa9931648cf..333ae07a5ebd 100644
--- a/include/f2fs_fs.h
+++ b/include/f2fs_fs.h
@@ -1631,10 +1631,13 @@ static inline double get_best_overprovision(struct f2fs_super_block *sb)
 	}
 
 	for (; candidate <= end; candidate += diff) {
-		reserved = (2 * (100 / candidate + 1) + 6) *
+		reserved = (100 / candidate + 1 + NR_CURSEG_TYPE) *
 				round_up(usable_main_segs, get_sb(section_count));
 		ovp = (usable_main_segs - reserved) * candidate / 100;
-		space = usable_main_segs - reserved - ovp;
+		if (ovp < 0)
+			continue;
+		space = usable_main_segs - max(reserved, ovp) -
+					2 * get_sb(segs_per_sec);
 		if (max_space < space) {
 			max_space = space;
 			max_ovp = candidate;
diff --git a/mkfs/f2fs_format.c b/mkfs/f2fs_format.c
index f19a6c5a27d6..f4a49acc498c 100644
--- a/mkfs/f2fs_format.c
+++ b/mkfs/f2fs_format.c
@@ -484,7 +484,7 @@ static int f2fs_prepare_super_block(void)
 		c.overprovision = get_best_overprovision(sb);
 
 	c.reserved_segments =
-			(2 * (100 / c.overprovision + 1) + NR_CURSEG_TYPE) *
+			(100 / c.overprovision + 1 + NR_CURSEG_TYPE) *
 			round_up(f2fs_get_usable_segments(sb), get_sb(section_count));
 
 	if (c.feature & cpu_to_le32(F2FS_FEATURE_RO)) {
@@ -764,8 +764,12 @@ static int f2fs_write_check_point_pack(void)
 	set_cp(overprov_segment_count, (f2fs_get_usable_segments(sb) -
 			get_cp(rsvd_segment_count)) *
 			c.overprovision / 100);
+
+	if (get_cp(overprov_segment_count) < get_cp(rsvd_segment_count))
+		set_cp(overprov_segment_count, get_cp(rsvd_segment_count));
+
 	set_cp(overprov_segment_count, get_cp(overprov_segment_count) +
-			get_cp(rsvd_segment_count));
+			2 * get_sb(segs_per_sec));
 
 	if (f2fs_get_usable_segments(sb) <= get_cp(overprov_segment_count)) {
 		MSG(0, "\tError: Not enough segments to create F2FS Volume\n");
-- 
2.38.0.135.g90850a2211-goog



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