f2fs: issue more large discard command

o Changes from v1
  Use find_next(_zero)_bit suggested by jg.kim

When f2fs issues discard command, if segment is contiguous,
let's issue more large segment to gather adjacent segments.

** blktrace **
179,1    0     5859    42.619023770   971  C   D 131072 + 2097152 [0]
179,1    0    33665   108.840475468   971  C   D 2228224 + 2494464 [0]
179,1    0    33671   109.131616427   971  C   D 14909440 + 344064 [0]
179,1    0    33677   109.137100677   971  C   D 15261696 + 4096 [0]

Signed-off-by: Changman Lee <cm224.lee@samsung.com>
Signed-off-by: Jaegeuk Kim <jaegeuk.kim@samsung.com>

1 files changed, 21 insertions, 15 deletions

diff --git a/fs/f2fs/segment.c b/fs/f2fs/segment.c
index 86dc28949192..fa284d397199 100644
--- a/fs/f2fs/segment.c
+++ b/fs/f2fs/segment.c
@@ -139,27 +139,33 @@ static void set_prefree_as_free_segments(struct f2fs_sb_info *sbi)
 void clear_prefree_segments(struct f2fs_sb_info *sbi)
 {
         struct dirty_seglist_info *dirty_i = DIRTY_I(sbi);
-        unsigned int segno = -1;
+        unsigned long *prefree_map = dirty_i->dirty_segmap[PRE];
         unsigned int total_segs = TOTAL_SEGS(sbi);
+        unsigned int start = 0, end = -1;
 
         mutex_lock(&dirty_i->seglist_lock);
+
         while (1) {
-                segno = find_next_bit(dirty_i->dirty_segmap[PRE], total_segs,
-                                segno + 1);
-                if (segno >= total_segs)
+                int i;
+                start = find_next_bit(prefree_map, total_segs, end + 1);
+                if (start >= total_segs)
                         break;
+                end = find_next_zero_bit(prefree_map, total_segs, start + 1);
+
+                for (i = start; i < end; i++)
+                        clear_bit(i, prefree_map);
+
+                dirty_i->nr_dirty[PRE] -= end - start;
+
+                if (!test_opt(sbi, DISCARD))
+                        continue;
 
-                if (test_and_clear_bit(segno, dirty_i->dirty_segmap[PRE]))
-                        dirty_i->nr_dirty[PRE]--;
-
-                /* Let's use trim */
-                if (test_opt(sbi, DISCARD))
-                        blkdev_issue_discard(sbi->sb->s_bdev,
-                                        START_BLOCK(sbi, segno) <<
-                                        sbi->log_sectors_per_block,
-                                        1 << (sbi->log_sectors_per_block +
-                                                sbi->log_blocks_per_seg),
-                                        GFP_NOFS, 0);
+                blkdev_issue_discard(sbi->sb->s_bdev,
+                                START_BLOCK(sbi, start) <<
+                                sbi->log_sectors_per_block,
+                                (1 << (sbi->log_sectors_per_block +
+                                sbi->log_blocks_per_seg)) * (end - start),
+                                GFP_NOFS, 0);
         }
         mutex_unlock(&dirty_i->seglist_lock);
 }