f2fs: fix to avoid redundant discard during fstrim

With below test steps, f2fs will issue redundant discard when doing fstrim,
the reason is that we issue discards for both prefree segments and
consecutive freed region user wants to trim, part regions they covered are
overlapped, here, we change to do not to issue any discards for prefree
segments in trimmed range.

1. mount -t f2fs -o discard /dev/zram0 /mnt/f2fs
2. fstrim -o 0 -l 3221225472 -m 2097152 -v /mnt/f2fs/
3. dd if=/dev/zero  of=/mnt/f2fs/a bs=2M count=1
4. dd if=/dev/zero  of=/mnt/f2fs/b bs=1M count=1
5. sync
6. rm /mnt/f2fs/a /mnt/f2fs/b
7. fstrim -o 0 -l 3221225472 -m 2097152 -v /mnt/f2fs/

Before:
<...>-5428  [001] ...1  9511.052125: f2fs_issue_discard: dev = (251,0), blkstart = 0x2200, blklen = 0x200
<...>-5428  [001] ...1  9511.052787: f2fs_issue_discard: dev = (251,0), blkstart = 0x2200, blklen = 0x300

After:
<...>-6764  [000] ...1  9720.382504: f2fs_issue_discard: dev = (251,0), blkstart = 0x2200, blklen = 0x300

Signed-off-by: Chao Yu <yuchao0@huawei.com>
Signed-off-by: Jaegeuk Kim <jaegeuk@kernel.org>

diff --git a/fs/f2fs/segment.c b/fs/f2fs/segment.c
index 9e13db05e3f09e2472ebf7461806d536a16eec4a..08f6c0be20cf44042d363ace1851f6e6575c1b7a 100644 (file)
--- a/fs/f2fs/segment.c
+++ b/fs/f2fs/segment.c
@@ -714,6 +714,7 @@ void clear_prefree_segments(struct f2fs_sb_info *sbi, struct cp_control *cpc)
        unsigned long *prefree_map = dirty_i->dirty_segmap[PRE];
        unsigned int start = 0, end = -1;
        unsigned int secno, start_segno;
+       bool force = (cpc->reason == CP_DISCARD);
 
        mutex_lock(&dirty_i->seglist_lock);
 
@@ -730,7 +731,7 @@ void clear_prefree_segments(struct f2fs_sb_info *sbi, struct cp_control *cpc)
 
                dirty_i->nr_dirty[PRE] -= end - start;
 
-               if (!test_opt(sbi, DISCARD))
+               if (force || !test_opt(sbi, DISCARD))
                        continue;
 
                if (!test_opt(sbi, LFS) || sbi->segs_per_sec == 1) {
@@ -754,7 +755,7 @@ next:
 
        /* send small discards */
        list_for_each_entry_safe(entry, this, head, list) {
-               if (cpc->reason == CP_DISCARD && entry->len < cpc->trim_minlen)
+               if (force && entry->len < cpc->trim_minlen)
                        goto skip;
                f2fs_issue_discard(sbi, entry->blkaddr, entry->len);
                cpc->trimmed += entry->len;