Commit c24a0fd6 authored Jul 07, 2016 by Chao Yu Committed by Jaegeuk Kim Jul 08, 2016

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>

parent c7b41e16

fs/f2fs/segment.c

+3 −2

Original line number	Diff line number	Diff line
		@@ -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;

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