Messages in this thread Patch in this message | | | Subject | Re: [PATCH 2/5] f2fs: clear the remaining prefree_map of the section | From | Yunlong Song <> | Date | Fri, 13 Jul 2018 11:28:22 +0800 |
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round 1: section bitmap : 1 1 1 1 1, all valid, prefree_map: 0 0 0 0 0 then rm data block NO.2, block NO.2 becomes invalid, prefree_map: 0 0 1 0 0 write_checkpoint: section bitmap: 1 1 0 1 1, prefree_map: 0 0 0 0 0, prefree of NO.2 is cleared, and no discard issued
round2: rm data block NO.0, NO.1, NO.3, NO.4 all invalid, but prefree bit of NO.2 is set and cleared in round1, then prefree_map: 1 1 0 1 1 write_checkpoint: section bitmap: 0 0 0 0 0, prefree_map: 0 0 0 1 1, no valid blocks of this section, so discard issued but this time prefree bit of NO.3 and NO.4 is skipped...
round3: write_checkpoint: section bitmap: 0 0 0 0 0, prefree_map: 0 0 0 1 1 - > 0 0 0 0 0, no valid blocks of this section, so discard issued this time prefree bit of NO.3 and NO.4 is cleared, but the discard of this section is sent again...
On 2018/7/13 11:13, Chao Yu wrote: > On 2018/7/12 23:09, Yunlong Song wrote: >> For the case when sbi->segs_per_sec > 1, take section:segment = 5 for >> example, if the section prefree_map is ...previous section | current >> section (1 1 0 1 1) | next section..., then the start = x, end = x + 1, >> after start = start_segno + sbi->segs_per_sec, start = x + 5, then it >> will skip x + 3 and x + 4, but their bitmap is still set, which will >> cause duplicated f2fs_issue_discard of this same section in the next >> write_checkpoint, so fix it. > I didn't get it, if # 2 segment is not prefree state, so it still has valid > blocks there, so we won't issue discard due to below condition, right? > > if (!IS_CURSEC(sbi, secno) && > !get_valid_blocks(sbi, start, true)) > > Thanks, > >> Signed-off-by: Yunlong Song <yunlong.song@huawei.com> >> --- >> fs/f2fs/segment.c | 19 +++++++++++++++++-- >> 1 file changed, 17 insertions(+), 2 deletions(-) >> >> diff --git a/fs/f2fs/segment.c b/fs/f2fs/segment.c >> index 47b6595..fd38b61 100644 >> --- a/fs/f2fs/segment.c >> +++ b/fs/f2fs/segment.c >> @@ -1684,8 +1684,23 @@ void f2fs_clear_prefree_segments(struct f2fs_sb_info *sbi, >> start = start_segno + sbi->segs_per_sec; >> if (start < end) >> goto next; >> - else >> - end = start - 1; >> + else { >> + start_segno = start; >> + >> + while (1) { >> + start = find_next_bit(prefree_map, start_segno, >> + end + 1); >> + if (start >= start_segno) >> + break; >> + end = find_next_zero_bit(prefree_map, start_segno, >> + start + 1); >> + for (i = start; i < end; i++) >> + clear_bit(i, prefree_map); >> + dirty_i->nr_dirty[PRE] -= end - start; >> + } >> + >> + end = start_segno - 1; >> + } >> } >> mutex_unlock(&dirty_i->seglist_lock); >> >> > > . >
-- Thanks, Yunlong Song
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