4.18-stable review patch. If anyone has any objections, please let me know.
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From: Yunlong Song yunlong.song@huawei.com
[ Upstream commit ad6672bbc527727dc8968e8d92687f55ae928ce5 ]
For the case when sbi->segs_per_sec > 1 with lfs mode, 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:
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
round 2: rm data block NO.0, NO.1, NO.3, NO.4 all invalid, but prefree bit of NO.2 is set and cleared in round 1, 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 due to start = start_segno + sbi->segs_per_sec;
round 3: 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...
To fix this problem, we can align the start and end value to section boundary for fstrim and real-time discard operation, and decide to issue discard only when the whole section is invalid, which can issue discard aligned to section size as much as possible and avoid redundant discard.
Signed-off-by: Yunlong Song yunlong.song@huawei.com Signed-off-by: Chao Yu yuchao0@huawei.com Reviewed-by: Chao Yu yuchao0@huawei.com Signed-off-by: Jaegeuk Kim jaegeuk@kernel.org Signed-off-by: Sasha Levin alexander.levin@microsoft.com Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org --- fs/f2fs/segment.c | 20 +++++++++++++++++--- 1 file changed, 17 insertions(+), 3 deletions(-)
--- a/fs/f2fs/segment.c +++ b/fs/f2fs/segment.c @@ -1643,21 +1643,30 @@ void f2fs_clear_prefree_segments(struct unsigned int start = 0, end = -1; unsigned int secno, start_segno; bool force = (cpc->reason & CP_DISCARD); + bool need_align = test_opt(sbi, LFS) && sbi->segs_per_sec > 1;
mutex_lock(&dirty_i->seglist_lock);
while (1) { int i; + + if (need_align && end != -1) + end--; start = find_next_bit(prefree_map, MAIN_SEGS(sbi), end + 1); if (start >= MAIN_SEGS(sbi)) break; end = find_next_zero_bit(prefree_map, MAIN_SEGS(sbi), start + 1);
- for (i = start; i < end; i++) - clear_bit(i, prefree_map); + if (need_align) { + start = rounddown(start, sbi->segs_per_sec); + end = roundup(end, sbi->segs_per_sec); + }
- dirty_i->nr_dirty[PRE] -= end - start; + for (i = start; i < end; i++) { + if (test_and_clear_bit(i, prefree_map)) + dirty_i->nr_dirty[PRE]--; + }
if (!test_opt(sbi, DISCARD)) continue; @@ -2437,6 +2446,7 @@ int f2fs_trim_fs(struct f2fs_sb_info *sb struct discard_policy dpolicy; unsigned long long trimmed = 0; int err = 0; + bool need_align = test_opt(sbi, LFS) && sbi->segs_per_sec > 1;
if (start >= MAX_BLKADDR(sbi) || range->len < sbi->blocksize) return -EINVAL; @@ -2454,6 +2464,10 @@ int f2fs_trim_fs(struct f2fs_sb_info *sb start_segno = (start <= MAIN_BLKADDR(sbi)) ? 0 : GET_SEGNO(sbi, start); end_segno = (end >= MAX_BLKADDR(sbi)) ? MAIN_SEGS(sbi) - 1 : GET_SEGNO(sbi, end); + if (need_align) { + start_segno = rounddown(start_segno, sbi->segs_per_sec); + end_segno = roundup(end_segno + 1, sbi->segs_per_sec) - 1; + }
cpc.reason = CP_DISCARD; cpc.trim_minlen = max_t(__u64, 1, F2FS_BYTES_TO_BLK(range->minlen));