On 03/24, Chao Yu wrote:
> In CP disabling mode, there are two issues when using LFS or SSR | AT_SSR
> mode to select victim:
>
> 1. LFS is set to find source section during GC, the victim should have
> no checkpointed data, since after GC, section could not be set free for
> reuse.
>
> Previously, we only check valid chpt blocks in current segment rather
> than section, fix it.
>
> 2. SSR | AT_SSR are set to find target segment for writes which can be
> fully filled by checkpointed and newly written blocks, we should never
> select such segment, otherwise it can cause panic or data corruption
> during allocation, potential case is described as below:
>
> a) target segment has 128 ckpt valid blocks
> b) GC migrates 'n' (n < 512) valid blocks to other segment (segment is
> still in dirty list)
> c) GC migrates '512 - n' blocks to target segment (segment has 'n'
> cp_vblocks and '512 - n' vblocks)
> d) If GC selects target segment via {AT,}SSR allocator, however there
> is no free space in targe segment.
>
> Fixes: 4354994f097d ("f2fs: checkpoint disabling")
> Fixes: 093749e296e2 ("f2fs: support age threshold based garbage collection")
> Signed-off-by: Chao Yu <yuch...@huawei.com>
> ---
> v2:
> - fix to check checkpointed data in section rather than segment for
> LFS mode.
> - update commit title and message.
> fs/f2fs/f2fs.h | 1 +
> fs/f2fs/gc.c | 28 ++++++++++++++++++++--------
> fs/f2fs/segment.c | 39 ++++++++++++++++++++++++---------------
> fs/f2fs/segment.h | 14 +++++++++++++-
> 4 files changed, 58 insertions(+), 24 deletions(-)
>
> diff --git a/fs/f2fs/f2fs.h b/fs/f2fs/f2fs.h
> index eb154d9cb063..29e634d08a27 100644
> --- a/fs/f2fs/f2fs.h
> +++ b/fs/f2fs/f2fs.h
> @@ -3387,6 +3387,7 @@ block_t f2fs_get_unusable_blocks(struct f2fs_sb_info
> *sbi);
> int f2fs_disable_cp_again(struct f2fs_sb_info *sbi, block_t unusable);
> void f2fs_release_discard_addrs(struct f2fs_sb_info *sbi);
> int f2fs_npages_for_summary_flush(struct f2fs_sb_info *sbi, bool for_ra);
> +bool segment_has_free_slot(struct f2fs_sb_info *sbi, int segno);
> void f2fs_init_inmem_curseg(struct f2fs_sb_info *sbi);
> void f2fs_save_inmem_curseg(struct f2fs_sb_info *sbi);
> void f2fs_restore_inmem_curseg(struct f2fs_sb_info *sbi);
> diff --git a/fs/f2fs/gc.c b/fs/f2fs/gc.c
> index d96acc6531f2..4d9616373a4a 100644
> --- a/fs/f2fs/gc.c
> +++ b/fs/f2fs/gc.c
> @@ -392,10 +392,6 @@ static void add_victim_entry(struct f2fs_sb_info *sbi,
> if (p->gc_mode == GC_AT &&
> get_valid_blocks(sbi, segno, true) == 0)
> return;
> -
> - if (p->alloc_mode == AT_SSR &&
> - get_seg_entry(sbi, segno)->ckpt_valid_blocks == 0)
> - return;
> }
>
> for (i = 0; i < sbi->segs_per_sec; i++)
> @@ -728,11 +724,27 @@ static int get_victim_by_default(struct f2fs_sb_info
> *sbi,
>
> if (sec_usage_check(sbi, secno))
> goto next;
> +
> /* Don't touch checkpointed data */
> - if (unlikely(is_sbi_flag_set(sbi, SBI_CP_DISABLED) &&
> - get_ckpt_valid_blocks(sbi, segno) &&
> - p.alloc_mode == LFS))
> - goto next;
> + if (unlikely(is_sbi_flag_set(sbi, SBI_CP_DISABLED))) {
> + if (p.alloc_mode == LFS) {
> + /*
> + * LFS is set to find source section during GC.
> + * The victim should have no checkpointed data.
> + */
> + if (get_ckpt_valid_blocks(sbi, segno, true))
> + goto next;
> + } else {
> + /*
> + * SSR | AT_SSR are set to find target segment
> + * for writes which can be full by checkpointed
> + * and newly written blocks.
> + */
> + if (!segment_has_free_slot(sbi, segno))
> + goto next;
> + }
> + }
> +
> if (gc_type == BG_GC && test_bit(secno, dirty_i->victim_secmap))
> goto next;
>
> diff --git a/fs/f2fs/segment.c b/fs/f2fs/segment.c
> index 6e1a5f5657bf..f6a30856ceda 100644
> --- a/fs/f2fs/segment.c
> +++ b/fs/f2fs/segment.c
> @@ -865,7 +865,7 @@ static void locate_dirty_segment(struct f2fs_sb_info
> *sbi, unsigned int segno)
> mutex_lock(&dirty_i->seglist_lock);
>
> valid_blocks = get_valid_blocks(sbi, segno, false);
> - ckpt_valid_blocks = get_ckpt_valid_blocks(sbi, segno);
> + ckpt_valid_blocks = get_ckpt_valid_blocks(sbi, segno, false);
>
> if (valid_blocks == 0 && (!is_sbi_flag_set(sbi, SBI_CP_DISABLED) ||
> ckpt_valid_blocks == usable_blocks)) {
> @@ -950,7 +950,7 @@ static unsigned int get_free_segment(struct f2fs_sb_info
> *sbi)
> for_each_set_bit(segno, dirty_i->dirty_segmap[DIRTY], MAIN_SEGS(sbi)) {
> if (get_valid_blocks(sbi, segno, false))
> continue;
> - if (get_ckpt_valid_blocks(sbi, segno))
> + if (get_ckpt_valid_blocks(sbi, segno, false))
> continue;
> mutex_unlock(&dirty_i->seglist_lock);
> return segno;
> @@ -2643,6 +2643,26 @@ static void __refresh_next_blkoff(struct f2fs_sb_info
> *sbi,
> seg->next_blkoff++;
> }
>
> +bool segment_has_free_slot(struct f2fs_sb_info *sbi, int segno)
> +{
> + struct sit_info *sit = SIT_I(sbi);
> + struct seg_entry *se = get_seg_entry(sbi, segno);
> + int entries = SIT_VBLOCK_MAP_SIZE / sizeof(unsigned long);
> + unsigned long *target_map = SIT_I(sbi)->tmp_map;
> + unsigned long *ckpt_map = (unsigned long *)se->ckpt_valid_map;
> + unsigned long *cur_map = (unsigned long *)se->cur_valid_map;
> + int i, pos;
> +
> + down_write(&sit->sentry_lock);
Should remove this lock.
https://git.kernel.org/pub/scm/linux/kernel/git/jaegeuk/f2fs.git/commit/?h=dev
> + for (i = 0; i < entries; i++)
> + target_map[i] = ckpt_map[i] | cur_map[i];
> +
> + pos = __find_rev_next_zero_bit(target_map, sbi->blocks_per_seg, 0);
> + up_write(&sit->sentry_lock);
> +
> + return pos < sbi->blocks_per_seg;
> +}
> +
> /*
> * This function always allocates a used segment(from dirty seglist) by SSR
> * manner, so it should recover the existing segment information of valid
> blocks
> @@ -2913,19 +2933,8 @@ static void __allocate_new_segment(struct f2fs_sb_info
> *sbi, int type,
> get_valid_blocks(sbi, curseg->segno, new_sec))
> goto alloc;
>
> - if (new_sec) {
> - unsigned int segno = START_SEGNO(curseg->segno);
> - int i;
> -
> - for (i = 0; i < sbi->segs_per_sec; i++, segno++) {
> - if (get_ckpt_valid_blocks(sbi, segno))
> - goto alloc;
> - }
> - } else {
> - if (!get_ckpt_valid_blocks(sbi, curseg->segno))
> - return;
> - }
> -
> + if (!get_ckpt_valid_blocks(sbi, curseg->segno, new_sec))
> + return;
> alloc:
> old_segno = curseg->segno;
> SIT_I(sbi)->s_ops->allocate_segment(sbi, type, true);
> diff --git a/fs/f2fs/segment.h b/fs/f2fs/segment.h
> index 144980b62f9e..dab87ecba2b5 100644
> --- a/fs/f2fs/segment.h
> +++ b/fs/f2fs/segment.h
> @@ -359,8 +359,20 @@ static inline unsigned int get_valid_blocks(struct
> f2fs_sb_info *sbi,
> }
>
> static inline unsigned int get_ckpt_valid_blocks(struct f2fs_sb_info *sbi,
> - unsigned int segno)
> + unsigned int segno, bool use_section)
> {
> + if (use_section && __is_large_section(sbi)) {
> + unsigned int start_segno = START_SEGNO(segno);
> + unsigned int blocks = 0;
> + int i;
> +
> + for (i = 0; i < sbi->segs_per_sec; i++, start_segno++) {
> + struct seg_entry *se = get_seg_entry(sbi, start_segno);
> +
> + blocks += se->ckpt_valid_blocks;
> + }
> + return blocks;
> + }
> return get_seg_entry(sbi, segno)->ckpt_valid_blocks;
> }
>
> --
> 2.29.2
