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Message-ID: <CACOAw_xQpov14gw2-e_dW9xXW_LvPnz-0BBX4jR4W4REe4xn-Q@mail.gmail.com>
Date: Mon, 27 Oct 2025 07:34:39 -0700
From: Daeho Jeong <daeho43@...il.com>
To: Chao Yu <chao@...nel.org>
Cc: linux-kernel@...r.kernel.org, linux-f2fs-devel@...ts.sourceforge.net,
kernel-team@...roid.com, Daeho Jeong <daehojeong@...gle.com>
Subject: Re: [f2fs-dev] [PATCH v3] f2fs: revert summary entry count from 2048
to 512 in 16kb block support
On Mon, Oct 27, 2025 at 12:00 AM Chao Yu <chao@...nel.org> wrote:
>
> On 10/16/25 05:11, Daeho Jeong wrote:
> > From: Daeho Jeong <daehojeong@...gle.com>
> >
> > The recent increase in the number of Segment Summary Area (SSA) entries
> > from 512 to 2048 was an unintentional change in logic of 16kb block
> > support. This commit corrects the issue.
> >
> > To better utilize the space available from the erroneous 2048-entry
> > calculation, we are implementing a solution to share the currently
> > unused SSA space with neighboring segments. This enhances overall
> > SSA utilization without impacting the established 8MB segment size.
> >
> > Fixes: d7e9a9037de2 ("f2fs: Support Block Size == Page Size")
> > Signed-off-by: Daeho Jeong <daehojeong@...gle.com>
> > ---
> > v2: detect legacy layout and prevent mount.
> > v3: error handling for a failure of f2fs_get_meta_folio().
> > ---
> > fs/f2fs/gc.c | 117 +++++++++++++++++++++++-----------------
> > fs/f2fs/recovery.c | 2 +-
> > fs/f2fs/segment.c | 29 ++++++----
> > fs/f2fs/segment.h | 8 ++-
> > fs/f2fs/super.c | 38 +++++++++++++
> > include/linux/f2fs_fs.h | 5 +-
> > 6 files changed, 136 insertions(+), 63 deletions(-)
> >
> > diff --git a/fs/f2fs/gc.c b/fs/f2fs/gc.c
> > index 8abf521530ff..af2f4d28462c 100644
> > --- a/fs/f2fs/gc.c
> > +++ b/fs/f2fs/gc.c
> > @@ -1732,7 +1732,7 @@ static int do_garbage_collect(struct f2fs_sb_info *sbi,
> > unsigned char type = IS_DATASEG(get_seg_entry(sbi, segno)->type) ?
> > SUM_TYPE_DATA : SUM_TYPE_NODE;
> > unsigned char data_type = (type == SUM_TYPE_DATA) ? DATA : NODE;
> > - int submitted = 0;
> > + int submitted = 0, sum_blk_cnt;
> >
> > if (__is_large_section(sbi)) {
> > sec_end_segno = rounddown(end_segno, SEGS_PER_SEC(sbi));
> > @@ -1766,22 +1766,28 @@ static int do_garbage_collect(struct f2fs_sb_info *sbi,
> >
> > sanity_check_seg_type(sbi, get_seg_entry(sbi, segno)->type);
> >
> > + segno = rounddown(segno, SUMS_PER_BLOCK);
> > + sum_blk_cnt = DIV_ROUND_UP(end_segno - segno, SUMS_PER_BLOCK);
> > /* readahead multi ssa blocks those have contiguous address */
> > if (__is_large_section(sbi))
> > f2fs_ra_meta_pages(sbi, GET_SUM_BLOCK(sbi, segno),
> > - end_segno - segno, META_SSA, true);
> > + sum_blk_cnt, META_SSA, true);
> >
> > /* reference all summary page */
> > while (segno < end_segno) {
> > - struct folio *sum_folio = f2fs_get_sum_folio(sbi, segno++);
> > + struct folio *sum_folio = f2fs_get_sum_folio(sbi, segno);
> > +
> > + segno += SUMS_PER_BLOCK;
> > if (IS_ERR(sum_folio)) {
> > int err = PTR_ERR(sum_folio);
> >
> > - end_segno = segno - 1;
> > - for (segno = start_segno; segno < end_segno; segno++) {
> > + end_segno = segno - SUMS_PER_BLOCK;
> > + segno = rounddown(start_segno, SUMS_PER_BLOCK);
> > + while (segno < end_segno) {
> > sum_folio = filemap_get_folio(META_MAPPING(sbi),
> > GET_SUM_BLOCK(sbi, segno));
> > folio_put_refs(sum_folio, 2);
> > + segno += SUMS_PER_BLOCK;
> > }
> > return err;
> > }
> > @@ -1790,68 +1796,83 @@ static int do_garbage_collect(struct f2fs_sb_info *sbi,
> >
> > blk_start_plug(&plug);
> >
> > - for (segno = start_segno; segno < end_segno; segno++) {
> > - struct f2fs_summary_block *sum;
> > + segno = start_segno;
> > + while (segno < end_segno) {
> > + unsigned int cur_segno;
> >
> > /* find segment summary of victim */
> > struct folio *sum_folio = filemap_get_folio(META_MAPPING(sbi),
> > GET_SUM_BLOCK(sbi, segno));
> > + unsigned int block_end_segno = rounddown(segno, SUMS_PER_BLOCK)
> > + + SUMS_PER_BLOCK;
> > +
> > + if (block_end_segno > end_segno)
> > + block_end_segno = end_segno;
> >
> > if (is_cursec(sbi, GET_SEC_FROM_SEG(sbi, segno))) {
> > f2fs_err(sbi, "%s: segment %u is used by log",
> > __func__, segno);
> > f2fs_bug_on(sbi, 1);
> > - goto skip;
> > + goto next_block;
> > }
> >
> > - if (get_valid_blocks(sbi, segno, false) == 0)
> > - goto freed;
> > - if (gc_type == BG_GC && __is_large_section(sbi) &&
> > - migrated >= sbi->migration_granularity)
> > - goto skip;
> > if (!folio_test_uptodate(sum_folio) ||
> > unlikely(f2fs_cp_error(sbi)))
> > - goto skip;
> > + goto next_block;
> >
> > - sum = folio_address(sum_folio);
> > - if (type != GET_SUM_TYPE((&sum->footer))) {
> > - f2fs_err(sbi, "Inconsistent segment (%u) type [%d, %d] in SIT and SSA",
> > - segno, type, GET_SUM_TYPE((&sum->footer)));
> > - f2fs_stop_checkpoint(sbi, false,
> > - STOP_CP_REASON_CORRUPTED_SUMMARY);
> > - goto skip;
> > - }
> > + for (cur_segno = segno; cur_segno < block_end_segno;
> > + cur_segno++) {
> > + struct f2fs_summary_block *sum;
> >
> > - /*
> > - * this is to avoid deadlock:
> > - * - lock_page(sum_page) - f2fs_replace_block
> > - * - check_valid_map() - down_write(sentry_lock)
> > - * - down_read(sentry_lock) - change_curseg()
> > - * - lock_page(sum_page)
> > - */
> > - if (type == SUM_TYPE_NODE)
> > - submitted += gc_node_segment(sbi, sum->entries, segno,
> > - gc_type);
> > - else
> > - submitted += gc_data_segment(sbi, sum->entries, gc_list,
> > - segno, gc_type,
> > - force_migrate);
> > + if (get_valid_blocks(sbi, cur_segno, false) == 0)
> > + goto freed;
> > + if (gc_type == BG_GC && __is_large_section(sbi) &&
> > + migrated >= sbi->migration_granularity)
> > + continue;
> >
> > - stat_inc_gc_seg_count(sbi, data_type, gc_type);
> > - sbi->gc_reclaimed_segs[sbi->gc_mode]++;
> > - migrated++;
> > + sum = SUM_BLK_PAGE_ADDR(sum_folio, cur_segno);
> > + if (type != GET_SUM_TYPE((&sum->footer))) {
> > + f2fs_err(sbi, "Inconsistent segment (%u) type "
> > + "[%d, %d] in SSA and SIT",
> > + cur_segno, type,
> > + GET_SUM_TYPE((&sum->footer)));
> > + f2fs_stop_checkpoint(sbi, false,
> > + STOP_CP_REASON_CORRUPTED_SUMMARY);
> > + continue;
> > + }
> >
> > -freed:
> > - if (gc_type == FG_GC &&
> > - get_valid_blocks(sbi, segno, false) == 0)
> > - seg_freed++;
> > + /*
> > + * this is to avoid deadlock:
> > + * - lock_page(sum_page) - f2fs_replace_block
> > + * - check_valid_map() - down_write(sentry_lock)
> > + * - down_read(sentry_lock) - change_curseg()
> > + * - lock_page(sum_page)
> > + */
> > + if (type == SUM_TYPE_NODE)
> > + submitted += gc_node_segment(sbi, sum->entries,
> > + cur_segno, gc_type);
> > + else
> > + submitted += gc_data_segment(sbi, sum->entries,
> > + gc_list, cur_segno,
> > + gc_type, force_migrate);
> >
> > - if (__is_large_section(sbi))
> > - sbi->next_victim_seg[gc_type] =
> > - (segno + 1 < sec_end_segno) ?
> > - segno + 1 : NULL_SEGNO;
> > -skip:
> > + stat_inc_gc_seg_count(sbi, data_type, gc_type);
> > + sbi->gc_reclaimed_segs[sbi->gc_mode]++;
> > + migrated++;
> > +
> > +freed:
> > + if (gc_type == FG_GC &&
> > + get_valid_blocks(sbi, cur_segno, false) == 0)
> > + seg_freed++;
> > +
> > + if (__is_large_section(sbi))
> > + sbi->next_victim_seg[gc_type] =
> > + (cur_segno + 1 < sec_end_segno) ?
> > + cur_segno + 1 : NULL_SEGNO;
> > + }
> > +next_block:
> > folio_put_refs(sum_folio, 2);
> > + segno = block_end_segno;
> > }
> >
> > if (submitted)
> > diff --git a/fs/f2fs/recovery.c b/fs/f2fs/recovery.c
> > index 215e442db72c..af72309b9bfc 100644
> > --- a/fs/f2fs/recovery.c
> > +++ b/fs/f2fs/recovery.c
> > @@ -519,7 +519,7 @@ static int check_index_in_prev_nodes(struct f2fs_sb_info *sbi,
> > sum_folio = f2fs_get_sum_folio(sbi, segno);
> > if (IS_ERR(sum_folio))
> > return PTR_ERR(sum_folio);
> > - sum_node = folio_address(sum_folio);
> > + sum_node = SUM_BLK_PAGE_ADDR(sum_folio, segno);
> > sum = sum_node->entries[blkoff];
> > f2fs_folio_put(sum_folio, true);
> > got_it:
> > diff --git a/fs/f2fs/segment.c b/fs/f2fs/segment.c
> > index b45eace879d7..77aa2125b8ca 100644
> > --- a/fs/f2fs/segment.c
> > +++ b/fs/f2fs/segment.c
> > @@ -2712,7 +2712,10 @@ struct folio *f2fs_get_sum_folio(struct f2fs_sb_info *sbi, unsigned int segno)
> > void f2fs_update_meta_page(struct f2fs_sb_info *sbi,
> > void *src, block_t blk_addr)
> > {
> > - struct folio *folio = f2fs_grab_meta_folio(sbi, blk_addr);
> > + struct folio *folio = f2fs_get_meta_folio_retry(sbi, blk_addr);
> > +
> > + if (IS_ERR(folio))
> > + return;
> >
> > memcpy(folio_address(folio), src, PAGE_SIZE);
> > folio_mark_dirty(folio);
> > @@ -2720,9 +2723,17 @@ void f2fs_update_meta_page(struct f2fs_sb_info *sbi,
> > }
> >
> > static void write_sum_page(struct f2fs_sb_info *sbi,
> > - struct f2fs_summary_block *sum_blk, block_t blk_addr)
> > + struct f2fs_summary_block *sum_blk, unsigned int segno)
> > {
> > - f2fs_update_meta_page(sbi, (void *)sum_blk, blk_addr);
> > + struct folio *folio;
> > +
> > + folio = f2fs_get_sum_folio(sbi, segno);
> > + if (IS_ERR(folio))
> > + return;
> > +
> > + memcpy(SUM_BLK_PAGE_ADDR(folio, segno), sum_blk, sizeof(*sum_blk));
> > + folio_mark_dirty(folio);
> > + f2fs_folio_put(folio, true);
> > }
> >
> > static void write_current_sum_page(struct f2fs_sb_info *sbi,
> > @@ -2987,7 +2998,7 @@ static int new_curseg(struct f2fs_sb_info *sbi, int type, bool new_sec)
> > int ret;
> >
> > if (curseg->inited)
> > - write_sum_page(sbi, curseg->sum_blk, GET_SUM_BLOCK(sbi, segno));
> > + write_sum_page(sbi, curseg->sum_blk, segno);
> >
> > segno = __get_next_segno(sbi, type);
> > ret = get_new_segment(sbi, &segno, new_sec, pinning);
> > @@ -3046,7 +3057,7 @@ static int change_curseg(struct f2fs_sb_info *sbi, int type)
> > struct folio *sum_folio;
> >
> > if (curseg->inited)
> > - write_sum_page(sbi, curseg->sum_blk, GET_SUM_BLOCK(sbi, curseg->segno));
> > + write_sum_page(sbi, curseg->sum_blk, curseg->segno);
> >
> > __set_test_and_inuse(sbi, new_segno);
> >
> > @@ -3065,7 +3076,7 @@ static int change_curseg(struct f2fs_sb_info *sbi, int type)
> > memset(curseg->sum_blk, 0, SUM_ENTRY_SIZE);
> > return PTR_ERR(sum_folio);
> > }
> > - sum_node = folio_address(sum_folio);
> > + sum_node = SUM_BLK_PAGE_ADDR(sum_folio, new_segno);
> > memcpy(curseg->sum_blk, sum_node, SUM_ENTRY_SIZE);
> > f2fs_folio_put(sum_folio, true);
> > return 0;
> > @@ -3154,8 +3165,7 @@ static void __f2fs_save_inmem_curseg(struct f2fs_sb_info *sbi, int type)
> > goto out;
> >
> > if (get_valid_blocks(sbi, curseg->segno, false)) {
> > - write_sum_page(sbi, curseg->sum_blk,
> > - GET_SUM_BLOCK(sbi, curseg->segno));
> > + write_sum_page(sbi, curseg->sum_blk, curseg->segno);
> > } else {
> > mutex_lock(&DIRTY_I(sbi)->seglist_lock);
> > __set_test_and_free(sbi, curseg->segno, true);
> > @@ -3833,8 +3843,7 @@ int f2fs_allocate_data_block(struct f2fs_sb_info *sbi, struct folio *folio,
> > if (segment_full) {
> > if (type == CURSEG_COLD_DATA_PINNED &&
> > !((curseg->segno + 1) % sbi->segs_per_sec)) {
> > - write_sum_page(sbi, curseg->sum_blk,
> > - GET_SUM_BLOCK(sbi, curseg->segno));
> > + write_sum_page(sbi, curseg->sum_blk, curseg->segno);
> > reset_curseg_fields(curseg);
> > goto skip_new_segment;
> > }
> > diff --git a/fs/f2fs/segment.h b/fs/f2fs/segment.h
> > index 1ce2c8abaf48..e883f14c228f 100644
> > --- a/fs/f2fs/segment.h
> > +++ b/fs/f2fs/segment.h
> > @@ -85,8 +85,12 @@ static inline void sanity_check_seg_type(struct f2fs_sb_info *sbi,
> > #define GET_ZONE_FROM_SEG(sbi, segno) \
> > GET_ZONE_FROM_SEC(sbi, GET_SEC_FROM_SEG(sbi, segno))
> >
> > -#define GET_SUM_BLOCK(sbi, segno) \
> > - ((sbi)->sm_info->ssa_blkaddr + (segno))
> > +#define SUMS_PER_BLOCK (F2FS_BLKSIZE / F2FS_SUM_BLKSIZE)
> > +#define GET_SUM_BLOCK(sbi, segno) \
> > + (SM_I(sbi)->ssa_blkaddr + (segno / SUMS_PER_BLOCK))
> > +#define GET_SUM_BLKOFF(segno) (segno % SUMS_PER_BLOCK)
> > +#define SUM_BLK_PAGE_ADDR(folio, segno) \
> > + (folio_address(folio) + GET_SUM_BLKOFF(segno) * F2FS_SUM_BLKSIZE)
> >
> > #define GET_SUM_TYPE(footer) ((footer)->entry_type)
> > #define SET_SUM_TYPE(footer, type) ((footer)->entry_type = (type))
> > diff --git a/fs/f2fs/super.c b/fs/f2fs/super.c
> > index 6e52e36c1f1a..5c323850e298 100644
> > --- a/fs/f2fs/super.c
> > +++ b/fs/f2fs/super.c
> > @@ -4052,6 +4052,44 @@ static int sanity_check_raw_super(struct f2fs_sb_info *sbi,
> > if (sanity_check_area_boundary(sbi, folio, index))
> > return -EFSCORRUPTED;
> >
> > + /*
> > + * Check for legacy summary layout on 16KB+ block devices.
> > + * Modern f2fs-tools packs multiple 4KB summary areas into one block,
> > + * whereas legacy versions used one block per summary, leading
> > + * to a much larger SSA.
> > + */
> > + if (SUMS_PER_BLOCK > 1) {
> > + unsigned int required_ssa_blocks;
> > + unsigned int expected_ssa_segs;
> > + unsigned int total_meta_segments, diff;
> > + unsigned int segment_count_ssa =
> > + le32_to_cpu(raw_super->segment_count_ssa);
> > + unsigned int segs_per_zone = segs_per_sec * secs_per_zone;
> > +
> > + required_ssa_blocks = DIV_ROUND_UP(segment_count_main,
> > + SUMS_PER_BLOCK);
> > + expected_ssa_segs = DIV_ROUND_UP(required_ssa_blocks,
> > + blocks_per_seg);
> > + total_meta_segments =
> > + le32_to_cpu(raw_super->segment_count_ckpt) +
> > + le32_to_cpu(raw_super->segment_count_sit) +
> > + le32_to_cpu(raw_super->segment_count_nat) +
> > + expected_ssa_segs;
> > + diff = total_meta_segments % segs_per_zone;
> > + if (diff)
> > + expected_ssa_segs += segs_per_zone - diff;
> > +
> > + if (segment_count_ssa > expected_ssa_segs) {
>
> Daeho,
>
> Not sure, for an extreme small-sized image, e.g. 64MB, at most, filesystem
> has 32 segments, so 32 summary blocks are enough? Then, segment_count_ssa and
> expected_ssa_segs could be the same (one segment)? Or am I missing something?
In that case, segment_count_ssa and expected_ssa_segs will be the
same, 1. Then, it's fine.
What do you worry about? Could you elaborate?
>
> Thanks,
>
> > + f2fs_info(sbi, "Error: Device formatted with a legacy "
> > + "version. Please reformat.");
> > + f2fs_info(sbi, "\tSSA segment count (%u) is larger "
> > + "than expected (%u) for block "
> > + "size (%lu).", segment_count_ssa,
> > + expected_ssa_segs, F2FS_BLKSIZE);
> > + return -EOPNOTSUPP;
> > + }
> > + }
> > +
> > return 0;
> > }
> >
> > diff --git a/include/linux/f2fs_fs.h b/include/linux/f2fs_fs.h
> > index 6afb4a13b81d..a7880787cad3 100644
> > --- a/include/linux/f2fs_fs.h
> > +++ b/include/linux/f2fs_fs.h
> > @@ -17,6 +17,7 @@
> > #define F2FS_LOG_SECTORS_PER_BLOCK (PAGE_SHIFT - 9) /* log number for sector/blk */
> > #define F2FS_BLKSIZE PAGE_SIZE /* support only block == page */
> > #define F2FS_BLKSIZE_BITS PAGE_SHIFT /* bits for F2FS_BLKSIZE */
> > +#define F2FS_SUM_BLKSIZE 4096 /* only support 4096 byte sum block */
> > #define F2FS_MAX_EXTENSION 64 /* # of extension entries */
> > #define F2FS_EXTENSION_LEN 8 /* max size of extension */
> >
> > @@ -441,7 +442,7 @@ struct f2fs_sit_block {
> > * from node's page's beginning to get a data block address.
> > * ex) data_blkaddr = (block_t)(nodepage_start_address + ofs_in_node)
> > */
> > -#define ENTRIES_IN_SUM (F2FS_BLKSIZE / 8)
> > +#define ENTRIES_IN_SUM (F2FS_SUM_BLKSIZE / 8)
> > #define SUMMARY_SIZE (7) /* sizeof(struct f2fs_summary) */
> > #define SUM_FOOTER_SIZE (5) /* sizeof(struct summary_footer) */
> > #define SUM_ENTRY_SIZE (SUMMARY_SIZE * ENTRIES_IN_SUM)
> > @@ -467,7 +468,7 @@ struct summary_footer {
> > __le32 check_sum; /* summary checksum */
> > } __packed;
> >
> > -#define SUM_JOURNAL_SIZE (F2FS_BLKSIZE - SUM_FOOTER_SIZE -\
> > +#define SUM_JOURNAL_SIZE (F2FS_SUM_BLKSIZE - SUM_FOOTER_SIZE -\
> > SUM_ENTRY_SIZE)
> > #define NAT_JOURNAL_ENTRIES ((SUM_JOURNAL_SIZE - 2) /\
> > sizeof(struct nat_journal_entry))
>
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