[PATCH] f2fs: only fragment segment in the same section

Sheng Yong
2024-06-25T07:59:11Z

If mode=fragment:xxx is enabled in large section mode, segno returned by
__get_next_segno() may located in new section with different type, which
messes up ssa type. This could be reproduced by the following steps:

dd if=/dev/zero of=test.img bs=1M count=10240
mkfs.f2fs -s 128 test.img
mount -t f2fs test.img /mnt -o mode=fragment:block
echo 1 > /sys/fs/f2fs/loop0/max_fragment_chunk
echo 512 > /sys/fs/f2fs/loop0/max_fragment_hole
dd if=/dev/zero of=/mnt/testfile bs=4K count=100
umount /mnt

F2FS-fs (loop0): Inconsistent segment (4377) type [0, 1] in SSA and SIT

In order to allow simulate segment fragmentation in large section mode,
this patch limits the random range within the same section.

Signed-off-by: Sheng Yong <shengyong@oppo.com>
---
fs/f2fs/segment.c | 15 +++++++++++++--
1 file changed, 13 insertions(+), 2 deletions(-)

diff --git a/fs/f2fs/segment.c b/fs/f2fs/segment.c
index a0ce3d080f80a..55d474f5c2103 100644
--- a/fs/f2fs/segment.c
+++ b/fs/f2fs/segment.c
@@ -2782,10 +2782,21 @@ static unsigned int __get_next_segno(struct f2fs_sb_info *sbi, int type)
{
struct curseg_info *curseg = CURSEG_I(sbi, type);
unsigned short seg_type = curseg->seg_type;
+ unsigned int hint;

sanity_check_seg_type(sbi, seg_type);
- if (f2fs_need_rand_seg(sbi))
- return get_random_u32_below(MAIN_SECS(sbi) * SEGS_PER_SEC(sbi));
+ if (f2fs_need_rand_seg(sbi)) {
+ if (__is_large_section(sbi)) {
+ hint = GET_SEC_FROM_SEG(sbi, curseg->segno);
+ if (GET_SEC_FROM_SEG(sbi, curseg->segno + 1) != hint)
+ return curseg->segno;
+ return get_random_u32_inclusive(curseg->segno + 1,
+ GET_SEG_FROM_SEC(sbi, hint + 1) - 1);
+ } else {
+ return get_random_u32_below(MAIN_SECS(sbi) *
+ SEGS_PER_SEC(sbi));
+ }
+ }

if (__is_large_section(sbi))
return curseg->segno;
--
2.40.1