On 2024/6/25 20:15, Sheng Yong wrote:
When new_curseg() is allocating a new segment, if mode=fragment:xxx is
switched on in large section scenario, __get_next_segno() will select
the next segno randomly in the range of [0, maxsegno] in order to
fragment segments.

If the candidate segno is free, get_new_segment() will use it directly
as the new segment.

However, if the section of the candidate is not empty, and some other
segments have already been used, and have a different type (e.g NODE)
with the candidate (e.g DATA), GC will complain inconsistent segment
type later.

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 simulating segment fragmentation in large section
scenario, this patch reduces the candidate range:
  * if curseg is the last segment in the section, return curseg->segno
    to make get_new_segment() itself find the next free segment.
  * if curseg is in the middle of the secion, select candicate randomly in
    the range of [curseg + 1, last_seg_in_the_same_section] to keep type
    consistent.

Signed-off-by: Sheng Yong <shengy...@oppo.com>

Reviewed-by: Chao Yu <c...@kernel.org>

Thanks,


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