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    Subject[PATCH] f2fs: fix small discards when se->valid_blocks is zero
    Date
    In the small discard case, when se->valid_blocks is zero, the add_discard_addrs
    will directly return without __add_discard_entry. This will cause the file
    delete have no small discard. The case is like this:

    1. Allocate free 2M segment
    2. Write a file (size n blocks < 512) in that 2M segment, se->valid_blocks = n
    3. Delete that file, se->valid_blocks = 0, add_discard_addrs will return without
    sending any discard of that file, and forever due to cur_map[i] ^ ckpt_map[i] =
    0 after that checkpoint

    Signed-off-by: Yunlong Song <yunlong.song@huawei.com>
    ---
    fs/f2fs/segment.c | 2 +-
    1 file changed, 1 insertion(+), 1 deletion(-)

    diff --git a/fs/f2fs/segment.c b/fs/f2fs/segment.c
    index 0738f48..8610f14 100644
    --- a/fs/f2fs/segment.c
    +++ b/fs/f2fs/segment.c
    @@ -838,7 +838,7 @@ static void add_discard_addrs(struct f2fs_sb_info *sbi, struct cp_control *cpc)
    return;

    if (!force) {
    - if (!test_opt(sbi, DISCARD) || !se->valid_blocks ||
    + if (!test_opt(sbi, DISCARD) ||
    SM_I(sbi)->nr_discards >= SM_I(sbi)->max_discards)
    return;
    }
    --
    1.8.5.2
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