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    Subject[PATCH 6.0 124/862] f2fs: complete checkpoints during remount
    Date
    From: Jaegeuk Kim <jaegeuk@kernel.org>

    commit 4f99484d27961cb194cebcd917176fa038a5025f upstream.

    Otherwise, pending checkpoints can contribute a race condition to give a
    quota warning.

    - Thread - checkpoint thread
    add checkpoints to the list
    do_remount()
    down_write(&sb->s_umount);
    f2fs_remount()
    block_operations()
    down_read_trylock(&sb->s_umount) = 0
    up_write(&sb->s_umount);
    f2fs_quota_sync()
    dquot_writeback_dquots()
    WARN_ON_ONCE(!rwsem_is_locked(&sb->s_umount));

    Or,

    do_remount()
    down_write(&sb->s_umount);
    f2fs_remount()
    create a ckpt thread
    f2fs_enable_checkpoint() adds checkpoints
    wait for f2fs_sync_fs()
    trigger another pending checkpoint
    block_operations()
    down_read_trylock(&sb->s_umount) = 0
    up_write(&sb->s_umount);
    f2fs_quota_sync()
    dquot_writeback_dquots()
    WARN_ON_ONCE(!rwsem_is_locked(&sb->s_umount));

    Cc: stable@vger.kernel.org
    Reviewed-by: Chao Yu <chao@kernel.org>
    Signed-off-by: Jaegeuk Kim <jaegeuk@kernel.org>
    Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
    ---
    fs/f2fs/super.c | 6 ++++++
    1 file changed, 6 insertions(+)

    --- a/fs/f2fs/super.c
    +++ b/fs/f2fs/super.c
    @@ -2181,6 +2181,9 @@ static void f2fs_enable_checkpoint(struc
    f2fs_up_write(&sbi->gc_lock);

    f2fs_sync_fs(sbi->sb, 1);
    +
    + /* Let's ensure there's no pending checkpoint anymore */
    + f2fs_flush_ckpt_thread(sbi);
    }

    static int f2fs_remount(struct super_block *sb, int *flags, char *data)
    @@ -2346,6 +2349,9 @@ static int f2fs_remount(struct super_blo
    f2fs_stop_ckpt_thread(sbi);
    need_restart_ckpt = true;
    } else {
    + /* Flush if the prevous checkpoint, if exists. */
    + f2fs_flush_ckpt_thread(sbi);
    +
    err = f2fs_start_ckpt_thread(sbi);
    if (err) {
    f2fs_err(sbi,

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