On Mon, Jan 14, 2013 at 8:08 PM, majianpeng <majianpeng@xxxxxxxxx> wrote:
> There is an race between umount f2fs and read f2fs/status.
> It will case oops.
> Fox example:
> Thread A Thread B
> umount f2fs cat f2fs/status
> f2fs_destroy_stats() { stat_show() {
> list_for_each_entry_safe(&f2fs_stat_list)
> list_del(&si->stat_list);
> mutex_lock(&si->stat_lock);
> si->sbi = NULL;
> mutex_unlock(&si->stat_lock);
> kfree(sbi->stat_info);
> mutex_lock(&si->stat_lock)
>
> Signed-off-by: Jianpeng Ma <majianpeng@xxxxxxxxx>
> ---
> fs/f2fs/debug.c | 9 +++++++++
> 1 file changed, 9 insertions(+)
>
> diff --git a/fs/f2fs/debug.c b/fs/f2fs/debug.c
> index 0e0380a..ec6d004 100644
> --- a/fs/f2fs/debug.c
> +++ b/fs/f2fs/debug.c
> @@ -26,6 +26,7 @@
>
> static LIST_HEAD(f2fs_stat_list);
> static struct dentry *debugfs_root;
> +static DEFINE_MUTEX(f2fs_stat_mutex);
>
> static void update_general_status(struct f2fs_sb_info *sbi)
> {
> @@ -180,6 +181,7 @@ static int stat_show(struct seq_file *s, void *v)
> int i = 0;
> int j;
>
> + mutex_lock(&f2fs_stat_mutex);
> list_for_each_entry_safe(si, next, &f2fs_stat_list, stat_list) {
>
> mutex_lock(&si->stat_lock);
> @@ -288,6 +290,7 @@ static int stat_show(struct seq_file *s, void *v)
> si->base_mem >> 10, si->cache_mem >> 10);
> mutex_unlock(&si->stat_lock);
> }
> + mutex_unlock(&f2fs_stat_mutex);
> return 0;
> }
>
> @@ -314,7 +317,10 @@ static int init_stats(struct f2fs_sb_info *sbi)
>
> si = sbi->stat_info;
> mutex_init(&si->stat_lock);
> +
> + mutex_lock(&f2fs_stat_mutex);
> list_add_tail(&si->stat_list, &f2fs_stat_list);
> + mutex_unlock(&f2fs_stat_mutex);
>
> si->all_area_segs = le32_to_cpu(raw_super->segment_count);
> si->sit_area_segs = le32_to_cpu(raw_super->segment_count_sit);
> @@ -347,7 +353,10 @@ void f2fs_destroy_stats(struct f2fs_sb_info *sbi)
> {
> struct f2fs_stat_info *si = sbi->stat_info;
>
> + mutex_lock(&f2fs_stat_mutex);
> list_del(&si->stat_list);
> + mutex_unlock(&f2fs_stat_mutex);
> +
Hi Jianpeng,
Is it possible to fix the issue by holding si->stat_lock while
executing list_del(&si->stat_list) ? this can avoid introducing new
variable.
> mutex_lock(&si->stat_lock);
> si->sbi = NULL;
> mutex_unlock(&si->stat_lock);
> --
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