Commit 66af62ce authored by majianpeng's avatar majianpeng Committed by Jaegeuk Kim
Browse files

f2fs: add global mutex_lock to protect f2fs_stat_list 



There is an race condition between umounting f2fs and reading f2fs/status, which
results in 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) <- si is gone.
				 ...
				}

Solution with a global lock: f2fs_stat_mutex:
Thread A			Thread B
umount f2fs 			cat f2fs/status

f2fs_destroy_stats() {		stat_show() {
 mutex_lock(&f2fs_stat_mutex);
 list_del(&si->stat_list);
 mutex_unlock(&f2fs_stat_mutex);
 kfree(sbi->stat_info);		 mutex_lock(&f2fs_stat_mutex);
}				 list_for_each_entry_safe(&f2fs_stat_list)
				 ...
				 mutex_unlock(&f2fs_stat_mutex);
				}

Signed-off-by: default avatarJianpeng Ma <majianpeng@gmail.com>
[jaegeuk.kim@samsung.com: fix typos, description, and remove the existing lock]
Signed-off-by: default avatarJaegeuk Kim <jaegeuk.kim@samsung.com>
parent fa9150a8

fs/f2fs/debug.c

+11 −12
Original line number Diff line number Diff line
@@ -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)

{
@@ -180,13 +181,9 @@ 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);

		if (!si->sbi) {

			mutex_unlock(&si->stat_lock);

			continue;

		}

		update_general_status(si->sbi);



		seq_printf(s, "\n=====[ partition info. #%d ]=====\n", i++);
@@ -286,8 +283,8 @@ static int stat_show(struct seq_file *s, void *v) 
		seq_printf(s, "\nMemory: %u KB = static: %u + cached: %u\n",

				(si->base_mem + si->cache_mem) >> 10,

				si->base_mem >> 10, si->cache_mem >> 10);

		mutex_unlock(&si->stat_lock);

	}

	mutex_unlock(&f2fs_stat_mutex);

	return 0;

}
@@ -313,9 +310,6 @@ static int init_stats(struct f2fs_sb_info *sbi) 
		return -ENOMEM;



	si = sbi->stat_info;

	mutex_init(&si->stat_lock);

	list_add_tail(&si->stat_list, &f2fs_stat_list);



	si->all_area_segs = le32_to_cpu(raw_super->segment_count);

	si->sit_area_segs = le32_to_cpu(raw_super->segment_count_sit);

	si->nat_area_segs = le32_to_cpu(raw_super->segment_count_nat);
@@ -325,6 +319,11 @@ static int init_stats(struct f2fs_sb_info *sbi) 
	si->main_area_zones = si->main_area_sections /

				le32_to_cpu(raw_super->secs_per_zone);

	si->sbi = sbi;



	mutex_lock(&f2fs_stat_mutex);

	list_add_tail(&si->stat_list, &f2fs_stat_list);

	mutex_unlock(&f2fs_stat_mutex);



	return 0;

}
@@ -347,10 +346,10 @@ 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_lock(&si->stat_lock);

	si->sbi = NULL;

	mutex_unlock(&si->stat_lock);

	mutex_unlock(&f2fs_stat_mutex);



	kfree(sbi->stat_info);

}

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