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f2fs: add global mutex_lock to protect f2fs_stat_list

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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: Jianpeng Ma <majianpeng@gmail.com>
[jaegeuk.kim@samsung.com: fix typos, description, and remove the existing lock]
Signed-off-by: Jaegeuk Kim <jaegeuk.kim@samsung.com>
This commit is contained in:
majianpeng 2013-01-14 20:08:16 +08:00 committed by Jaegeuk Kim
parent fa9150a84c
commit 66af62ce75
1 changed files with 11 additions and 12 deletions
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23
fs/f2fs/debug.c
View File

@ -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);
}