From: majianpeng Date: Mon, 14 Jan 2013 12:08:16 +0000 (+0800) Subject: f2fs: add global mutex_lock to protect f2fs_stat_list X-Git-Url: https://git.stricted.de/?a=commitdiff_plain;h=66af62ce7588736ae65edfdb1c0df597775c4d21;p=GitHub%2Fexynos8895%2Fandroid_kernel_samsung_universal8895.git 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: Jianpeng Ma [jaegeuk.kim@samsung.com: fix typos, description, and remove the existing lock] Signed-off-by: Jaegeuk Kim --- diff --git a/fs/f2fs/debug.c b/fs/f2fs/debug.c index b8ed7a72c6e9..73f034a94182 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) { @@ -180,13 +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); }