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Message-ID: <52286374-ebf6-522b-7e0a-9c3c538f93fb@huawei.com>
Date: Fri, 20 Apr 2018 11:28:39 +0800
From: Chao Yu <yuchao0@...wei.com>
To: Jaegeuk Kim <jaegeuk@...nel.org>
CC: <linux-f2fs-devel@...ts.sourceforge.net>,
<linux-kernel@...r.kernel.org>, <chao@...nel.org>
Subject: Re: [PATCH 5/5] f2fs: fix to avoid race during access gc_thread
pointer
On 2018/4/20 11:19, Jaegeuk Kim wrote:
> On 04/18, Chao Yu wrote:
>> Thread A Thread B Thread C
>> - f2fs_remount
>> - stop_gc_thread
>> - f2fs_sbi_store
>> - issue_discard_thread
>> sbi->gc_thread = NULL;
>> sbi->gc_thread->gc_wake = 1
>> access sbi->gc_thread->gc_urgent
>
> Do we simply need a lock for this?
Code will be more complicated for handling existed and new coming fields with
the sbi->gc_thread pointer, and causing unneeded lock overhead, right?
So let's just allocate memory during fill_super?
Thanks,
>
>>
>> Previously, we allocate memory for sbi->gc_thread based on background
>> gc thread mount option, the memory can be released if we turn off
>> that mount option, but still there are several places access gc_thread
>> pointer without considering race condition, result in NULL point
>> dereference.
>>
>> In order to fix this issue, keep gc_thread structure valid in sbi all
>> the time instead of alloc/free it dynamically.
>>
>> Signed-off-by: Chao Yu <yuchao0@...wei.com>
>> ---
>> fs/f2fs/debug.c | 3 +--
>> fs/f2fs/f2fs.h | 7 +++++++
>> fs/f2fs/gc.c | 58 +++++++++++++++++++++++++++++++++----------------------
>> fs/f2fs/segment.c | 4 ++--
>> fs/f2fs/super.c | 13 +++++++++++--
>> fs/f2fs/sysfs.c | 8 ++++----
>> 6 files changed, 60 insertions(+), 33 deletions(-)
>>
>> diff --git a/fs/f2fs/debug.c b/fs/f2fs/debug.c
>> index 715beb85e9db..7bb036a3bb81 100644
>> --- a/fs/f2fs/debug.c
>> +++ b/fs/f2fs/debug.c
>> @@ -223,8 +223,7 @@ static void update_mem_info(struct f2fs_sb_info *sbi)
>> si->cache_mem = 0;
>>
>> /* build gc */
>> - if (sbi->gc_thread)
>> - si->cache_mem += sizeof(struct f2fs_gc_kthread);
>> + si->cache_mem += sizeof(struct f2fs_gc_kthread);
>>
>> /* build merge flush thread */
>> if (SM_I(sbi)->fcc_info)
>> diff --git a/fs/f2fs/f2fs.h b/fs/f2fs/f2fs.h
>> index 567c6bb57ae3..c553f63199e8 100644
>> --- a/fs/f2fs/f2fs.h
>> +++ b/fs/f2fs/f2fs.h
>> @@ -1412,6 +1412,11 @@ static inline struct sit_info *SIT_I(struct f2fs_sb_info *sbi)
>> return (struct sit_info *)(SM_I(sbi)->sit_info);
>> }
>>
>> +static inline struct f2fs_gc_kthread *GC_I(struct f2fs_sb_info *sbi)
>> +{
>> + return (struct f2fs_gc_kthread *)(sbi->gc_thread);
>> +}
>> +
>> static inline struct free_segmap_info *FREE_I(struct f2fs_sb_info *sbi)
>> {
>> return (struct free_segmap_info *)(SM_I(sbi)->free_info);
>> @@ -2954,6 +2959,8 @@ bool f2fs_overwrite_io(struct inode *inode, loff_t pos, size_t len);
>> /*
>> * gc.c
>> */
>> +int init_gc_context(struct f2fs_sb_info *sbi);
>> +void destroy_gc_context(struct f2fs_sb_info * sbi);
>> int start_gc_thread(struct f2fs_sb_info *sbi);
>> void stop_gc_thread(struct f2fs_sb_info *sbi);
>> block_t start_bidx_of_node(unsigned int node_ofs, struct inode *inode);
>> diff --git a/fs/f2fs/gc.c b/fs/f2fs/gc.c
>> index da89ca16a55d..7d310e454b77 100644
>> --- a/fs/f2fs/gc.c
>> +++ b/fs/f2fs/gc.c
>> @@ -26,8 +26,8 @@
>> static int gc_thread_func(void *data)
>> {
>> struct f2fs_sb_info *sbi = data;
>> - struct f2fs_gc_kthread *gc_th = sbi->gc_thread;
>> - wait_queue_head_t *wq = &sbi->gc_thread->gc_wait_queue_head;
>> + struct f2fs_gc_kthread *gc_th = GC_I(sbi);
>> + wait_queue_head_t *wq = &gc_th->gc_wait_queue_head;
>> unsigned int wait_ms;
>>
>> wait_ms = gc_th->min_sleep_time;
>> @@ -114,17 +114,15 @@ static int gc_thread_func(void *data)
>> return 0;
>> }
>>
>> -int start_gc_thread(struct f2fs_sb_info *sbi)
>> +int init_gc_context(struct f2fs_sb_info *sbi)
>> {
>> struct f2fs_gc_kthread *gc_th;
>> - dev_t dev = sbi->sb->s_bdev->bd_dev;
>> - int err = 0;
>>
>> gc_th = f2fs_kmalloc(sbi, sizeof(struct f2fs_gc_kthread), GFP_KERNEL);
>> - if (!gc_th) {
>> - err = -ENOMEM;
>> - goto out;
>> - }
>> + if (!gc_th)
>> + return -ENOMEM;
>> +
>> + gc_th->f2fs_gc_task = NULL;
>>
>> gc_th->urgent_sleep_time = DEF_GC_THREAD_URGENT_SLEEP_TIME;
>> gc_th->min_sleep_time = DEF_GC_THREAD_MIN_SLEEP_TIME;
>> @@ -139,26 +137,41 @@ int start_gc_thread(struct f2fs_sb_info *sbi)
>> gc_th->atomic_file[FG_GC] = 0;
>>
>> sbi->gc_thread = gc_th;
>> - init_waitqueue_head(&sbi->gc_thread->gc_wait_queue_head);
>> - sbi->gc_thread->f2fs_gc_task = kthread_run(gc_thread_func, sbi,
>> +
>> + return 0;
>> +}
>> +
>> +void destroy_gc_context(struct f2fs_sb_info *sbi)
>> +{
>> + kfree(GC_I(sbi));
>> + sbi->gc_thread = NULL;
>> +}
>> +
>> +int start_gc_thread(struct f2fs_sb_info *sbi)
>> +{
>> + struct f2fs_gc_kthread *gc_th = GC_I(sbi);
>> + dev_t dev = sbi->sb->s_bdev->bd_dev;
>> + int err = 0;
>> +
>> + init_waitqueue_head(&gc_th->gc_wait_queue_head);
>> + gc_th->f2fs_gc_task = kthread_run(gc_thread_func, sbi,
>> "f2fs_gc-%u:%u", MAJOR(dev), MINOR(dev));
>> if (IS_ERR(gc_th->f2fs_gc_task)) {
>> err = PTR_ERR(gc_th->f2fs_gc_task);
>> - kfree(gc_th);
>> - sbi->gc_thread = NULL;
>> + gc_th->f2fs_gc_task = NULL;
>> }
>> -out:
>> +
>> return err;
>> }
>>
>> void stop_gc_thread(struct f2fs_sb_info *sbi)
>> {
>> - struct f2fs_gc_kthread *gc_th = sbi->gc_thread;
>> - if (!gc_th)
>> - return;
>> - kthread_stop(gc_th->f2fs_gc_task);
>> - kfree(gc_th);
>> - sbi->gc_thread = NULL;
>> + struct f2fs_gc_kthread *gc_th = GC_I(sbi);
>> +
>> + if (gc_th->f2fs_gc_task) {
>> + kthread_stop(gc_th->f2fs_gc_task);
>> + gc_th->f2fs_gc_task = NULL;
>> + }
>> }
>>
>> static int select_gc_type(struct f2fs_gc_kthread *gc_th, int gc_type)
>> @@ -190,15 +203,14 @@ static void select_policy(struct f2fs_sb_info *sbi, int gc_type,
>> p->max_search = dirty_i->nr_dirty[type];
>> p->ofs_unit = 1;
>> } else {
>> - p->gc_mode = select_gc_type(sbi->gc_thread, gc_type);
>> + p->gc_mode = select_gc_type(GC_I(sbi), gc_type);
>> p->dirty_segmap = dirty_i->dirty_segmap[DIRTY];
>> p->max_search = dirty_i->nr_dirty[DIRTY];
>> p->ofs_unit = sbi->segs_per_sec;
>> }
>>
>> /* we need to check every dirty segments in the FG_GC case */
>> - if (gc_type != FG_GC &&
>> - (sbi->gc_thread && !sbi->gc_thread->gc_urgent) &&
>> + if (gc_type != FG_GC && !GC_I(sbi)->gc_urgent &&
>> p->max_search > sbi->max_victim_search)
>> p->max_search = sbi->max_victim_search;
>>
>> diff --git a/fs/f2fs/segment.c b/fs/f2fs/segment.c
>> index 831cefa088bc..c869ce54be4d 100644
>> --- a/fs/f2fs/segment.c
>> +++ b/fs/f2fs/segment.c
>> @@ -177,7 +177,7 @@ bool need_SSR(struct f2fs_sb_info *sbi)
>>
>> if (test_opt(sbi, LFS))
>> return false;
>> - if (sbi->gc_thread && sbi->gc_thread->gc_urgent)
>> + if (GC_I(sbi)->gc_urgent)
>> return true;
>>
>> return free_sections(sbi) <= (node_secs + 2 * dent_secs + imeta_secs +
>> @@ -1422,7 +1422,7 @@ static int issue_discard_thread(void *data)
>> if (dcc->discard_wake)
>> dcc->discard_wake = 0;
>>
>> - if (sbi->gc_thread && sbi->gc_thread->gc_urgent)
>> + if (GC_I(sbi)->gc_urgent)
>> init_discard_policy(&dpolicy, DPOLICY_FORCE, 1);
>>
>> sb_start_intwrite(sbi->sb);
>> diff --git a/fs/f2fs/super.c b/fs/f2fs/super.c
>> index d01c11f5e9c1..f3a5f463496f 100644
>> --- a/fs/f2fs/super.c
>> +++ b/fs/f2fs/super.c
>> @@ -1012,6 +1012,8 @@ static void f2fs_put_super(struct super_block *sb)
>> write_checkpoint(sbi, &cpc);
>> }
>>
>> + destroy_gc_context(sbi);
>> +
>> /* write_checkpoint can update stat informaion */
>> f2fs_destroy_stats(sbi);
>>
>> @@ -1044,6 +1046,7 @@ static void f2fs_put_super(struct super_block *sb)
>> kfree(sbi->raw_super);
>>
>> destroy_device_list(sbi);
>> + destroy_gc_context(sbi);
>> mempool_destroy(sbi->write_io_dummy);
>> #ifdef CONFIG_QUOTA
>> for (i = 0; i < MAXQUOTAS; i++)
>> @@ -1476,11 +1479,11 @@ static int f2fs_remount(struct super_block *sb, int *flags, char *data)
>> * option. Also sync the filesystem.
>> */
>> if ((*flags & SB_RDONLY) || !test_opt(sbi, BG_GC)) {
>> - if (sbi->gc_thread) {
>> + if (GC_I(sbi)->f2fs_gc_task) {
>> stop_gc_thread(sbi);
>> need_restart_gc = true;
>> }
>> - } else if (!sbi->gc_thread) {
>> + } else if (!GC_I(sbi)->f2fs_gc_task) {
>> err = start_gc_thread(sbi);
>> if (err)
>> goto restore_opts;
>> @@ -2771,6 +2774,10 @@ static int f2fs_fill_super(struct super_block *sb, void *data, int silent)
>> goto free_meta_inode;
>> }
>>
>> + err = init_gc_context(sbi);
>> + if (err)
>> + goto free_checkpoint;
>> +
>> /* Initialize device list */
>> err = f2fs_scan_devices(sbi);
>> if (err) {
>> @@ -2981,6 +2988,8 @@ static int f2fs_fill_super(struct super_block *sb, void *data, int silent)
>> destroy_segment_manager(sbi);
>> free_devices:
>> destroy_device_list(sbi);
>> + destroy_gc_context(sbi);
>> +free_checkpoint:
>> kfree(sbi->ckpt);
>> free_meta_inode:
>> make_bad_inode(sbi->meta_inode);
>> diff --git a/fs/f2fs/sysfs.c b/fs/f2fs/sysfs.c
>> index 2c53de9251be..fb3cd477d985 100644
>> --- a/fs/f2fs/sysfs.c
>> +++ b/fs/f2fs/sysfs.c
>> @@ -46,7 +46,7 @@ struct f2fs_attr {
>> static unsigned char *__struct_ptr(struct f2fs_sb_info *sbi, int struct_type)
>> {
>> if (struct_type == GC_THREAD)
>> - return (unsigned char *)sbi->gc_thread;
>> + return (unsigned char *)GC_I(sbi);
>> else if (struct_type == SM_INFO)
>> return (unsigned char *)SM_I(sbi);
>> else if (struct_type == DCC_INFO)
>> @@ -252,9 +252,9 @@ static ssize_t f2fs_sbi_store(struct f2fs_attr *a,
>>
>> if (!strcmp(a->attr.name, "iostat_enable") && *ui == 0)
>> f2fs_reset_iostat(sbi);
>> - if (!strcmp(a->attr.name, "gc_urgent") && t == 1 && sbi->gc_thread) {
>> - sbi->gc_thread->gc_wake = 1;
>> - wake_up_interruptible_all(&sbi->gc_thread->gc_wait_queue_head);
>> + if (!strcmp(a->attr.name, "gc_urgent") && t == 1) {
>> + GC_I(sbi)->gc_wake = 1;
>> + wake_up_interruptible_all(&GC_I(sbi)->gc_wait_queue_head);
>> wake_up_discard_thread(sbi, true);
>> }
>>
>> --
>> 2.15.0.55.gc2ece9dc4de6
>
> .
>
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