On 2016/9/20 10:41, Jaegeuk Kim wrote:
> On Tue, Sep 20, 2016 at 09:47:20AM +0800, Chao Yu wrote:
>> Hi Jaegeuk,
>>
>> On 2016/9/20 5:49, Jaegeuk Kim wrote:
>>> Hi Chao,
>>>
>>> On Sun, Sep 18, 2016 at 11:30:06PM +0800, Chao Yu wrote:
>>>> From: Chao Yu <yuch...@huawei.com>
>>>>
>>>> This patch introduces spinlock to protect updating process of ckpt_flags
>>>> field in struct f2fs_checkpoint, it avoids incorrectly updating in race
>>>> condition.
>>>
>>> So, I'm seeing a race condition between f2fs_stop_checkpoint(),
>>> write_checkpoint(), and f2fs_fill_super().
>>>
>>> How about just adding f2fs_lock_op() in f2fs_stop_checkpoint()?
>>
>> I'm afraid there will be a potential deadlock here:
>>
>> Thread A                             Thread B
>> - write_checkpoint
>>  - block_operations
>>   - f2fs_lock_all
>>  - do_checkpoint
>>  - wait_on_all_pages_writeback
>>                                      - f2fs_write_end_io
>>                                       - f2fs_stop_checkpoint
>>                                        - f2fs_lock_op
>>                                       - end_page_writeback
>>                                       - atomic_dec_and_test
>>                                       - wake_up
>>
>> Right?
> 
> Okay, I see. Let me try to understand in more details.
> Basically, there'd be no problem if there is no f2fs_stop_checkpoint(), since
> every {set|clear}_ckpt_flags() are called under f2fs_lock_op() or in
> fill_super(). And, you're probably concerned about any breakage of ckpt->flags
> due to accidental f2fs_stop_checkpoint() trigger. So, we're able to lose
> ERROR_FLAG because of data race.
> 
> Oh, I found one potential corruption case in f2fs_write_checkpoint().
> Before writing the last checkpoint block, we used to check its IO error.
> But, if set_ckpt_flags() and f2fs_stop_checkpoint() were called concurrently,
> ckpt_flags was able to lose ERROR_FLAG, resulting in finalizing its checkpoint
> pack. So, we can get valid checkpoint pack with EIO'ed metadata block.

That's right.

> 
> BTW, we can do multiple set/clear flags in do_checkpoint() with single 
> spin_lock
> call, tho.

Agree, let me refactor the code. :)

Thanks,

> 
> Thanks,
> 
>>>
>>>> Signed-off-by: Chao Yu <yuch...@huawei.com>
>>>> ---
>>>>  fs/f2fs/checkpoint.c | 24 ++++++++++++------------
>>>>  fs/f2fs/f2fs.h       | 29 +++++++++++++++++++++--------
>>>>  fs/f2fs/recovery.c   |  2 +-
>>>>  fs/f2fs/segment.c    |  4 ++--
>>>>  fs/f2fs/super.c      |  5 +++--
>>>>  5 files changed, 39 insertions(+), 25 deletions(-)
>>>>
>>>> diff --git a/fs/f2fs/checkpoint.c b/fs/f2fs/checkpoint.c
>>>> index df56a43..0338f8c 100644
>>>> --- a/fs/f2fs/checkpoint.c
>>>> +++ b/fs/f2fs/checkpoint.c
>>>> @@ -28,7 +28,7 @@ struct kmem_cache *inode_entry_slab;
>>>>  
>>>>  void f2fs_stop_checkpoint(struct f2fs_sb_info *sbi, bool end_io)
>>>>  {
>>>> -  set_ckpt_flags(sbi->ckpt, CP_ERROR_FLAG);
>>>> +  set_ckpt_flags(sbi, CP_ERROR_FLAG);
>>>>    sbi->sb->s_flags |= MS_RDONLY;
>>>>    if (!end_io)
>>>>            f2fs_flush_merged_bios(sbi);
>>>> @@ -571,7 +571,7 @@ int recover_orphan_inodes(struct f2fs_sb_info *sbi)
>>>>    block_t start_blk, orphan_blocks, i, j;
>>>>    int err;
>>>>  
>>>> -  if (!is_set_ckpt_flags(F2FS_CKPT(sbi), CP_ORPHAN_PRESENT_FLAG))
>>>> +  if (!is_set_ckpt_flags(sbi, CP_ORPHAN_PRESENT_FLAG))
>>>>            return 0;
>>>>  
>>>>    start_blk = __start_cp_addr(sbi) + 1 + __cp_payload(sbi);
>>>> @@ -595,7 +595,7 @@ int recover_orphan_inodes(struct f2fs_sb_info *sbi)
>>>>            f2fs_put_page(page, 1);
>>>>    }
>>>>    /* clear Orphan Flag */
>>>> -  clear_ckpt_flags(F2FS_CKPT(sbi), CP_ORPHAN_PRESENT_FLAG);
>>>> +  clear_ckpt_flags(sbi, CP_ORPHAN_PRESENT_FLAG);
>>>>    return 0;
>>>>  }
>>>>  
>>>> @@ -1054,9 +1054,9 @@ static int do_checkpoint(struct f2fs_sb_info *sbi, 
>>>> struct cp_control *cpc)
>>>>    /* 2 cp  + n data seg summary + orphan inode blocks */
>>>>    data_sum_blocks = npages_for_summary_flush(sbi, false);
>>>>    if (data_sum_blocks < NR_CURSEG_DATA_TYPE)
>>>> -          set_ckpt_flags(ckpt, CP_COMPACT_SUM_FLAG);
>>>> +          set_ckpt_flags(sbi, CP_COMPACT_SUM_FLAG);
>>>>    else
>>>> -          clear_ckpt_flags(ckpt, CP_COMPACT_SUM_FLAG);
>>>> +          clear_ckpt_flags(sbi, CP_COMPACT_SUM_FLAG);
>>>>  
>>>>    orphan_blocks = GET_ORPHAN_BLOCKS(orphan_num);
>>>>    ckpt->cp_pack_start_sum = cpu_to_le32(1 + cp_payload_blks +
>>>> @@ -1072,22 +1072,22 @@ static int do_checkpoint(struct f2fs_sb_info *sbi, 
>>>> struct cp_control *cpc)
>>>>                            orphan_blocks);
>>>>  
>>>>    if (cpc->reason == CP_UMOUNT)
>>>> -          set_ckpt_flags(ckpt, CP_UMOUNT_FLAG);
>>>> +          set_ckpt_flags(sbi, CP_UMOUNT_FLAG);
>>>>    else
>>>> -          clear_ckpt_flags(ckpt, CP_UMOUNT_FLAG);
>>>> +          clear_ckpt_flags(sbi, CP_UMOUNT_FLAG);
>>>>  
>>>>    if (cpc->reason == CP_FASTBOOT)
>>>> -          set_ckpt_flags(ckpt, CP_FASTBOOT_FLAG);
>>>> +          set_ckpt_flags(sbi, CP_FASTBOOT_FLAG);
>>>>    else
>>>> -          clear_ckpt_flags(ckpt, CP_FASTBOOT_FLAG);
>>>> +          clear_ckpt_flags(sbi, CP_FASTBOOT_FLAG);
>>>>  
>>>>    if (orphan_num)
>>>> -          set_ckpt_flags(ckpt, CP_ORPHAN_PRESENT_FLAG);
>>>> +          set_ckpt_flags(sbi, CP_ORPHAN_PRESENT_FLAG);
>>>>    else
>>>> -          clear_ckpt_flags(ckpt, CP_ORPHAN_PRESENT_FLAG);
>>>> +          clear_ckpt_flags(sbi, CP_ORPHAN_PRESENT_FLAG);
>>>>  
>>>>    if (is_sbi_flag_set(sbi, SBI_NEED_FSCK))
>>>> -          set_ckpt_flags(ckpt, CP_FSCK_FLAG);
>>>> +          set_ckpt_flags(sbi, CP_FSCK_FLAG);
>>>>  
>>>>    /* update SIT/NAT bitmap */
>>>>    get_sit_bitmap(sbi, __bitmap_ptr(sbi, SIT_BITMAP));
>>>> diff --git a/fs/f2fs/f2fs.h b/fs/f2fs/f2fs.h
>>>> index c30f744b..b615f3f 100644
>>>> --- a/fs/f2fs/f2fs.h
>>>> +++ b/fs/f2fs/f2fs.h
>>>> @@ -814,6 +814,7 @@ struct f2fs_sb_info {
>>>>  
>>>>    /* for checkpoint */
>>>>    struct f2fs_checkpoint *ckpt;           /* raw checkpoint pointer */
>>>> +  spinlock_t cp_lock;                     /* for flag in ckpt */
>>>>    struct inode *meta_inode;               /* cache meta blocks */
>>>>    struct mutex cp_mutex;                  /* checkpoint procedure lock */
>>>>    struct rw_semaphore cp_rwsem;           /* blocking FS operations */
>>>> @@ -1083,24 +1084,36 @@ static inline unsigned long long 
>>>> cur_cp_version(struct f2fs_checkpoint *cp)
>>>>    return le64_to_cpu(cp->checkpoint_ver);
>>>>  }
>>>>  
>>>> -static inline bool is_set_ckpt_flags(struct f2fs_checkpoint *cp, unsigned 
>>>> int f)
>>>> +static inline bool is_set_ckpt_flags(struct f2fs_sb_info *sbi, unsigned 
>>>> int f)
>>>>  {
>>>> +  struct f2fs_checkpoint *cp = F2FS_CKPT(sbi);
>>>>    unsigned int ckpt_flags = le32_to_cpu(cp->ckpt_flags);
>>>> +
>>>>    return ckpt_flags & f;
>>>>  }
>>>>  
>>>> -static inline void set_ckpt_flags(struct f2fs_checkpoint *cp, unsigned 
>>>> int f)
>>>> +static inline void set_ckpt_flags(struct f2fs_sb_info *sbi, unsigned int 
>>>> f)
>>>>  {
>>>> -  unsigned int ckpt_flags = le32_to_cpu(cp->ckpt_flags);
>>>> +  struct f2fs_checkpoint *cp = F2FS_CKPT(sbi);
>>>> +  unsigned int ckpt_flags;
>>>> +
>>>> +  spin_lock(&sbi->cp_lock);
>>>> +  ckpt_flags = le32_to_cpu(cp->ckpt_flags);
>>>>    ckpt_flags |= f;
>>>>    cp->ckpt_flags = cpu_to_le32(ckpt_flags);
>>>> +  spin_unlock(&sbi->cp_lock);
>>>>  }
>>>>  
>>>> -static inline void clear_ckpt_flags(struct f2fs_checkpoint *cp, unsigned 
>>>> int f)
>>>> +static inline void clear_ckpt_flags(struct f2fs_sb_info *sbi, unsigned 
>>>> int f)
>>>>  {
>>>> -  unsigned int ckpt_flags = le32_to_cpu(cp->ckpt_flags);
>>>> +  struct f2fs_checkpoint *cp = F2FS_CKPT(sbi);
>>>> +  unsigned int ckpt_flags;
>>>> +
>>>> +  spin_lock(&sbi->cp_lock);
>>>> +  ckpt_flags = le32_to_cpu(cp->ckpt_flags);
>>>>    ckpt_flags &= (~f);
>>>>    cp->ckpt_flags = cpu_to_le32(ckpt_flags);
>>>> +  spin_unlock(&sbi->cp_lock);
>>>>  }
>>>>  
>>>>  static inline bool f2fs_discard_en(struct f2fs_sb_info *sbi)
>>>> @@ -1148,8 +1161,8 @@ static inline bool __remain_node_summaries(int 
>>>> reason)
>>>>  
>>>>  static inline bool __exist_node_summaries(struct f2fs_sb_info *sbi)
>>>>  {
>>>> -  return (is_set_ckpt_flags(F2FS_CKPT(sbi), CP_UMOUNT_FLAG) ||
>>>> -                  is_set_ckpt_flags(F2FS_CKPT(sbi), CP_FASTBOOT_FLAG));
>>>> +  return (is_set_ckpt_flags(sbi, CP_UMOUNT_FLAG) ||
>>>> +                  is_set_ckpt_flags(sbi, CP_FASTBOOT_FLAG));
>>>>  }
>>>>  
>>>>  /*
>>>> @@ -1851,7 +1864,7 @@ static inline int f2fs_readonly(struct super_block 
>>>> *sb)
>>>>  
>>>>  static inline bool f2fs_cp_error(struct f2fs_sb_info *sbi)
>>>>  {
>>>> -  return is_set_ckpt_flags(sbi->ckpt, CP_ERROR_FLAG);
>>>> +  return is_set_ckpt_flags(sbi, CP_ERROR_FLAG);
>>>>  }
>>>>  
>>>>  static inline bool is_dot_dotdot(const struct qstr *str)
>>>> diff --git a/fs/f2fs/recovery.c b/fs/f2fs/recovery.c
>>>> index ad748e5..37d99d2 100644
>>>> --- a/fs/f2fs/recovery.c
>>>> +++ b/fs/f2fs/recovery.c
>>>> @@ -649,7 +649,7 @@ out:
>>>>                    invalidate_mapping_pages(META_MAPPING(sbi),
>>>>                                                    blkaddr, blkaddr);
>>>>  
>>>> -          set_ckpt_flags(sbi->ckpt, CP_ERROR_FLAG);
>>>> +          set_ckpt_flags(sbi, CP_ERROR_FLAG);
>>>>            mutex_unlock(&sbi->cp_mutex);
>>>>    } else if (need_writecp) {
>>>>            struct cp_control cpc = {
>>>> diff --git a/fs/f2fs/segment.c b/fs/f2fs/segment.c
>>>> index 101b58f..dc68f30 100644
>>>> --- a/fs/f2fs/segment.c
>>>> +++ b/fs/f2fs/segment.c
>>>> @@ -1825,7 +1825,7 @@ static int restore_curseg_summaries(struct 
>>>> f2fs_sb_info *sbi)
>>>>    int type = CURSEG_HOT_DATA;
>>>>    int err;
>>>>  
>>>> -  if (is_set_ckpt_flags(F2FS_CKPT(sbi), CP_COMPACT_SUM_FLAG)) {
>>>> +  if (is_set_ckpt_flags(sbi, CP_COMPACT_SUM_FLAG)) {
>>>>            int npages = npages_for_summary_flush(sbi, true);
>>>>  
>>>>            if (npages >= 2)
>>>> @@ -1922,7 +1922,7 @@ static void write_normal_summaries(struct 
>>>> f2fs_sb_info *sbi,
>>>>  
>>>>  void write_data_summaries(struct f2fs_sb_info *sbi, block_t start_blk)
>>>>  {
>>>> -  if (is_set_ckpt_flags(F2FS_CKPT(sbi), CP_COMPACT_SUM_FLAG))
>>>> +  if (is_set_ckpt_flags(sbi, CP_COMPACT_SUM_FLAG))
>>>>            write_compacted_summaries(sbi, start_blk);
>>>>    else
>>>>            write_normal_summaries(sbi, start_blk, CURSEG_HOT_DATA);
>>>> diff --git a/fs/f2fs/super.c b/fs/f2fs/super.c
>>>> index 555217f..f809729 100644
>>>> --- a/fs/f2fs/super.c
>>>> +++ b/fs/f2fs/super.c
>>>> @@ -735,7 +735,7 @@ static void f2fs_put_super(struct super_block *sb)
>>>>     * clean checkpoint again.
>>>>     */
>>>>    if (is_sbi_flag_set(sbi, SBI_IS_DIRTY) ||
>>>> -                  !is_set_ckpt_flags(F2FS_CKPT(sbi), CP_UMOUNT_FLAG)) {
>>>> +                  !is_set_ckpt_flags(sbi, CP_UMOUNT_FLAG)) {
>>>>            struct cp_control cpc = {
>>>>                    .reason = CP_UMOUNT,
>>>>            };
>>>> @@ -1477,6 +1477,7 @@ static void init_sb_info(struct f2fs_sb_info *sbi)
>>>>    mutex_init(&sbi->umount_mutex);
>>>>    mutex_init(&sbi->wio_mutex[NODE]);
>>>>    mutex_init(&sbi->wio_mutex[DATA]);
>>>> +  spin_lock_init(&sbi->cp_lock);
>>>>  
>>>>  #ifdef CONFIG_F2FS_FS_ENCRYPTION
>>>>    memcpy(sbi->key_prefix, F2FS_KEY_DESC_PREFIX,
>>>> @@ -1818,7 +1819,7 @@ try_onemore:
>>>>             * previous checkpoint was not done by clean system shutdown.
>>>>             */
>>>>            if (bdev_read_only(sb->s_bdev) &&
>>>> -                          !is_set_ckpt_flags(sbi->ckpt, CP_UMOUNT_FLAG)) {
>>>> +                          !is_set_ckpt_flags(sbi, CP_UMOUNT_FLAG)) {
>>>>                    err = -EROFS;
>>>>                    goto free_kobj;
>>>>            }
>>>> -- 
>>>> 2.7.2
>>>
>>> .
>>>
> 
> .
> 


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