Re: [PATCH 4/6] f2fs: introduce cp_lock to protect updating of ckpt_flags

From: Chao Yu
Date: Mon Sep 19 2016 - 21:47:48 EST

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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 <yuchao0@xxxxxxxxxx>
>>
>> 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?

Thanks,

>
> Thanks,
>
>> Signed-off-by: Chao Yu <yuchao0@xxxxxxxxxx>
>> ---
>> 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
>
> .
>

Next message: David Miller: "Re: [PATCH] phy: mark lan88xx_suspend() static"
Previous message: Chao Yu: "Re: [PATCH 3/6] f2fs: fix to avoid race condition when updating sbi flag"
In reply to: Jaegeuk Kim: "Re: [PATCH 4/6] f2fs: introduce cp_lock to protect updating of ckpt_flags"
Next in thread: Jaegeuk Kim: "Re: [PATCH 4/6] f2fs: introduce cp_lock to protect updating of ckpt_flags"
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