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Date: Tue, 18 Jun 2019 14:52:52 +0800
From: Chao Yu <yuchao0@...wei.com>
To: Jaegeuk Kim <jaegeuk@...nel.org>
CC: <linux-kernel@...r.kernel.org>,
<linux-f2fs-devel@...ts.sourceforge.net>
Subject: Re: [f2fs-dev] [PATCH v3] f2fs: add a rw_sem to cover quota flag
changes
On 2019/6/14 10:46, Jaegeuk Kim wrote:
> On 06/11, Chao Yu wrote:
>> On 2019/6/5 2:36, Jaegeuk Kim wrote:
>>> Two paths to update quota and f2fs_lock_op:
>>>
>>> 1.
>>> - lock_op
>>> | - quota_update
>>> `- unlock_op
>>>
>>> 2.
>>> - quota_update
>>> - lock_op
>>> `- unlock_op
>>>
>>> But, we need to make a transaction on quota_update + lock_op in #2 case.
>>> So, this patch introduces:
>>> 1. lock_op
>>> 2. down_write
>>> 3. check __need_flush
>>> 4. up_write
>>> 5. if there is dirty quota entries, flush them
>>> 6. otherwise, good to go
>>>
>>> Signed-off-by: Jaegeuk Kim <jaegeuk@...nel.org>
>>> ---
>>>
>>> v3 from v2:
>>> - refactor to fix quota corruption issue
>>> : it seems that the previous scenario is not real and no deadlock case was
>>> encountered.
>>
>> - f2fs_dquot_commit
>> - down_read(&sbi->quota_sem)
>> - block_operation
>> - f2fs_lock_all
>> - need_flush_quota
>> - down_write(&sbi->quota_sem)
>> - f2fs_quota_write
>> - f2fs_lock_op
>>
>> Why can't this happen?
>>
>> Once more question, should we hold quota_sem during checkpoint to avoid further
>> quota update? f2fs_lock_op can do this job as well?
>
> I couldn't find write_dquot() call to make this happen, and f2fs_lock_op was not
- f2fs_dquot_commit
- dquot_commit
->commit_dqblk (v2_write_dquot)
- qtree_write_dquot
->quota_write (f2fs_quota_write)
- f2fs_lock_op
Do you mean there is no such way that calling f2fs_lock_op() from
f2fs_quota_write()? So that deadlock condition is not existing?
Thanks,
> enough to cover quota updates. Current stress & power-cut tests are running for
> several days without problem with this patch.
>
>>
>> Thanks,
>>
>>>
>>> fs/f2fs/checkpoint.c | 41 +++++++++++++++++++----------------------
>>> fs/f2fs/f2fs.h | 1 +
>>> fs/f2fs/super.c | 26 +++++++++++++++++++++-----
>>> 3 files changed, 41 insertions(+), 27 deletions(-)
>>>
>>> diff --git a/fs/f2fs/checkpoint.c b/fs/f2fs/checkpoint.c
>>> index 89825261d474..43f65f0962e5 100644
>>> --- a/fs/f2fs/checkpoint.c
>>> +++ b/fs/f2fs/checkpoint.c
>>> @@ -1131,17 +1131,24 @@ static void __prepare_cp_block(struct f2fs_sb_info *sbi)
>>>
>>> static bool __need_flush_quota(struct f2fs_sb_info *sbi)
>>> {
>>> + bool ret = false;
>>> +
>>> if (!is_journalled_quota(sbi))
>>> return false;
>>> - if (is_sbi_flag_set(sbi, SBI_QUOTA_SKIP_FLUSH))
>>> - return false;
>>> - if (is_sbi_flag_set(sbi, SBI_QUOTA_NEED_REPAIR))
>>> - return false;
>>> - if (is_sbi_flag_set(sbi, SBI_QUOTA_NEED_FLUSH))
>>> - return true;
>>> - if (get_pages(sbi, F2FS_DIRTY_QDATA))
>>> - return true;
>>> - return false;
>>> +
>>> + down_write(&sbi->quota_sem);
>>> + if (is_sbi_flag_set(sbi, SBI_QUOTA_SKIP_FLUSH)) {
>>> + ret = false;
>>> + } else if (is_sbi_flag_set(sbi, SBI_QUOTA_NEED_REPAIR)) {
>>> + ret = false;
>>> + } else if (is_sbi_flag_set(sbi, SBI_QUOTA_NEED_FLUSH)) {
>>> + clear_sbi_flag(sbi, SBI_QUOTA_NEED_FLUSH);
>>> + ret = true;
>>> + } else if (get_pages(sbi, F2FS_DIRTY_QDATA)) {
>>> + ret = true;
>>> + }
>>> + up_write(&sbi->quota_sem);
>>> + return ret;
>>> }
>>>
>>> /*
>>> @@ -1160,26 +1167,22 @@ static int block_operations(struct f2fs_sb_info *sbi)
>>> blk_start_plug(&plug);
>>>
>>> retry_flush_quotas:
>>> + f2fs_lock_all(sbi);
>>> if (__need_flush_quota(sbi)) {
>>> int locked;
>>>
>>> if (++cnt > DEFAULT_RETRY_QUOTA_FLUSH_COUNT) {
>>> set_sbi_flag(sbi, SBI_QUOTA_SKIP_FLUSH);
>>> - f2fs_lock_all(sbi);
>>> + set_sbi_flag(sbi, SBI_QUOTA_NEED_FLUSH);
>>> goto retry_flush_dents;
>>> }
>>> - clear_sbi_flag(sbi, SBI_QUOTA_NEED_FLUSH);
>>> + f2fs_unlock_all(sbi);
>>>
>>> /* only failed during mount/umount/freeze/quotactl */
>>> locked = down_read_trylock(&sbi->sb->s_umount);
>>> f2fs_quota_sync(sbi->sb, -1);
>>> if (locked)
>>> up_read(&sbi->sb->s_umount);
>>> - }
>>> -
>>> - f2fs_lock_all(sbi);
>>> - if (__need_flush_quota(sbi)) {
>>> - f2fs_unlock_all(sbi);
>>> cond_resched();
>>> goto retry_flush_quotas;
>>> }
>>> @@ -1201,12 +1204,6 @@ static int block_operations(struct f2fs_sb_info *sbi)
>>> */
>>> down_write(&sbi->node_change);
>>>
>>> - if (__need_flush_quota(sbi)) {
>>> - up_write(&sbi->node_change);
>>> - f2fs_unlock_all(sbi);
>>> - goto retry_flush_quotas;
>>> - }
>>> -
>>> if (get_pages(sbi, F2FS_DIRTY_IMETA)) {
>>> up_write(&sbi->node_change);
>>> f2fs_unlock_all(sbi);
>>> diff --git a/fs/f2fs/f2fs.h b/fs/f2fs/f2fs.h
>>> index 9674a85154b2..9bd2bf0f559b 100644
>>> --- a/fs/f2fs/f2fs.h
>>> +++ b/fs/f2fs/f2fs.h
>>> @@ -1253,6 +1253,7 @@ struct f2fs_sb_info {
>>> block_t unusable_block_count; /* # of blocks saved by last cp */
>>>
>>> unsigned int nquota_files; /* # of quota sysfile */
>>> + struct rw_semaphore quota_sem; /* blocking cp for flags */
>>>
>>> /* # of pages, see count_type */
>>> atomic_t nr_pages[NR_COUNT_TYPE];
>>> diff --git a/fs/f2fs/super.c b/fs/f2fs/super.c
>>> index 15d7e30bfc72..5a318399a2fa 100644
>>> --- a/fs/f2fs/super.c
>>> +++ b/fs/f2fs/super.c
>>> @@ -1964,6 +1964,7 @@ int f2fs_quota_sync(struct super_block *sb, int type)
>>> int cnt;
>>> int ret;
>>>
>>> + down_read(&sbi->quota_sem);
>>> ret = dquot_writeback_dquots(sb, type);
>>> if (ret)
>>> goto out;
>>> @@ -2001,6 +2002,7 @@ int f2fs_quota_sync(struct super_block *sb, int type)
>>> out:
>>> if (ret)
>>> set_sbi_flag(F2FS_SB(sb), SBI_QUOTA_NEED_REPAIR);
>>> + up_read(&sbi->quota_sem);
>>> return ret;
>>> }
>>>
>>> @@ -2094,32 +2096,40 @@ static void f2fs_truncate_quota_inode_pages(struct super_block *sb)
>>>
>>> static int f2fs_dquot_commit(struct dquot *dquot)
>>> {
>>> + struct f2fs_sb_info *sbi = F2FS_SB(dquot->dq_sb);
>>> int ret;
>>>
>>> + down_read(&sbi->quota_sem);
>>> ret = dquot_commit(dquot);
>>> if (ret < 0)
>>> - set_sbi_flag(F2FS_SB(dquot->dq_sb), SBI_QUOTA_NEED_REPAIR);
>>> + set_sbi_flag(sbi, SBI_QUOTA_NEED_REPAIR);
>>> + up_read(&sbi->quota_sem);
>>> return ret;
>>> }
>>>
>>> static int f2fs_dquot_acquire(struct dquot *dquot)
>>> {
>>> + struct f2fs_sb_info *sbi = F2FS_SB(dquot->dq_sb);
>>> int ret;
>>>
>>> + down_read(&sbi->quota_sem);
>>> ret = dquot_acquire(dquot);
>>> if (ret < 0)
>>> - set_sbi_flag(F2FS_SB(dquot->dq_sb), SBI_QUOTA_NEED_REPAIR);
>>> -
>>> + set_sbi_flag(sbi, SBI_QUOTA_NEED_REPAIR);
>>> + up_read(&sbi->quota_sem);
>>> return ret;
>>> }
>>>
>>> static int f2fs_dquot_release(struct dquot *dquot)
>>> {
>>> + struct f2fs_sb_info *sbi = F2FS_SB(dquot->dq_sb);
>>> int ret;
>>>
>>> + down_read(&sbi->quota_sem);
>>> ret = dquot_release(dquot);
>>> if (ret < 0)
>>> - set_sbi_flag(F2FS_SB(dquot->dq_sb), SBI_QUOTA_NEED_REPAIR);
>>> + set_sbi_flag(sbi, SBI_QUOTA_NEED_REPAIR);
>>> + up_read(&sbi->quota_sem);
>>> return ret;
>>> }
>>>
>>> @@ -2129,22 +2139,27 @@ static int f2fs_dquot_mark_dquot_dirty(struct dquot *dquot)
>>> struct f2fs_sb_info *sbi = F2FS_SB(sb);
>>> int ret;
>>>
>>> + down_read(&sbi->quota_sem);
>>> ret = dquot_mark_dquot_dirty(dquot);
>>>
>>> /* if we are using journalled quota */
>>> if (is_journalled_quota(sbi))
>>> set_sbi_flag(sbi, SBI_QUOTA_NEED_FLUSH);
>>>
>>> + up_read(&sbi->quota_sem);
>>> return ret;
>>> }
>>>
>>> static int f2fs_dquot_commit_info(struct super_block *sb, int type)
>>> {
>>> + struct f2fs_sb_info *sbi = F2FS_SB(sb);
>>> int ret;
>>>
>>> + down_read(&sbi->quota_sem);
>>> ret = dquot_commit_info(sb, type);
>>> if (ret < 0)
>>> - set_sbi_flag(F2FS_SB(sb), SBI_QUOTA_NEED_REPAIR);
>>> + set_sbi_flag(sbi, SBI_QUOTA_NEED_REPAIR);
>>> + up_read(&sbi->quota_sem);
>>> return ret;
>>> }
>>>
>>> @@ -3253,6 +3268,7 @@ static int f2fs_fill_super(struct super_block *sb, void *data, int silent)
>>> }
>>>
>>> init_rwsem(&sbi->cp_rwsem);
>>> + init_rwsem(&sbi->quota_sem);
>>> init_waitqueue_head(&sbi->cp_wait);
>>> init_sb_info(sbi);
>>>
>>>
> .
>
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