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Subject: Re: [PATCH v2] f2fs: reduce expensive checkpoint trigger frequency
To:     Yunlei He <heyunlei@hihonor.com>
CC:     Jaegeuk Kim <jaegeuk@kernel.org>,
        <linux-f2fs-devel@lists.sourceforge.net>,
        <linux-kernel@vger.kernel.org>, <chao@kernel.org>
References: <20210425011053.44436-1-yuchao0@huawei.com>
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 <591a2572-8025-5c9f-13ce-a90f26733775@huawei.com>
 <YJlS8CldaPiT42d8@google.com>
From:   Chao Yu <yuchao0@huawei.com>
Message-ID: <f50150e3-f5ff-b8a1-24ec-ad4936c1b13b@huawei.com>
Date:   Tue, 11 May 2021 09:33:11 +0800
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On 2021/5/10 23:36, Jaegeuk Kim wrote:
> On 05/06, Chao Yu wrote:
>> On 2021/5/6 12:43, Jaegeuk Kim wrote:
>>> On 05/06, Chao Yu wrote:
>>>> On 2021/5/4 22:36, Jaegeuk Kim wrote:
>>>>> On 04/27, Chao Yu wrote:
>>>>>> On 2021/4/27 1:09, Jaegeuk Kim wrote:
>>>>>>> On 04/25, Chao Yu wrote:
>>>>>>>> We may trigger high frequent checkpoint for below case:
>>>>>>>> 1. mkdir /mnt/dir1; set dir1 encrypted
>>>>>>>> 2. touch /mnt/file1; fsync /mnt/file1
>>>>>>>> 3. mkdir /mnt/dir2; set dir2 encrypted
>>>>>>>> 4. touch /mnt/file2; fsync /mnt/file2
>>>>>>>> ...
>>>>>>>>
>>>>>>>> Although, newly created dir and file are not related, due to
>>>>>>>> commit bbf156f7afa7 ("f2fs: fix lost xattrs of directories"), we will
>>>>>>>> trigger checkpoint whenever fsync() comes after a new encrypted dir
>>>>>>>> created.
>>>>>>>>
>>>>>>>> In order to avoid such condition, let's record an entry including
>>>>>>>> directory's ino into global cache when we initialize encryption policy
>>>>>>>> in a checkpointed directory, and then only trigger checkpoint() when
>>>>>>>> target file's parent has non-persisted encryption policy, for the case
>>>>>>>> its parent is not checkpointed, need_do_checkpoint() has cover that
>>>>>>>> by verifying it with f2fs_is_checkpointed_node().
>>>>>>>>
>>>>>>>> Reported-by: Yunlei He <heyunlei@hihonor.com>
>>>>>>>> Signed-off-by: Chao Yu <yuchao0@huawei.com>
>>>>>>>> ---
>>>>>>>> v2:
>>>>>>>> - fix to set ENC_DIR_INO only for encrypted directory
>>>>>>>>      fs/f2fs/f2fs.h              | 2 ++
>>>>>>>>      fs/f2fs/file.c              | 3 +++
>>>>>>>>      fs/f2fs/xattr.c             | 6 ++++--
>>>>>>>>      include/trace/events/f2fs.h | 3 ++-
>>>>>>>>      4 files changed, 11 insertions(+), 3 deletions(-)
>>>>>>>>
>>>>>>>> diff --git a/fs/f2fs/f2fs.h b/fs/f2fs/f2fs.h
>>>>>>>> index b9d5317db0a7..0fe881309a20 100644
>>>>>>>> --- a/fs/f2fs/f2fs.h
>>>>>>>> +++ b/fs/f2fs/f2fs.h
>>>>>>>> @@ -246,6 +246,7 @@ enum {
>>>>>>>>      	APPEND_INO,		/* for append ino list */
>>>>>>>>      	UPDATE_INO,		/* for update ino list */
>>>>>>>>      	TRANS_DIR_INO,		/* for trasactions dir ino list */
>>>>>>>> +	ENC_DIR_INO,		/* for encrypted dir ino list */
>>>>>>>>      	FLUSH_INO,		/* for multiple device flushing */
>>>>>>>>      	MAX_INO_ENTRY,		/* max. list */
>>>>>>>>      };
>>>>>>>> @@ -1090,6 +1091,7 @@ enum cp_reason_type {
>>>>>>>>      	CP_FASTBOOT_MODE,
>>>>>>>>      	CP_SPEC_LOG_NUM,
>>>>>>>>      	CP_RECOVER_DIR,
>>>>>>>> +	CP_ENC_DIR,
>>>>>>>>      };
>>>>>>>>      enum iostat_type {
>>>>>>>> diff --git a/fs/f2fs/file.c b/fs/f2fs/file.c
>>>>>>>> index a595050c56d3..62af29ec0879 100644
>>>>>>>> --- a/fs/f2fs/file.c
>>>>>>>> +++ b/fs/f2fs/file.c
>>>>>>>> @@ -218,6 +218,9 @@ static inline enum cp_reason_type need_do_checkpoint(struct inode *inode)
>>>>>>>>      		f2fs_exist_written_data(sbi, F2FS_I(inode)->i_pino,
>>>>>>>>      							TRANS_DIR_INO))
>>>>>>>>      		cp_reason = CP_RECOVER_DIR;
>>>>>>>> +	else if (f2fs_exist_written_data(sbi, F2FS_I(inode)->i_pino,
>>>>>>>> +							ENC_DIR_INO))
>>>>>>>> +		cp_reason = CP_ENC_DIR;
>>>>>>>>      	return cp_reason;
>>>>>>>>      }
>>>>>>>> diff --git a/fs/f2fs/xattr.c b/fs/f2fs/xattr.c
>>>>>>>> index c8f34decbf8e..70615d504f7e 100644
>>>>>>>> --- a/fs/f2fs/xattr.c
>>>>>>>> +++ b/fs/f2fs/xattr.c
>>>>>>>> @@ -630,6 +630,7 @@ static int __f2fs_setxattr(struct inode *inode, int index,
>>>>>>>>      			const char *name, const void *value, size_t size,
>>>>>>>>      			struct page *ipage, int flags)
>>>>>>>>      {
>>>>>>>> +	struct f2fs_sb_info *sbi = F2FS_I_SB(inode);
>>>>>>>>      	struct f2fs_xattr_entry *here, *last;
>>>>>>>>      	void *base_addr, *last_base_addr;
>>>>>>>>      	int found, newsize;
>>>>>>>> @@ -745,8 +746,9 @@ static int __f2fs_setxattr(struct inode *inode, int index,
>>>>>>>>      			!strcmp(name, F2FS_XATTR_NAME_ENCRYPTION_CONTEXT))
>>>>>>>>      		f2fs_set_encrypted_inode(inode);
>>>>>>>>      	f2fs_mark_inode_dirty_sync(inode, true);
>>>>>>>> -	if (!error && S_ISDIR(inode->i_mode))
>>>>>>>> -		set_sbi_flag(F2FS_I_SB(inode), SBI_NEED_CP);
>>>>>>>> +	if (!error && S_ISDIR(inode->i_mode) && f2fs_encrypted_file(inode) &&
>>>>>>>> +			f2fs_is_checkpointed_node(sbi, inode->i_ino))
>>>>>>>> +		f2fs_add_ino_entry(sbi, inode->i_ino, ENC_DIR_INO);
>>>>>>>
>>>>>>> What will happen, if we need to checkpoint xattr_nid on this directory?
>>>>>>
>>>>>> need_do_checkpoint()
>>>>>>
>>>>>> a)	else if (!f2fs_is_checkpointed_node(sbi, F2FS_I(inode)->i_pino))
>>>>>> 		cp_reason = CP_NODE_NEED_CP;
>>>>>
>>>>> This will change the current behavior which does checkpoint regardless of the
>>>>> parent being checkpointed. If i_pino was checkpointed but xnid wasn't, can we
>>>>> get xnid being checkpointed?
>>>>
>>>> Yes,
>>>>
>>>>>> If parent is checkpointed, after converting parent to encrypted directory
>>>>>> and create the file in parent, fsync this file will trigger checkpoint() due
>>>>>> to b)
>>>>
>>>> If i_pino was checkpointed, but xnid wasn't due to enable encryption on this
>>>
>>> I keep asking no encryption case where
>>> 1) parent is checkpointed
>>> 2) set_xattr(dir) w/ new new xnid
>>> 3) create(file)
>>> 4) fsync(file)
>>>
>>> In that case, previousely we do checkpoint, but this change does not. Yes?
>>
>> In this case, we won't checkpoint xnid, instead, just flushing file's data/node.
>>
>> So yes, actually this patch will change the policy, which looks posix compliance,
>> that mean we only persist the file's meta/data after fsync(file).
>>
>> How about keeping original policy in FSYNC_MODE_STRICT mode, and using current
>> policy in FSYNC_MODE_POSIX mode?
> 
> IIRC, it'd be much important to keep directory's xnid, so worry about stability

Understood your concern.

> regression. Is that case a really performance blocker?

Hi, Yunlei, does this performance issue block anything?

Thanks,

> 
>>
>> Thanks,
>>
>>>
>>>> directory, fsync() this file will trigger checkpoint() to make sure xnid
>>>> checkpointed due to b) case.
>>>>
>>>> Thanks,
>>>>
>>>>>
>>>>>>
>>>>>> b)	else if (f2fs_exist_written_data(sbi, F2FS_I(inode)->i_pino,
>>>>>> 							ENC_DIR_INO))
>>>>>> 		cp_reason = CP_ENC_DIR;
>>>>>>
>>>>>> If parent is not checkpointed, after converting parent to encrypted directory
>>>>>> and create the file in parent, fsync this file will trigger checkpoint() due
>>>>>> to a)
>>>>>>
>>>>>> If parent is checkpointed, after converting parent to encrypted directory
>>>>>> and create the file in parent, fsync this file will trigger checkpoint() due
>>>>>> to b)
>>>>>>
>>>>>> Am I missing any cases?
>>>>>>
>>>>>> Thanks,
>>>>>>
>>>>>>>
>>>>>>>>      same:
>>>>>>>>      	if (is_inode_flag_set(inode, FI_ACL_MODE)) {
>>>>>>>> diff --git a/include/trace/events/f2fs.h b/include/trace/events/f2fs.h
>>>>>>>> index 56b113e3cd6a..ca0cf12226e9 100644
>>>>>>>> --- a/include/trace/events/f2fs.h
>>>>>>>> +++ b/include/trace/events/f2fs.h
>>>>>>>> @@ -145,7 +145,8 @@ TRACE_DEFINE_ENUM(CP_RESIZE);
>>>>>>>>      		{ CP_NODE_NEED_CP,	"node needs cp" },		\
>>>>>>>>      		{ CP_FASTBOOT_MODE,	"fastboot mode" },		\
>>>>>>>>      		{ CP_SPEC_LOG_NUM,	"log type is 2" },		\
>>>>>>>> -		{ CP_RECOVER_DIR,	"dir needs recovery" })
>>>>>>>> +		{ CP_RECOVER_DIR,	"dir needs recovery" },		\
>>>>>>>> +		{ CP_ENC_DIR,		"persist encryption policy" })
>>>>>>>>      #define show_shutdown_mode(type)					\
>>>>>>>>      	__print_symbolic(type,						\
>>>>>>>> -- 
>>>>>>>> 2.29.2
>>>>>>> .
>>>>>>>
>>>>> .
>>>>>
>>> .
>>>
> .
>