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Subject: Re: [PATCH v2] f2fs: reduce expensive checkpoint trigger frequency
To:     Jaegeuk Kim <jaegeuk@kernel.org>
CC:     <linux-f2fs-devel@lists.sourceforge.net>,
        <linux-kernel@vger.kernel.org>, <chao@kernel.org>,
        Yunlei He <heyunlei@hihonor.com>
References: <20210425011053.44436-1-yuchao0@huawei.com>
 <YIbzwPGOJoKZvFnv@google.com>
 <3338f2bc-6985-c1a4-9f3d-e59a474027f9@huawei.com>
 <YJFb5GWijGzHOAV6@google.com>
 <912459e6-3eef-59b7-e8a3-1097efd22750@huawei.com>
 <YJNz6YJC1oSF8wL4@google.com>
From:   Chao Yu <yuchao0@huawei.com>
Message-ID: <591a2572-8025-5c9f-13ce-a90f26733775@huawei.com>
Date:   Thu, 6 May 2021 14:27:17 +0800
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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?

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
>>>>> .
>>>>>
>>> .
>>>
> .
>