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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>
From:   Chao Yu <yuchao0@huawei.com>
Message-ID: <912459e6-3eef-59b7-e8a3-1097efd22750@huawei.com>
Date:   Thu, 6 May 2021 10:15:19 +0800
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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
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
>>> .
>>>
> .
>