linux-kernel - Re: [RFC PATCH] f2fs: reduce expensive checkpoint trigger frequency

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Message-ID: <733ba2da-4047-045b-5223-05012b980603@huawei.com>
Date:   Thu, 22 Apr 2021 15:14:35 +0800
From:   Chao Yu <yuchao0@...wei.com>
To:     Jaegeuk Kim <jaegeuk@...nel.org>
CC:     <linux-f2fs-devel@...ts.sourceforge.net>,
        <linux-kernel@...r.kernel.org>, <chao@...nel.org>,
        <heyunlei@...onor.com>
Subject: Re: [RFC PATCH] f2fs: reduce expensive checkpoint trigger frequency

On 2021/4/22 12:06, Jaegeuk Kim wrote:
> On 04/16, 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.
> 
> It'll happen once? How much impact will we hit due to this?

Yunlei reports me this issue, the problems here in Honer device's specified
environment, most fsync() on regular file triggers a checkpoint() when mkdir()
happened concurrently, result in causing the performance issue.

Yunlei could explain more about details of this issue. @Yunlei

> 
>>
>> 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().
>>
>> Signed-off-by: Chao Yu <yuchao0@...wei.com>
>> ---
>>   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 87d734f5589d..34487e527d12 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 6284b2f4a60b..a6c38d8b1ec3 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..38796d488d15 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_is_checkpointed_node(sbi, inode->i_ino))
>> +		f2fs_add_ino_entry(sbi, inode->i_ino, ENC_DIR_INO);
> 
> Is it right to say ENC_DIR_INO in this case?

Sorry, I didn't get it.

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
> .
>