linux-kernel - Re: [PATCH v3] f2fs: reduce expensive checkpoint trigger frequency

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Date: Mon, 19 Feb 2024 15:19:04 +0800
From: Chao Yu <chao@...nel.org>
To: jaegeuk@...nel.org
Cc: linux-f2fs-devel@...ts.sourceforge.net, linux-kernel@...r.kernel.org,
 Zhiguo Niu <zhiguo.niu@...soc.com>
Subject: Re: [PATCH v3] f2fs: reduce expensive checkpoint trigger frequency

Jaegeuk,

Any comments?

On 2024/1/11 16:17, 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: Zhiguo Niu <zhiguo.niu@...soc.com>
> Tested-by: Zhiguo Niu <zhiguo.niu@...soc.com>
> Reported-by: Yunlei He <heyunlei@...onor.com>
> Signed-off-by: Chao Yu <chao@...nel.org>
> ---
> v3:
> - Recently, Zhiguo Niu reported the same issue, so I repost this
> patch for comments.
>   fs/f2fs/f2fs.h              |  2 ++
>   fs/f2fs/file.c              |  3 +++
>   fs/f2fs/xattr.c             | 16 ++++++++++++++--
>   include/trace/events/f2fs.h |  3 ++-
>   4 files changed, 21 insertions(+), 3 deletions(-)
> 
> diff --git a/fs/f2fs/f2fs.h b/fs/f2fs/f2fs.h
> index e2e0ca45f881..0094a8c85f4a 100644
> --- a/fs/f2fs/f2fs.h
> +++ b/fs/f2fs/f2fs.h
> @@ -279,6 +279,7 @@ enum {
>   	APPEND_INO,		/* for append ino list */
>   	UPDATE_INO,		/* for update ino list */
>   	TRANS_DIR_INO,		/* for transactions dir ino list */
> +	ENC_DIR_INO,		/* for encrypted dir ino list */
>   	FLUSH_INO,		/* for multiple device flushing */
>   	MAX_INO_ENTRY,		/* max. list */
>   };
> @@ -1147,6 +1148,7 @@ 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 8198afb5fb9c..18b33b1f0c83 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 f290fe9327c4..cbd1b88297fe 100644
> --- a/fs/f2fs/xattr.c
> +++ b/fs/f2fs/xattr.c
> @@ -629,6 +629,7 @@ 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;
> @@ -772,8 +773,19 @@ static int __f2fs_setxattr(struct inode *inode, int index,
>   	if (index == F2FS_XATTR_INDEX_ENCRYPTION &&
>   			!strcmp(name, F2FS_XATTR_NAME_ENCRYPTION_CONTEXT))
>   		f2fs_set_encrypted_inode(inode);
> -	if (S_ISDIR(inode->i_mode))
> -		set_sbi_flag(F2FS_I_SB(inode), SBI_NEED_CP);
> +
> +	if (S_ISDIR(inode->i_mode)) {
> +		/*
> +		 * In restrict mode, fsync() always tries triggering checkpoint
> +		 * for all metadata consistency, in other mode, it only triggers
> +		 * checkpoint when parent's encryption metadata updates.
> +		 */
> +		if (F2FS_OPTION(sbi).fsync_mode == FSYNC_MODE_STRICT)
> +			set_sbi_flag(F2FS_I_SB(inode), SBI_NEED_CP);
> +		else if (IS_ENCRYPTED(inode) &&
> +			f2fs_is_checkpointed_node(sbi, inode->i_ino))
> +			f2fs_add_ino_entry(sbi, inode->i_ino, ENC_DIR_INO);
> +	}
>   
>   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 7ed0fc430dc6..48f2e399e184 100644
> --- a/include/trace/events/f2fs.h
> +++ b/include/trace/events/f2fs.h
> @@ -139,7 +139,8 @@ TRACE_DEFINE_ENUM(EX_BLOCK_AGE);
>   		{ 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,						\