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Date:   Wed, 21 Apr 2021 21:06:36 -0700
From:   Jaegeuk Kim <jaegeuk@kernel.org>
To:     Chao Yu <yuchao0@huawei.com>
Cc:     linux-f2fs-devel@lists.sourceforge.net,
        linux-kernel@vger.kernel.org, chao@kernel.org
Subject: Re: [RFC PATCH] f2fs: reduce expensive checkpoint trigger frequency
Message-ID: <YID2TOCsgKdi0aLf@google.com>
References: <20210416095838.29568-1-yuchao0@huawei.com>
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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?

> 
> 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@huawei.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?

>  
>  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