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Date:   Tue, 4 May 2021 07:36:20 -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,
        Yunlei He <heyunlei@hihonor.com>
Subject: Re: [PATCH v2] f2fs: reduce expensive checkpoint trigger frequency
Message-ID: <YJFb5GWijGzHOAV6@google.com>
References: <20210425011053.44436-1-yuchao0@huawei.com>
 <YIbzwPGOJoKZvFnv@google.com>
 <3338f2bc-6985-c1a4-9f3d-e59a474027f9@huawei.com>
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In-Reply-To: <3338f2bc-6985-c1a4-9f3d-e59a474027f9@huawei.com>
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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?

> 
> 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
> > .
> >