[RFC PATCH] f2fs: reduce expensive checkpoint trigger frequency

[Chao Yu]

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().

Signed-off-by: Chao Yu <yuchao0@xxxxxxxxxx>
---
 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);
 
 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