[RFC PATCH v2 08/16] fs: add pending file update time flag.

[Stefan Roesch <shr@fb.com>]

This introduces an optimization for the update time flag and async
buffered writes. While an update of the file modification time is
pending and is handled by the workers, concurrent writes do not need
to wait for this time update to complete.

Signed-off-by: Stefan Roesch <shr@fb.com>
---
 fs/inode.c         | 1 +
 include/linux/fs.h | 3 +++
 2 files changed, 4 insertions(+)

diff --git a/fs/inode.c b/fs/inode.c
index 1d0b02763e98..fd18b2c1b7c4 100644
--- a/fs/inode.c
+++ b/fs/inode.c
@@ -2091,6 +2091,7 @@ static int do_file_update_time(struct inode *inode, struct file *file,
 		return 0;
 
 	ret = inode_update_time(inode, now, sync_mode);
+	inode->i_flags &= ~S_PENDING_TIME;
 	__mnt_drop_write_file(file);
 
 	return ret;
diff --git a/include/linux/fs.h b/include/linux/fs.h
index 3b479d02e210..3da641dfa6d9 100644
--- a/include/linux/fs.h
+++ b/include/linux/fs.h
@@ -2141,6 +2141,8 @@ struct super_operations {
 #define S_CASEFOLD	(1 << 15) /* Casefolded file */
 #define S_VERITY	(1 << 16) /* Verity file (using fs/verity/) */
 #define S_KERNEL_FILE	(1 << 17) /* File is in use by the kernel (eg. fs/cachefiles) */
+#define S_PENDING_TIME (1 << 18) /* File update time is pending */
+
 
 /*
  * Note that nosuid etc flags are inode-specific: setting some file-system
@@ -2183,6 +2185,7 @@ static inline bool sb_rdonly(const struct super_block *sb) { return sb->s_flags
 #define IS_ENCRYPTED(inode)	((inode)->i_flags & S_ENCRYPTED)
 #define IS_CASEFOLDED(inode)	((inode)->i_flags & S_CASEFOLD)
 #define IS_VERITY(inode)	((inode)->i_flags & S_VERITY)
+#define IS_PENDING_TIME(inode) ((inode)->i_flags & S_PENDING_TIME)
 
 #define IS_WHITEOUT(inode)	(S_ISCHR(inode->i_mode) && \
 				 (inode)->i_rdev == WHITEOUT_DEV)
-- 
2.30.2