[PATCH 10/29] vfs: add S_NOWAIT for nowait time update

[Hao Xu]

From: Hao Xu <howeyxu at tencent.com>

Add a new time flag S_NOWAIT to support nowait time update. Deliver it
to specific filesystem and error out -EAGAIN when it would block.

Signed-off-by: Hao Xu <howeyxu at tencent.com>
---
 fs/inode.c         | 9 +++++----
 fs/xfs/xfs_iops.c  | 8 +++++++-
 include/linux/fs.h | 1 +
 3 files changed, 13 insertions(+), 5 deletions(-)

diff --git a/fs/inode.c b/fs/inode.c
index e83b836f2d09..eb3db34a3e6e 100644
--- a/fs/inode.c
+++ b/fs/inode.c
@@ -1966,12 +1966,13 @@ int touch_atime(const struct path *path, bool nowait)
 	struct vfsmount *mnt = path->mnt;
 	struct inode *inode = d_inode(path->dentry);
 	struct timespec64 now;
+	int ret = 0;
 
 	if (!atime_needs_update(path, inode))
-		return 0;
+		return ret;
 
 	if (!sb_start_write_trylock(inode->i_sb))
-		return 0;
+		return ret;
 
 	if (__mnt_want_write(mnt) != 0)
 		goto skip_update;
@@ -1985,11 +1986,11 @@ int touch_atime(const struct path *path, bool nowait)
 	 * of the fs read only, e.g. subvolumes in Btrfs.
 	 */
 	now = current_time(inode);
-	inode_update_time(inode, &now, S_ATIME);
+	ret = inode_update_time(inode, &now, S_ATIME | (nowait ? S_NOWAIT : 0));
 	__mnt_drop_write(mnt);
 skip_update:
 	sb_end_write(inode->i_sb);
-	return 0;
+	return ret;
 }
 EXPORT_SYMBOL(touch_atime);
 
diff --git a/fs/xfs/xfs_iops.c b/fs/xfs/xfs_iops.c
index 24718adb3c16..bf1d4c31f009 100644
--- a/fs/xfs/xfs_iops.c
+++ b/fs/xfs/xfs_iops.c
@@ -1053,7 +1053,13 @@ xfs_vn_update_time(
 	if (error)
 		return error;
 
-	xfs_ilock(ip, XFS_ILOCK_EXCL);
+	if (flags & S_NOWAIT) {
+		if (!xfs_ilock_nowait(ip, XFS_ILOCK_EXCL))
+			return -EAGAIN;
+	} else {
+		xfs_ilock(ip, XFS_ILOCK_EXCL);
+	}
+
 	if (flags & S_CTIME)
 		inode->i_ctime = *now;
 	if (flags & S_MTIME)
diff --git a/include/linux/fs.h b/include/linux/fs.h
index ed60b3d70d1e..f8c267ee5cb7 100644
--- a/include/linux/fs.h
+++ b/include/linux/fs.h
@@ -2198,6 +2198,7 @@ enum file_time_flags {
 	S_MTIME = 2,
 	S_CTIME = 4,
 	S_VERSION = 8,
+	S_NOWAIT = 16,
 };
 
 extern bool atime_needs_update(const struct path *, struct inode *);
-- 
2.25.1