vfs: add ATTR_CTIME_SET flag

When ATTR_ATIME_SET and ATTR_MTIME_SET are set in the ia_valid mask, the
notify_change() logic takes that to mean that the request should set
those values explicitly, and not override them with "now".

With the advent of delegated timestamps, similar functionality is needed
for the ctime. Add a ATTR_CTIME_SET flag, and use that to indicate that
the ctime should be accepted as-is. Also, clean up the if statements to
eliminate the extra negatives.

In setattr_copy() and setattr_copy_mgtime() use inode_set_ctime_deleg()
when ATTR_CTIME_SET is set, instead of basing the decision on ATTR_DELEG.

Signed-off-by: Jeff Layton <jlayton@kernel.org>
Signed-off-by: Chuck Lever <chuck.lever@oracle.com>

Author: jtlayton

fs/attr.c

@@ -286,20 +286,12 @@ static void setattr_copy_mgtime(struct inode *inode, const struct iattr *attr)
 	unsigned int ia_valid = attr->ia_valid;
 	struct timespec64 now;
 
-	if (ia_valid & ATTR_CTIME) {
-		/*
-		 * In the case of an update for a write delegation, we must respect
-		 * the value in ia_ctime and not use the current time.
-		 */
-		if (ia_valid & ATTR_DELEG)
-			now = inode_set_ctime_deleg(inode, attr->ia_ctime);
-		else
-			now = inode_set_ctime_current(inode);
-	} else {
-		/* If ATTR_CTIME isn't set, then ATTR_MTIME shouldn't be either. */
-		WARN_ON_ONCE(ia_valid & ATTR_MTIME);
+	if (ia_valid & ATTR_CTIME_SET)
+		now = inode_set_ctime_deleg(inode, attr->ia_ctime);
+	else if (ia_valid & ATTR_CTIME)
+		now = inode_set_ctime_current(inode);
+	else
 		now = current_time(inode);
-	}
 
 	if (ia_valid & ATTR_ATIME_SET)
 		inode_set_atime_to_ts(inode, attr->ia_atime);
@@ -359,12 +351,11 @@ void setattr_copy(struct mnt_idmap *idmap, struct inode *inode,
 		inode_set_atime_to_ts(inode, attr->ia_atime);
 	if (ia_valid & ATTR_MTIME)
 		inode_set_mtime_to_ts(inode, attr->ia_mtime);
-	if (ia_valid & ATTR_CTIME) {
-		if (ia_valid & ATTR_DELEG)
-			inode_set_ctime_deleg(inode, attr->ia_ctime);
-		else
-			inode_set_ctime_to_ts(inode, attr->ia_ctime);
-	}
+
+	if (ia_valid & ATTR_CTIME_SET)
+		inode_set_ctime_deleg(inode, attr->ia_ctime);
+	else if (ia_valid & ATTR_CTIME)
+		inode_set_ctime_to_ts(inode, attr->ia_ctime);
 }
 EXPORT_SYMBOL(setattr_copy);
 
@@ -463,15 +454,18 @@ int notify_change(struct mnt_idmap *idmap, struct dentry *dentry,
 
 	now = current_time(inode);
 
-	attr->ia_ctime = now;
-	if (!(ia_valid & ATTR_ATIME_SET))
-		attr->ia_atime = now;
-	else
+	if (ia_valid & ATTR_ATIME_SET)
 		attr->ia_atime = timestamp_truncate(attr->ia_atime, inode);
-	if (!(ia_valid & ATTR_MTIME_SET))
-		attr->ia_mtime = now;
 	else
+		attr->ia_atime = now;
+	if (ia_valid & ATTR_CTIME_SET)
+		attr->ia_ctime = timestamp_truncate(attr->ia_ctime, inode);
+	else
+		attr->ia_ctime = now;
+	if (ia_valid & ATTR_MTIME_SET)
 		attr->ia_mtime = timestamp_truncate(attr->ia_mtime, inode);
+	else
+		attr->ia_mtime = now;
 
 	if (ia_valid & ATTR_KILL_PRIV) {
 		error = security_inode_need_killpriv(dentry);

include/linux/fs.h

@@ -238,6 +238,7 @@ typedef int (dio_iodone_t)(struct kiocb *iocb, loff_t offset,
 #define ATTR_ATIME_SET	(1 << 7)
 #define ATTR_MTIME_SET	(1 << 8)
 #define ATTR_FORCE	(1 << 9) /* Not a change, but a change it */
+#define ATTR_CTIME_SET	(1 << 10)
 #define ATTR_KILL_SUID	(1 << 11)
 #define ATTR_KILL_SGID	(1 << 12)
 #define ATTR_FILE	(1 << 13)