diff --git a/fs/inode.c b/fs/inode.c
index d4ab92233062..369621e7faf5 100644
--- a/fs/inode.c
+++ b/fs/inode.c
@@ -1919,6 +1919,21 @@ int inode_update_time(struct inode *inode, struct timespec64 *time, int flags)
 }
 EXPORT_SYMBOL(inode_update_time);
 
+/**
+ * current_coarse_time - Return FS time
+ * @inode: inode.
+ *
+ * Return the current coarse-grained time truncated to the time
+ * granularity supported by the fs.
+ */
+static struct timespec64 current_coarse_time(struct inode *inode)
+{
+	struct timespec64 now;
+
+	ktime_get_coarse_real_ts64(&now);
+	return timestamp_truncate(now, inode);
+}
+
 /**
  *	atime_needs_update	-	update the access time
  *	@path: the &struct path to update
@@ -1952,7 +1967,7 @@ bool atime_needs_update(const struct path *path, struct inode *inode)
 	if ((mnt->mnt_flags & MNT_NODIRATIME) && S_ISDIR(inode->i_mode))
 		return false;
 
-	now = current_time(inode);
+	now = current_coarse_time(inode);
 
 	if (!relatime_need_update(mnt, inode, now))
 		return false;
@@ -1986,7 +2001,7 @@ void touch_atime(const struct path *path)
 	 * We may also fail on filesystems that have the ability to make parts
 	 * of the fs read only, e.g. subvolumes in Btrfs.
 	 */
-	now = current_time(inode);
+	now = current_coarse_time(inode);
 	inode_update_time(inode, &now, S_ATIME);
 	__mnt_drop_write(mnt);
 skip_update:
@@ -2072,6 +2087,56 @@ int file_remove_privs(struct file *file)
 }
 EXPORT_SYMBOL(file_remove_privs);
 
+/**
+ * current_mgtime - Return FS time (possibly fine-grained)
+ * @inode: inode.
+ *
+ * Return the current time truncated to the time granularity supported by
+ * the fs, as suitable for a ctime/mtime change. If the ctime is flagged
+ * as having been QUERIED, get a fine-grained timestamp.
+ */
+static struct timespec64 current_mgtime(struct inode *inode)
+{
+	struct timespec64 now;
+	atomic_long_t *pnsec = (atomic_long_t *)&inode->__i_ctime.tv_nsec;
+	long nsec = atomic_long_read(pnsec);
+
+	if (nsec & I_CTIME_QUERIED) {
+		ktime_get_real_ts64(&now);
+	} else {
+		struct timespec64 ctime;
+
+		ktime_get_coarse_real_ts64(&now);
+
+		/*
+		 * If we've recently fetched a fine-grained timestamp
+		 * then the coarse-grained one may still be earlier than the
+		 * existing one. Just keep the existing ctime if so.
+		 */
+		ctime = inode_get_ctime(inode);
+		if (timespec64_compare(&ctime, &now) > 0)
+			now = ctime;
+	}
+
+	return timestamp_truncate(now, inode);
+}
+
+/**
+ * current_time - Return timestamp suitable for ctime update
+ * @inode: inode to eventually be updated
+ *
+ * Return the current time, which is usually coarse-grained but may be fine
+ * grained if the filesystem uses multigrain timestamps and the existing
+ * ctime was queried since the last update.
+ */
+struct timespec64 current_time(struct inode *inode)
+{
+	if (is_mgtime(inode))
+		return current_mgtime(inode);
+	return current_coarse_time(inode);
+}
+EXPORT_SYMBOL(current_time);
+
 static int inode_needs_update_time(struct inode *inode, struct timespec64 *now)
 {
 	int sync_it = 0;
@@ -2480,37 +2545,12 @@ struct timespec64 timestamp_truncate(struct timespec64 t, struct inode *inode)
 }
 EXPORT_SYMBOL(timestamp_truncate);
 
-/**
- * current_time - Return FS time
- * @inode: inode.
- *
- * Return the current time truncated to the time granularity supported by
- * the fs.
- *
- * Note that inode and inode->sb cannot be NULL.
- * Otherwise, the function warns and returns time without truncation.
- */
-struct timespec64 current_time(struct inode *inode)
-{
-	struct timespec64 now;
-
-	ktime_get_coarse_real_ts64(&now);
-
-	if (unlikely(!inode->i_sb)) {
-		WARN(1, "current_time() called with uninitialized super_block in the inode");
-		return now;
-	}
-
-	return timestamp_truncate(now, inode);
-}
-EXPORT_SYMBOL(current_time);
-
 /**
  * inode_set_ctime_current - set the ctime to current_time
  * @inode: inode
  *
- * Set the inode->i_ctime to the current value for the inode. Returns
- * the current value that was assigned to i_ctime.
+ * Set the inode->__i_ctime to the current value for the inode. Returns
+ * the current value that was assigned to __i_ctime.
  */
 struct timespec64 inode_set_ctime_current(struct inode *inode)
 {
diff --git a/fs/stat.c b/fs/stat.c
index 062f311b5386..51effd1c2bc2 100644
--- a/fs/stat.c
+++ b/fs/stat.c
@@ -26,6 +26,37 @@
 #include "internal.h"
 #include "mount.h"
 
+/**
+ * fill_mg_cmtime - Fill in the mtime and ctime and flag ctime as QUERIED
+ * @request_mask: STATX_* values requested
+ * @inode: inode from which to grab the c/mtime
+ * @stat: where to store the resulting values
+ *
+ * Given @inode, grab the ctime and mtime out if it and store the result
+ * in @stat. When fetching the value, flag it as queried so the next write
+ * will use a fine-grained timestamp.
+ */
+void fill_mg_cmtime(u32 request_mask, struct inode *inode, struct kstat *stat)
+{
+	atomic_long_t *pnsec = (atomic_long_t *)&inode->__i_ctime.tv_nsec;
+
+	/* If neither time was requested, then don't report them */
+	if (!(request_mask & (STATX_CTIME|STATX_MTIME))) {
+		stat->result_mask &= ~(STATX_CTIME|STATX_MTIME);
+		return;
+	}
+
+	stat->mtime = inode->i_mtime;
+	stat->ctime.tv_sec = inode->__i_ctime.tv_sec;
+	/*
+	 * Atomically set the QUERIED flag and fetch the new value with
+	 * the flag masked off.
+	 */
+	stat->ctime.tv_nsec = atomic_long_fetch_or(I_CTIME_QUERIED, pnsec) &
+					~I_CTIME_QUERIED;
+}
+EXPORT_SYMBOL(fill_mg_cmtime);
+
 /**
  * generic_fillattr - Fill in the basic attributes from the inode struct
  * @idmap:	idmap of the mount the inode was found from
@@ -58,8 +89,14 @@ void generic_fillattr(struct mnt_idmap *idmap, u32 request_mask,
 	stat->rdev = inode->i_rdev;
 	stat->size = i_size_read(inode);
 	stat->atime = inode->i_atime;
-	stat->mtime = inode->i_mtime;
-	stat->ctime = inode_get_ctime(inode);
+
+	if (is_mgtime(inode)) {
+		fill_mg_cmtime(request_mask, inode, stat);
+	} else {
+		stat->mtime = inode->i_mtime;
+		stat->ctime = inode_get_ctime(inode);
+	}
+
 	stat->blksize = i_blocksize(inode);
 	stat->blocks = inode->i_blocks;
 
diff --git a/include/linux/fs.h b/include/linux/fs.h
index 42d1434cc427..a0bdbefbf293 100644
--- a/include/linux/fs.h
+++ b/include/linux/fs.h
@@ -1477,15 +1477,43 @@ static inline bool fsuidgid_has_mapping(struct super_block *sb,
 struct timespec64 current_time(struct inode *inode);
 struct timespec64 inode_set_ctime_current(struct inode *inode);
 
+/*
+ * Multigrain timestamps
+ *
+ * Conditionally use fine-grained ctime and mtime timestamps when there
+ * are users actively observing them via getattr. The primary use-case
+ * for this is NFS clients that use the ctime to distinguish between
+ * different states of the file, and that are often fooled by multiple
+ * operations that occur in the same coarse-grained timer tick.
+ *
+ * The kernel always keeps normalized struct timespec64 values in the ctime,
+ * which means that only the first 30 bits of the value are used. Use the
+ * 31st bit of the ctime's tv_nsec field as a flag to indicate that the value
+ * has been queried since it was last updated.
+ */
+#define I_CTIME_QUERIED		(1L<<30)
+
 /**
  * inode_get_ctime - fetch the current ctime from the inode
  * @inode: inode from which to fetch ctime
  *
- * Grab the current ctime from the inode and return it.
+ * Grab the current ctime tv_nsec field from the inode, mask off the
+ * I_CTIME_QUERIED flag and return it. This is mostly intended for use by
+ * internal consumers of the ctime that aren't concerned with ensuring a
+ * fine-grained update on the next change (e.g. when preparing to store
+ * the value in the backing store for later retrieval).
+ *
+ * This is safe to call regardless of whether the underlying filesystem
+ * is using multigrain timestamps.
  */
 static inline struct timespec64 inode_get_ctime(const struct inode *inode)
 {
-	return inode->__i_ctime;
+	struct timespec64 ctime;
+
+	ctime.tv_sec = inode->__i_ctime.tv_sec;
+	ctime.tv_nsec = inode->__i_ctime.tv_nsec & ~I_CTIME_QUERIED;
+
+	return ctime;
 }
 
 /**
@@ -2261,6 +2289,7 @@ struct file_system_type {
 #define FS_USERNS_MOUNT		8	/* Can be mounted by userns root */
 #define FS_DISALLOW_NOTIFY_PERM	16	/* Disable fanotify permission events */
 #define FS_ALLOW_IDMAP         32      /* FS has been updated to handle vfs idmappings. */
+#define FS_MGTIME		64	/* FS uses multigrain timestamps */
 #define FS_RENAME_DOES_D_MOVE	32768	/* FS will handle d_move() during rename() internally. */
 	int (*init_fs_context)(struct fs_context *);
 	const struct fs_parameter_spec *parameters;
@@ -2284,6 +2313,17 @@ struct file_system_type {
 
 #define MODULE_ALIAS_FS(NAME) MODULE_ALIAS("fs-" NAME)
 
+/**
+ * is_mgtime: is this inode using multigrain timestamps
+ * @inode: inode to test for multigrain timestamps
+ *
+ * Return true if the inode uses multigrain timestamps, false otherwise.
+ */
+static inline bool is_mgtime(const struct inode *inode)
+{
+	return inode->i_sb->s_type->fs_flags & FS_MGTIME;
+}
+
 extern struct dentry *mount_bdev(struct file_system_type *fs_type,
 	int flags, const char *dev_name, void *data,
 	int (*fill_super)(struct super_block *, void *, int));
@@ -2919,6 +2959,7 @@ extern void page_put_link(void *);
 extern int page_symlink(struct inode *inode, const char *symname, int len);
 extern const struct inode_operations page_symlink_inode_operations;
 extern void kfree_link(void *);
+void fill_mg_cmtime(u32 request_mask, struct inode *inode, struct kstat *stat);
 void generic_fillattr(struct mnt_idmap *, u32, struct inode *, struct kstat *);
 void generic_fill_statx_attr(struct inode *inode, struct kstat *stat);
 extern int vfs_getattr_nosec(const struct path *, struct kstat *, u32, unsigned int);
