diff --git a/fs/inode.c b/fs/inode.c
index 0612ad9c0227..83c3378053bc 100644
--- a/fs/inode.c
+++ b/fs/inode.c
@@ -2108,10 +2108,40 @@ 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 mtime or ctime update. If the ctime is flagged
+ * as having been QUERIED, get the most current fine-grained timestamp
+ * (without advancing the coarse-grained mgtime), otherwise get the
+ * latest coarse multigrain timestamp.
+ */
+static struct timespec64 current_mgtime(struct inode *inode)
+{
+	struct timespec64 now;
+	atomic_t *pnsec = (atomic_t *)&inode->i_ctime_nsec;
+	u32 nsec = atomic_read(pnsec);
+
+	if (nsec & I_CTIME_QUERIED) {
+		ktime_get_real_ts64(&now);
+		return timestamp_truncate(now, inode);
+	}
+	return current_time(inode);
+}
+
+static struct timespec64 current_ctime(struct inode *inode)
+{
+	if (is_mgtime(inode))
+		return current_mgtime(inode);
+	return current_time(inode);
+}
+
 static int inode_needs_update_time(struct inode *inode)
 {
 	int sync_it = 0;
-	struct timespec64 now = current_time(inode);
+	struct timespec64 now = current_ctime(inode);
 	struct timespec64 ts;
 
 	/* First try to exhaust all avenues to not sync */
@@ -2529,7 +2559,7 @@ struct timespec64 current_time(struct inode *inode)
 {
 	struct timespec64 now;
 
-	ktime_get_coarse_real_ts64(&now);
+	ktime_get_mg_coarse_ts64(&now);
 	return timestamp_truncate(now, inode);
 }
 EXPORT_SYMBOL(current_time);
@@ -2544,8 +2574,42 @@ EXPORT_SYMBOL(current_time);
 struct timespec64 inode_set_ctime_current(struct inode *inode)
 {
 	struct timespec64 now = current_time(inode);
+	struct timespec64 ctime;
+	bool queried;
+	int tscomp;
+
+	/* Just copy it into place if it's not multigrain */
+	if (!is_mgtime(inode)) {
+		inode_set_ctime_to_ts(inode, now);
+		return now;
+	}
+
+	ctime.tv_sec = inode_get_ctime_sec(inode);
+	ctime.tv_nsec = READ_ONCE(inode->i_ctime_nsec);
+	queried = ctime.tv_nsec & I_CTIME_QUERIED;
+
+	tscomp = timespec64_compare(&ctime, &now);
 
-	inode_set_ctime(inode, now.tv_sec, now.tv_nsec);
+	/*
+	 * We can use a coarse-grained timestamp if no one has queried for it,
+	 * or coarse time is already later than the existing ctime.
+	 */
+	if (!queried || tscomp < 0) {
+		/*
+		 * Ctime updates are usually protected by the inode_lock, but
+		 * we can still race with someone setting the QUERIED flag.
+		 * Try to swap the new nsec value into place. If it's changed
+		 * in the interim, then just go with a fine-grained timestamp.
+		 */
+		if (cmpxchg(&inode->i_ctime_nsec, ctime.tv_nsec,
+			    now.tv_nsec) != ctime.tv_nsec)
+			goto fine_grained;
+		inode->i_ctime_sec = now.tv_sec;
+		return now;
+	}
+fine_grained:
+	ktime_get_mg_fine_ts64(&now);
+	inode_set_ctime_to_ts(inode, timestamp_truncate(now, inode));
 	return now;
 }
 EXPORT_SYMBOL(inode_set_ctime_current);
diff --git a/fs/stat.c b/fs/stat.c
index 24bb0209e459..02d8857bac9f 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
+ * @stat: where to store the resulting values
+ * @request_mask: STATX_* values requested
+ * @inode: inode from which to grab the c/mtime
+ *
+ * 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(struct kstat *stat, u32 request_mask, struct inode *inode)
+{
+	atomic_t *pnsec = (atomic_t *)&inode->i_ctime_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_get_mtime(inode);
+	stat->ctime.tv_sec = inode_get_ctime_sec(inode);
+	/*
+	 * Atomically set the QUERIED flag and fetch the new value with
+	 * the flag masked off.
+	 */
+	stat->ctime.tv_nsec = atomic_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_get_atime(inode);
-	stat->mtime = inode_get_mtime(inode);
-	stat->ctime = inode_get_ctime(inode);
+
+	if (is_mgtime(inode)) {
+		fill_mg_cmtime(stat, request_mask, inode);
+	} else {
+		stat->mtime = inode_get_mtime(inode);
+		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 78786c1c32fd..c9823ec0da65 100644
--- a/include/linux/fs.h
+++ b/include/linux/fs.h
@@ -1515,6 +1515,22 @@ 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)
+
 static inline time64_t inode_get_atime_sec(const struct inode *inode)
 {
 	return inode->i_atime_sec;
@@ -1590,7 +1606,7 @@ static inline time64_t inode_get_ctime_sec(const struct inode *inode)
 
 static inline long inode_get_ctime_nsec(const struct inode *inode)
 {
-	return inode->i_ctime_nsec;
+	return inode->i_ctime_nsec & ~I_CTIME_QUERIED;
 }
 
 static inline struct timespec64 inode_get_ctime(const struct inode *inode)
@@ -2372,6 +2388,7 @@ 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;
@@ -2395,6 +2412,17 @@ 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));
@@ -3080,6 +3108,7 @@ 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(struct kstat *stat, u32 request_mask, struct inode *inode);
 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);
