Revert "fs: add infrastructure for multigrain timestamps"

This reverts commit ffb6cf19e06334062744b7e3493f71e500964f8e.

Users reported regressions due to enabling multi-grained timestamps
unconditionally. As no clear consensus on a solution has come up and the
discussion has gone back to the drawing board revert the infrastructure
changes for. If it isn't code that's here to stay, make it go away.

Message-ID: <20230920-keine-eile-c9755b5825db@brauner>
Acked-by: Jan Kara <jack@suse.cz>
Acked-by: Jeff Layton <jlayton@kernel.org>
Signed-off-by: Christian Brauner <brauner@kernel.org>

1 files changed, 2 insertions, 44 deletions

diff --git a/include/linux/fs.h b/include/linux/fs.h
index 4aeb3fa11927..b528f063e8ff 100644
--- a/include/linux/fs.h
+++ b/include/linux/fs.h
@@ -1508,47 +1508,18 @@ static inline bool fsuidgid_has_mapping(struct super_block *sb,
 	       kgid_has_mapping(fs_userns, kgid);
 }
 
-struct timespec64 current_mgtime(struct inode *inode);
 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 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.
+ * Grab the current ctime from the inode and return it.
  */
 static inline struct timespec64 inode_get_ctime(const struct inode *inode)
 {
-	struct timespec64 ctime;
-
-	ctime.tv_sec = inode->__i_ctime.tv_sec;
-	ctime.tv_nsec = inode->__i_ctime.tv_nsec & ~I_CTIME_QUERIED;
-
-	return ctime;
+	return inode->__i_ctime;
 }
 
 /**
@@ -2334,7 +2305,6 @@ 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;
@@ -2358,17 +2328,6 @@ 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));
@@ -3054,7 +3013,6 @@ 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);