From 9b6304c1d53745c300b86f202d0dcff395e2d2db Mon Sep 17 00:00:00 2001
From: Jeff Layton <jlayton@kernel.org>
Date: Wed, 5 Jul 2023 14:58:10 -0400
Subject: fs: add ctime accessors infrastructure

struct timespec64 has unused bits in the tv_nsec field that can be used
for other purposes. In future patches, we're going to change how the
inode->i_ctime is accessed in certain inodes in order to make use of
them. In order to do that safely though, we'll need to eradicate raw
accesses of the inode->i_ctime field from the kernel.

Add new accessor functions for the ctime that we use to replace them.

Reviewed-by: Jan Kara <jack@suse.cz>
Reviewed-by: Luis Chamberlain <mcgrof@kernel.org>
Signed-off-by: Jeff Layton <jlayton@kernel.org>
Reviewed-by: Damien Le Moal <dlemoal@kernel.org>
Message-Id: <20230705185812.579118-2-jlayton@kernel.org>
Signed-off-by: Christian Brauner <brauner@kernel.org>
---
 fs/inode.c | 16 ++++++++++++++++
 1 file changed, 16 insertions(+)

(limited to 'fs/inode.c')

diff --git a/fs/inode.c b/fs/inode.c
index 8fefb69e1f84..aac5cdcf5e89 100644
--- a/fs/inode.c
+++ b/fs/inode.c
@@ -2501,6 +2501,22 @@ struct timespec64 current_time(struct inode *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.
+ */
+struct timespec64 inode_set_ctime_current(struct inode *inode)
+{
+	struct timespec64 now = current_time(inode);
+
+	inode_set_ctime(inode, now.tv_sec, now.tv_nsec);
+	return now;
+}
+EXPORT_SYMBOL(inode_set_ctime_current);
+
 /**
  * in_group_or_capable - check whether caller is CAP_FSETID privileged
  * @idmap:	idmap of the mount @inode was found from
-- 
cgit v1.2.3


From 2276e5ba8567f683c49a36ba885d0fe6abe2b45e Mon Sep 17 00:00:00 2001
From: Jeff Layton <jlayton@kernel.org>
Date: Wed, 5 Jul 2023 15:00:50 -0400
Subject: fs: convert to ctime accessor functions

In later patches, we're going to change how the inode's ctime field is
used. Switch to using accessor functions instead of raw accesses of
inode->i_ctime.

Reviewed-by: Jan Kara <jack@suse.cz>
Signed-off-by: Jeff Layton <jlayton@kernel.org>
Message-Id: <20230705190309.579783-23-jlayton@kernel.org>
Signed-off-by: Christian Brauner <brauner@kernel.org>
---
 fs/attr.c        |  2 +-
 fs/bad_inode.c   |  3 +--
 fs/binfmt_misc.c |  3 +--
 fs/inode.c       | 10 +++++++---
 fs/nsfs.c        |  2 +-
 fs/pipe.c        |  2 +-
 fs/posix_acl.c   |  2 +-
 fs/stack.c       |  2 +-
 fs/stat.c        |  2 +-
 9 files changed, 15 insertions(+), 13 deletions(-)

(limited to 'fs/inode.c')

diff --git a/fs/attr.c b/fs/attr.c
index d60dc1edb526..599f6d14c0ed 100644
--- a/fs/attr.c
+++ b/fs/attr.c
@@ -312,7 +312,7 @@ void setattr_copy(struct mnt_idmap *idmap, struct inode *inode,
 	if (ia_valid & ATTR_MTIME)
 		inode->i_mtime = attr->ia_mtime;
 	if (ia_valid & ATTR_CTIME)
-		inode->i_ctime = attr->ia_ctime;
+		inode_set_ctime_to_ts(inode, attr->ia_ctime);
 	if (ia_valid & ATTR_MODE) {
 		umode_t mode = attr->ia_mode;
 		if (!in_group_or_capable(idmap, inode,
diff --git a/fs/bad_inode.c b/fs/bad_inode.c
index db649487d58c..6e21f7412a85 100644
--- a/fs/bad_inode.c
+++ b/fs/bad_inode.c
@@ -209,8 +209,7 @@ void make_bad_inode(struct inode *inode)
 	remove_inode_hash(inode);
 
 	inode->i_mode = S_IFREG;
-	inode->i_atime = inode->i_mtime = inode->i_ctime =
-		current_time(inode);
+	inode->i_atime = inode->i_mtime = inode_set_ctime_current(inode);
 	inode->i_op = &bad_inode_ops;	
 	inode->i_opflags &= ~IOP_XATTR;
 	inode->i_fop = &bad_file_ops;	
diff --git a/fs/binfmt_misc.c b/fs/binfmt_misc.c
index bb202ad369d5..e0108d17b085 100644
--- a/fs/binfmt_misc.c
+++ b/fs/binfmt_misc.c
@@ -547,8 +547,7 @@ static struct inode *bm_get_inode(struct super_block *sb, int mode)
 	if (inode) {
 		inode->i_ino = get_next_ino();
 		inode->i_mode = mode;
-		inode->i_atime = inode->i_mtime = inode->i_ctime =
-			current_time(inode);
+		inode->i_atime = inode->i_mtime = inode_set_ctime_current(inode);
 	}
 	return inode;
 }
diff --git a/fs/inode.c b/fs/inode.c
index aac5cdcf5e89..d4ab92233062 100644
--- a/fs/inode.c
+++ b/fs/inode.c
@@ -1853,6 +1853,7 @@ EXPORT_SYMBOL(bmap);
 static int relatime_need_update(struct vfsmount *mnt, struct inode *inode,
 			     struct timespec64 now)
 {
+	struct timespec64 ctime;
 
 	if (!(mnt->mnt_flags & MNT_RELATIME))
 		return 1;
@@ -1864,7 +1865,8 @@ static int relatime_need_update(struct vfsmount *mnt, struct inode *inode,
 	/*
 	 * Is ctime younger than or equal to atime? If yes, update atime:
 	 */
-	if (timespec64_compare(&inode->i_ctime, &inode->i_atime) >= 0)
+	ctime = inode_get_ctime(inode);
+	if (timespec64_compare(&ctime, &inode->i_atime) >= 0)
 		return 1;
 
 	/*
@@ -1887,7 +1889,7 @@ int generic_update_time(struct inode *inode, struct timespec64 *time, int flags)
 		if (flags & S_ATIME)
 			inode->i_atime = *time;
 		if (flags & S_CTIME)
-			inode->i_ctime = *time;
+			inode_set_ctime_to_ts(inode, *time);
 		if (flags & S_MTIME)
 			inode->i_mtime = *time;
 
@@ -2073,6 +2075,7 @@ EXPORT_SYMBOL(file_remove_privs);
 static int inode_needs_update_time(struct inode *inode, struct timespec64 *now)
 {
 	int sync_it = 0;
+	struct timespec64 ctime;
 
 	/* First try to exhaust all avenues to not sync */
 	if (IS_NOCMTIME(inode))
@@ -2081,7 +2084,8 @@ static int inode_needs_update_time(struct inode *inode, struct timespec64 *now)
 	if (!timespec64_equal(&inode->i_mtime, now))
 		sync_it = S_MTIME;
 
-	if (!timespec64_equal(&inode->i_ctime, now))
+	ctime = inode_get_ctime(inode);
+	if (!timespec64_equal(&ctime, now))
 		sync_it |= S_CTIME;
 
 	if (IS_I_VERSION(inode) && inode_iversion_need_inc(inode))
diff --git a/fs/nsfs.c b/fs/nsfs.c
index f602a96a1afe..647a22433bd8 100644
--- a/fs/nsfs.c
+++ b/fs/nsfs.c
@@ -84,7 +84,7 @@ slow:
 		return -ENOMEM;
 	}
 	inode->i_ino = ns->inum;
-	inode->i_mtime = inode->i_atime = inode->i_ctime = current_time(inode);
+	inode->i_mtime = inode->i_atime = inode_set_ctime_current(inode);
 	inode->i_flags |= S_IMMUTABLE;
 	inode->i_mode = S_IFREG | S_IRUGO;
 	inode->i_fop = &ns_file_operations;
diff --git a/fs/pipe.c b/fs/pipe.c
index 2d88f73f585a..174682103669 100644
--- a/fs/pipe.c
+++ b/fs/pipe.c
@@ -899,7 +899,7 @@ static struct inode * get_pipe_inode(void)
 	inode->i_mode = S_IFIFO | S_IRUSR | S_IWUSR;
 	inode->i_uid = current_fsuid();
 	inode->i_gid = current_fsgid();
-	inode->i_atime = inode->i_mtime = inode->i_ctime = current_time(inode);
+	inode->i_atime = inode->i_mtime = inode_set_ctime_current(inode);
 
 	return inode;
 
diff --git a/fs/posix_acl.c b/fs/posix_acl.c
index 7fa1b738bbab..a05fe94970ce 100644
--- a/fs/posix_acl.c
+++ b/fs/posix_acl.c
@@ -1027,7 +1027,7 @@ int simple_set_acl(struct mnt_idmap *idmap, struct dentry *dentry,
 			return error;
 	}
 
-	inode->i_ctime = current_time(inode);
+	inode_set_ctime_current(inode);
 	if (IS_I_VERSION(inode))
 		inode_inc_iversion(inode);
 	set_cached_acl(inode, type, acl);
diff --git a/fs/stack.c b/fs/stack.c
index c9830924eb12..b5e01bdb5f5f 100644
--- a/fs/stack.c
+++ b/fs/stack.c
@@ -68,7 +68,7 @@ void fsstack_copy_attr_all(struct inode *dest, const struct inode *src)
 	dest->i_rdev = src->i_rdev;
 	dest->i_atime = src->i_atime;
 	dest->i_mtime = src->i_mtime;
-	dest->i_ctime = src->i_ctime;
+	inode_set_ctime_to_ts(dest, inode_get_ctime(src));
 	dest->i_blkbits = src->i_blkbits;
 	dest->i_flags = src->i_flags;
 	set_nlink(dest, src->i_nlink);
diff --git a/fs/stat.c b/fs/stat.c
index 7c238da22ef0..8c2b30af19f5 100644
--- a/fs/stat.c
+++ b/fs/stat.c
@@ -58,7 +58,7 @@ void generic_fillattr(struct mnt_idmap *idmap, struct inode *inode,
 	stat->size = i_size_read(inode);
 	stat->atime = inode->i_atime;
 	stat->mtime = inode->i_mtime;
-	stat->ctime = inode->i_ctime;
+	stat->ctime = inode_get_ctime(inode);
 	stat->blksize = i_blocksize(inode);
 	stat->blocks = inode->i_blocks;
 }
-- 
cgit v1.2.3


From b3030e4f23441347cd5d18b2610fb299ed98d739 Mon Sep 17 00:00:00 2001
From: Jeff Layton <jlayton@kernel.org>
Date: Mon, 7 Aug 2023 15:38:32 -0400
Subject: fs: remove silly warning from current_time

An inode with no superblock? Unpossible!

Signed-off-by: Jeff Layton <jlayton@kernel.org>
Reviewed-by: Jan Kara <jack@suse.cz>
Message-Id: <20230807-mgctime-v7-1-d1dec143a704@kernel.org>
Signed-off-by: Christian Brauner <brauner@kernel.org>
---
 fs/inode.c | 6 ------
 1 file changed, 6 deletions(-)

(limited to 'fs/inode.c')

diff --git a/fs/inode.c b/fs/inode.c
index d4ab92233062..3fc251bfaf73 100644
--- a/fs/inode.c
+++ b/fs/inode.c
@@ -2495,12 +2495,6 @@ 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);
-- 
cgit v1.2.3


From 541d4c798a598854fcce7326d947cbcbd35701d6 Mon Sep 17 00:00:00 2001
From: Jeff Layton <jlayton@kernel.org>
Date: Mon, 7 Aug 2023 15:38:34 -0400
Subject: fs: drop the timespec64 arg from generic_update_time

In future patches we're going to change how the ctime is updated
to keep track of when it has been queried. The way that the update_time
operation works (and a lot of its callers) make this difficult, since
they grab a timestamp early and then pass it down to eventually be
copied into the inode.

All of the existing update_time callers pass in the result of
current_time() in some fashion. Drop the "time" parameter from
generic_update_time, and rework it to fetch its own timestamp.

This change means that an update_time could fetch a different timestamp
than was seen in inode_needs_update_time. update_time is only ever
called with one of two flag combinations: Either S_ATIME is set, or
S_MTIME|S_CTIME|S_VERSION are set.

With this change we now treat the flags argument as an indicator that
some value needed to be updated when last checked, rather than an
indication to update specific timestamps.

Rework the logic for updating the timestamps and put it in a new
inode_update_timestamps helper that other update_time routines can use.
S_ATIME is as treated as we always have, but if any of the other three
are set, then we attempt to update all three.

Also, some callers of generic_update_time need to know what timestamps
were actually updated. Change it to return an S_* flag mask to indicate
that and rework the callers to expect it.

Signed-off-by: Jeff Layton <jlayton@kernel.org>
Reviewed-by: Jan Kara <jack@suse.cz>
Message-Id: <20230807-mgctime-v7-3-d1dec143a704@kernel.org>
Signed-off-by: Christian Brauner <brauner@kernel.org>
---
 fs/gfs2/inode.c     |  3 +-
 fs/inode.c          | 84 +++++++++++++++++++++++++++++++++++++++++------------
 fs/orangefs/inode.c |  3 +-
 fs/ubifs/file.c     |  6 ++--
 fs/xfs/xfs_iops.c   |  6 ++--
 include/linux/fs.h  |  3 +-
 6 files changed, 80 insertions(+), 25 deletions(-)

(limited to 'fs/inode.c')

diff --git a/fs/gfs2/inode.c b/fs/gfs2/inode.c
index 200cabf3b393..f1f04557aa21 100644
--- a/fs/gfs2/inode.c
+++ b/fs/gfs2/inode.c
@@ -2155,7 +2155,8 @@ static int gfs2_update_time(struct inode *inode, struct timespec64 *time,
 		if (error)
 			return error;
 	}
-	return generic_update_time(inode, time, flags);
+	generic_update_time(inode, flags);
+	return 0;
 }
 
 static const struct inode_operations gfs2_file_iops = {
diff --git a/fs/inode.c b/fs/inode.c
index 3fc251bfaf73..e07e45f6cd01 100644
--- a/fs/inode.c
+++ b/fs/inode.c
@@ -1881,29 +1881,76 @@ static int relatime_need_update(struct vfsmount *mnt, struct inode *inode,
 	return 0;
 }
 
-int generic_update_time(struct inode *inode, struct timespec64 *time, int flags)
+/**
+ * inode_update_timestamps - update the timestamps on the inode
+ * @inode: inode to be updated
+ * @flags: S_* flags that needed to be updated
+ *
+ * The update_time function is called when an inode's timestamps need to be
+ * updated for a read or write operation. This function handles updating the
+ * actual timestamps. It's up to the caller to ensure that the inode is marked
+ * dirty appropriately.
+ *
+ * In the case where any of S_MTIME, S_CTIME, or S_VERSION need to be updated,
+ * attempt to update all three of them. S_ATIME updates can be handled
+ * independently of the rest.
+ *
+ * Returns a set of S_* flags indicating which values changed.
+ */
+int inode_update_timestamps(struct inode *inode, int flags)
 {
-	int dirty_flags = 0;
+	int updated = 0;
+	struct timespec64 now;
+
+	if (flags & (S_MTIME|S_CTIME|S_VERSION)) {
+		struct timespec64 ctime = inode_get_ctime(inode);
 
-	if (flags & (S_ATIME | S_CTIME | S_MTIME)) {
-		if (flags & S_ATIME)
-			inode->i_atime = *time;
-		if (flags & S_CTIME)
-			inode_set_ctime_to_ts(inode, *time);
-		if (flags & S_MTIME)
-			inode->i_mtime = *time;
-
-		if (inode->i_sb->s_flags & SB_LAZYTIME)
-			dirty_flags |= I_DIRTY_TIME;
-		else
-			dirty_flags |= I_DIRTY_SYNC;
+		now = inode_set_ctime_current(inode);
+		if (!timespec64_equal(&now, &ctime))
+			updated |= S_CTIME;
+		if (!timespec64_equal(&now, &inode->i_mtime)) {
+			inode->i_mtime = now;
+			updated |= S_MTIME;
+		}
+		if (IS_I_VERSION(inode) && inode_maybe_inc_iversion(inode, updated))
+			updated |= S_VERSION;
+	} else {
+		now = current_time(inode);
 	}
 
-	if ((flags & S_VERSION) && inode_maybe_inc_iversion(inode, false))
-		dirty_flags |= I_DIRTY_SYNC;
+	if (flags & S_ATIME) {
+		if (!timespec64_equal(&now, &inode->i_atime)) {
+			inode->i_atime = now;
+			updated |= S_ATIME;
+		}
+	}
+	return updated;
+}
+EXPORT_SYMBOL(inode_update_timestamps);
+
+/**
+ * generic_update_time - update the timestamps on the inode
+ * @inode: inode to be updated
+ * @flags: S_* flags that needed to be updated
+ *
+ * The update_time function is called when an inode's timestamps need to be
+ * updated for a read or write operation. In the case where any of S_MTIME, S_CTIME,
+ * or S_VERSION need to be updated we attempt to update all three of them. S_ATIME
+ * updates can be handled done independently of the rest.
+ *
+ * Returns a S_* mask indicating which fields were updated.
+ */
+int generic_update_time(struct inode *inode, int flags)
+{
+	int updated = inode_update_timestamps(inode, flags);
+	int dirty_flags = 0;
 
+	if (updated & (S_ATIME|S_MTIME|S_CTIME))
+		dirty_flags = inode->i_sb->s_flags & SB_LAZYTIME ? I_DIRTY_TIME : I_DIRTY_SYNC;
+	if (updated & S_VERSION)
+		dirty_flags |= I_DIRTY_SYNC;
 	__mark_inode_dirty(inode, dirty_flags);
-	return 0;
+	return updated;
 }
 EXPORT_SYMBOL(generic_update_time);
 
@@ -1915,7 +1962,8 @@ int inode_update_time(struct inode *inode, struct timespec64 *time, int flags)
 {
 	if (inode->i_op->update_time)
 		return inode->i_op->update_time(inode, time, flags);
-	return generic_update_time(inode, time, flags);
+	generic_update_time(inode, flags);
+	return 0;
 }
 EXPORT_SYMBOL(inode_update_time);
 
diff --git a/fs/orangefs/inode.c b/fs/orangefs/inode.c
index a52c30e80f45..3afa2a69bc63 100644
--- a/fs/orangefs/inode.c
+++ b/fs/orangefs/inode.c
@@ -903,9 +903,10 @@ int orangefs_permission(struct mnt_idmap *idmap,
 int orangefs_update_time(struct inode *inode, struct timespec64 *time, int flags)
 {
 	struct iattr iattr;
+
 	gossip_debug(GOSSIP_INODE_DEBUG, "orangefs_update_time: %pU\n",
 	    get_khandle_from_ino(inode));
-	generic_update_time(inode, time, flags);
+	flags = generic_update_time(inode, flags);
 	memset(&iattr, 0, sizeof iattr);
         if (flags & S_ATIME)
 		iattr.ia_valid |= ATTR_ATIME;
diff --git a/fs/ubifs/file.c b/fs/ubifs/file.c
index 436b27d7c58f..df9086b19cd0 100644
--- a/fs/ubifs/file.c
+++ b/fs/ubifs/file.c
@@ -1387,8 +1387,10 @@ int ubifs_update_time(struct inode *inode, struct timespec64 *time,
 			.dirtied_ino_d = ALIGN(ui->data_len, 8) };
 	int err, release;
 
-	if (!IS_ENABLED(CONFIG_UBIFS_ATIME_SUPPORT))
-		return generic_update_time(inode, time, flags);
+	if (!IS_ENABLED(CONFIG_UBIFS_ATIME_SUPPORT)) {
+		generic_update_time(inode, flags);
+		return 0;
+	}
 
 	err = ubifs_budget_space(c, &req);
 	if (err)
diff --git a/fs/xfs/xfs_iops.c b/fs/xfs/xfs_iops.c
index 3a9363953ef2..731f45391baa 100644
--- a/fs/xfs/xfs_iops.c
+++ b/fs/xfs/xfs_iops.c
@@ -1042,8 +1042,10 @@ xfs_vn_update_time(
 
 	if (inode->i_sb->s_flags & SB_LAZYTIME) {
 		if (!((flags & S_VERSION) &&
-		      inode_maybe_inc_iversion(inode, false)))
-			return generic_update_time(inode, now, flags);
+		      inode_maybe_inc_iversion(inode, false))) {
+			generic_update_time(inode, flags);
+			return 0;
+		}
 
 		/* Capture the iversion update that just occurred */
 		log_flags |= XFS_ILOG_CORE;
diff --git a/include/linux/fs.h b/include/linux/fs.h
index 85977cdeda94..bb3c2c4f871f 100644
--- a/include/linux/fs.h
+++ b/include/linux/fs.h
@@ -2343,7 +2343,8 @@ extern int current_umask(void);
 
 extern void ihold(struct inode * inode);
 extern void iput(struct inode *);
-extern int generic_update_time(struct inode *, struct timespec64 *, int);
+int inode_update_timestamps(struct inode *inode, int flags);
+int generic_update_time(struct inode *, int);
 
 /* /sys/fs */
 extern struct kobject *fs_kobj;
-- 
cgit v1.2.3


From 913e99287b98fd051ac1976140a2764a8ef9dfbf Mon Sep 17 00:00:00 2001
From: Jeff Layton <jlayton@kernel.org>
Date: Mon, 7 Aug 2023 15:38:39 -0400
Subject: fs: drop the timespec64 argument from update_time

Now that all of the update_time operations are prepared for it, we can
drop the timespec64 argument from the update_time operation. Do that and
remove it from some associated functions like inode_update_time and
inode_needs_update_time.

Signed-off-by: Jeff Layton <jlayton@kernel.org>
Reviewed-by: Jan Kara <jack@suse.cz>
Message-Id: <20230807-mgctime-v7-8-d1dec143a704@kernel.org>
Signed-off-by: Christian Brauner <brauner@kernel.org>
---
 fs/bad_inode.c                |  3 +--
 fs/btrfs/inode.c              |  3 +--
 fs/btrfs/volumes.c            |  4 +---
 fs/fat/fat.h                  |  3 +--
 fs/fat/misc.c                 |  2 +-
 fs/gfs2/inode.c               |  3 +--
 fs/inode.c                    | 30 +++++++++++++-----------------
 fs/orangefs/inode.c           |  2 +-
 fs/orangefs/orangefs-kernel.h |  2 +-
 fs/overlayfs/inode.c          |  2 +-
 fs/overlayfs/overlayfs.h      |  2 +-
 fs/ubifs/file.c               |  3 +--
 fs/ubifs/ubifs.h              |  2 +-
 fs/xfs/xfs_iops.c             |  1 -
 include/linux/fs.h            |  4 ++--
 15 files changed, 27 insertions(+), 39 deletions(-)

(limited to 'fs/inode.c')

diff --git a/fs/bad_inode.c b/fs/bad_inode.c
index 6e21f7412a85..83f9566c973b 100644
--- a/fs/bad_inode.c
+++ b/fs/bad_inode.c
@@ -133,8 +133,7 @@ static int bad_inode_fiemap(struct inode *inode,
 	return -EIO;
 }
 
-static int bad_inode_update_time(struct inode *inode, struct timespec64 *time,
-				 int flags)
+static int bad_inode_update_time(struct inode *inode, int flags)
 {
 	return -EIO;
 }
diff --git a/fs/btrfs/inode.c b/fs/btrfs/inode.c
index d52e7d64570a..0964c66411a1 100644
--- a/fs/btrfs/inode.c
+++ b/fs/btrfs/inode.c
@@ -6059,8 +6059,7 @@ static int btrfs_dirty_inode(struct btrfs_inode *inode)
  * This is a copy of file_update_time.  We need this so we can return error on
  * ENOSPC for updating the inode in the case of file write and mmap writes.
  */
-static int btrfs_update_time(struct inode *inode, struct timespec64 *now,
-			     int flags)
+static int btrfs_update_time(struct inode *inode, int flags)
 {
 	struct btrfs_root *root = BTRFS_I(inode)->root;
 	bool dirty = flags & ~S_VERSION;
diff --git a/fs/btrfs/volumes.c b/fs/btrfs/volumes.c
index 73f9ea7672db..264c71590370 100644
--- a/fs/btrfs/volumes.c
+++ b/fs/btrfs/volumes.c
@@ -1917,15 +1917,13 @@ out:
 static void update_dev_time(const char *device_path)
 {
 	struct path path;
-	struct timespec64 now;
 	int ret;
 
 	ret = kern_path(device_path, LOOKUP_FOLLOW, &path);
 	if (ret)
 		return;
 
-	now = current_time(d_inode(path.dentry));
-	inode_update_time(d_inode(path.dentry), &now, S_MTIME | S_CTIME | S_VERSION);
+	inode_update_time(d_inode(path.dentry), S_MTIME | S_CTIME | S_VERSION);
 	path_put(&path);
 }
 
diff --git a/fs/fat/fat.h b/fs/fat/fat.h
index e3b690b48e3e..66cf4778cf3b 100644
--- a/fs/fat/fat.h
+++ b/fs/fat/fat.h
@@ -460,8 +460,7 @@ extern struct timespec64 fat_truncate_mtime(const struct msdos_sb_info *sbi,
 					    const struct timespec64 *ts);
 extern int fat_truncate_time(struct inode *inode, struct timespec64 *now,
 			     int flags);
-extern int fat_update_time(struct inode *inode, struct timespec64 *now,
-			   int flags);
+extern int fat_update_time(struct inode *inode, int flags);
 extern int fat_sync_bhs(struct buffer_head **bhs, int nr_bhs);
 
 int fat_cache_init(void);
diff --git a/fs/fat/misc.c b/fs/fat/misc.c
index e783792c2fc3..f2304a1054aa 100644
--- a/fs/fat/misc.c
+++ b/fs/fat/misc.c
@@ -339,7 +339,7 @@ int fat_truncate_time(struct inode *inode, struct timespec64 *now, int flags)
 }
 EXPORT_SYMBOL_GPL(fat_truncate_time);
 
-int fat_update_time(struct inode *inode, struct timespec64 *now, int flags)
+int fat_update_time(struct inode *inode, int flags)
 {
 	int dirty_flags = 0;
 
diff --git a/fs/gfs2/inode.c b/fs/gfs2/inode.c
index f1f04557aa21..a21ac41d6669 100644
--- a/fs/gfs2/inode.c
+++ b/fs/gfs2/inode.c
@@ -2139,8 +2139,7 @@ loff_t gfs2_seek_hole(struct file *file, loff_t offset)
 	return vfs_setpos(file, ret, inode->i_sb->s_maxbytes);
 }
 
-static int gfs2_update_time(struct inode *inode, struct timespec64 *time,
-			    int flags)
+static int gfs2_update_time(struct inode *inode, int flags)
 {
 	struct gfs2_inode *ip = GFS2_I(inode);
 	struct gfs2_glock *gl = ip->i_gl;
diff --git a/fs/inode.c b/fs/inode.c
index e07e45f6cd01..e50d94a136fe 100644
--- a/fs/inode.c
+++ b/fs/inode.c
@@ -1958,10 +1958,10 @@ EXPORT_SYMBOL(generic_update_time);
  * This does the actual work of updating an inodes time or version.  Must have
  * had called mnt_want_write() before calling this.
  */
-int inode_update_time(struct inode *inode, struct timespec64 *time, int flags)
+int inode_update_time(struct inode *inode, int flags)
 {
 	if (inode->i_op->update_time)
-		return inode->i_op->update_time(inode, time, flags);
+		return inode->i_op->update_time(inode, flags);
 	generic_update_time(inode, flags);
 	return 0;
 }
@@ -2015,7 +2015,6 @@ void touch_atime(const struct path *path)
 {
 	struct vfsmount *mnt = path->mnt;
 	struct inode *inode = d_inode(path->dentry);
-	struct timespec64 now;
 
 	if (!atime_needs_update(path, inode))
 		return;
@@ -2034,8 +2033,7 @@ 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);
-	inode_update_time(inode, &now, S_ATIME);
+	inode_update_time(inode, S_ATIME);
 	__mnt_drop_write(mnt);
 skip_update:
 	sb_end_write(inode->i_sb);
@@ -2120,20 +2118,21 @@ int file_remove_privs(struct file *file)
 }
 EXPORT_SYMBOL(file_remove_privs);
 
-static int inode_needs_update_time(struct inode *inode, struct timespec64 *now)
+static int inode_needs_update_time(struct inode *inode)
 {
 	int sync_it = 0;
+	struct timespec64 now = current_time(inode);
 	struct timespec64 ctime;
 
 	/* First try to exhaust all avenues to not sync */
 	if (IS_NOCMTIME(inode))
 		return 0;
 
-	if (!timespec64_equal(&inode->i_mtime, now))
+	if (!timespec64_equal(&inode->i_mtime, &now))
 		sync_it = S_MTIME;
 
 	ctime = inode_get_ctime(inode);
-	if (!timespec64_equal(&ctime, now))
+	if (!timespec64_equal(&ctime, &now))
 		sync_it |= S_CTIME;
 
 	if (IS_I_VERSION(inode) && inode_iversion_need_inc(inode))
@@ -2142,15 +2141,14 @@ static int inode_needs_update_time(struct inode *inode, struct timespec64 *now)
 	return sync_it;
 }
 
-static int __file_update_time(struct file *file, struct timespec64 *now,
-			int sync_mode)
+static int __file_update_time(struct file *file, int sync_mode)
 {
 	int ret = 0;
 	struct inode *inode = file_inode(file);
 
 	/* try to update time settings */
 	if (!__mnt_want_write_file(file)) {
-		ret = inode_update_time(inode, now, sync_mode);
+		ret = inode_update_time(inode, sync_mode);
 		__mnt_drop_write_file(file);
 	}
 
@@ -2175,13 +2173,12 @@ int file_update_time(struct file *file)
 {
 	int ret;
 	struct inode *inode = file_inode(file);
-	struct timespec64 now = current_time(inode);
 
-	ret = inode_needs_update_time(inode, &now);
+	ret = inode_needs_update_time(inode);
 	if (ret <= 0)
 		return ret;
 
-	return __file_update_time(file, &now, ret);
+	return __file_update_time(file, ret);
 }
 EXPORT_SYMBOL(file_update_time);
 
@@ -2204,7 +2201,6 @@ static int file_modified_flags(struct file *file, int flags)
 {
 	int ret;
 	struct inode *inode = file_inode(file);
-	struct timespec64 now = current_time(inode);
 
 	/*
 	 * Clear the security bits if the process is not being run by root.
@@ -2217,13 +2213,13 @@ static int file_modified_flags(struct file *file, int flags)
 	if (unlikely(file->f_mode & FMODE_NOCMTIME))
 		return 0;
 
-	ret = inode_needs_update_time(inode, &now);
+	ret = inode_needs_update_time(inode);
 	if (ret <= 0)
 		return ret;
 	if (flags & IOCB_NOWAIT)
 		return -EAGAIN;
 
-	return __file_update_time(file, &now, ret);
+	return __file_update_time(file, ret);
 }
 
 /**
diff --git a/fs/orangefs/inode.c b/fs/orangefs/inode.c
index 3afa2a69bc63..085912268442 100644
--- a/fs/orangefs/inode.c
+++ b/fs/orangefs/inode.c
@@ -900,7 +900,7 @@ int orangefs_permission(struct mnt_idmap *idmap,
 	return generic_permission(&nop_mnt_idmap, inode, mask);
 }
 
-int orangefs_update_time(struct inode *inode, struct timespec64 *time, int flags)
+int orangefs_update_time(struct inode *inode, int flags)
 {
 	struct iattr iattr;
 
diff --git a/fs/orangefs/orangefs-kernel.h b/fs/orangefs/orangefs-kernel.h
index ce20d3443869..b711654ca18a 100644
--- a/fs/orangefs/orangefs-kernel.h
+++ b/fs/orangefs/orangefs-kernel.h
@@ -370,7 +370,7 @@ int orangefs_getattr(struct mnt_idmap *idmap, const struct path *path,
 int orangefs_permission(struct mnt_idmap *idmap,
 			struct inode *inode, int mask);
 
-int orangefs_update_time(struct inode *, struct timespec64 *, int);
+int orangefs_update_time(struct inode *, int);
 
 /*
  * defined in xattr.c
diff --git a/fs/overlayfs/inode.c b/fs/overlayfs/inode.c
index a63e57447be9..f22e27b78025 100644
--- a/fs/overlayfs/inode.c
+++ b/fs/overlayfs/inode.c
@@ -693,7 +693,7 @@ int ovl_set_acl(struct mnt_idmap *idmap, struct dentry *dentry,
 }
 #endif
 
-int ovl_update_time(struct inode *inode, struct timespec64 *ts, int flags)
+int ovl_update_time(struct inode *inode, int flags)
 {
 	if (flags & S_ATIME) {
 		struct ovl_fs *ofs = inode->i_sb->s_fs_info;
diff --git a/fs/overlayfs/overlayfs.h b/fs/overlayfs/overlayfs.h
index 9402591f12aa..8bbe6173bef4 100644
--- a/fs/overlayfs/overlayfs.h
+++ b/fs/overlayfs/overlayfs.h
@@ -665,7 +665,7 @@ static inline struct posix_acl *ovl_get_acl_path(const struct path *path,
 }
 #endif
 
-int ovl_update_time(struct inode *inode, struct timespec64 *ts, int flags);
+int ovl_update_time(struct inode *inode, int flags);
 bool ovl_is_private_xattr(struct super_block *sb, const char *name);
 
 struct ovl_inode_params {
diff --git a/fs/ubifs/file.c b/fs/ubifs/file.c
index 81d44a1b2414..e5382f0b2587 100644
--- a/fs/ubifs/file.c
+++ b/fs/ubifs/file.c
@@ -1378,8 +1378,7 @@ static inline int mctime_update_needed(const struct inode *inode,
  *
  * This function updates time of the inode.
  */
-int ubifs_update_time(struct inode *inode, struct timespec64 *time,
-			     int flags)
+int ubifs_update_time(struct inode *inode, int flags)
 {
 	struct ubifs_inode *ui = ubifs_inode(inode);
 	struct ubifs_info *c = inode->i_sb->s_fs_info;
diff --git a/fs/ubifs/ubifs.h b/fs/ubifs/ubifs.h
index 4c36044140e7..ebb3ad6b5e7e 100644
--- a/fs/ubifs/ubifs.h
+++ b/fs/ubifs/ubifs.h
@@ -2027,7 +2027,7 @@ int ubifs_calc_dark(const struct ubifs_info *c, int spc);
 int ubifs_fsync(struct file *file, loff_t start, loff_t end, int datasync);
 int ubifs_setattr(struct mnt_idmap *idmap, struct dentry *dentry,
 		  struct iattr *attr);
-int ubifs_update_time(struct inode *inode, struct timespec64 *time, int flags);
+int ubifs_update_time(struct inode *inode, int flags);
 
 /* dir.c */
 struct inode *ubifs_new_inode(struct ubifs_info *c, struct inode *dir,
diff --git a/fs/xfs/xfs_iops.c b/fs/xfs/xfs_iops.c
index 549ad1fb4d65..1c1e6171209d 100644
--- a/fs/xfs/xfs_iops.c
+++ b/fs/xfs/xfs_iops.c
@@ -1029,7 +1029,6 @@ xfs_vn_setattr(
 STATIC int
 xfs_vn_update_time(
 	struct inode		*inode,
-	struct timespec64	*time,
 	int			flags)
 {
 	struct xfs_inode	*ip = XFS_I(inode);
diff --git a/include/linux/fs.h b/include/linux/fs.h
index bb3c2c4f871f..a83313f90fe3 100644
--- a/include/linux/fs.h
+++ b/include/linux/fs.h
@@ -1887,7 +1887,7 @@ struct inode_operations {
 	ssize_t (*listxattr) (struct dentry *, char *, size_t);
 	int (*fiemap)(struct inode *, struct fiemap_extent_info *, u64 start,
 		      u64 len);
-	int (*update_time)(struct inode *, struct timespec64 *, int);
+	int (*update_time)(struct inode *, int);
 	int (*atomic_open)(struct inode *, struct dentry *,
 			   struct file *, unsigned open_flag,
 			   umode_t create_mode);
@@ -2237,7 +2237,7 @@ enum file_time_flags {
 
 extern bool atime_needs_update(const struct path *, struct inode *);
 extern void touch_atime(const struct path *);
-int inode_update_time(struct inode *inode, struct timespec64 *time, int flags);
+int inode_update_time(struct inode *inode, int flags);
 
 static inline void file_accessed(struct file *file)
 {
-- 
cgit v1.2.3


From ffb6cf19e06334062744b7e3493f71e500964f8e Mon Sep 17 00:00:00 2001
From: Jeff Layton <jlayton@kernel.org>
Date: Mon, 7 Aug 2023 15:38:40 -0400
Subject: fs: add infrastructure for multigrain timestamps

The VFS always uses coarse-grained timestamps when updating the ctime
and mtime after a change. This has the benefit of allowing filesystems
to optimize away a lot metadata updates, down to around 1 per jiffy,
even when a file is under heavy writes.

Unfortunately, this has always been an issue when we're exporting via
NFSv3, which relies on timestamps to validate caches. A lot of changes
can happen in a jiffy, so timestamps aren't sufficient to help the
client decide to invalidate the cache. Even with NFSv4, a lot of
exported filesystems don't properly support a change attribute and are
subject to the same problems with timestamp granularity. Other
applications have similar issues with timestamps (e.g backup
applications).

If we were to always use fine-grained timestamps, that would improve the
situation, but that becomes rather expensive, as the underlying
filesystem would have to log a lot more metadata updates.

What we need is a way to only use fine-grained timestamps when they are
being actively queried.

POSIX generally mandates that when the the mtime changes, the ctime must
also change. The kernel always stores normalized ctime values, so only
the first 30 bits of the tv_nsec field are ever used.

Use the 31st bit of the ctime tv_nsec field to indicate that something
has queried the inode for the mtime or ctime. When this flag is set,
on the next mtime or ctime update, the kernel will fetch a fine-grained
timestamp instead of the usual coarse-grained one.

Filesytems can opt into this behavior by setting the FS_MGTIME flag in
the fstype. Filesystems that don't set this flag will continue to use
coarse-grained timestamps.

Later patches will convert individual filesystems to use the new
infrastructure.

Signed-off-by: Jeff Layton <jlayton@kernel.org>
Reviewed-by: Jan Kara <jack@suse.cz>
Message-Id: <20230807-mgctime-v7-9-d1dec143a704@kernel.org>
Signed-off-by: Christian Brauner <brauner@kernel.org>
---
 fs/inode.c         | 82 ++++++++++++++++++++++++++++++++++++++++++++++++++++--
 fs/stat.c          | 41 +++++++++++++++++++++++++--
 include/linux/fs.h | 46 ++++++++++++++++++++++++++++--
 3 files changed, 162 insertions(+), 7 deletions(-)

(limited to 'fs/inode.c')

diff --git a/fs/inode.c b/fs/inode.c
index e50d94a136fe..f55957ac80e6 100644
--- a/fs/inode.c
+++ b/fs/inode.c
@@ -2118,10 +2118,52 @@ 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.
+ */
+struct timespec64 current_mgtime(struct inode *inode)
+{
+	struct timespec64 now, ctime;
+	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);
+		return timestamp_truncate(now, inode);
+	}
+
+	ktime_get_coarse_real_ts64(&now);
+	now = timestamp_truncate(now, inode);
+
+	/*
+	 * If we've recently fetched a fine-grained timestamp
+	 * then the coarse-grained one may still be earlier than the
+	 * existing ctime. Just keep the existing value if so.
+	 */
+	ctime = inode_get_ctime(inode);
+	if (timespec64_compare(&ctime, &now) > 0)
+		now = ctime;
+
+	return now;
+}
+EXPORT_SYMBOL(current_mgtime);
+
+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 ctime;
 
 	/* First try to exhaust all avenues to not sync */
@@ -2552,9 +2594,43 @@ EXPORT_SYMBOL(current_time);
  */
 struct timespec64 inode_set_ctime_current(struct inode *inode)
 {
-	struct timespec64 now = current_time(inode);
+	struct timespec64 now;
+	struct timespec64 ctime;
+
+	ctime.tv_nsec = READ_ONCE(inode->__i_ctime.tv_nsec);
+	if (!(ctime.tv_nsec & I_CTIME_QUERIED)) {
+		now = current_time(inode);
 
-	inode_set_ctime(inode, now.tv_sec, now.tv_nsec);
+		/* Just copy it into place if it's not multigrain */
+		if (!is_mgtime(inode)) {
+			inode_set_ctime_to_ts(inode, now);
+			return now;
+		}
+
+		/*
+		 * If we've recently updated with a fine-grained timestamp,
+		 * then the coarse-grained one may still be earlier than the
+		 * existing ctime. Just keep the existing value if so.
+		 */
+		ctime.tv_sec = inode->__i_ctime.tv_sec;
+		if (timespec64_compare(&ctime, &now) > 0)
+			return ctime;
+
+		/*
+		 * 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.tv_nsec, ctime.tv_nsec,
+			    now.tv_nsec) != ctime.tv_nsec)
+			goto fine_grained;
+		inode->__i_ctime.tv_sec = now.tv_sec;
+		return now;
+	}
+fine_grained:
+	ktime_get_real_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 7644e5997035..136711ae72fb 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_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(stat, request_mask, inode);
+	} 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 a83313f90fe3..455835d0e963 100644
--- a/include/linux/fs.h
+++ b/include/linux/fs.h
@@ -1474,18 +1474,47 @@ 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 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;
 }
 
 /**
@@ -2259,6 +2288,7 @@ 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;
@@ -2282,6 +2312,17 @@ 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));
@@ -2918,6 +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(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);
-- 
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