Merge tag 'fs.mount_setattr.v5.17-rc4' of git://git.kernel.org/pub/scm/linux/kernel/git/brauner/linux

7f25f041 · Linus Torvalds <[email protected]> · 2022-02-20 11:01:47 -08:00

Pull mount_setattr test/doc fixes from Christian Brauner:
 "This contains a fix for one of the selftests for the mount_setattr
  syscall to create idmapped mounts, an entry for idmapped mounts for
  maintainers, and missing kernel documentation for the helper we split
  out some time ago to get and yield write access to a mount when
  changing mount properties"

* tag 'fs.mount_setattr.v5.17-rc4' of git://git.kernel.org/pub/scm/linux/kernel/git/brauner/linux:
  fs: add kernel doc for mnt_{hold,unhold}_writers()
  MAINTAINERS: add entry for idmapped mounts
  tests: fix idmapped mount_setattr test

Commit: 7f25f0412c9e2be6811e8aedbd10ef795fff85f2
Parents: c1034d24 · 538f4f02

Merge commit. Changes below are compared with the first parent: c1034d24.

Changes

3 files changed · +41 −2

File	Status	Add	Del	Content
MAINTAINERS	modified	+9	−0	View file
fs/namespace.c	modified	+30	−0	View file
tools/testing/selftests/mount_setattr/mount_setattr_test.c	modified	+2	−2	View file

MAINTAINERS

View file

diff --git a/MAINTAINERS b/MAINTAINERS
index bd86ed9..7c85c4d 100644
--- a/MAINTAINERS
+++ b/MAINTAINERS
@@ -9263,6 +9263,15 @@ S:	Maintained
 W:	https://github.com/o2genum/ideapad-slidebar
 F:	drivers/input/misc/ideapad_slidebar.c
 
+IDMAPPED MOUNTS
+M:	Christian Brauner <[email protected]>
+L:	[email protected]
+S:	Maintained
+T:	git git://git.kernel.org/pub/scm/linux/kernel/git/brauner/linux.git
+F:	Documentation/filesystems/idmappings.rst
+F:	tools/testing/selftests/mount_setattr/
+F:	include/linux/mnt_idmapping.h
+
 IDT VersaClock 5 CLOCK DRIVER
 M:	Luca Ceresoli <[email protected]>
 S:	Maintained

fs/namespace.c

View file

diff --git a/fs/namespace.c b/fs/namespace.c
index 40b994a..de6fae8 100644
--- a/fs/namespace.c
+++ b/fs/namespace.c
@@ -469,6 +469,24 @@ void mnt_drop_write_file(struct file *file)
 }
 EXPORT_SYMBOL(mnt_drop_write_file);
 
+/**
+ * mnt_hold_writers - prevent write access to the given mount
+ * @mnt: mnt to prevent write access to
+ *
+ * Prevents write access to @mnt if there are no active writers for @mnt.
+ * This function needs to be called and return successfully before changing
+ * properties of @mnt that need to remain stable for callers with write access
+ * to @mnt.
+ *
+ * After this functions has been called successfully callers must pair it with
+ * a call to mnt_unhold_writers() in order to stop preventing write access to
+ * @mnt.
+ *
+ * Context: This function expects lock_mount_hash() to be held serializing
+ *          setting MNT_WRITE_HOLD.
+ * Return: On success 0 is returned.
+ *	   On error, -EBUSY is returned.
+ */
 static inline int mnt_hold_writers(struct mount *mnt)
 {
 	mnt->mnt.mnt_flags |= MNT_WRITE_HOLD;
@@ -500,6 +518,18 @@ static inline int mnt_hold_writers(struct mount *mnt)
 	return 0;
 }
 
+/**
+ * mnt_unhold_writers - stop preventing write access to the given mount
+ * @mnt: mnt to stop preventing write access to
+ *
+ * Stop preventing write access to @mnt allowing callers to gain write access
+ * to @mnt again.
+ *
+ * This function can only be called after a successful call to
+ * mnt_hold_writers().
+ *
+ * Context: This function expects lock_mount_hash() to be held.
+ */
 static inline void mnt_unhold_writers(struct mount *mnt)
 {
 	/*

tools/testing/selftests/mount_setattr/mount_setattr_test.c

View file

diff --git a/tools/testing/selftests/mount_setattr/mount_setattr_test.c b/tools/testing/selftests/mount_setattr/mount_setattr_test.c
index f31205f..8c5fea6 100644
--- a/tools/testing/selftests/mount_setattr/mount_setattr_test.c
+++ b/tools/testing/selftests/mount_setattr/mount_setattr_test.c
@@ -1236,7 +1236,7 @@ static int get_userns_fd(unsigned long nsid, unsigned long hostid, unsigned long
 }
 
 /**
- * Validate that an attached mount in our mount namespace can be idmapped.
+ * Validate that an attached mount in our mount namespace cannot be idmapped.
  * (The kernel enforces that the mount's mount namespace and the caller's mount
  *  namespace match.)
  */
@@ -1259,7 +1259,7 @@ TEST_F(mount_setattr_idmapped, attached_mount_inside_current_mount_namespace)
 
 	attr.userns_fd	= get_userns_fd(0, 10000, 10000);
 	ASSERT_GE(attr.userns_fd, 0);
-	ASSERT_EQ(sys_mount_setattr(open_tree_fd, "", AT_EMPTY_PATH, &attr, sizeof(attr)), 0);
+	ASSERT_NE(sys_mount_setattr(open_tree_fd, "", AT_EMPTY_PATH, &attr, sizeof(attr)), 0);
 	ASSERT_EQ(close(attr.userns_fd), 0);
 	ASSERT_EQ(close(open_tree_fd), 0);
 }