VFS: Differentiate mount flags (MS_*) from internal superblock flags

Differentiate the MS_* flags passed to mount(2) from the internal flags set
in the super_block's s_flags.  s_flags are now called SB_*, with the names
and the values for the moment mirroring the MS_* flags that they're
equivalent to.

In this patch, just the headers are altered and some kernel code where
blind automated conversion isn't necessarily correct.

Note that this shows up some interesting issues:

 (1) Some MS_* flags get translated to MNT_* flags (such as MS_NODEV ->
     MNT_NODEV) without passing this on to the filesystem, but some
     filesystems set such flags anyway.

 (2) The ->remount_fs() methods of some filesystems adjust the *flags
     argument by setting MS_* flags in it, such as MS_NOATIME - but these
     flags are then scrubbed by do_remount_sb() (only the occupants of
     MS_RMT_MASK are permitted: MS_RDONLY, MS_SYNCHRONOUS, MS_MANDLOCK,
     MS_I_VERSION and MS_LAZYTIME)

I'm not sure what's the best way to solve all these cases.

Suggested-by: Al Viro <viro@ZenIV.linux.org.uk>
Signed-off-by: David Howells <dhowells@redhat.com>

1 files changed, 34 insertions, 34 deletions

diff --git a/fs/super.c b/fs/super.c
index 7321958d81d8..d956e62e5866 100644
--- a/fs/super.c
+++ b/fs/super.c
@@ -360,7 +360,7 @@ static int grab_super(struct super_block *s) __releases(sb_lock)
 	s->s_count++;
 	spin_unlock(&sb_lock);
 	down_write(&s->s_umount);
-	if ((s->s_flags & MS_BORN) && atomic_inc_not_zero(&s->s_active)) {
+	if ((s->s_flags & SB_BORN) && atomic_inc_not_zero(&s->s_active)) {
 		put_super(s);
 		return 1;
 	}
@@ -390,7 +390,7 @@ bool trylock_super(struct super_block *sb)
 {
 	if (down_read_trylock(&sb->s_umount)) {
 		if (!hlist_unhashed(&sb->s_instances) &&
-		    sb->s_root && (sb->s_flags & MS_BORN))
+		    sb->s_root && (sb->s_flags & SB_BORN))
 			return true;
 		up_read(&sb->s_umount);
 	}
@@ -419,7 +419,7 @@ void generic_shutdown_super(struct super_block *sb)
 	if (sb->s_root) {
 		shrink_dcache_for_umount(sb);
 		sync_filesystem(sb);
-		sb->s_flags &= ~MS_ACTIVE;
+		sb->s_flags &= ~SB_ACTIVE;
 
 		fsnotify_unmount_inodes(sb);
 		cgroup_writeback_umount();
@@ -472,7 +472,7 @@ struct super_block *sget_userns(struct file_system_type *type,
 	struct super_block *old;
 	int err;
 
-	if (!(flags & (MS_KERNMOUNT|MS_SUBMOUNT)) &&
+	if (!(flags & (SB_KERNMOUNT|SB_SUBMOUNT)) &&
 	    !(type->fs_flags & FS_USERNS_MOUNT) &&
 	    !capable(CAP_SYS_ADMIN))
 		return ERR_PTR(-EPERM);
@@ -502,7 +502,7 @@ retry:
 	}
 	if (!s) {
 		spin_unlock(&sb_lock);
-		s = alloc_super(type, (flags & ~MS_SUBMOUNT), user_ns);
+		s = alloc_super(type, (flags & ~SB_SUBMOUNT), user_ns);
 		if (!s)
 			return ERR_PTR(-ENOMEM);
 		goto retry;
@@ -547,11 +547,11 @@ struct super_block *sget(struct file_system_type *type,
 	 * mount through to here so always use &init_user_ns
 	 * until that changes.
 	 */
-	if (flags & MS_SUBMOUNT)
+	if (flags & SB_SUBMOUNT)
 		user_ns = &init_user_ns;
 
 	/* Ensure the requestor has permissions over the target filesystem */
-	if (!(flags & (MS_KERNMOUNT|MS_SUBMOUNT)) && !ns_capable(user_ns, CAP_SYS_ADMIN))
+	if (!(flags & (SB_KERNMOUNT|SB_SUBMOUNT)) && !ns_capable(user_ns, CAP_SYS_ADMIN))
 		return ERR_PTR(-EPERM);
 
 	return sget_userns(type, test, set, flags, user_ns, data);
@@ -594,7 +594,7 @@ void iterate_supers(void (*f)(struct super_block *, void *), void *arg)
 		spin_unlock(&sb_lock);
 
 		down_read(&sb->s_umount);
-		if (sb->s_root && (sb->s_flags & MS_BORN))
+		if (sb->s_root && (sb->s_flags & SB_BORN))
 			f(sb, arg);
 		up_read(&sb->s_umount);
 
@@ -628,7 +628,7 @@ void iterate_supers_type(struct file_system_type *type,
 		spin_unlock(&sb_lock);
 
 		down_read(&sb->s_umount);
-		if (sb->s_root && (sb->s_flags & MS_BORN))
+		if (sb->s_root && (sb->s_flags & SB_BORN))
 			f(sb, arg);
 		up_read(&sb->s_umount);
 
@@ -664,7 +664,7 @@ rescan:
 			else
 				down_write(&sb->s_umount);
 			/* still alive? */
-			if (sb->s_root && (sb->s_flags & MS_BORN))
+			if (sb->s_root && (sb->s_flags & SB_BORN))
 				return sb;
 			if (!excl)
 				up_read(&sb->s_umount);
@@ -785,7 +785,7 @@ rescan:
 			spin_unlock(&sb_lock);
 			down_read(&sb->s_umount);
 			/* still alive? */
-			if (sb->s_root && (sb->s_flags & MS_BORN))
+			if (sb->s_root && (sb->s_flags & SB_BORN))
 				return sb;
 			up_read(&sb->s_umount);
 			/* nope, got unmounted */
@@ -801,13 +801,13 @@ rescan:
 /**
  *	do_remount_sb - asks filesystem to change mount options.
  *	@sb:	superblock in question
- *	@flags:	numeric part of options
+ *	@sb_flags: revised superblock flags
  *	@data:	the rest of options
  *      @force: whether or not to force the change
  *
  *	Alters the mount options of a mounted file system.
  */
-int do_remount_sb(struct super_block *sb, int flags, void *data, int force)
+int do_remount_sb(struct super_block *sb, int sb_flags, void *data, int force)
 {
 	int retval;
 	int remount_ro;
@@ -816,11 +816,11 @@ int do_remount_sb(struct super_block *sb, int flags, void *data, int force)
 		return -EBUSY;
 
 #ifdef CONFIG_BLOCK
-	if (!(flags & MS_RDONLY) && bdev_read_only(sb->s_bdev))
+	if (!(sb_flags & SB_RDONLY) && bdev_read_only(sb->s_bdev))
 		return -EACCES;
 #endif
 
-	remount_ro = (flags & MS_RDONLY) && !sb_rdonly(sb);
+	remount_ro = (sb_flags & SB_RDONLY) && !sb_rdonly(sb);
 
 	if (remount_ro) {
 		if (!hlist_empty(&sb->s_pins)) {
@@ -831,7 +831,7 @@ int do_remount_sb(struct super_block *sb, int flags, void *data, int force)
 				return 0;
 			if (sb->s_writers.frozen != SB_UNFROZEN)
 				return -EBUSY;
-			remount_ro = (flags & MS_RDONLY) && !sb_rdonly(sb);
+			remount_ro = (sb_flags & SB_RDONLY) && !sb_rdonly(sb);
 		}
 	}
 	shrink_dcache_sb(sb);
@@ -850,7 +850,7 @@ int do_remount_sb(struct super_block *sb, int flags, void *data, int force)
 	}
 
 	if (sb->s_op->remount_fs) {
-		retval = sb->s_op->remount_fs(sb, &flags, data);
+		retval = sb->s_op->remount_fs(sb, &sb_flags, data);
 		if (retval) {
 			if (!force)
 				goto cancel_readonly;
@@ -859,7 +859,7 @@ int do_remount_sb(struct super_block *sb, int flags, void *data, int force)
 			     sb->s_type->name, retval);
 		}
 	}
-	sb->s_flags = (sb->s_flags & ~MS_RMT_MASK) | (flags & MS_RMT_MASK);
+	sb->s_flags = (sb->s_flags & ~MS_RMT_MASK) | (sb_flags & MS_RMT_MASK);
 	/* Needs to be ordered wrt mnt_is_readonly() */
 	smp_wmb();
 	sb->s_readonly_remount = 0;
@@ -892,12 +892,12 @@ static void do_emergency_remount(struct work_struct *work)
 		sb->s_count++;
 		spin_unlock(&sb_lock);
 		down_write(&sb->s_umount);
-		if (sb->s_root && sb->s_bdev && (sb->s_flags & MS_BORN) &&
+		if (sb->s_root && sb->s_bdev && (sb->s_flags & SB_BORN) &&
 		    !sb_rdonly(sb)) {
 			/*
 			 * What lock protects sb->s_flags??
 			 */
-			do_remount_sb(sb, MS_RDONLY, NULL, 1);
+			do_remount_sb(sb, SB_RDONLY, NULL, 1);
 		}
 		up_write(&sb->s_umount);
 		spin_lock(&sb_lock);
@@ -1023,7 +1023,7 @@ struct dentry *mount_ns(struct file_system_type *fs_type,
 	/* Don't allow mounting unless the caller has CAP_SYS_ADMIN
 	 * over the namespace.
 	 */
-	if (!(flags & MS_KERNMOUNT) && !ns_capable(user_ns, CAP_SYS_ADMIN))
+	if (!(flags & SB_KERNMOUNT) && !ns_capable(user_ns, CAP_SYS_ADMIN))
 		return ERR_PTR(-EPERM);
 
 	sb = sget_userns(fs_type, ns_test_super, ns_set_super, flags,
@@ -1033,13 +1033,13 @@ struct dentry *mount_ns(struct file_system_type *fs_type,
 
 	if (!sb->s_root) {
 		int err;
-		err = fill_super(sb, data, flags & MS_SILENT ? 1 : 0);
+		err = fill_super(sb, data, flags & SB_SILENT ? 1 : 0);
 		if (err) {
 			deactivate_locked_super(sb);
 			return ERR_PTR(err);
 		}
 
-		sb->s_flags |= MS_ACTIVE;
+		sb->s_flags |= SB_ACTIVE;
 	}
 
 	return dget(sb->s_root);
@@ -1071,7 +1071,7 @@ struct dentry *mount_bdev(struct file_system_type *fs_type,
 	fmode_t mode = FMODE_READ | FMODE_EXCL;
 	int error = 0;
 
-	if (!(flags & MS_RDONLY))
+	if (!(flags & SB_RDONLY))
 		mode |= FMODE_WRITE;
 
 	bdev = blkdev_get_by_path(dev_name, mode, fs_type);
@@ -1089,14 +1089,14 @@ struct dentry *mount_bdev(struct file_system_type *fs_type,
 		error = -EBUSY;
 		goto error_bdev;
 	}
-	s = sget(fs_type, test_bdev_super, set_bdev_super, flags | MS_NOSEC,
+	s = sget(fs_type, test_bdev_super, set_bdev_super, flags | SB_NOSEC,
 		 bdev);
 	mutex_unlock(&bdev->bd_fsfreeze_mutex);
 	if (IS_ERR(s))
 		goto error_s;
 
 	if (s->s_root) {
-		if ((flags ^ s->s_flags) & MS_RDONLY) {
+		if ((flags ^ s->s_flags) & SB_RDONLY) {
 			deactivate_locked_super(s);
 			error = -EBUSY;
 			goto error_bdev;
@@ -1116,13 +1116,13 @@ struct dentry *mount_bdev(struct file_system_type *fs_type,
 		s->s_mode = mode;
 		snprintf(s->s_id, sizeof(s->s_id), "%pg", bdev);
 		sb_set_blocksize(s, block_size(bdev));
-		error = fill_super(s, data, flags & MS_SILENT ? 1 : 0);
+		error = fill_super(s, data, flags & SB_SILENT ? 1 : 0);
 		if (error) {
 			deactivate_locked_super(s);
 			goto error;
 		}
 
-		s->s_flags |= MS_ACTIVE;
+		s->s_flags |= SB_ACTIVE;
 		bdev->bd_super = s;
 	}
 
@@ -1162,12 +1162,12 @@ struct dentry *mount_nodev(struct file_system_type *fs_type,
 	if (IS_ERR(s))
 		return ERR_CAST(s);
 
-	error = fill_super(s, data, flags & MS_SILENT ? 1 : 0);
+	error = fill_super(s, data, flags & SB_SILENT ? 1 : 0);
 	if (error) {
 		deactivate_locked_super(s);
 		return ERR_PTR(error);
 	}
-	s->s_flags |= MS_ACTIVE;
+	s->s_flags |= SB_ACTIVE;
 	return dget(s->s_root);
 }
 EXPORT_SYMBOL(mount_nodev);
@@ -1188,12 +1188,12 @@ struct dentry *mount_single(struct file_system_type *fs_type,
 	if (IS_ERR(s))
 		return ERR_CAST(s);
 	if (!s->s_root) {
-		error = fill_super(s, data, flags & MS_SILENT ? 1 : 0);
+		error = fill_super(s, data, flags & SB_SILENT ? 1 : 0);
 		if (error) {
 			deactivate_locked_super(s);
 			return ERR_PTR(error);
 		}
-		s->s_flags |= MS_ACTIVE;
+		s->s_flags |= SB_ACTIVE;
 	} else {
 		do_remount_sb(s, flags, data, 0);
 	}
@@ -1227,7 +1227,7 @@ mount_fs(struct file_system_type *type, int flags, const char *name, void *data)
 	sb = root->d_sb;
 	BUG_ON(!sb);
 	WARN_ON(!sb->s_bdi);
-	sb->s_flags |= MS_BORN;
+	sb->s_flags |= SB_BORN;
 
 	error = security_sb_kern_mount(sb, flags, secdata);
 	if (error)
@@ -1434,7 +1434,7 @@ int freeze_super(struct super_block *sb)
 		return -EBUSY;
 	}
 
-	if (!(sb->s_flags & MS_BORN)) {
+	if (!(sb->s_flags & SB_BORN)) {
 		up_write(&sb->s_umount);
 		return 0;	/* sic - it's "nothing to do" */
 	}