On Fri, Oct 13, 2017 at 04:09:23PM -0400, Nicolas Pitre wrote:
> On Fri, 13 Oct 2017, Al Viro wrote:
>
> > OK... I wonder if it should simply define stubs for kill_mtd_super(),
> > mtd_unpoint() and kill_block_super() in !CONFIG_MTD and !CONFIG_BLOCK
> > cases. mount_mtd() and mount_bdev() as well - e.g. mount_bdev()
> > returning ERR_PTR(-ENODEV) and kill_block_super() being simply BUG()
> > in !CONFIG_BLOCK case. Then cramfs_kill_sb() would be
> > if (sb->s_mtd) {
> > if (sbi->mtd_point_size)
> > mtd_unpoint(sb->s_mtd, 0, sbi->mtd_point_size);
> > kill_mtd_super(sb);
> > } else {
> > kill_block_super(sb);
> > }
> > kfree(sbi);
>
> Well... Stubs have to be named differently or they conflict with
> existing declarations. At that point that makes for more lines of code
> compared to the current patch and the naming indirection makes it less
> obvious when reading the code. Alternatively I could add those stubs in
> the corresponding header files and #ifdef the existing declarations
> away. That might look somewhat less cluttered in the main code but it
> also hides what is actually going on and left me unconvinced. And I'm
> not sure this is worth it in the end given this is not a common
> occurrence in the kernel either.
What I mean is this (completely untested) for CONFIG_BLOCK side of things,
with something similar for CONFIG_MTD one:
Provide definitions of mount_bdev/kill_block_super() in case !CONFIG_BLOCK
mount_bdev() and kill_block_super() are defined only when CONFIG_BLOCK is
defined; however, their declarations in fs.h are unconditional. We could
make these conditional upon CONFIG_BLOCK as well, but it's easy to provide
inline definitions for !CONFIG_BLOCK case - mount_bdev() should fail with
ENODEV, while kill_block_super() can be simply BUG(); there should be no
superblock instances with non-NULL ->s_bdev on such configs.
Signed-off-by: Al Viro <viro@xxxxxxxxxxxxxxxxxx>
---
diff --git a/include/linux/fs.h b/include/linux/fs.h
index 339e73742e73..e773c1c51aad 100644
--- a/include/linux/fs.h
+++ b/include/linux/fs.h
@@ -2094,9 +2094,18 @@ struct file_system_type {
extern struct dentry *mount_ns(struct file_system_type *fs_type,
int flags, void *data, void *ns, struct user_namespace *user_ns,
int (*fill_super)(struct super_block *, void *, int));
+#ifdef CONFIG_BLOCK
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));
+#else
+static inline 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))
+{
+ return ERR_PTR(-ENODEV);
+}
+#endif
extern struct dentry *mount_single(struct file_system_type *fs_type,
int flags, void *data,
int (*fill_super)(struct super_block *, void *, int));
@@ -2105,7 +2114,14 @@ extern struct dentry *mount_nodev(struct file_system_type *fs_type,
int (*fill_super)(struct super_block *, void *, int));
extern struct dentry *mount_subtree(struct vfsmount *mnt, const char *path);
void generic_shutdown_super(struct super_block *sb);
+#ifdef CONFIG_BLOCK
void kill_block_super(struct super_block *sb);
+#else
+static inline void kill_block_super(struct super_block *sb)
+{
+ BUG();
+}
+#endif
void kill_anon_super(struct super_block *sb);
void kill_litter_super(struct super_block *sb);
void deactivate_super(struct super_block *sb);
