[Re: [RFC PATCH] hugetlbfs: fix the hugetlbfs can not be mounted] On 03/11/2016 (Thu 12:17) Andrew Morton wrote: > On Sat, 29 Oct 2016 14:08:31 +0800 zhongjiang <zhongjiang@xxxxxxxxxx> wrote: > > > From: zhong jiang <zhongjiang@xxxxxxxxxx> > > > > Since 'commit 3e89e1c5ea84 ("hugetlb: make mm and fs code explicitly non-modular")' > > bring in the mainline. mount hugetlbfs will result in the following issue. > > > > mount: unknown filesystme type 'hugetlbfs' The fact that the above has a typo makes me doubt it was real output from "mount". In any case, that just means they didn't enable the Kconfig option for it and hence it is not in /proc/filesystems as they can easily verify. > > > > because previous patch remove the module_alias_fs, when we mount the fs type, > > the caller get_fs_type can not find the filesystem. > > > > The patch just recover the module_alias_fs to identify the hugetlbfs. > > hm, 3e89e1c5ea84 ("hugetlb: make mm and fs code explicitly > non-modular") was merged almost a year ago. And you are apparently the > first person to discover this regression. Can you think why that is? Agreed -- I'd like to know just how this conclusion was reached. Maybe they are running some out-of-tree patches to make it modular? Who knows. It would be nice if we hear back, but I don't have high hopes. In any case, 3e89e1c5ea84 commit log says: Also note that MODULE_ALIAS is a no-op for non-modular code. This isn't fundamentally hard to verify; the macros are: #define MODULE_ALIAS_FS(NAME) MODULE_ALIAS("fs-" NAME) #define MODULE_ALIAS(_alias) MODULE_INFO(alias, _alias) #define MODULE_INFO(tag, info) __MODULE_INFO(tag, tag, info) ...and then finally: #ifdef MODULE #define __MODULE_INFO(tag, name, info) \ static const char __UNIQUE_ID(name)[] \ __used __attribute__((section(".modinfo"), unused, aligned(1))) \ = __stringify(tag) "=" info #else /* !MODULE */ /* This struct is here for syntactic coherency, it is not used */ #define __MODULE_INFO(tag, name, info) \ struct __UNIQUE_ID(name) {} #endif ...so a commit like this would have to explain how the patch does anything in the !MODULE case, when the syntax comment above even indicates it is not used. I remember this commit since there was patch order issue that the kbuild robot uncovered (as listed in the commit log) in an earlier version of it. So I can assure the patch poster that hugetlbfs was mounted for testing, and they should revisit the logic that led to this no-op patch. Paul. -- > > > index 4fb7b10..b63e7de 100644 > > --- a/fs/hugetlbfs/inode.c > > +++ b/fs/hugetlbfs/inode.c > > @@ -35,6 +35,7 @@ > > #include <linux/security.h> > > #include <linux/magic.h> > > #include <linux/migrate.h> > > +#include <linux/module.h> > > #include <linux/uio.h> > > > > #include <asm/uaccess.h> > > @@ -1209,6 +1210,7 @@ static struct dentry *hugetlbfs_mount(struct file_system_type *fs_type, > > .mount = hugetlbfs_mount, > > .kill_sb = kill_litter_super, > > }; > > +MODULE_ALIAS_FS("hugetlbfs"); > > > > static struct vfsmount *hugetlbfs_vfsmount[HUGE_MAX_HSTATE]; > > > -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@xxxxxxxxx. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: <a href=mailto:"dont@xxxxxxxxx"> email@xxxxxxxxx </a>