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mm: Add a vm_special_mapping.fault() method

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Requiring special mappings to give a list of struct pages is
inflexible: it prevents sane use of IO memory in a special
mapping, it's inefficient (it requires arch code to initialize a
list of struct pages, and it requires the mm core to walk the
entire list just to figure out how long it is), and it prevents
arch code from doing anything fancy when a special mapping fault
occurs.

Add a .fault method as an alternative to filling in a .pages
array.

Looks-OK-to: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Andy Lutomirski <luto@kernel.org>
Reviewed-by: Kees Cook <keescook@chromium.org>
Cc: Andy Lutomirski <luto@amacapital.net>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Dave Hansen <dave.hansen@linux.intel.com>
Cc: Fenghua Yu <fenghua.yu@intel.com>
Cc: H. Peter Anvin <hpa@zytor.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Oleg Nesterov <oleg@redhat.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Quentin Casasnovas <quentin.casasnovas@oracle.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Link: http://lkml.kernel.org/r/a26d1677c0bc7e774c33f469451a78ca31e9e6af.1451446564.git.luto@kernel.org
Signed-off-by: Ingo Molnar <mingo@kernel.org>
This commit is contained in:
Andy Lutomirski 2015-12-29 20:12:19 -08:00 committed by Ingo Molnar
parent aa0421410f
commit f872f5400c
2 changed files with 28 additions and 7 deletions
Show stats Download patch file Download diff file Expand all files Collapse all files

22
include/linux/mm_types.h
View file

@ -568,10 +568,26 @@ static inline void clear_tlb_flush_pending(struct mm_struct *mm)
}
#endif
struct vm_special_mapping
{
const char *name;
struct vm_fault;
struct vm_special_mapping {
const char *name; /* The name, e.g. "[vdso]". */
/*
* If .fault is not provided, this points to a
* NULL-terminated array of pages that back the special mapping.
*
* This must not be NULL unless .fault is provided.
*/
struct page **pages;
/*
* If non-NULL, then this is called to resolve page faults
* on the special mapping. If used, .pages is not checked.
*/
int (*fault)(const struct vm_special_mapping *sm,
struct vm_area_struct *vma,
struct vm_fault *vmf);
};
enum tlb_flush_reason {

13
mm/mmap.c
View file

@ -3030,11 +3030,16 @@ static int special_mapping_fault(struct vm_area_struct *vma,
pgoff_t pgoff;
struct page **pages;
if (vma->vm_ops == &legacy_special_mapping_vmops)
if (vma->vm_ops == &legacy_special_mapping_vmops) {
pages = vma->vm_private_data;
else
pages = ((struct vm_special_mapping *)vma->vm_private_data)->
pages;
} else {
struct vm_special_mapping *sm = vma->vm_private_data;
if (sm->fault)
return sm->fault(sm, vma, vmf);
pages = sm->pages;
}
for (pgoff = vmf->pgoff; pgoff && *pages; ++pages)
pgoff--;