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VM: add "vm_insert_page()" function

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This is what a lot of drivers will actually want to use to insert
individual pages into a user VMA.  It doesn't have the old PageReserved
restrictions of remap_pfn_range(), and it doesn't complain about partial
remappings.

The page you insert needs to be a nice clean kernel allocation, so you
can't insert arbitrary page mappings with this, but that's not what
people want.

Signed-off-by: Linus Torvalds <torvalds@osdl.org>
This commit is contained in:
Linus Torvalds 2005-11-30 09:35:19 -08:00
parent f8e988436b
commit a145dd411e
2 changed files with 35 additions and 2 deletions
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1
include/linux/mm.h
View File

@ -956,6 +956,7 @@ struct page *vmalloc_to_page(void *addr);
unsigned long vmalloc_to_pfn(void *addr);
int remap_pfn_range(struct vm_area_struct *, unsigned long addr,
unsigned long pfn, unsigned long size, pgprot_t);
int vm_insert_page(struct vm_area_struct *, unsigned long addr, struct page *);
struct page *follow_page(struct vm_area_struct *, unsigned long address,
unsigned int foll_flags);

36
mm/memory.c
View File

@ -1172,7 +1172,7 @@ static int insert_page(struct mm_struct *mm, unsigned long addr, struct page *pa
spinlock_t *ptl;
retval = -EINVAL;
if (PageAnon(page) || !PageReserved(page))
if (PageAnon(page))
goto out;
retval = -ENOMEM;
flush_dcache_page(page);
@ -1196,6 +1196,35 @@ out:
return retval;
}
/*
* This allows drivers to insert individual pages they've allocated
* into a user vma.
*
* The page has to be a nice clean _individual_ kernel allocation.
* If you allocate a compound page, you need to have marked it as
* such (__GFP_COMP), or manually just split the page up yourself
* (which is mainly an issue of doing "set_page_count(page, 1)" for
* each sub-page, and then freeing them one by one when you free
* them rather than freeing it as a compound page).
*
* NOTE! Traditionally this was done with "remap_pfn_range()" which
* took an arbitrary page protection parameter. This doesn't allow
* that. Your vma protection will have to be set up correctly, which
* means that if you want a shared writable mapping, you'd better
* ask for a shared writable mapping!
*
* The page does not need to be reserved.
*/
int vm_insert_page(struct vm_area_struct *vma, unsigned long addr, struct page *page)
{
if (addr < vma->vm_start || addr >= vma->vm_end)
return -EFAULT;
if (!page_count(page))
return -EINVAL;
return insert_page(vma->vm_mm, addr, page, vma->vm_page_prot);
}
EXPORT_SYMBOL_GPL(vm_insert_page);
/*
* Somebody does a pfn remapping that doesn't actually work as a vma.
*
@ -1225,8 +1254,11 @@ static int incomplete_pfn_remap(struct vm_area_struct *vma,
if (!pfn_valid(pfn))
return -EINVAL;
retval = 0;
page = pfn_to_page(pfn);
if (!PageReserved(page))
return -EINVAL;
retval = 0;
while (start < end) {
retval = insert_page(vma->vm_mm, start, page, prot);
if (retval < 0)