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Commit 08ef4729 authored by Hugh Dickins's avatar Hugh Dickins Committed by Linus Torvalds
Browse files

[PATCH] get_user_pages: kill get_page_map 



Since its birth, get_user_pages has been calling a misguided get_page_map
function.  follow_page has already returned NULL if the pfn is invalid, we
cannot reach an invalid pfn from a validated struct page.

Remove get_page_map, and the messy rewind in get_user_pages to cope with
its failure.  Oh, and could we please call that "struct page *page" like
everywhere else, instead of "struct page *map"?

Signed-off-by: default avatarHugh Dickins <hugh@veritas.com>
Signed-off-by: default avatarAndrew Morton <akpm@osdl.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@osdl.org>
parent 7c2f3fda

mm/memory.c

+10 −35
Original line number Diff line number Diff line
@@ -840,23 +840,8 @@ check_user_page_readable(struct mm_struct *mm, unsigned long address) 
{

	return __follow_page(mm, address, /*read*/1, /*write*/0) != NULL;

}



EXPORT_SYMBOL(check_user_page_readable);



/* 

 * Given a physical address, is there a useful struct page pointing to

 * it?  This may become more complex in the future if we start dealing

 * with IO-aperture pages for direct-IO.

 */



static inline struct page *get_page_map(struct page *page)

{

	if (!pfn_valid(page_to_pfn(page)))

		return NULL;

	return page;

}





static inline int

untouched_anonymous_page(struct mm_struct* mm, struct vm_area_struct *vma,

			 unsigned long address)
@@ -887,7 +872,6 @@ untouched_anonymous_page(struct mm_struct* mm, struct vm_area_struct *vma, 
	return 0;

}





int get_user_pages(struct task_struct *tsk, struct mm_struct *mm,

		unsigned long start, int len, int write, int force,

		struct page **pages, struct vm_area_struct **vmas)
@@ -951,21 +935,21 @@ int get_user_pages(struct task_struct *tsk, struct mm_struct *mm, 
		}

		spin_lock(&mm->page_table_lock);

		do {

			struct page *map;

			struct page *page;

			int lookup_write = write;



			cond_resched_lock(&mm->page_table_lock);

			while (!(map = follow_page(mm, start, lookup_write))) {

			while (!(page = follow_page(mm, start, lookup_write))) {

				/*

				 * Shortcut for anonymous pages. We don't want

				 * to force the creation of pages tables for

				 * insanly big anonymously mapped areas that

				 * insanely big anonymously mapped areas that

				 * nobody touched so far. This is important

				 * for doing a core dump for these mappings.

				 */

				if (!lookup_write &&

				    untouched_anonymous_page(mm,vma,start)) {

					map = ZERO_PAGE(start);

					page = ZERO_PAGE(start);

					break;

				}

				spin_unlock(&mm->page_table_lock);
@@ -994,17 +978,10 @@ int get_user_pages(struct task_struct *tsk, struct mm_struct *mm, 
				spin_lock(&mm->page_table_lock);

			}

			if (pages) {

				pages[i] = get_page_map(map);

				if (!pages[i]) {

					spin_unlock(&mm->page_table_lock);

					while (i--)

						page_cache_release(pages[i]);

					i = -EFAULT;

					goto out;

				}

				flush_dcache_page(pages[i]);

				if (!PageReserved(pages[i]))

					page_cache_get(pages[i]);

				pages[i] = page;

				flush_dcache_page(page);

				if (!PageReserved(page))

					page_cache_get(page);

			}

			if (vmas)

				vmas[i] = vma;
@@ -1014,10 +991,8 @@ int get_user_pages(struct task_struct *tsk, struct mm_struct *mm, 
		} while (len && start < vma->vm_end);

		spin_unlock(&mm->page_table_lock);

	} while (len);

out:

	return i;

}



EXPORT_SYMBOL(get_user_pages);



static int zeromap_pte_range(struct mm_struct *mm, pmd_t *pmd,