Commit 8a5f14a2 authored by Kirill A. Shutemov's avatar Kirill A. Shutemov Committed by Linus Torvalds
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mm: drop support of non-linear mapping from unmap/zap codepath 



We have remap_file_pages(2) emulation in -mm tree for few release cycles
and we plan to have it mainline in v3.20. This patchset removes rest of
VM_NONLINEAR infrastructure.

Patches 1-8 take care about generic code. They are pretty
straight-forward and can be applied without other of patches.

Rest patches removes pte_file()-related stuff from architecture-specific
code. It usually frees up one bit in non-present pte. I've tried to reuse
that bit for swap offset, where I was able to figure out how to do that.

For obvious reason I cannot test all that arch-specific code and would
like to see acks from maintainers.

In total, remap_file_pages(2) required about 1.4K lines of not-so-trivial
kernel code. That's too much for functionality nobody uses.

Tested-by: default avatarFelipe Balbi <balbi@ti.com>

This patch (of 38):

We don't create non-linear mappings anymore. Let's drop code which
handles them on unmap/zap.

Signed-off-by: default avatarKirill A. Shutemov <kirill.shutemov@linux.intel.com>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
parent c8d78c18

include/linux/mm.h

+0 −1
Original line number Diff line number Diff line
@@ -1146,7 +1146,6 @@ extern void user_shm_unlock(size_t, struct user_struct *); 
 * Parameter block passed down to zap_pte_range in exceptional cases.

 */

struct zap_details {

	struct vm_area_struct *nonlinear_vma;	/* Check page->index if set */

	struct address_space *check_mapping;	/* Check page->mapping if set */

	pgoff_t	first_index;			/* Lowest page->index to unmap */

	pgoff_t last_index;			/* Highest page->index to unmap */

mm/madvise.c

+1 −8
Original line number Diff line number Diff line
@@ -278,13 +278,6 @@ static long madvise_dontneed(struct vm_area_struct *vma, 
	if (vma->vm_flags & (VM_LOCKED|VM_HUGETLB|VM_PFNMAP))

		return -EINVAL;



	if (unlikely(vma->vm_flags & VM_NONLINEAR)) {

		struct zap_details details = {

			.nonlinear_vma = vma,

			.last_index = ULONG_MAX,

		};

		zap_page_range(vma, start, end - start, &details);

	} else

	zap_page_range(vma, start, end - start, NULL);

	return 0;

}

mm/memory.c

+21 −61
Original line number Diff line number Diff line
@@ -1082,6 +1082,7 @@ static unsigned long zap_pte_range(struct mmu_gather *tlb, 
	spinlock_t *ptl;

	pte_t *start_pte;

	pte_t *pte;

	swp_entry_t entry;



again:

	init_rss_vec(rss);
@@ -1107,28 +1108,12 @@ again: 
				if (details->check_mapping &&

				    details->check_mapping != page->mapping)

					continue;

				/*

				 * Each page->index must be checked when

				 * invalidating or truncating nonlinear.

				 */

				if (details->nonlinear_vma &&

				    (page->index < details->first_index ||

				     page->index > details->last_index))

					continue;

			}

			ptent = ptep_get_and_clear_full(mm, addr, pte,

							tlb->fullmm);

			tlb_remove_tlb_entry(tlb, pte, addr);

			if (unlikely(!page))

				continue;

			if (unlikely(details) && details->nonlinear_vma

			    && linear_page_index(details->nonlinear_vma,

						addr) != page->index) {

				pte_t ptfile = pgoff_to_pte(page->index);

				if (pte_soft_dirty(ptent))

					ptfile = pte_file_mksoft_dirty(ptfile);

				set_pte_at(mm, addr, pte, ptfile);

			}

			if (PageAnon(page))

				rss[MM_ANONPAGES]--;

			else {
@@ -1151,18 +1136,11 @@ again: 
			}

			continue;

		}

		/*

		 * If details->check_mapping, we leave swap entries;

		 * if details->nonlinear_vma, we leave file entries.

		 */

		/* If details->check_mapping, we leave swap entries. */

		if (unlikely(details))

			continue;

		if (pte_file(ptent)) {

			if (unlikely(!(vma->vm_flags & VM_NONLINEAR)))

				print_bad_pte(vma, addr, ptent, NULL);

		} else {

			swp_entry_t entry = pte_to_swp_entry(ptent);



		entry = pte_to_swp_entry(ptent);

		if (!non_swap_entry(entry))

			rss[MM_SWAPENTS]--;

		else if (is_migration_entry(entry)) {
@@ -1177,7 +1155,6 @@ again: 
		}

		if (unlikely(!free_swap_and_cache(entry)))

			print_bad_pte(vma, addr, ptent, NULL);

		}

		pte_clear_not_present_full(mm, addr, pte, tlb->fullmm);

	} while (pte++, addr += PAGE_SIZE, addr != end);
@@ -1277,7 +1254,7 @@ static void unmap_page_range(struct mmu_gather *tlb, 
	pgd_t *pgd;

	unsigned long next;



	if (details && !details->check_mapping && !details->nonlinear_vma)

	if (details && !details->check_mapping)

		details = NULL;



	BUG_ON(addr >= end);
@@ -1371,7 +1348,7 @@ void unmap_vmas(struct mmu_gather *tlb, 
 * @vma: vm_area_struct holding the applicable pages

 * @start: starting address of pages to zap

 * @size: number of bytes to zap

 * @details: details of nonlinear truncation or shared cache invalidation

 * @details: details of shared cache invalidation

 *

 * Caller must protect the VMA list

 */
@@ -1397,7 +1374,7 @@ void zap_page_range(struct vm_area_struct *vma, unsigned long start, 
 * @vma: vm_area_struct holding the applicable pages

 * @address: starting address of pages to zap

 * @size: number of bytes to zap

 * @details: details of nonlinear truncation or shared cache invalidation

 * @details: details of shared cache invalidation

 *

 * The range must fit into one VMA.

 */
@@ -2331,25 +2308,11 @@ static inline void unmap_mapping_range_tree(struct rb_root *root, 
	}

}



static inline void unmap_mapping_range_list(struct list_head *head,

					    struct zap_details *details)

{

	struct vm_area_struct *vma;



	/*

	 * In nonlinear VMAs there is no correspondence between virtual address

	 * offset and file offset.  So we must perform an exhaustive search

	 * across *all* the pages in each nonlinear VMA, not just the pages

	 * whose virtual address lies outside the file truncation point.

	 */

	list_for_each_entry(vma, head, shared.nonlinear) {

		details->nonlinear_vma = vma;

		unmap_mapping_range_vma(vma, vma->vm_start, vma->vm_end, details);

	}

}



/**

 * unmap_mapping_range - unmap the portion of all mmaps in the specified address_space corresponding to the specified page range in the underlying file.

 * unmap_mapping_range - unmap the portion of all mmaps in the specified

 * address_space corresponding to the specified page range in the underlying

 * file.

 *

 * @mapping: the address space containing mmaps to be unmapped.

 * @holebegin: byte in first page to unmap, relative to the start of

 * the underlying file.  This will be rounded down to a PAGE_SIZE
@@ -2378,7 +2341,6 @@ void unmap_mapping_range(struct address_space *mapping, 
	}



	details.check_mapping = even_cows? NULL: mapping;

	details.nonlinear_vma = NULL;

	details.first_index = hba;

	details.last_index = hba + hlen - 1;

	if (details.last_index < details.first_index)
@@ -2388,8 +2350,6 @@ void unmap_mapping_range(struct address_space *mapping, 
	i_mmap_lock_write(mapping);

	if (unlikely(!RB_EMPTY_ROOT(&mapping->i_mmap)))

		unmap_mapping_range_tree(&mapping->i_mmap, &details);

	if (unlikely(!list_empty(&mapping->i_mmap_nonlinear)))

		unmap_mapping_range_list(&mapping->i_mmap_nonlinear, &details);

	i_mmap_unlock_write(mapping);

}

EXPORT_SYMBOL(unmap_mapping_range);

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