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mm: drop support of non-linear mapping from unmap/zap codepath
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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: Felipe Balbi <[email protected]>

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: Kirill A. Shutemov <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>
Signed-off-by: Linus Torvalds <[email protected]>
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@kiryl @torvalds
kiryl authored and torvalds committed Feb 10, 2015
1 parent c8d78c1 commit 8a5f14a
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Showing 3 changed files with 22 additions and 70 deletions.
1 change: 0 additions & 1 deletion include/linux/mm.h
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Original file line number Diff line number Diff line change
Expand Up @@ -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 */
Expand Down
9 changes: 1 addition & 8 deletions mm/madvise.c
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Original file line number Diff line number Diff line change
Expand Up @@ -278,14 +278,7 @@ 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);
zap_page_range(vma, start, end - start, NULL);
return 0;
}

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82 changes: 21 additions & 61 deletions mm/memory.c
View file
Original file line number Diff line number Diff line change
Expand Up @@ -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);
Expand All @@ -1107,28 +1108,12 @@ static unsigned long zap_pte_range(struct mmu_gather *tlb,
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 {
Expand All @@ -1151,33 +1136,25 @@ static unsigned long zap_pte_range(struct mmu_gather *tlb,
}
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);

if (!non_swap_entry(entry))
rss[MM_SWAPENTS]--;
else if (is_migration_entry(entry)) {
struct page *page;
entry = pte_to_swp_entry(ptent);
if (!non_swap_entry(entry))
rss[MM_SWAPENTS]--;
else if (is_migration_entry(entry)) {
struct page *page;

page = migration_entry_to_page(entry);
page = migration_entry_to_page(entry);

if (PageAnon(page))
rss[MM_ANONPAGES]--;
else
rss[MM_FILEPAGES]--;
}
if (unlikely(!free_swap_and_cache(entry)))
print_bad_pte(vma, addr, ptent, NULL);
if (PageAnon(page))
rss[MM_ANONPAGES]--;
else
rss[MM_FILEPAGES]--;
}
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);

Expand Down Expand Up @@ -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);
Expand Down Expand Up @@ -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
*/
Expand All @@ -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.
*/
Expand Down Expand Up @@ -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
Expand Down Expand Up @@ -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)
Expand All @@ -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);
Expand Down

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