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Date: Fri, 20 Apr 2007 11:02:34 -0700 (PDT)
From: Christoph Lameter <clameter@....com>
To: William Lee Irwin III <wli@...omorphy.com>
cc: Mel Gorman <mel@...net.ie>, linux-kernel@...r.kernel.org,
Peter Zijlstra <a.p.zijlstra@...llo.nl>,
Nick Piggin <nickpiggin@...oo.com.au>, Andi Kleen <ak@...e.de>,
Paul Jackson <pj@....com>, Dave Chinner <dgc@....com>
Subject: Re: [RFC 7/8] Enhance ramfs to support higher order pages
Some ideas for memory.c pieces. Just junk like the earlier patches.
---
mm/memory.c | 108 ++++++++++++++++++++++++++++++++++++------------------------
1 file changed, 66 insertions(+), 42 deletions(-)
Index: linux-2.6.21-rc7/mm/memory.c
===================================================================
--- linux-2.6.21-rc7.orig/mm/memory.c 2007-04-20 10:55:49.000000000 -0700
+++ linux-2.6.21-rc7/mm/memory.c 2007-04-20 10:56:13.000000000 -0700
@@ -368,6 +368,12 @@ static inline int is_cow_mapping(unsigne
/*
* This function gets the "struct page" associated with a pte.
*
+ * NOTE! For compound pages it may get to a tail page (maybe we
+ * only deal with a portion of a compound page after all). This
+ * means that the result of vm_normal_page may not directly be
+ * used to manipulate the page state. Use compound_head() if
+ * operations (like getting a ref count) are necessary.
+ *
* NOTE! Some mappings do not have "struct pages". A raw PFN mapping
* will have each page table entry just pointing to a raw page frame
* number, and as far as the VM layer is concerned, those do not have
@@ -480,9 +486,11 @@ copy_one_pte(struct mm_struct *dst_mm, s
page = vm_normal_page(vma, addr, pte);
if (page) {
- get_page(page);
- page_dup_rmap(page);
- rss[!!PageAnon(page)]++;
+ struct page *head_page = compound_head(page);
+
+ get_page(head_page);
+ page_dup_rmap(head_page);
+ rss[!!PageAnon(head_page)]++;
}
out_set_pte:
@@ -642,8 +650,14 @@ static unsigned long zap_pte_range(struc
if (pte_present(ptent)) {
struct page *page;
+ struct page *head_page;
page = vm_normal_page(vma, addr, ptent);
+ if (page)
+ head_page = compound_head(page);
+ else
+ head_page = NULL;
+
if (unlikely(details) && page) {
/*
* unmap_shared_mapping_pages() wants to
@@ -651,15 +665,15 @@ static unsigned long zap_pte_range(struc
* unmap shared but keep private pages.
*/
if (details->check_mapping &&
- details->check_mapping != page->mapping)
+ details->check_mapping != head_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))
+ (head_page->index < details->first_index ||
+ head_page->index > details->last_index))
continue;
}
ptent = ptep_get_and_clear_full(mm, addr, pte,
@@ -668,21 +682,24 @@ static unsigned long zap_pte_range(struc
if (unlikely(!page))
continue;
if (unlikely(details) && details->nonlinear_vma
- && linear_page_index(details->nonlinear_vma,
- addr) != page->index)
+ && linear_page_index_mapping(details->nonlinear_vma,
+ addr, compound_order(head_page))
+ != head_page->index)
set_pte_at(mm, addr, pte,
- pgoff_to_pte(page->index));
- if (PageAnon(page))
+ pgoff_to_pte(
+ (head_page->index << compound_page(order))
+ + page - head_page));
+ if (PageAnon(head_page))
anon_rss--;
else {
if (pte_dirty(ptent))
- set_page_dirty(page);
+ set_page_dirty(head_page);
if (pte_young(ptent))
- SetPageReferenced(page);
+ SetPageReferenced(head_page);
file_rss--;
}
- page_remove_rmap(page, vma);
- tlb_remove_page(tlb, page);
+ page_remove_rmap(head_page, vma);
+ tlb_remove_page(tlb, head_page);
continue;
}
/*
@@ -899,6 +916,10 @@ unsigned long zap_page_range(struct vm_a
/*
* Do a quick page-table lookup for a single page.
+ *
+ * Note: This function may return a pointer to a tail page. However,
+ * any operations like getting a page reference and touching it will
+ * have to be performed on the head page.
*/
struct page *follow_page(struct vm_area_struct *vma, unsigned long address,
unsigned int flags)
@@ -949,13 +970,14 @@ struct page *follow_page(struct vm_area_
if (unlikely(!page))
goto unlock;
+ head_page = compound_head(page);
if (flags & FOLL_GET)
- get_page(page);
+ get_page(head_page);
if (flags & FOLL_TOUCH) {
if ((flags & FOLL_WRITE) &&
- !pte_dirty(pte) && !PageDirty(page))
- set_page_dirty(page);
- mark_page_accessed(page);
+ !pte_dirty(pte) && !PageDirty(head_page))
+ set_page_dirty(head_page);
+ mark_page_accessed(head_page);
}
unlock:
pte_unmap_unlock(ptep, ptl);
@@ -1537,6 +1559,7 @@ static int do_wp_page(struct mm_struct *
spinlock_t *ptl, pte_t orig_pte)
{
struct page *old_page, *new_page;
+ struct page *old_page_head, *new_page_head;
pte_t entry;
int reuse = 0, ret = VM_FAULT_MINOR;
struct page *dirty_page = NULL;
@@ -1545,14 +1568,15 @@ static int do_wp_page(struct mm_struct *
if (!old_page)
goto gotten;
+ old_page_head = compound_head(old_page);
/*
* Take out anonymous pages first, anonymous shared vmas are
* not dirty accountable.
*/
- if (PageAnon(old_page)) {
- if (!TestSetPageLocked(old_page)) {
- reuse = can_share_swap_page(old_page);
- unlock_page(old_page);
+ if (PageAnon(old_page_head)) {
+ if (!TestSetPageLocked(old_page_head)) {
+ reuse = can_share_swap_page(old_page_head);
+ unlock_page(old_page_head);
}
} else if (unlikely((vma->vm_flags & (VM_WRITE|VM_SHARED)) ==
(VM_WRITE|VM_SHARED))) {
@@ -1570,10 +1594,10 @@ static int do_wp_page(struct mm_struct *
* We do this without the lock held, so that it can
* sleep if it needs to.
*/
- page_cache_get(old_page);
+ page_cache_get(old_page_head);
pte_unmap_unlock(page_table, ptl);
- if (vma->vm_ops->page_mkwrite(vma, old_page) < 0)
+ if (vma->vm_ops->page_mkwrite(vma, old_page_head) < 0)
goto unwritable_page;
/*
@@ -1584,11 +1608,11 @@ static int do_wp_page(struct mm_struct *
*/
page_table = pte_offset_map_lock(mm, pmd, address,
&ptl);
- page_cache_release(old_page);
+ page_cache_release(old_page_head);
if (!pte_same(*page_table, orig_pte))
goto unlock;
}
- dirty_page = old_page;
+ dirty_page = old_page_head;
get_page(dirty_page);
reuse = 1;
}
@@ -1607,7 +1631,7 @@ static int do_wp_page(struct mm_struct *
/*
* Ok, we need to copy. Oh, well..
*/
- page_cache_get(old_page);
+ page_cache_get(old_page_head);
gotten:
pte_unmap_unlock(page_table, ptl);
@@ -1630,8 +1654,8 @@ gotten:
page_table = pte_offset_map_lock(mm, pmd, address, &ptl);
if (likely(pte_same(*page_table, orig_pte))) {
if (old_page) {
- page_remove_rmap(old_page, vma);
- if (!PageAnon(old_page)) {
+ page_remove_rmap(old_page_head, vma);
+ if (!PageAnon(old_page_head)) {
dec_mm_counter(mm, file_rss);
inc_mm_counter(mm, anon_rss);
}
@@ -1654,13 +1678,13 @@ gotten:
page_add_new_anon_rmap(new_page, vma, address);
/* Free the old page.. */
- new_page = old_page;
+ new_page = old_page_head;
ret |= VM_FAULT_WRITE;
}
if (new_page)
page_cache_release(new_page);
if (old_page)
- page_cache_release(old_page);
+ page_cache_release(old_page_head);
unlock:
pte_unmap_unlock(page_table, ptl);
if (dirty_page) {
@@ -1669,8 +1693,8 @@ unlock:
}
return ret;
oom:
- if (old_page)
- page_cache_release(old_page);
+ if (old_page_head)
+ page_cache_release(old_page_head);
return VM_FAULT_OOM;
unwritable_page:
@@ -2243,7 +2267,7 @@ retry:
if (!page)
goto oom;
copy_user_highpage(page, new_page, address, vma);
- page_cache_release(new_page);
+ page_cache_release(compound_head(new_page));
new_page = page;
anon = 1;
@@ -2254,7 +2278,7 @@ retry:
if (vma->vm_ops->page_mkwrite &&
vma->vm_ops->page_mkwrite(vma, new_page) < 0
) {
- page_cache_release(new_page);
+ page_cache_release(compound_head(new_page));
return VM_FAULT_SIGBUS;
}
}
@@ -2268,7 +2292,7 @@ retry:
*/
if (mapping && unlikely(sequence != mapping->truncate_count)) {
pte_unmap_unlock(page_table, ptl);
- page_cache_release(new_page);
+ page_cache_release(compound_head(new_page));
cond_resched();
sequence = mapping->truncate_count;
smp_rmb();
@@ -2298,15 +2322,15 @@ retry:
page_add_new_anon_rmap(new_page, vma, address);
} else {
inc_mm_counter(mm, file_rss);
- page_add_file_rmap(new_page);
+ page_add_file_rmap(compound_head(new_page));
if (write_access) {
- dirty_page = new_page;
+ dirty_page = compound_head(new_page);
get_page(dirty_page);
}
}
} else {
/* One of our sibling threads was faster, back out. */
- page_cache_release(new_page);
+ page_cache_release(compound_head(new_page));
goto unlock;
}
@@ -2321,7 +2345,7 @@ unlock:
}
return ret;
oom:
- page_cache_release(new_page);
+ page_cache_release(compound_head(new_page));
return VM_FAULT_OOM;
}
@@ -2720,13 +2744,13 @@ int access_process_vm(struct task_struct
if (write) {
copy_to_user_page(vma, page, addr,
maddr + offset, buf, bytes);
- set_page_dirty_lock(page);
+ set_page_dirty_lock(compound_head(page));
} else {
copy_from_user_page(vma, page, addr,
buf, maddr + offset, bytes);
}
kunmap(page);
- page_cache_release(page);
+ page_cache_release(compound_head(page));
len -= bytes;
buf += bytes;
addr += bytes;
-
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