[PATCH] core remove PageReserved
Remove PageReserved() calls from core code by tightening VM_RESERVED
handling in mm/ to cover PageReserved functionality.
PageReserved special casing is removed from get_page and put_page.
All setting and clearing of PageReserved is retained, and it is now flagged
in the page_alloc checks to help ensure we don't introduce any refcount
based freeing of Reserved pages.
MAP_PRIVATE, PROT_WRITE of VM_RESERVED regions is tentatively being
deprecated. We never completely handled it correctly anyway, and is be
reintroduced in future if required (Hugh has a proof of concept).
Once PageReserved() calls are removed from kernel/power/swsusp.c, and all
arch/ and driver code, the Set and Clear calls, and the PG_reserved bit can
be trivially removed.
Last real user of PageReserved is swsusp, which uses PageReserved to
determine whether a struct page points to valid memory or not. This still
needs to be addressed (a generic page_is_ram() should work).
A last caveat: the ZERO_PAGE is now refcounted and managed with rmap (and
thus mapcounted and count towards shared rss). These writes to the struct
page could cause excessive cacheline bouncing on big systems. There are a
number of ways this could be addressed if it is an issue.
Signed-off-by: Nick Piggin <npiggin@suse.de>
Refcount bug fix for filemap_xip.c
Signed-off-by: Carsten Otte <cotte@de.ibm.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
diff --git a/mm/memory.c b/mm/memory.c
index da642b5..e83f944 100644
--- a/mm/memory.c
+++ b/mm/memory.c
@@ -343,6 +343,23 @@
#define NO_RSS 2 /* Increment neither file_rss nor anon_rss */
/*
+ * This function is called to print an error when a pte in a
+ * !VM_RESERVED region is found pointing to an invalid pfn (which
+ * is an error.
+ *
+ * The calling function must still handle the error.
+ */
+void print_bad_pte(struct vm_area_struct *vma, pte_t pte, unsigned long vaddr)
+{
+ printk(KERN_ERR "Bad pte = %08llx, process = %s, "
+ "vm_flags = %lx, vaddr = %lx\n",
+ (long long)pte_val(pte),
+ (vma->vm_mm == current->mm ? current->comm : "???"),
+ vma->vm_flags, vaddr);
+ dump_stack();
+}
+
+/*
* copy one vm_area from one task to the other. Assumes the page tables
* already present in the new task to be cleared in the whole range
* covered by this vma.
@@ -353,9 +370,10 @@
static inline int
copy_one_pte(struct mm_struct *dst_mm, struct mm_struct *src_mm,
- pte_t *dst_pte, pte_t *src_pte, unsigned long vm_flags,
+ pte_t *dst_pte, pte_t *src_pte, struct vm_area_struct *vma,
unsigned long addr)
{
+ unsigned long vm_flags = vma->vm_flags;
pte_t pte = *src_pte;
struct page *page;
unsigned long pfn;
@@ -375,19 +393,23 @@
goto out_set_pte;
}
- pfn = pte_pfn(pte);
- /* the pte points outside of valid memory, the
- * mapping is assumed to be good, meaningful
- * and not mapped via rmap - duplicate the
- * mapping as is.
+ /* If the region is VM_RESERVED, the mapping is not
+ * mapped via rmap - duplicate the pte as is.
*/
- page = NULL;
- if (pfn_valid(pfn))
- page = pfn_to_page(pfn);
-
- if (!page || PageReserved(page))
+ if (vm_flags & VM_RESERVED)
goto out_set_pte;
+ pfn = pte_pfn(pte);
+ /* If the pte points outside of valid memory but
+ * the region is not VM_RESERVED, we have a problem.
+ */
+ if (unlikely(!pfn_valid(pfn))) {
+ print_bad_pte(vma, pte, addr);
+ goto out_set_pte; /* try to do something sane */
+ }
+
+ page = pfn_to_page(pfn);
+
/*
* If it's a COW mapping, write protect it both
* in the parent and the child
@@ -418,7 +440,6 @@
unsigned long addr, unsigned long end)
{
pte_t *src_pte, *dst_pte;
- unsigned long vm_flags = vma->vm_flags;
int progress = 0;
int rss[NO_RSS+1], anon;
@@ -446,8 +467,7 @@
progress++;
continue;
}
- anon = copy_one_pte(dst_mm, src_mm, dst_pte, src_pte,
- vm_flags, addr);
+ anon = copy_one_pte(dst_mm, src_mm, dst_pte, src_pte, vma,addr);
rss[anon]++;
progress += 8;
} while (dst_pte++, src_pte++, addr += PAGE_SIZE, addr != end);
@@ -541,10 +561,12 @@
return 0;
}
-static void zap_pte_range(struct mmu_gather *tlb, pmd_t *pmd,
+static void zap_pte_range(struct mmu_gather *tlb,
+ struct vm_area_struct *vma, pmd_t *pmd,
unsigned long addr, unsigned long end,
struct zap_details *details)
{
+ struct mm_struct *mm = tlb->mm;
pte_t *pte;
int file_rss = 0;
int anon_rss = 0;
@@ -556,11 +578,12 @@
continue;
if (pte_present(ptent)) {
struct page *page = NULL;
- unsigned long pfn = pte_pfn(ptent);
- if (pfn_valid(pfn)) {
- page = pfn_to_page(pfn);
- if (PageReserved(page))
- page = NULL;
+ if (!(vma->vm_flags & VM_RESERVED)) {
+ unsigned long pfn = pte_pfn(ptent);
+ if (unlikely(!pfn_valid(pfn)))
+ print_bad_pte(vma, ptent, addr);
+ else
+ page = pfn_to_page(pfn);
}
if (unlikely(details) && page) {
/*
@@ -580,7 +603,7 @@
page->index > details->last_index))
continue;
}
- ptent = ptep_get_and_clear_full(tlb->mm, addr, pte,
+ ptent = ptep_get_and_clear_full(mm, addr, pte,
tlb->fullmm);
tlb_remove_tlb_entry(tlb, pte, addr);
if (unlikely(!page))
@@ -588,7 +611,7 @@
if (unlikely(details) && details->nonlinear_vma
&& linear_page_index(details->nonlinear_vma,
addr) != page->index)
- set_pte_at(tlb->mm, addr, pte,
+ set_pte_at(mm, addr, pte,
pgoff_to_pte(page->index));
if (PageAnon(page))
anon_rss++;
@@ -611,14 +634,15 @@
continue;
if (!pte_file(ptent))
free_swap_and_cache(pte_to_swp_entry(ptent));
- pte_clear_full(tlb->mm, addr, pte, tlb->fullmm);
+ pte_clear_full(mm, addr, pte, tlb->fullmm);
} while (pte++, addr += PAGE_SIZE, addr != end);
- add_mm_rss(tlb->mm, -file_rss, -anon_rss);
+ add_mm_rss(mm, -file_rss, -anon_rss);
pte_unmap(pte - 1);
}
-static inline void zap_pmd_range(struct mmu_gather *tlb, pud_t *pud,
+static inline void zap_pmd_range(struct mmu_gather *tlb,
+ struct vm_area_struct *vma, pud_t *pud,
unsigned long addr, unsigned long end,
struct zap_details *details)
{
@@ -630,11 +654,12 @@
next = pmd_addr_end(addr, end);
if (pmd_none_or_clear_bad(pmd))
continue;
- zap_pte_range(tlb, pmd, addr, next, details);
+ zap_pte_range(tlb, vma, pmd, addr, next, details);
} while (pmd++, addr = next, addr != end);
}
-static inline void zap_pud_range(struct mmu_gather *tlb, pgd_t *pgd,
+static inline void zap_pud_range(struct mmu_gather *tlb,
+ struct vm_area_struct *vma, pgd_t *pgd,
unsigned long addr, unsigned long end,
struct zap_details *details)
{
@@ -646,7 +671,7 @@
next = pud_addr_end(addr, end);
if (pud_none_or_clear_bad(pud))
continue;
- zap_pmd_range(tlb, pud, addr, next, details);
+ zap_pmd_range(tlb, vma, pud, addr, next, details);
} while (pud++, addr = next, addr != end);
}
@@ -667,7 +692,7 @@
next = pgd_addr_end(addr, end);
if (pgd_none_or_clear_bad(pgd))
continue;
- zap_pud_range(tlb, pgd, addr, next, details);
+ zap_pud_range(tlb, vma, pgd, addr, next, details);
} while (pgd++, addr = next, addr != end);
tlb_end_vma(tlb, vma);
}
@@ -967,7 +992,7 @@
continue;
}
- if (!vma || (vma->vm_flags & VM_IO)
+ if (!vma || (vma->vm_flags & (VM_IO | VM_RESERVED))
|| !(flags & vma->vm_flags))
return i ? : -EFAULT;
@@ -1027,8 +1052,7 @@
if (pages) {
pages[i] = page;
flush_dcache_page(page);
- if (!PageReserved(page))
- page_cache_get(page);
+ page_cache_get(page);
}
if (vmas)
vmas[i] = vma;
@@ -1051,7 +1075,11 @@
if (!pte)
return -ENOMEM;
do {
- pte_t zero_pte = pte_wrprotect(mk_pte(ZERO_PAGE(addr), prot));
+ struct page *page = ZERO_PAGE(addr);
+ pte_t zero_pte = pte_wrprotect(mk_pte(page, prot));
+ page_cache_get(page);
+ page_add_file_rmap(page);
+ inc_mm_counter(mm, file_rss);
BUG_ON(!pte_none(*pte));
set_pte_at(mm, addr, pte, zero_pte);
} while (pte++, addr += PAGE_SIZE, addr != end);
@@ -1132,8 +1160,7 @@
return -ENOMEM;
do {
BUG_ON(!pte_none(*pte));
- if (!pfn_valid(pfn) || PageReserved(pfn_to_page(pfn)))
- set_pte_at(mm, addr, pte, pfn_pte(pfn, prot));
+ set_pte_at(mm, addr, pte, pfn_pte(pfn, prot));
pfn++;
} while (pte++, addr += PAGE_SIZE, addr != end);
pte_unmap(pte - 1);
@@ -1195,8 +1222,8 @@
* rest of the world about it:
* VM_IO tells people not to look at these pages
* (accesses can have side effects).
- * VM_RESERVED tells swapout not to try to touch
- * this region.
+ * VM_RESERVED tells the core MM not to "manage" these pages
+ * (e.g. refcount, mapcount, try to swap them out).
*/
vma->vm_flags |= VM_IO | VM_RESERVED;
@@ -1256,11 +1283,13 @@
pte_t entry;
int ret = VM_FAULT_MINOR;
+ BUG_ON(vma->vm_flags & VM_RESERVED);
+
if (unlikely(!pfn_valid(pfn))) {
/*
* Page table corrupted: show pte and kill process.
*/
- pte_ERROR(orig_pte);
+ print_bad_pte(vma, orig_pte, address);
ret = VM_FAULT_OOM;
goto unlock;
}
@@ -1284,8 +1313,7 @@
/*
* Ok, we need to copy. Oh, well..
*/
- if (!PageReserved(old_page))
- page_cache_get(old_page);
+ page_cache_get(old_page);
pte_unmap(page_table);
spin_unlock(&mm->page_table_lock);
@@ -1308,14 +1336,10 @@
spin_lock(&mm->page_table_lock);
page_table = pte_offset_map(pmd, address);
if (likely(pte_same(*page_table, orig_pte))) {
- if (PageReserved(old_page))
+ page_remove_rmap(old_page);
+ if (!PageAnon(old_page)) {
inc_mm_counter(mm, anon_rss);
- else {
- page_remove_rmap(old_page);
- if (!PageAnon(old_page)) {
- inc_mm_counter(mm, anon_rss);
- dec_mm_counter(mm, file_rss);
- }
+ dec_mm_counter(mm, file_rss);
}
flush_cache_page(vma, address, pfn);
entry = mk_pte(new_page, vma->vm_page_prot);
@@ -1769,14 +1793,13 @@
unsigned long address, pte_t *page_table, pmd_t *pmd,
int write_access)
{
+ struct page *page = ZERO_PAGE(addr);
pte_t entry;
/* Mapping of ZERO_PAGE - vm_page_prot is readonly */
- entry = mk_pte(ZERO_PAGE(addr), vma->vm_page_prot);
+ entry = mk_pte(page, vma->vm_page_prot);
if (write_access) {
- struct page *page;
-
/* Allocate our own private page. */
pte_unmap(page_table);
spin_unlock(&mm->page_table_lock);
@@ -1800,6 +1823,10 @@
lru_cache_add_active(page);
SetPageReferenced(page);
page_add_anon_rmap(page, vma, address);
+ } else {
+ inc_mm_counter(mm, file_rss);
+ page_add_file_rmap(page);
+ page_cache_get(page);
}
set_pte_at(mm, address, page_table, entry);
@@ -1916,7 +1943,7 @@
inc_mm_counter(mm, anon_rss);
lru_cache_add_active(new_page);
page_add_anon_rmap(new_page, vma, address);
- } else if (!PageReserved(new_page)) {
+ } else if (!(vma->vm_flags & VM_RESERVED)) {
inc_mm_counter(mm, file_rss);
page_add_file_rmap(new_page);
}
@@ -1957,7 +1984,7 @@
/*
* Page table corrupted: show pte and kill process.
*/
- pte_ERROR(orig_pte);
+ print_bad_pte(vma, orig_pte, address);
return VM_FAULT_OOM;
}
/* We can then assume vm->vm_ops && vma->vm_ops->populate */
@@ -2232,7 +2259,7 @@
gate_vma.vm_start = FIXADDR_USER_START;
gate_vma.vm_end = FIXADDR_USER_END;
gate_vma.vm_page_prot = PAGE_READONLY;
- gate_vma.vm_flags = 0;
+ gate_vma.vm_flags = VM_RESERVED;
return 0;
}
__initcall(gate_vma_init);
