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Subject[PATCH 10/21] mm: page fault handlers tidyup
Impose a little more consistency on the page fault handlers do_wp_page, 
do_swap_page, do_anonymous_page, do_no_page, do_file_page: why not pass
their arguments in the same order, called the same names?

break_cow is all very well, but what it did was inlined elsewhere:
easier to compare if it's brought back into do_wp_page.

do_file_page's fallback to do_no_page dates from a time when we were
testing pte_file by using it wherever possible: currently it's peculiar
to nonlinear vmas, so just check that. BUG_ON if not? Better not, it's
probably page table corruption, so just show the pte: hmm, there's a
pte_ERROR macro, let's use that for do_wp_page's invalid pfn too.

Hah! Someone in the ppc64 world noticed pte_ERROR was unused so removed
it: restored (and say "pud" not "pmd" in its pud_ERROR).

Signed-off-by: Hugh Dickins <hugh@veritas.com>
---

include/asm-ppc64/pgtable.h | 4
mm/memory.c | 220 +++++++++++++++++++-------------------------
2 files changed, 100 insertions(+), 124 deletions(-)

--- mm09/include/asm-ppc64/pgtable.h 2005-09-21 12:16:55.000000000 +0100
+++ mm10/include/asm-ppc64/pgtable.h 2005-09-24 19:28:28.000000000 +0100
@@ -478,10 +478,12 @@ extern pgprot_t phys_mem_access_prot(str
#define __HAVE_ARCH_PTE_SAME
#define pte_same(A,B) (((pte_val(A) ^ pte_val(B)) & ~_PAGE_HPTEFLAGS) == 0)

+#define pte_ERROR(e) \
+ printk("%s:%d: bad pte %08lx.\n", __FILE__, __LINE__, pte_val(e))
#define pmd_ERROR(e) \
printk("%s:%d: bad pmd %08lx.\n", __FILE__, __LINE__, pmd_val(e))
#define pud_ERROR(e) \
- printk("%s:%d: bad pmd %08lx.\n", __FILE__, __LINE__, pud_val(e))
+ printk("%s:%d: bad pud %08lx.\n", __FILE__, __LINE__, pud_val(e))
#define pgd_ERROR(e) \
printk("%s:%d: bad pgd %08lx.\n", __FILE__, __LINE__, pgd_val(e))

--- mm09/mm/memory.c 2005-09-24 19:27:19.000000000 +0100
+++ mm10/mm/memory.c 2005-09-24 19:28:28.000000000 +0100
@@ -1213,28 +1213,10 @@ static inline pte_t maybe_mkwrite(pte_t
}

/*
- * We hold the mm semaphore for reading and vma->vm_mm->page_table_lock
- */
-static inline void break_cow(struct vm_area_struct * vma, struct page * new_page, unsigned long address,
- pte_t *page_table)
-{
- pte_t entry;
-
- entry = maybe_mkwrite(pte_mkdirty(mk_pte(new_page, vma->vm_page_prot)),
- vma);
- ptep_establish(vma, address, page_table, entry);
- update_mmu_cache(vma, address, entry);
- lazy_mmu_prot_update(entry);
-}
-
-/*
* This routine handles present pages, when users try to write
* to a shared page. It is done by copying the page to a new address
* and decrementing the shared-page counter for the old page.
*
- * Goto-purists beware: the only reason for goto's here is that it results
- * in better assembly code.. The "default" path will see no jumps at all.
- *
* Note that this routine assumes that the protection checks have been
* done by the caller (the low-level page fault routine in most cases).
* Thus we can safely just mark it writable once we've done any necessary
@@ -1247,25 +1229,22 @@ static inline void break_cow(struct vm_a
* We hold the mm semaphore and the page_table_lock on entry and exit
* with the page_table_lock released.
*/
-static int do_wp_page(struct mm_struct *mm, struct vm_area_struct * vma,
- unsigned long address, pte_t *page_table, pmd_t *pmd, pte_t pte)
+static int do_wp_page(struct mm_struct *mm, struct vm_area_struct *vma,
+ unsigned long address, pte_t *page_table, pmd_t *pmd,
+ pte_t orig_pte)
{
struct page *old_page, *new_page;
- unsigned long pfn = pte_pfn(pte);
+ unsigned long pfn = pte_pfn(orig_pte);
pte_t entry;
- int ret;
+ int ret = VM_FAULT_MINOR;

if (unlikely(!pfn_valid(pfn))) {
/*
- * This should really halt the system so it can be debugged or
- * at least the kernel stops what it's doing before it corrupts
- * data, but for the moment just pretend this is OOM.
+ * Page table corrupted: show pte and kill process.
*/
- pte_unmap(page_table);
- printk(KERN_ERR "do_wp_page: bogus page at address %08lx\n",
- address);
- spin_unlock(&mm->page_table_lock);
- return VM_FAULT_OOM;
+ pte_ERROR(orig_pte);
+ ret = VM_FAULT_OOM;
+ goto unlock;
}
old_page = pfn_to_page(pfn);

@@ -1274,52 +1253,57 @@ static int do_wp_page(struct mm_struct *
unlock_page(old_page);
if (reuse) {
flush_cache_page(vma, address, pfn);
- entry = maybe_mkwrite(pte_mkyoung(pte_mkdirty(pte)),
- vma);
+ entry = pte_mkyoung(orig_pte);
+ entry = maybe_mkwrite(pte_mkdirty(entry), vma);
ptep_set_access_flags(vma, address, page_table, entry, 1);
update_mmu_cache(vma, address, entry);
lazy_mmu_prot_update(entry);
- pte_unmap(page_table);
- spin_unlock(&mm->page_table_lock);
- return VM_FAULT_MINOR|VM_FAULT_WRITE;
+ ret |= VM_FAULT_WRITE;
+ goto unlock;
}
}
- pte_unmap(page_table);

/*
* Ok, we need to copy. Oh, well..
*/
if (!PageReserved(old_page))
page_cache_get(old_page);
+ pte_unmap(page_table);
spin_unlock(&mm->page_table_lock);

if (unlikely(anon_vma_prepare(vma)))
- goto no_new_page;
+ goto oom;
if (old_page == ZERO_PAGE(address)) {
new_page = alloc_zeroed_user_highpage(vma, address);
if (!new_page)
- goto no_new_page;
+ goto oom;
} else {
new_page = alloc_page_vma(GFP_HIGHUSER, vma, address);
if (!new_page)
- goto no_new_page;
+ goto oom;
copy_user_highpage(new_page, old_page, address);
}
+
/*
* Re-check the pte - we dropped the lock
*/
- ret = VM_FAULT_MINOR;
spin_lock(&mm->page_table_lock);
page_table = pte_offset_map(pmd, address);
- if (likely(pte_same(*page_table, pte))) {
+ if (likely(pte_same(*page_table, orig_pte))) {
if (PageAnon(old_page))
dec_mm_counter(mm, anon_rss);
if (PageReserved(old_page))
inc_mm_counter(mm, rss);
else
page_remove_rmap(old_page);
+
flush_cache_page(vma, address, pfn);
- break_cow(vma, new_page, address, page_table);
+ entry = mk_pte(new_page, vma->vm_page_prot);
+ entry = maybe_mkwrite(pte_mkdirty(entry), vma);
+ ptep_establish(vma, address, page_table, entry);
+ update_mmu_cache(vma, address, entry);
+ lazy_mmu_prot_update(entry);
+
lru_cache_add_active(new_page);
page_add_anon_rmap(new_page, vma, address);

@@ -1327,13 +1311,13 @@ static int do_wp_page(struct mm_struct *
new_page = old_page;
ret |= VM_FAULT_WRITE;
}
- pte_unmap(page_table);
page_cache_release(new_page);
page_cache_release(old_page);
+unlock:
+ pte_unmap(page_table);
spin_unlock(&mm->page_table_lock);
return ret;
-
-no_new_page:
+oom:
page_cache_release(old_page);
return VM_FAULT_OOM;
}
@@ -1661,17 +1645,19 @@ void swapin_readahead(swp_entry_t entry,
* We hold the mm semaphore and the page_table_lock on entry and
* should release the pagetable lock on exit..
*/
-static int do_swap_page(struct mm_struct * mm,
- struct vm_area_struct * vma, unsigned long address,
- pte_t *page_table, pmd_t *pmd, pte_t orig_pte, int write_access)
+static int do_swap_page(struct mm_struct *mm, struct vm_area_struct *vma,
+ unsigned long address, pte_t *page_table, pmd_t *pmd,
+ int write_access, pte_t orig_pte)
{
struct page *page;
- swp_entry_t entry = pte_to_swp_entry(orig_pte);
+ swp_entry_t entry;
pte_t pte;
int ret = VM_FAULT_MINOR;

pte_unmap(page_table);
spin_unlock(&mm->page_table_lock);
+
+ entry = pte_to_swp_entry(orig_pte);
page = lookup_swap_cache(entry);
if (!page) {
swapin_readahead(entry, address, vma);
@@ -1685,11 +1671,7 @@ static int do_swap_page(struct mm_struct
page_table = pte_offset_map(pmd, address);
if (likely(pte_same(*page_table, orig_pte)))
ret = VM_FAULT_OOM;
- else
- ret = VM_FAULT_MINOR;
- pte_unmap(page_table);
- spin_unlock(&mm->page_table_lock);
- goto out;
+ goto unlock;
}

/* Had to read the page from swap area: Major fault */
@@ -1745,6 +1727,7 @@ static int do_swap_page(struct mm_struct
/* No need to invalidate - it was non-present before */
update_mmu_cache(vma, address, pte);
lazy_mmu_prot_update(pte);
+unlock:
pte_unmap(page_table);
spin_unlock(&mm->page_table_lock);
out:
@@ -1754,7 +1737,7 @@ out_nomap:
spin_unlock(&mm->page_table_lock);
unlock_page(page);
page_cache_release(page);
- goto out;
+ return ret;
}

/*
@@ -1762,17 +1745,15 @@ out_nomap:
* spinlock held to protect against concurrent faults in
* multithreaded programs.
*/
-static int
-do_anonymous_page(struct mm_struct *mm, struct vm_area_struct *vma,
- pte_t *page_table, pmd_t *pmd, int write_access,
- unsigned long addr)
+static int do_anonymous_page(struct mm_struct *mm, struct vm_area_struct *vma,
+ unsigned long address, pte_t *page_table, pmd_t *pmd,
+ int write_access)
{
pte_t entry;

/* Mapping of ZERO_PAGE - vm_page_prot is readonly */
entry = mk_pte(ZERO_PAGE(addr), vma->vm_page_prot);

- /* ..except if it's a write access */
if (write_access) {
struct page *page;

@@ -1781,39 +1762,36 @@ do_anonymous_page(struct mm_struct *mm,
spin_unlock(&mm->page_table_lock);

if (unlikely(anon_vma_prepare(vma)))
- goto no_mem;
- page = alloc_zeroed_user_highpage(vma, addr);
+ goto oom;
+ page = alloc_zeroed_user_highpage(vma, address);
if (!page)
- goto no_mem;
+ goto oom;

spin_lock(&mm->page_table_lock);
- page_table = pte_offset_map(pmd, addr);
+ page_table = pte_offset_map(pmd, address);

if (!pte_none(*page_table)) {
- pte_unmap(page_table);
page_cache_release(page);
- spin_unlock(&mm->page_table_lock);
- goto out;
+ goto unlock;
}
inc_mm_counter(mm, rss);
- entry = maybe_mkwrite(pte_mkdirty(mk_pte(page,
- vma->vm_page_prot)),
- vma);
+ entry = mk_pte(page, vma->vm_page_prot);
+ entry = maybe_mkwrite(pte_mkdirty(entry), vma);
lru_cache_add_active(page);
SetPageReferenced(page);
- page_add_anon_rmap(page, vma, addr);
+ page_add_anon_rmap(page, vma, address);
}

- set_pte_at(mm, addr, page_table, entry);
- pte_unmap(page_table);
+ set_pte_at(mm, address, page_table, entry);

/* No need to invalidate - it was non-present before */
- update_mmu_cache(vma, addr, entry);
+ update_mmu_cache(vma, address, entry);
lazy_mmu_prot_update(entry);
+unlock:
+ pte_unmap(page_table);
spin_unlock(&mm->page_table_lock);
-out:
return VM_FAULT_MINOR;
-no_mem:
+oom:
return VM_FAULT_OOM;
}

@@ -1829,20 +1807,17 @@ no_mem:
* This is called with the MM semaphore held and the page table
* spinlock held. Exit with the spinlock released.
*/
-static int
-do_no_page(struct mm_struct *mm, struct vm_area_struct *vma,
- unsigned long address, int write_access, pte_t *page_table, pmd_t *pmd)
+static int do_no_page(struct mm_struct *mm, struct vm_area_struct *vma,
+ unsigned long address, pte_t *page_table, pmd_t *pmd,
+ int write_access)
{
- struct page * new_page;
+ struct page *new_page;
struct address_space *mapping = NULL;
pte_t entry;
unsigned int sequence = 0;
int ret = VM_FAULT_MINOR;
int anon = 0;

- if (!vma->vm_ops || !vma->vm_ops->nopage)
- return do_anonymous_page(mm, vma, page_table,
- pmd, write_access, address);
pte_unmap(page_table);
spin_unlock(&mm->page_table_lock);

@@ -1852,7 +1827,6 @@ do_no_page(struct mm_struct *mm, struct
smp_rmb(); /* serializes i_size against truncate_count */
}
retry:
- cond_resched();
new_page = vma->vm_ops->nopage(vma, address & PAGE_MASK, &ret);
/*
* No smp_rmb is needed here as long as there's a full
@@ -1892,9 +1866,11 @@ retry:
* retry getting the page.
*/
if (mapping && unlikely(sequence != mapping->truncate_count)) {
- sequence = mapping->truncate_count;
spin_unlock(&mm->page_table_lock);
page_cache_release(new_page);
+ cond_resched();
+ sequence = mapping->truncate_count;
+ smp_rmb();
goto retry;
}
page_table = pte_offset_map(pmd, address);
@@ -1924,25 +1900,22 @@ retry:
page_add_anon_rmap(new_page, vma, address);
} else
page_add_file_rmap(new_page);
- pte_unmap(page_table);
} else {
/* One of our sibling threads was faster, back out. */
- pte_unmap(page_table);
page_cache_release(new_page);
- spin_unlock(&mm->page_table_lock);
- goto out;
+ goto unlock;
}

/* no need to invalidate: a not-present page shouldn't be cached */
update_mmu_cache(vma, address, entry);
lazy_mmu_prot_update(entry);
+unlock:
+ pte_unmap(page_table);
spin_unlock(&mm->page_table_lock);
-out:
return ret;
oom:
page_cache_release(new_page);
- ret = VM_FAULT_OOM;
- goto out;
+ return VM_FAULT_OOM;
}

/*
@@ -1950,29 +1923,28 @@ oom:
* from the encoded file_pte if possible. This enables swappable
* nonlinear vmas.
*/
-static int do_file_page(struct mm_struct * mm, struct vm_area_struct * vma,
- unsigned long address, int write_access, pte_t *pte, pmd_t *pmd)
+static int do_file_page(struct mm_struct *mm, struct vm_area_struct *vma,
+ unsigned long address, pte_t *page_table, pmd_t *pmd,
+ int write_access, pte_t orig_pte)
{
- unsigned long pgoff;
+ pgoff_t pgoff;
int err;

- BUG_ON(!vma->vm_ops || !vma->vm_ops->nopage);
- /*
- * Fall back to the linear mapping if the fs does not support
- * ->populate:
- */
- if (!vma->vm_ops->populate ||
- (write_access && !(vma->vm_flags & VM_SHARED))) {
- pte_clear(mm, address, pte);
- return do_no_page(mm, vma, address, write_access, pte, pmd);
- }
-
- pgoff = pte_to_pgoff(*pte);
-
- pte_unmap(pte);
+ pte_unmap(page_table);
spin_unlock(&mm->page_table_lock);

- err = vma->vm_ops->populate(vma, address & PAGE_MASK, PAGE_SIZE, vma->vm_page_prot, pgoff, 0);
+ if (unlikely(!(vma->vm_flags & VM_NONLINEAR))) {
+ /*
+ * Page table corrupted: show pte and kill process.
+ */
+ pte_ERROR(orig_pte);
+ return VM_FAULT_OOM;
+ }
+ /* We can then assume vm->vm_ops && vma->vm_ops->populate */
+
+ pgoff = pte_to_pgoff(orig_pte);
+ err = vma->vm_ops->populate(vma, address & PAGE_MASK, PAGE_SIZE,
+ vma->vm_page_prot, pgoff, 0);
if (err == -ENOMEM)
return VM_FAULT_OOM;
if (err)
@@ -2002,23 +1974,25 @@ static int do_file_page(struct mm_struct
* release it when done.
*/
static inline int handle_pte_fault(struct mm_struct *mm,
- struct vm_area_struct * vma, unsigned long address,
- int write_access, pte_t *pte, pmd_t *pmd)
+ struct vm_area_struct *vma, unsigned long address,
+ pte_t *pte, pmd_t *pmd, int write_access)
{
pte_t entry;

entry = *pte;
if (!pte_present(entry)) {
- /*
- * If it truly wasn't present, we know that kswapd
- * and the PTE updates will not touch it later. So
- * drop the lock.
- */
- if (pte_none(entry))
- return do_no_page(mm, vma, address, write_access, pte, pmd);
+ if (pte_none(entry)) {
+ if (!vma->vm_ops || !vma->vm_ops->nopage)
+ return do_anonymous_page(mm, vma, address,
+ pte, pmd, write_access);
+ return do_no_page(mm, vma, address,
+ pte, pmd, write_access);
+ }
if (pte_file(entry))
- return do_file_page(mm, vma, address, write_access, pte, pmd);
- return do_swap_page(mm, vma, address, pte, pmd, entry, write_access);
+ return do_file_page(mm, vma, address,
+ pte, pmd, write_access, entry);
+ return do_swap_page(mm, vma, address,
+ pte, pmd, write_access, entry);
}

if (write_access) {
@@ -2038,7 +2012,7 @@ static inline int handle_pte_fault(struc
/*
* By the time we get here, we already hold the mm semaphore
*/
-int __handle_mm_fault(struct mm_struct *mm, struct vm_area_struct * vma,
+int __handle_mm_fault(struct mm_struct *mm, struct vm_area_struct *vma,
unsigned long address, int write_access)
{
pgd_t *pgd;
@@ -2072,7 +2046,7 @@ int __handle_mm_fault(struct mm_struct *
if (!pte)
goto oom;

- return handle_pte_fault(mm, vma, address, write_access, pte, pmd);
+ return handle_pte_fault(mm, vma, address, pte, pmd, write_access);

oom:
spin_unlock(&mm->page_table_lock);
-
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