Commit 65500d23 authored by Hugh Dickins's avatar Hugh Dickins Committed by Linus Torvalds

[PATCH] 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: default avatarHugh Dickins <hugh@veritas.com>
Signed-off-by: default avatarAndrew Morton <akpm@osdl.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@osdl.org>
parent 7c1fd6b9
......@@ -478,10 +478,12 @@ extern pgprot_t phys_mem_access_prot(struct file *file, unsigned long addr,
#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))
......
......@@ -1520,7 +1520,7 @@ repeat:
page_cache_release(page);
return err;
}
} else {
} else if (vma->vm_flags & VM_NONLINEAR) {
/* No page was found just because we can't read it in now (being
* here implies nonblock != 0), but the page may exist, so set
* the PTE to fault it in later. */
......
......@@ -1212,29 +1212,11 @@ static inline pte_t maybe_mkwrite(pte_t pte, struct vm_area_struct *vma)
return pte;
}
/*
* 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_area_struct * vma, struct page * new_page
* 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 *mm, struct vm_area_struct * vma,
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 *mm, struct vm_area_struct * vma,
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, unsigned long addr,struct vm_area_struc
* 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 * mm,
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 * mm,
/* 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, struct vm_area_struct *vma,
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 vm_area_struct *vma,
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 * mm, struct vm_area_struct * vma,
* 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(struct mm_struct *mm,
/*
* 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 *mm, struct vm_area_struct * vma,
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);
......
......@@ -1201,7 +1201,7 @@ static int shmem_populate(struct vm_area_struct *vma,
page_cache_release(page);
return err;
}
} else {
} else if (vma->vm_flags & VM_NONLINEAR) {
/* No page was found just because we can't read it in
* now (being here implies nonblock != 0), but the page
* may exist, so set the PTE to fault it in later. */
......
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