Skip to content

Commit

Permalink
mm: introduce do_shared_fault() and drop do_fault()
Browse files Browse the repository at this point in the history 
Introduce do_shared_fault().  The function does what do_fault() does for
write faults to shared mappings

Unlike do_fault(), do_shared_fault() is relatively clean and
straight-forward.

Old do_fault() is not needed anymore.  Let it die.

[lliubbo@gmail.com: fix NULL pointer dereference]
Signed-off-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
Cc: Mel Gorman <mgorman@suse.de>
Cc: Rik van Riel <riel@redhat.com>
Cc: Andi Kleen <ak@linux.intel.com>
Cc: Matthew Wilcox <matthew.r.wilcox@intel.com>
Cc: Dave Hansen <dave.hansen@linux.intel.com>
Cc: Naoya Horiguchi <n-horiguchi@ah.jp.nec.com>
Signed-off-by: Bob Liu <bob.liu@oracle.com>
Cc: Sasha Levin <sasha.levin@oracle.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
  • Loading branch information
Kirill A. Shutemov authored and Linus Torvalds committed Apr 3, 2014
1 parent ec47c3b commit f0c6d4d
Showing 1 changed file with 62 additions and 164 deletions.
226 changes: 62 additions & 164 deletions mm/memory.c
View file
Original file line number Diff line number Diff line change
Expand Up @@ -2748,7 +2748,7 @@ static int do_wp_page(struct mm_struct *mm, struct vm_area_struct *vma,
* bit after it clear all dirty ptes, but before a racing
* do_wp_page installs a dirty pte.
*
* do_fault is protected similarly.
* do_shared_fault is protected similarly.
*/
if (!page_mkwrite) {
wait_on_page_locked(dirty_page);
Expand Down Expand Up @@ -3410,188 +3410,86 @@ static int do_cow_fault(struct mm_struct *mm, struct vm_area_struct *vma,
return ret;
}

/*
* do_fault() tries to create a new page mapping. It aggressively
* tries to share with existing pages, but makes a separate copy if
* the FAULT_FLAG_WRITE is set in the flags parameter in order to avoid
* the next page fault.
*
* As this is called only for pages that do not currently exist, we
* do not need to flush old virtual caches or the TLB.
*
* We enter with non-exclusive mmap_sem (to exclude vma changes,
* but allow concurrent faults), and pte neither mapped nor locked.
* We return with mmap_sem still held, but pte unmapped and unlocked.
*/
static int do_fault(struct mm_struct *mm, struct vm_area_struct *vma,
static int do_shared_fault(struct mm_struct *mm, struct vm_area_struct *vma,
unsigned long address, pmd_t *pmd,
pgoff_t pgoff, unsigned int flags, pte_t orig_pte)
{
pte_t *page_table;
struct page *fault_page;
struct address_space *mapping;
spinlock_t *ptl;
struct page *page, *fault_page;
struct page *cow_page;
pte_t entry;
int anon = 0;
struct page *dirty_page = NULL;
int ret;
int page_mkwrite = 0;

/*
* If we do COW later, allocate page befor taking lock_page()
* on the file cache page. This will reduce lock holding time.
*/
if ((flags & FAULT_FLAG_WRITE) && !(vma->vm_flags & VM_SHARED)) {

if (unlikely(anon_vma_prepare(vma)))
return VM_FAULT_OOM;

cow_page = alloc_page_vma(GFP_HIGHUSER_MOVABLE, vma, address);
if (!cow_page)
return VM_FAULT_OOM;

if (mem_cgroup_newpage_charge(cow_page, mm, GFP_KERNEL)) {
page_cache_release(cow_page);
return VM_FAULT_OOM;
}
} else
cow_page = NULL;
pte_t entry, *pte;
int dirtied = 0;
struct vm_fault vmf;
int ret, tmp;

ret = __do_fault(vma, address, pgoff, flags, &fault_page);
if (unlikely(ret & (VM_FAULT_ERROR | VM_FAULT_NOPAGE | VM_FAULT_RETRY)))
goto uncharge_out;
return ret;

/*
* Should we do an early C-O-W break?
* Check if the backing address space wants to know that the page is
* about to become writable
*/
page = fault_page;
if (flags & FAULT_FLAG_WRITE) {
if (!(vma->vm_flags & VM_SHARED)) {
page = cow_page;
anon = 1;
copy_user_highpage(page, fault_page, address, vma);
__SetPageUptodate(page);
} else {
/*
* If the page will be shareable, see if the backing
* address space wants to know that the page is about
* to become writable
*/
if (vma->vm_ops->page_mkwrite) {
struct vm_fault vmf;
int tmp;

vmf.virtual_address =
(void __user *)(address & PAGE_MASK);
vmf.pgoff = pgoff;
vmf.flags = flags;
vmf.page = fault_page;

unlock_page(page);
vmf.flags = FAULT_FLAG_WRITE|FAULT_FLAG_MKWRITE;
tmp = vma->vm_ops->page_mkwrite(vma, &vmf);
if (unlikely(tmp &
(VM_FAULT_ERROR | VM_FAULT_NOPAGE))) {
ret = tmp;
goto unwritable_page;
}
if (unlikely(!(tmp & VM_FAULT_LOCKED))) {
lock_page(page);
if (!page->mapping) {
ret = 0; /* retry the fault */
unlock_page(page);
goto unwritable_page;
}
} else
VM_BUG_ON_PAGE(!PageLocked(page), page);
page_mkwrite = 1;
}
}
if (!vma->vm_ops->page_mkwrite)
goto set_pte;

}
unlock_page(fault_page);
vmf.virtual_address = (void __user *)(address & PAGE_MASK);
vmf.pgoff = pgoff;
vmf.flags = FAULT_FLAG_WRITE|FAULT_FLAG_MKWRITE;
vmf.page = fault_page;

page_table = pte_offset_map_lock(mm, pmd, address, &ptl);
tmp = vma->vm_ops->page_mkwrite(vma, &vmf);
if (unlikely(tmp & (VM_FAULT_ERROR | VM_FAULT_NOPAGE))) {
page_cache_release(fault_page);
return tmp;
}

/*
* This silly early PAGE_DIRTY setting removes a race
* due to the bad i386 page protection. But it's valid
* for other architectures too.
*
* Note that if FAULT_FLAG_WRITE is set, we either now have
* an exclusive copy of the page, or this is a shared mapping,
* so we can make it writable and dirty to avoid having to
* handle that later.
*/
/* Only go through if we didn't race with anybody else... */
if (likely(pte_same(*page_table, orig_pte))) {
flush_icache_page(vma, page);
entry = mk_pte(page, vma->vm_page_prot);
if (flags & FAULT_FLAG_WRITE)
entry = maybe_mkwrite(pte_mkdirty(entry), vma);
else if (pte_file(orig_pte) && pte_file_soft_dirty(orig_pte))
pte_mksoft_dirty(entry);
if (anon) {
inc_mm_counter_fast(mm, MM_ANONPAGES);
page_add_new_anon_rmap(page, vma, address);
} else {
inc_mm_counter_fast(mm, MM_FILEPAGES);
page_add_file_rmap(page);
if (flags & FAULT_FLAG_WRITE) {
dirty_page = page;
get_page(dirty_page);
}
if (unlikely(!(tmp & VM_FAULT_LOCKED))) {
lock_page(fault_page);
if (!fault_page->mapping) {
unlock_page(fault_page);
page_cache_release(fault_page);
return 0; /* retry */
}
set_pte_at(mm, address, page_table, entry);

/* no need to invalidate: a not-present page won't be cached */
update_mmu_cache(vma, address, page_table);
} else {
if (cow_page)
mem_cgroup_uncharge_page(cow_page);
if (anon)
page_cache_release(page);
else
anon = 1; /* no anon but release faulted_page */
} else
VM_BUG_ON_PAGE(!PageLocked(fault_page), fault_page);
set_pte:
pte = pte_offset_map_lock(mm, pmd, address, &ptl);
if (unlikely(!pte_same(*pte, orig_pte))) {
pte_unmap_unlock(pte, ptl);
unlock_page(fault_page);
page_cache_release(fault_page);
return ret;
}

pte_unmap_unlock(page_table, ptl);

if (dirty_page) {
struct address_space *mapping = page->mapping;
int dirtied = 0;
flush_icache_page(vma, fault_page);
entry = mk_pte(fault_page, vma->vm_page_prot);
entry = maybe_mkwrite(pte_mkdirty(entry), vma);
inc_mm_counter_fast(mm, MM_FILEPAGES);
page_add_file_rmap(fault_page);
set_pte_at(mm, address, pte, entry);

if (set_page_dirty(dirty_page))
dirtied = 1;
unlock_page(dirty_page);
put_page(dirty_page);
if ((dirtied || page_mkwrite) && mapping) {
/*
* Some device drivers do not set page.mapping but still
* dirty their pages
*/
balance_dirty_pages_ratelimited(mapping);
}
/* no need to invalidate: a not-present page won't be cached */
update_mmu_cache(vma, address, pte);
pte_unmap_unlock(pte, ptl);

/* file_update_time outside page_lock */
if (vma->vm_file && !page_mkwrite)
file_update_time(vma->vm_file);
} else {
unlock_page(fault_page);
if (anon)
page_cache_release(fault_page);
if (set_page_dirty(fault_page))
dirtied = 1;
mapping = fault_page->mapping;
unlock_page(fault_page);
if ((dirtied || vma->vm_ops->page_mkwrite) && mapping) {
/*
* Some device drivers do not set page.mapping but still
* dirty their pages
*/
balance_dirty_pages_ratelimited(mapping);
}

return ret;
/* file_update_time outside page_lock */
if (vma->vm_file && !vma->vm_ops->page_mkwrite)
file_update_time(vma->vm_file);

unwritable_page:
page_cache_release(page);
return ret;
uncharge_out:
/* fs's fault handler get error */
if (cow_page) {
mem_cgroup_uncharge_page(cow_page);
page_cache_release(cow_page);
}
return ret;
}

Expand All @@ -3609,7 +3507,7 @@ static int do_linear_fault(struct mm_struct *mm, struct vm_area_struct *vma,
if (!(vma->vm_flags & VM_SHARED))
return do_cow_fault(mm, vma, address, pmd, pgoff, flags,
orig_pte);
return do_fault(mm, vma, address, pmd, pgoff, flags, orig_pte);
return do_shared_fault(mm, vma, address, pmd, pgoff, flags, orig_pte);
}

/*
Expand Down Expand Up @@ -3647,7 +3545,7 @@ static int do_nonlinear_fault(struct mm_struct *mm, struct vm_area_struct *vma,
if (!(vma->vm_flags & VM_SHARED))
return do_cow_fault(mm, vma, address, pmd, pgoff, flags,
orig_pte);
return do_fault(mm, vma, address, pmd, pgoff, flags, orig_pte);
return do_shared_fault(mm, vma, address, pmd, pgoff, flags, orig_pte);
}

static int numa_migrate_prep(struct page *page, struct vm_area_struct *vma,
Expand Down

0 comments on commit f0c6d4d

Please sign in to comment.