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page-flags: define PG_locked behavior on compound pages
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lock_page() must operate on the whole compound page.  It doesn't make
much sense to lock part of compound page.  Change code to use head
page's PG_locked, if tail page is passed.

This patch also gets rid of custom helper functions --
__set_page_locked() and __clear_page_locked().  They are replaced with
helpers generated by __SETPAGEFLAG/__CLEARPAGEFLAG.  Tail pages to these
helper would trigger VM_BUG_ON().

SLUB uses PG_locked as a bit spin locked.  IIUC, tail pages should never
appear there.  VM_BUG_ON() is added to make sure that this assumption is
correct.

[[email protected]: fix fs/cifs/file.c]
Signed-off-by: Kirill A. Shutemov <[email protected]>
Cc: Andrea Arcangeli <[email protected]>
Cc: Hugh Dickins <[email protected]>
Cc: Dave Hansen <[email protected]>
Cc: Mel Gorman <[email protected]>
Cc: Rik van Riel <[email protected]>
Cc: Vlastimil Babka <[email protected]>
Cc: Christoph Lameter <[email protected]>
Cc: Naoya Horiguchi <[email protected]>
Cc: Steve Capper <[email protected]>
Cc: "Aneesh Kumar K.V" <[email protected]>
Cc: Johannes Weiner <[email protected]>
Cc: Michal Hocko <[email protected]>
Cc: Jerome Marchand <[email protected]>
Cc: Jérôme Glisse <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>
Signed-off-by: Linus Torvalds <[email protected]>
kiryl authored and torvalds committed Jan 16, 2016

Verified

This commit was signed with the committer’s verified signature.
Duhemm Martin Duhem
1 parent 95ad975 commit 48c935a
Showing 11 changed files with 32 additions and 36 deletions.
8 changes: 4 additions & 4 deletions fs/cifs/file.c
Original file line number Diff line number Diff line change
@@ -3391,13 +3391,13 @@ readpages_get_pages(struct address_space *mapping, struct list_head *page_list,
* should have access to this page, we're safe to simply set
* PG_locked without checking it first.
*/
__set_page_locked(page);
__SetPageLocked(page);
rc = add_to_page_cache_locked(page, mapping,
page->index, gfp);

/* give up if we can't stick it in the cache */
if (rc) {
__clear_page_locked(page);
__ClearPageLocked(page);
return rc;
}

@@ -3418,9 +3418,9 @@ readpages_get_pages(struct address_space *mapping, struct list_head *page_list,
if (*bytes + PAGE_CACHE_SIZE > rsize)
break;

__set_page_locked(page);
__SetPageLocked(page);
if (add_to_page_cache_locked(page, mapping, page->index, gfp)) {
__clear_page_locked(page);
__ClearPageLocked(page);
break;
}
list_move_tail(&page->lru, tmplist);
2 changes: 1 addition & 1 deletion include/linux/page-flags.h
Original file line number Diff line number Diff line change
@@ -256,7 +256,7 @@ static inline int __TestClearPage##uname(struct page *page) { return 0; }
#define TESTSCFLAG_FALSE(uname) \
TESTSETFLAG_FALSE(uname) TESTCLEARFLAG_FALSE(uname)

TESTPAGEFLAG(Locked, locked, PF_ANY)
__PAGEFLAG(Locked, locked, PF_NO_TAIL)
PAGEFLAG(Error, error, PF_ANY) TESTCLEARFLAG(Error, error, PF_ANY)
PAGEFLAG(Referenced, referenced, PF_ANY) TESTCLEARFLAG(Referenced, referenced, PF_ANY)
__SETPAGEFLAG(Referenced, referenced, PF_ANY)
25 changes: 8 additions & 17 deletions include/linux/pagemap.h
Original file line number Diff line number Diff line change
@@ -433,18 +433,9 @@ extern int __lock_page_or_retry(struct page *page, struct mm_struct *mm,
unsigned int flags);
extern void unlock_page(struct page *page);

static inline void __set_page_locked(struct page *page)
{
__set_bit(PG_locked, &page->flags);
}

static inline void __clear_page_locked(struct page *page)
{
__clear_bit(PG_locked, &page->flags);
}

static inline int trylock_page(struct page *page)
{
page = compound_head(page);
return (likely(!test_and_set_bit_lock(PG_locked, &page->flags)));
}

@@ -497,9 +488,9 @@ extern int wait_on_page_bit_killable_timeout(struct page *page,

static inline int wait_on_page_locked_killable(struct page *page)
{
if (PageLocked(page))
return wait_on_page_bit_killable(page, PG_locked);
return 0;
if (!PageLocked(page))
return 0;
return wait_on_page_bit_killable(compound_head(page), PG_locked);
}

extern wait_queue_head_t *page_waitqueue(struct page *page);
@@ -518,7 +509,7 @@ static inline void wake_up_page(struct page *page, int bit)
static inline void wait_on_page_locked(struct page *page)
{
if (PageLocked(page))
wait_on_page_bit(page, PG_locked);
wait_on_page_bit(compound_head(page), PG_locked);
}

/*
@@ -664,17 +655,17 @@ int replace_page_cache_page(struct page *old, struct page *new, gfp_t gfp_mask);

/*
* Like add_to_page_cache_locked, but used to add newly allocated pages:
* the page is new, so we can just run __set_page_locked() against it.
* the page is new, so we can just run __SetPageLocked() against it.
*/
static inline int add_to_page_cache(struct page *page,
struct address_space *mapping, pgoff_t offset, gfp_t gfp_mask)
{
int error;

__set_page_locked(page);
__SetPageLocked(page);
error = add_to_page_cache_locked(page, mapping, offset, gfp_mask);
if (unlikely(error))
__clear_page_locked(page);
__ClearPageLocked(page);
return error;
}

15 changes: 9 additions & 6 deletions mm/filemap.c
Original file line number Diff line number Diff line change
@@ -682,11 +682,11 @@ int add_to_page_cache_lru(struct page *page, struct address_space *mapping,
void *shadow = NULL;
int ret;

__set_page_locked(page);
__SetPageLocked(page);
ret = __add_to_page_cache_locked(page, mapping, offset,
gfp_mask, &shadow);
if (unlikely(ret))
__clear_page_locked(page);
__ClearPageLocked(page);
else {
/*
* The page might have been evicted from cache only
@@ -809,6 +809,7 @@ EXPORT_SYMBOL_GPL(add_page_wait_queue);
*/
void unlock_page(struct page *page)
{
page = compound_head(page);
VM_BUG_ON_PAGE(!PageLocked(page), page);
clear_bit_unlock(PG_locked, &page->flags);
smp_mb__after_atomic();
@@ -873,18 +874,20 @@ EXPORT_SYMBOL_GPL(page_endio);
*/
void __lock_page(struct page *page)
{
DEFINE_WAIT_BIT(wait, &page->flags, PG_locked);
struct page *page_head = compound_head(page);
DEFINE_WAIT_BIT(wait, &page_head->flags, PG_locked);

__wait_on_bit_lock(page_waitqueue(page), &wait, bit_wait_io,
__wait_on_bit_lock(page_waitqueue(page_head), &wait, bit_wait_io,
TASK_UNINTERRUPTIBLE);
}
EXPORT_SYMBOL(__lock_page);

int __lock_page_killable(struct page *page)
{
DEFINE_WAIT_BIT(wait, &page->flags, PG_locked);
struct page *page_head = compound_head(page);
DEFINE_WAIT_BIT(wait, &page_head->flags, PG_locked);

return __wait_on_bit_lock(page_waitqueue(page), &wait,
return __wait_on_bit_lock(page_waitqueue(page_head), &wait,
bit_wait_io, TASK_KILLABLE);
}
EXPORT_SYMBOL_GPL(__lock_page_killable);
2 changes: 1 addition & 1 deletion mm/ksm.c
Original file line number Diff line number Diff line change
@@ -1899,7 +1899,7 @@ struct page *ksm_might_need_to_copy(struct page *page,

SetPageDirty(new_page);
__SetPageUptodate(new_page);
__set_page_locked(new_page);
__SetPageLocked(new_page);
}

return new_page;
2 changes: 1 addition & 1 deletion mm/memory-failure.c
Original file line number Diff line number Diff line change
@@ -1166,7 +1166,7 @@ int memory_failure(unsigned long pfn, int trapno, int flags)
/*
* We ignore non-LRU pages for good reasons.
* - PG_locked is only well defined for LRU pages and a few others
* - to avoid races with __set_page_locked()
* - to avoid races with __SetPageLocked()
* - to avoid races with __SetPageSlab*() (and more non-atomic ops)
* The check (unnecessarily) ignores LRU pages being isolated and
* walked by the page reclaim code, however that's not a big loss.
2 changes: 1 addition & 1 deletion mm/migrate.c
Original file line number Diff line number Diff line change
@@ -1767,7 +1767,7 @@ int migrate_misplaced_transhuge_page(struct mm_struct *mm,
flush_tlb_range(vma, mmun_start, mmun_end);

/* Prepare a page as a migration target */
__set_page_locked(new_page);
__SetPageLocked(new_page);
SetPageSwapBacked(new_page);

/* anon mapping, we can simply copy page->mapping to the new page: */
4 changes: 2 additions & 2 deletions mm/shmem.c
Original file line number Diff line number Diff line change
@@ -1085,7 +1085,7 @@ static int shmem_replace_page(struct page **pagep, gfp_t gfp,
copy_highpage(newpage, oldpage);
flush_dcache_page(newpage);

__set_page_locked(newpage);
__SetPageLocked(newpage);
SetPageUptodate(newpage);
SetPageSwapBacked(newpage);
set_page_private(newpage, swap_index);
@@ -1277,7 +1277,7 @@ static int shmem_getpage_gfp(struct inode *inode, pgoff_t index,
}

__SetPageSwapBacked(page);
__set_page_locked(page);
__SetPageLocked(page);
if (sgp == SGP_WRITE)
__SetPageReferenced(page);

2 changes: 2 additions & 0 deletions mm/slub.c
Original file line number Diff line number Diff line change
@@ -338,11 +338,13 @@ static inline int oo_objects(struct kmem_cache_order_objects x)
*/
static __always_inline void slab_lock(struct page *page)
{
VM_BUG_ON_PAGE(PageTail(page), page);
bit_spin_lock(PG_locked, &page->flags);
}

static __always_inline void slab_unlock(struct page *page)
{
VM_BUG_ON_PAGE(PageTail(page), page);
__bit_spin_unlock(PG_locked, &page->flags);
}

4 changes: 2 additions & 2 deletions mm/swap_state.c
Original file line number Diff line number Diff line change
@@ -353,7 +353,7 @@ struct page *__read_swap_cache_async(swp_entry_t entry, gfp_t gfp_mask,
}

/* May fail (-ENOMEM) if radix-tree node allocation failed. */
__set_page_locked(new_page);
__SetPageLocked(new_page);
SetPageSwapBacked(new_page);
err = __add_to_swap_cache(new_page, entry);
if (likely(!err)) {
@@ -367,7 +367,7 @@ struct page *__read_swap_cache_async(swp_entry_t entry, gfp_t gfp_mask,
}
radix_tree_preload_end();
ClearPageSwapBacked(new_page);
__clear_page_locked(new_page);
__ClearPageLocked(new_page);
/*
* add_to_swap_cache() doesn't return -EEXIST, so we can safely
* clear SWAP_HAS_CACHE flag.
2 changes: 1 addition & 1 deletion mm/vmscan.c
Original file line number Diff line number Diff line change
@@ -1184,7 +1184,7 @@ static unsigned long shrink_page_list(struct list_head *page_list,
* we obviously don't have to worry about waking up a process
* waiting on the page lock, because there are no references.
*/
__clear_page_locked(page);
__ClearPageLocked(page);
free_it:
nr_reclaimed++;

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