[PATCH 04/16] page-flags: define PG_locked behavior on compound pages

From: Kirill A. Shutemov
Date: Thu Sep 24 2015 - 10:51:35 EST

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Next in thread: Christoph Lameter: "Re: [PATCH 04/16] 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.

Signed-off-by: Kirill A. Shutemov <kirill.shutemov@xxxxxxxxxxxxxxx>
---
fs/cifs/file.c | 8 ++++----
include/linux/page-flags.h | 2 +-
include/linux/pagemap.h | 25 ++++++++-----------------
mm/filemap.c | 15 +++++++++------
mm/ksm.c | 2 +-
mm/memory-failure.c | 2 +-
mm/migrate.c | 2 +-
mm/shmem.c | 4 ++--
mm/slub.c | 2 ++
mm/swap_state.c | 4 ++--
mm/vmscan.c | 2 +-
11 files changed, 32 insertions(+), 36 deletions(-)

diff --git a/fs/cifs/file.c b/fs/cifs/file.c
index e2a6af1508af..94f81962368c 100644
--- a/fs/cifs/file.c
+++ b/fs/cifs/file.c
@@ -3390,13 +3390,13 @@ 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_KERNEL);

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

@@ -3417,10 +3417,10 @@ 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_KERNEL)) {
- __clear_page_locked(page);
+ __ClearPageLocked(page);
break;
}
list_move_tail(&page->lru, tmplist);
diff --git a/include/linux/page-flags.h b/include/linux/page-flags.h
index 1b3babe5ff69..26102813f0ac 100644
--- a/include/linux/page-flags.h
+++ b/include/linux/page-flags.h
@@ -244,7 +244,7 @@ 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)
diff --git a/include/linux/pagemap.h b/include/linux/pagemap.h
index a6c78e00ea96..3e95fb6a77af 100644
--- a/include/linux/pagemap.h
+++ b/include/linux/pagemap.h
@@ -426,18 +426,9 @@ 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)));
}

@@ -490,9 +481,9 @@ 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);
@@ -511,7 +502,7 @@ 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);
}

/*
@@ -657,17 +648,17 @@ 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;
}

diff --git a/mm/filemap.c b/mm/filemap.c
index 879747a42f6b..6cc2c17a0ca0 100644
--- a/mm/filemap.c
+++ b/mm/filemap.c
@@ -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);
diff --git a/mm/ksm.c b/mm/ksm.c
index 7ee101eaacdf..bc7be0ee2080 100644
--- a/mm/ksm.c
+++ b/mm/ksm.c
@@ -1884,7 +1884,7 @@ 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;
diff --git a/mm/memory-failure.c b/mm/memory-failure.c
index 8424b64711ac..5b965e27aaae 100644
--- a/mm/memory-failure.c
+++ b/mm/memory-failure.c
@@ -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.
diff --git a/mm/migrate.c b/mm/migrate.c
index 94961f4654b7..bd19c7339f8c 100644
--- a/mm/migrate.c
+++ b/mm/migrate.c
@@ -1765,7 +1765,7 @@ 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: */
diff --git a/mm/shmem.c b/mm/shmem.c
index 48ce82926d93..1425863f5322 100644
--- a/mm/shmem.c
+++ b/mm/shmem.c
@@ -996,7 +996,7 @@ 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);
@@ -1188,7 +1188,7 @@ repeat:
}

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

diff --git a/mm/slub.c b/mm/slub.c
index 999673c386d6..bda33cc4f7e4 100644
--- a/mm/slub.c
+++ b/mm/slub.c
@@ -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);
}

diff --git a/mm/swap_state.c b/mm/swap_state.c
index d504adb7fa5f..d783872d746c 100644
--- a/mm/swap_state.c
+++ b/mm/swap_state.c
@@ -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.
diff --git a/mm/vmscan.c b/mm/vmscan.c
index 38d04810e0ee..a0b8f08e6f62 100644
--- a/mm/vmscan.c
+++ b/mm/vmscan.c
@@ -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++;

--
2.5.1

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Next message: Kirill A. Shutemov: "[PATCH 13/16] page-flags: define PG_uncached behavior on compound pages"
Previous message: Kirill A. Shutemov: "[PATCH 10/16] page-flags: define PG_swapbacked behavior on compound pages"
In reply to: Kirill A. Shutemov: "[PATCH 10/16] page-flags: define PG_swapbacked behavior on compound pages"
Next in thread: Christoph Lameter: "Re: [PATCH 04/16] page-flags: define PG_locked behavior on compound pages"
Messages sorted by: [ date ] [ thread ] [ subject ] [ author ]