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

From: Mateusz Krawczuk <[email-masked]>
Date: Fri, 27 Mar 2015 16:13:08 +0100

Hi!

This patch breaks build of linux next since 2015-03-25 on arm using 
exynos_defconfig with arm-linux-gnueabi-linaro_4.7.4-2014.04, 
arm-linux-gnueabi-linaro_4.8.3-2014.04 and 
arm-linux-gnueabi-4.7.3-12ubuntu1(from ubuntu 14.04 lts). Compiler shows 
this error message:
mm/migrate.c: In function ‘migrate_pages’:
mm/migrate.c:1148:1: internal compiler error: in push_minipool_fix, at 
config/arm/arm.c:13500
Please submit a full bug report,
with preprocessed source if appropriate.
See <file:///usr/share/doc/gcc-4.7/README.Bugs> for instructions.

It builds fine with arm-linux-gnueabi-linaro_4.9.1-2014.07.

Best Regards
Mateusz Krawczuk
Samsung R&D Institute Poland

  dniu 19.03.2015 o 18:08, Kirill A. Shutemov pisze:
> 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 get rid of custom helprer functions --
> __set_page_locked() and __clear_page_locked(). They 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 <[email-masked]>
> ---
>   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                |  4 ++--
>   mm/zswap.c                 |  4 ++--
>   12 files changed, 35 insertions(+), 39 deletions(-)
>
> diff --git a/fs/cifs/file.c b/fs/cifs/file.c
> index ca30c391a894..b9fd85dfee9b 100644
> --- a/fs/cifs/file.c
> +++ b/fs/cifs/file.c
> @@ -3413,13 +3413,13 @@ 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;
>   	}
>
> @@ -3440,10 +3440,10 @@ 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 32ea62c0ad30..10bdde20b14c 100644
> --- a/include/linux/page-flags.h
> +++ b/include/linux/page-flags.h
> @@ -269,7 +269,7 @@ static inline struct page *compound_head_fast(struct page *page)
>   	return page;
>   }
>
> -TESTPAGEFLAG(Locked, locked, ANY)
> +__PAGEFLAG(Locked, locked, NO_TAIL)
>   PAGEFLAG(Error, error, ANY) TESTCLEARFLAG(Error, error, ANY)
>   PAGEFLAG(Referenced, referenced, ANY) TESTCLEARFLAG(Referenced, referenced, ANY)
>   	__SETPAGEFLAG(Referenced, referenced, ANY)
> diff --git a/include/linux/pagemap.h b/include/linux/pagemap.h
> index 4b3736f7065c..7c3790764795 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);
>   }
>
>   /*
> @@ -656,17 +647,17 @@ 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 12548d03c11d..467768d4263b 100644
> --- a/mm/filemap.c
> +++ b/mm/filemap.c
> @@ -615,11 +615,11 @@ 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
> @@ -742,6 +742,7 @@ 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();
> @@ -806,18 +807,20 @@ 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 4162dce2eb44..23138e99a531 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 d487f8dc6d39..399eee44d13d 100644
> --- a/mm/memory-failure.c
> +++ b/mm/memory-failure.c
> @@ -1136,7 +1136,7 @@ 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 6aa9a4222ea9..114602a68111 100644
> --- a/mm/migrate.c
> +++ b/mm/migrate.c
> @@ -1734,7 +1734,7 @@ 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 80b360c7bcd1..2e2b943c8e62 100644
> --- a/mm/shmem.c
> +++ b/mm/shmem.c
> @@ -981,7 +981,7 @@ 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);
> @@ -1173,7 +1173,7 @@ 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 2584d4ff02eb..f33ae2b7a5e7 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 405923f77334..d1c4a25b4362 100644
> --- a/mm/swap_state.c
> +++ b/mm/swap_state.c
> @@ -357,7 +357,7 @@ 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)) {
> @@ -371,7 +371,7 @@ 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 260c413d39cd..dc6cd51577a6 100644
> --- a/mm/vmscan.c
> +++ b/mm/vmscan.c
> @@ -1062,7 +1062,7 @@ unmap:
>   				VM_BUG_ON_PAGE(PageSwapCache(page), page);
>   				if (!page_freeze_refs(page, 1))
>   					goto keep_locked;
> -				__clear_page_locked(page);
> +				__ClearPageLocked(page);
>   				count_vm_event(PGLAZYFREED);
>   				goto free_it;
>   			}
> @@ -1174,7 +1174,7 @@ unmap:
>   		 * 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++;
>
> diff --git a/mm/zswap.c b/mm/zswap.c
> index 4249e82ff934..f8583f1fc938 100644
> --- a/mm/zswap.c
> +++ b/mm/zswap.c
> @@ -490,7 +490,7 @@ static int zswap_get_swap_cache_page(swp_entry_t entry,
>   		}
>
>   		/* 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)) {
> @@ -501,7 +501,7 @@ static int zswap_get_swap_cache_page(swp_entry_t entry,
>   		}
>   		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.
>

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