diff mbox series

[v10,22/33] mm/filemap: Add __folio_lock_or_retry

Message ID 20210511214735.1836149-23-willy@infradead.org (mailing list archive)
State New
Headers show
Series Memory folios | expand

Commit Message

Matthew Wilcox (Oracle) May 11, 2021, 9:47 p.m. UTC
Convert __lock_page_or_retry() to __folio_lock_or_retry().  This actually
saves 4 bytes in the only caller of lock_page_or_retry() (due to better
register allocation) and saves the 20 byte cost of calling page_folio()
in __folio_lock_or_retry() for a total saving of 24 bytes.

Signed-off-by: Matthew Wilcox (Oracle) <willy@infradead.org>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Acked-by: Jeff Layton <jlayton@kernel.org>
---
 include/linux/pagemap.h |  9 ++++++---
 mm/filemap.c            | 10 ++++------
 mm/memory.c             |  8 ++++----
 3 files changed, 14 insertions(+), 13 deletions(-)

Comments

Vlastimil Babka May 18, 2021, 10:38 a.m. UTC | #1
On 5/11/21 11:47 PM, Matthew Wilcox (Oracle) wrote:
> Convert __lock_page_or_retry() to __folio_lock_or_retry().  This actually
> saves 4 bytes in the only caller of lock_page_or_retry() (due to better
> register allocation) and saves the 20 byte cost of calling page_folio()
> in __folio_lock_or_retry() for a total saving of 24 bytes.
> 
> Signed-off-by: Matthew Wilcox (Oracle) <willy@infradead.org>
> Reviewed-by: Christoph Hellwig <hch@lst.de>
> Acked-by: Jeff Layton <jlayton@kernel.org>
> ---
>  include/linux/pagemap.h |  9 ++++++---
>  mm/filemap.c            | 10 ++++------
>  mm/memory.c             |  8 ++++----
>  3 files changed, 14 insertions(+), 13 deletions(-)
> 
> diff --git a/include/linux/pagemap.h b/include/linux/pagemap.h
> index 41224e4ca8cc..21e394964288 100644
> --- a/include/linux/pagemap.h
> +++ b/include/linux/pagemap.h
> @@ -640,7 +640,7 @@ static inline bool wake_page_match(struct wait_page_queue *wait_page,
>  
>  void __folio_lock(struct folio *folio);
>  int __folio_lock_killable(struct folio *folio);
> -extern int __lock_page_or_retry(struct page *page, struct mm_struct *mm,
> +int __folio_lock_or_retry(struct folio *folio, struct mm_struct *mm,
>  				unsigned int flags);
>  void unlock_page(struct page *page);
>  void folio_unlock(struct folio *folio);
> @@ -701,13 +701,16 @@ static inline int lock_page_killable(struct page *page)
>   * caller indicated that it can handle a retry.
>   *
>   * Return value and mmap_lock implications depend on flags; see
> - * __lock_page_or_retry().
> + * __folio_lock_or_retry().
>   */
>  static inline int lock_page_or_retry(struct page *page, struct mm_struct *mm,
>  				     unsigned int flags)
>  {
> +	struct folio *folio;
>  	might_sleep();
> -	return trylock_page(page) || __lock_page_or_retry(page, mm, flags);
> +
> +	folio = page_folio(page);
> +	return folio_trylock(folio) || __folio_lock_or_retry(folio, mm, flags);
>  }
>  
>  /*
> diff --git a/mm/filemap.c b/mm/filemap.c
> index 67334eb3fd94..28bf50041671 100644
> --- a/mm/filemap.c
> +++ b/mm/filemap.c
> @@ -1623,20 +1623,18 @@ static int __folio_lock_async(struct folio *folio, struct wait_page_queue *wait)
>  
>  /*
>   * Return values:
> - * 1 - page is locked; mmap_lock is still held.
> - * 0 - page is not locked.
> + * 1 - folio is locked; mmap_lock is still held.
> + * 0 - folio is not locked.
>   *     mmap_lock has been released (mmap_read_unlock(), unless flags had both
>   *     FAULT_FLAG_ALLOW_RETRY and FAULT_FLAG_RETRY_NOWAIT set, in
>   *     which case mmap_lock is still held.
>   *
>   * If neither ALLOW_RETRY nor KILLABLE are set, will always return 1
> - * with the page locked and the mmap_lock unperturbed.
> + * with the folio locked and the mmap_lock unperturbed.
>   */
> -int __lock_page_or_retry(struct page *page, struct mm_struct *mm,
> +int __folio_lock_or_retry(struct folio *folio, struct mm_struct *mm,
>  			 unsigned int flags)
>  {
> -	struct folio *folio = page_folio(page);
> -
>  	if (fault_flag_allow_retry_first(flags)) {
>  		/*
>  		 * CAUTION! In this case, mmap_lock is not released

A bit later in this branch, 'page' is accessed, but it no longer exists. And
thus as expected, it doesn't compile. Assuming it's fixed later, but
bisectability etc...

> diff --git a/mm/memory.c b/mm/memory.c
> index 86ba6c1f6821..fc3f50d0702c 100644
> --- a/mm/memory.c
> +++ b/mm/memory.c
> @@ -4065,7 +4065,7 @@ static vm_fault_t do_shared_fault(struct vm_fault *vmf)
>   * We enter with non-exclusive mmap_lock (to exclude vma changes,
>   * but allow concurrent faults).
>   * The mmap_lock may have been released depending on flags and our
> - * return value.  See filemap_fault() and __lock_page_or_retry().
> + * return value.  See filemap_fault() and __folio_lock_or_retry().
>   * If mmap_lock is released, vma may become invalid (for example
>   * by other thread calling munmap()).
>   */
> @@ -4307,7 +4307,7 @@ static vm_fault_t wp_huge_pud(struct vm_fault *vmf, pud_t orig_pud)
>   * concurrent faults).
>   *
>   * The mmap_lock may have been released depending on flags and our return value.
> - * See filemap_fault() and __lock_page_or_retry().
> + * See filemap_fault() and __folio_lock_or_retry().
>   */
>  static vm_fault_t handle_pte_fault(struct vm_fault *vmf)
>  {
> @@ -4411,7 +4411,7 @@ static vm_fault_t handle_pte_fault(struct vm_fault *vmf)
>   * By the time we get here, we already hold the mm semaphore
>   *
>   * The mmap_lock may have been released depending on flags and our
> - * return value.  See filemap_fault() and __lock_page_or_retry().
> + * return value.  See filemap_fault() and __folio_lock_or_retry().
>   */
>  static vm_fault_t __handle_mm_fault(struct vm_area_struct *vma,
>  		unsigned long address, unsigned int flags)
> @@ -4567,7 +4567,7 @@ static inline void mm_account_fault(struct pt_regs *regs,
>   * By the time we get here, we already hold the mm semaphore
>   *
>   * The mmap_lock may have been released depending on flags and our
> - * return value.  See filemap_fault() and __lock_page_or_retry().
> + * return value.  See filemap_fault() and __folio_lock_or_retry().
>   */
>  vm_fault_t handle_mm_fault(struct vm_area_struct *vma, unsigned long address,
>  			   unsigned int flags, struct pt_regs *regs)
>
Vlastimil Babka May 18, 2021, 10:45 a.m. UTC | #2
On 5/18/21 12:38 PM, Vlastimil Babka wrote:
>> --- a/mm/filemap.c
>> +++ b/mm/filemap.c
>> @@ -1623,20 +1623,18 @@ static int __folio_lock_async(struct folio *folio, struct wait_page_queue *wait)
>>  
>>  /*
>>   * Return values:
>> - * 1 - page is locked; mmap_lock is still held.
>> - * 0 - page is not locked.
>> + * 1 - folio is locked; mmap_lock is still held.
>> + * 0 - folio is not locked.
>>   *     mmap_lock has been released (mmap_read_unlock(), unless flags had both
>>   *     FAULT_FLAG_ALLOW_RETRY and FAULT_FLAG_RETRY_NOWAIT set, in
>>   *     which case mmap_lock is still held.
>>   *
>>   * If neither ALLOW_RETRY nor KILLABLE are set, will always return 1
>> - * with the page locked and the mmap_lock unperturbed.
>> + * with the folio locked and the mmap_lock unperturbed.
>>   */
>> -int __lock_page_or_retry(struct page *page, struct mm_struct *mm,
>> +int __folio_lock_or_retry(struct folio *folio, struct mm_struct *mm,
>>  			 unsigned int flags)
>>  {
>> -	struct folio *folio = page_folio(page);
>> -
>>  	if (fault_flag_allow_retry_first(flags)) {
>>  		/*
>>  		 * CAUTION! In this case, mmap_lock is not released
> 
> A bit later in this branch, 'page' is accessed, but it no longer exists. And
> thus as expected, it doesn't compile. Assuming it's fixed later, but
> bisectability etc...

Also, the switch from 'page' to &folio->page in there should probably have been
done already in "[PATCH v10 20/33] mm/filemap: Add folio_lock_killable", not in
this patch?
Matthew Wilcox (Oracle) May 18, 2021, 1:35 p.m. UTC | #3
On Tue, May 18, 2021 at 12:38:46PM +0200, Vlastimil Babka wrote:
> > -int __lock_page_or_retry(struct page *page, struct mm_struct *mm,
> > +int __folio_lock_or_retry(struct folio *folio, struct mm_struct *mm,
> >  			 unsigned int flags)
> >  {
> > -	struct folio *folio = page_folio(page);
> > -
> >  	if (fault_flag_allow_retry_first(flags)) {
> >  		/*
> >  		 * CAUTION! In this case, mmap_lock is not released
> 
> A bit later in this branch, 'page' is accessed, but it no longer exists. And
> thus as expected, it doesn't compile. Assuming it's fixed later, but
> bisectability etc...

Oops.  Thanks for catching that; I've reordered this patch and the
folio_wait_locked() patch, which makes the entire problem go away.
diff mbox series

Patch

diff --git a/include/linux/pagemap.h b/include/linux/pagemap.h
index 41224e4ca8cc..21e394964288 100644
--- a/include/linux/pagemap.h
+++ b/include/linux/pagemap.h
@@ -640,7 +640,7 @@  static inline bool wake_page_match(struct wait_page_queue *wait_page,
 
 void __folio_lock(struct folio *folio);
 int __folio_lock_killable(struct folio *folio);
-extern int __lock_page_or_retry(struct page *page, struct mm_struct *mm,
+int __folio_lock_or_retry(struct folio *folio, struct mm_struct *mm,
 				unsigned int flags);
 void unlock_page(struct page *page);
 void folio_unlock(struct folio *folio);
@@ -701,13 +701,16 @@  static inline int lock_page_killable(struct page *page)
  * caller indicated that it can handle a retry.
  *
  * Return value and mmap_lock implications depend on flags; see
- * __lock_page_or_retry().
+ * __folio_lock_or_retry().
  */
 static inline int lock_page_or_retry(struct page *page, struct mm_struct *mm,
 				     unsigned int flags)
 {
+	struct folio *folio;
 	might_sleep();
-	return trylock_page(page) || __lock_page_or_retry(page, mm, flags);
+
+	folio = page_folio(page);
+	return folio_trylock(folio) || __folio_lock_or_retry(folio, mm, flags);
 }
 
 /*
diff --git a/mm/filemap.c b/mm/filemap.c
index 67334eb3fd94..28bf50041671 100644
--- a/mm/filemap.c
+++ b/mm/filemap.c
@@ -1623,20 +1623,18 @@  static int __folio_lock_async(struct folio *folio, struct wait_page_queue *wait)
 
 /*
  * Return values:
- * 1 - page is locked; mmap_lock is still held.
- * 0 - page is not locked.
+ * 1 - folio is locked; mmap_lock is still held.
+ * 0 - folio is not locked.
  *     mmap_lock has been released (mmap_read_unlock(), unless flags had both
  *     FAULT_FLAG_ALLOW_RETRY and FAULT_FLAG_RETRY_NOWAIT set, in
  *     which case mmap_lock is still held.
  *
  * If neither ALLOW_RETRY nor KILLABLE are set, will always return 1
- * with the page locked and the mmap_lock unperturbed.
+ * with the folio locked and the mmap_lock unperturbed.
  */
-int __lock_page_or_retry(struct page *page, struct mm_struct *mm,
+int __folio_lock_or_retry(struct folio *folio, struct mm_struct *mm,
 			 unsigned int flags)
 {
-	struct folio *folio = page_folio(page);
-
 	if (fault_flag_allow_retry_first(flags)) {
 		/*
 		 * CAUTION! In this case, mmap_lock is not released
diff --git a/mm/memory.c b/mm/memory.c
index 86ba6c1f6821..fc3f50d0702c 100644
--- a/mm/memory.c
+++ b/mm/memory.c
@@ -4065,7 +4065,7 @@  static vm_fault_t do_shared_fault(struct vm_fault *vmf)
  * We enter with non-exclusive mmap_lock (to exclude vma changes,
  * but allow concurrent faults).
  * The mmap_lock may have been released depending on flags and our
- * return value.  See filemap_fault() and __lock_page_or_retry().
+ * return value.  See filemap_fault() and __folio_lock_or_retry().
  * If mmap_lock is released, vma may become invalid (for example
  * by other thread calling munmap()).
  */
@@ -4307,7 +4307,7 @@  static vm_fault_t wp_huge_pud(struct vm_fault *vmf, pud_t orig_pud)
  * concurrent faults).
  *
  * The mmap_lock may have been released depending on flags and our return value.
- * See filemap_fault() and __lock_page_or_retry().
+ * See filemap_fault() and __folio_lock_or_retry().
  */
 static vm_fault_t handle_pte_fault(struct vm_fault *vmf)
 {
@@ -4411,7 +4411,7 @@  static vm_fault_t handle_pte_fault(struct vm_fault *vmf)
  * By the time we get here, we already hold the mm semaphore
  *
  * The mmap_lock may have been released depending on flags and our
- * return value.  See filemap_fault() and __lock_page_or_retry().
+ * return value.  See filemap_fault() and __folio_lock_or_retry().
  */
 static vm_fault_t __handle_mm_fault(struct vm_area_struct *vma,
 		unsigned long address, unsigned int flags)
@@ -4567,7 +4567,7 @@  static inline void mm_account_fault(struct pt_regs *regs,
  * By the time we get here, we already hold the mm semaphore
  *
  * The mmap_lock may have been released depending on flags and our
- * return value.  See filemap_fault() and __lock_page_or_retry().
+ * return value.  See filemap_fault() and __folio_lock_or_retry().
  */
 vm_fault_t handle_mm_fault(struct vm_area_struct *vma, unsigned long address,
 			   unsigned int flags, struct pt_regs *regs)