Re: [PATCH v14 019/138] mm/filemap: Add folio_lock_killable()

Mike Rapoport
2021-07-20T10:54:35Z

On Thu, Jul 15, 2021 at 04:35:05AM +0100, Matthew Wilcox (Oracle) wrote:
> This is like lock_page_killable() but for use by callers who
> know they have a folio. Convert __lock_page_killable() to be
> __folio_lock_killable(). This saves one call to compound_head() per
> contended call to lock_page_killable().
>
> __folio_lock_killable() is 19 bytes smaller than __lock_page_killable()
> was. filemap_fault() shrinks by 74 bytes and __lock_page_or_retry()
> shrinks by 71 bytes. That's a total of 164 bytes of text saved.
>
> Signed-off-by: Matthew Wilcox (Oracle) <willy@infradead.org>
> Reviewed-by: Christoph Hellwig <hch@lst.de>
> Acked-by: Jeff Layton <jlayton@kernel.org>
> Acked-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
> Acked-by: Vlastimil Babka <vbabka@suse.cz>
> Reviewed-by: William Kucharski <william.kucharski@oracle.com>
> ---
> include/linux/pagemap.h | 15 ++++++++++-----
> mm/filemap.c | 17 +++++++++--------
> 2 files changed, 19 insertions(+), 13 deletions(-)

Acked-by: Mike Rapoport <rppt@linux.ibm.com>

> diff --git a/include/linux/pagemap.h b/include/linux/pagemap.h
> index c3673c55125b..88727c74e059 100644
> --- a/include/linux/pagemap.h
> +++ b/include/linux/pagemap.h
> @@ -654,7 +654,7 @@ static inline bool wake_page_match(struct wait_page_queue *wait_page,
> }
>
> void __folio_lock(struct folio *folio);
> -extern int __lock_page_killable(struct page *page);
> +int __folio_lock_killable(struct folio *folio);
> extern int __lock_page_async(struct page *page, struct wait_page_queue *wait);
> extern int __lock_page_or_retry(struct page *page, struct mm_struct *mm,
> unsigned int flags);
> @@ -694,6 +694,14 @@ static inline void lock_page(struct page *page)
> __folio_lock(folio);
> }
>
> +static inline int folio_lock_killable(struct folio *folio)
> +{
> + might_sleep();
> + if (!folio_trylock(folio))
> + return __folio_lock_killable(folio);
> + return 0;
> +}
> +
> /*
> * lock_page_killable is like lock_page but can be interrupted by fatal
> * signals. It returns 0 if it locked the page and -EINTR if it was
> @@ -701,10 +709,7 @@ static inline void lock_page(struct page *page)
> */
> static inline int lock_page_killable(struct page *page)
> {
> - might_sleep();
> - if (!trylock_page(page))
> - return __lock_page_killable(page);
> - return 0;
> + return folio_lock_killable(page_folio(page));
> }
>
> /*
> diff --git a/mm/filemap.c b/mm/filemap.c
> index 95f89656f126..962db5c38cd7 100644
> --- a/mm/filemap.c
> +++ b/mm/filemap.c
> @@ -1589,14 +1589,13 @@ void __folio_lock(struct folio *folio)
> }
> EXPORT_SYMBOL(__folio_lock);
>
> -int __lock_page_killable(struct page *__page)
> +int __folio_lock_killable(struct folio *folio)
> {
> - struct page *page = compound_head(__page);
> - wait_queue_head_t *q = page_waitqueue(page);
> - return wait_on_page_bit_common(q, page, PG_locked, TASK_KILLABLE,
> + wait_queue_head_t *q = page_waitqueue(&folio->page);
> + return wait_on_page_bit_common(q, &folio->page, PG_locked, TASK_KILLABLE,
> EXCLUSIVE);
> }
> -EXPORT_SYMBOL_GPL(__lock_page_killable);
> +EXPORT_SYMBOL_GPL(__folio_lock_killable);
>
> int __lock_page_async(struct page *page, struct wait_page_queue *wait)
> {
> @@ -1638,6 +1637,8 @@ int __lock_page_async(struct page *page, struct wait_page_queue *wait)
> int __lock_page_or_retry(struct page *page, 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
> @@ -1656,13 +1657,13 @@ int __lock_page_or_retry(struct page *page, struct mm_struct *mm,
> if (flags & FAULT_FLAG_KILLABLE) {
> int ret;
>
> - ret = __lock_page_killable(page);
> + ret = __folio_lock_killable(folio);
> if (ret) {
> mmap_read_unlock(mm);
> return 0;
> }
> } else {
> - __folio_lock(page_folio(page));
> + __folio_lock(folio);
> }
>
> return 1;
> @@ -2851,7 +2852,7 @@ static int lock_page_maybe_drop_mmap(struct vm_fault *vmf, struct page *page,
>
> *fpin = maybe_unlock_mmap_for_io(vmf, *fpin);
> if (vmf->flags & FAULT_FLAG_KILLABLE) {
> - if (__lock_page_killable(&folio->page)) {
> + if (__folio_lock_killable(folio)) {
> /*
> * We didn't have the right flags to drop the mmap_lock,
> * but all fault_handlers only check for fatal signals
> --
> 2.30.2
>
>

--
Sincerely yours,
Mike.