mm/filemap: Add folio_lock()

This is like lock_page() but for use by callers who know they have a folio.
Convert __lock_page() to be __folio_lock().  This saves one call to
compound_head() per contended call to lock_page().

Saves 455 bytes of text; mostly from improved register allocation and
inlining decisions.  __folio_lock is 59 bytes while __lock_page was 79.

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>
Reviewed-by: David Howells <dhowells@redhat.com>
Acked-by: Mike Rapoport <rppt@linux.ibm.com>

diff --git a/include/linux/pagemap.h b/include/linux/pagemap.h
index 8087921641a3331dbb4cf9b93e36f70b4020c974..6481a431ea40bcbd311de64987d3e1e5cdc2bf82 100644 (file)
--- a/include/linux/pagemap.h
+++ b/include/linux/pagemap.h
@@ -652,7 +652,7 @@ static inline bool wake_page_match(struct wait_page_queue *wait_page,
        return true;
 }
 
-extern void __lock_page(struct page *page);
+void __folio_lock(struct folio *folio);
 extern int __lock_page_killable(struct page *page);
 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,
@@ -660,13 +660,24 @@ extern int __lock_page_or_retry(struct page *page, struct mm_struct *mm,
 void unlock_page(struct page *page);
 void folio_unlock(struct folio *folio);
 
+static inline bool folio_trylock(struct folio *folio)
+{
+       return likely(!test_and_set_bit_lock(PG_locked, folio_flags(folio, 0)));
+}
+
 /*
  * Return true if the page was successfully locked
  */
 static inline int trylock_page(struct page *page)
 {
-       page = compound_head(page);
-       return (likely(!test_and_set_bit_lock(PG_locked, &page->flags)));
+       return folio_trylock(page_folio(page));
+}
+
+static inline void folio_lock(struct folio *folio)
+{
+       might_sleep();
+       if (!folio_trylock(folio))
+               __folio_lock(folio);
 }
 
 /*
@@ -674,9 +685,12 @@ static inline int trylock_page(struct page *page)
  */
 static inline void lock_page(struct page *page)
 {
+       struct folio *folio;
        might_sleep();
-       if (!trylock_page(page))
-               __lock_page(page);
+
+       folio = page_folio(page);
+       if (!folio_trylock(folio))
+               __folio_lock(folio);
 }
 
 /*

diff --git a/mm/filemap.c b/mm/filemap.c
index 191d7d39e838d38d8d958d7b9cbe3a3cf4a290c3..a1d3f67e1b49dcda638434d7be03a4f6449db6b0 100644 (file)
--- a/mm/filemap.c
+++ b/mm/filemap.c
@@ -1242,7 +1242,7 @@ static void wake_up_page(struct page *page, int bit)
  */
 enum behavior {
        EXCLUSIVE,      /* Hold ref to page and take the bit when woken, like
-                        * __lock_page() waiting on then setting PG_locked.
+                        * __folio_lock() waiting on then setting PG_locked.
                         */
        SHARED,         /* Hold ref to page and check the bit when woken, like
                         * wait_on_page_writeback() waiting on PG_writeback.
@@ -1633,17 +1633,16 @@ void page_endio(struct page *page, bool is_write, int err)
 EXPORT_SYMBOL_GPL(page_endio);
 
 /**
- * __lock_page - get a lock on the page, assuming we need to sleep to get it
- * @__page: the page to lock
+ * __folio_lock - Get a lock on the folio, assuming we need to sleep to get it.
+ * @folio: The folio to lock
  */
-void __lock_page(struct page *__page)
+void __folio_lock(struct folio *folio)
 {
-       struct page *page = compound_head(__page);
-       wait_queue_head_t *q = page_waitqueue(page);
-       wait_on_page_bit_common(q, page, PG_locked, TASK_UNINTERRUPTIBLE,
+       wait_queue_head_t *q = page_waitqueue(&folio->page);
+       wait_on_page_bit_common(q, &folio->page, PG_locked, TASK_UNINTERRUPTIBLE,
                                EXCLUSIVE);
 }
-EXPORT_SYMBOL(__lock_page);
+EXPORT_SYMBOL(__folio_lock);
 
 int __lock_page_killable(struct page *__page)
 {
@@ -1718,10 +1717,10 @@ int __lock_page_or_retry(struct page *page, struct mm_struct *mm,
                        return 0;
                }
        } else {
-               __lock_page(page);
+               __folio_lock(page_folio(page));
        }
-       return 1;
 
+       return 1;
 }
 
 /**
@@ -2915,7 +2914,9 @@ unlock:
 static int lock_page_maybe_drop_mmap(struct vm_fault *vmf, struct page *page,
                                     struct file **fpin)
 {
-       if (trylock_page(page))
+       struct folio *folio = page_folio(page);
+
+       if (folio_trylock(folio))
                return 1;
 
        /*
@@ -2928,7 +2929,7 @@ 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(page)) {
+               if (__lock_page_killable(&folio->page)) {
                        /*
                         * We didn't have the right flags to drop the mmap_lock,
                         * but all fault_handlers only check for fatal signals
@@ -2940,11 +2941,11 @@ static int lock_page_maybe_drop_mmap(struct vm_fault *vmf, struct page *page,
                        return 0;
                }
        } else
-               __lock_page(page);
+               __folio_lock(folio);
+
        return 1;
 }
 
-
 /*
  * Synchronous readahead happens when we don't even find a page in the page
  * cache at all.  We don't want to perform IO under the mmap sem, so if we have