1 files changed, 60 insertions, 21 deletions

diff --git a/mm/filemap.c b/mm/filemap.c
index 82f26cde830c..1944c631e3e6 100644
--- a/mm/filemap.c
+++ b/mm/filemap.c
@@ -138,7 +138,7 @@ static int page_cache_tree_insert(struct address_space *mapping,
 				dax_radix_locked_entry(0, RADIX_DAX_EMPTY));
 			/* Wakeup waiters for exceptional entry lock */
 			dax_wake_mapping_entry_waiter(mapping, page->index, p,
-						      false);
+						      true);
 		}
 	}
 	__radix_tree_replace(&mapping->page_tree, node, slot, page,
@@ -788,7 +788,7 @@ static int wake_page_function(wait_queue_t *wait, unsigned mode, int sync, void
 	return autoremove_wake_function(wait, mode, sync, key);
 }
 
-void wake_up_page_bit(struct page *page, int bit_nr)
+static void wake_up_page_bit(struct page *page, int bit_nr)
 {
 	wait_queue_head_t *q = page_waitqueue(page);
 	struct wait_page_key key;
@@ -821,7 +821,13 @@ void wake_up_page_bit(struct page *page, int bit_nr)
 	}
 	spin_unlock_irqrestore(&q->lock, flags);
 }
-EXPORT_SYMBOL(wake_up_page_bit);
+
+static void wake_up_page(struct page *page, int bit)
+{
+	if (!PageWaiters(page))
+		return;
+	wake_up_page_bit(page, bit);
+}
 
 static inline int wait_on_page_bit_common(wait_queue_head_t *q,
 		struct page *page, int bit_nr, int state, bool lock)
@@ -912,6 +918,29 @@ void add_page_wait_queue(struct page *page, wait_queue_t *waiter)
 }
 EXPORT_SYMBOL_GPL(add_page_wait_queue);
 
+#ifndef clear_bit_unlock_is_negative_byte
+
+/*
+ * PG_waiters is the high bit in the same byte as PG_lock.
+ *
+ * On x86 (and on many other architectures), we can clear PG_lock and
+ * test the sign bit at the same time. But if the architecture does
+ * not support that special operation, we just do this all by hand
+ * instead.
+ *
+ * The read of PG_waiters has to be after (or concurrently with) PG_locked
+ * being cleared, but a memory barrier should be unneccssary since it is
+ * in the same byte as PG_locked.
+ */
+static inline bool clear_bit_unlock_is_negative_byte(long nr, volatile void *mem)
+{
+	clear_bit_unlock(nr, mem);
+	/* smp_mb__after_atomic(); */
+	return test_bit(PG_waiters, mem);
+}
+
+#endif
+
 /**
  * unlock_page - unlock a locked page
  * @page: the page
@@ -921,16 +950,19 @@ EXPORT_SYMBOL_GPL(add_page_wait_queue);
  * mechanism between PageLocked pages and PageWriteback pages is shared.
  * But that's OK - sleepers in wait_on_page_writeback() just go back to sleep.
  *
- * The mb is necessary to enforce ordering between the clear_bit and the read
- * of the waitqueue (to avoid SMP races with a parallel wait_on_page_locked()).
+ * Note that this depends on PG_waiters being the sign bit in the byte
+ * that contains PG_locked - thus the BUILD_BUG_ON(). That allows us to
+ * clear the PG_locked bit and test PG_waiters at the same time fairly
+ * portably (architectures that do LL/SC can test any bit, while x86 can
+ * test the sign bit).
  */
 void unlock_page(struct page *page)
 {
+	BUILD_BUG_ON(PG_waiters != 7);
 	page = compound_head(page);
 	VM_BUG_ON_PAGE(!PageLocked(page), page);
-	clear_bit_unlock(PG_locked, &page->flags);
-	smp_mb__after_atomic();
-	wake_up_page(page, PG_locked);
+	if (clear_bit_unlock_is_negative_byte(PG_locked, &page->flags))
+		wake_up_page_bit(page, PG_locked);
 }
 EXPORT_SYMBOL(unlock_page);
 
@@ -976,9 +1008,12 @@ void page_endio(struct page *page, bool is_write, int err)
 		unlock_page(page);
 	} else {
 		if (err) {
+			struct address_space *mapping;
+
 			SetPageError(page);
-			if (page->mapping)
-				mapping_set_error(page->mapping, err);
+			mapping = page_mapping(page);
+			if (mapping)
+				mapping_set_error(mapping, err);
 		}
 		end_page_writeback(page);
 	}
@@ -987,7 +1022,7 @@ 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
+ * @__page: the page to lock
  */
 void __lock_page(struct page *__page)
 {
@@ -1765,6 +1800,11 @@ static ssize_t do_generic_file_read(struct file *filp, loff_t *ppos,
 
 		cond_resched();
 find_page:
+		if (fatal_signal_pending(current)) {
+			error = -EINTR;
+			goto out;
+		}
+
 		page = find_get_page(mapping, index);
 		if (!page) {
 			page_cache_sync_readahead(mapping,
@@ -2132,7 +2172,6 @@ static void do_async_mmap_readahead(struct vm_area_struct *vma,
 
 /**
  * filemap_fault - read in file data for page fault handling
- * @vma:	vma in which the fault was taken
  * @vmf:	struct vm_fault containing details of the fault
  *
  * filemap_fault() is invoked via the vma operations vector for a
@@ -2154,10 +2193,10 @@ static void do_async_mmap_readahead(struct vm_area_struct *vma,
  *
  * We never return with VM_FAULT_RETRY and a bit from VM_FAULT_ERROR set.
  */
-int filemap_fault(struct vm_area_struct *vma, struct vm_fault *vmf)
+int filemap_fault(struct vm_fault *vmf)
 {
 	int error;
-	struct file *file = vma->vm_file;
+	struct file *file = vmf->vma->vm_file;
 	struct address_space *mapping = file->f_mapping;
 	struct file_ra_state *ra = &file->f_ra;
 	struct inode *inode = mapping->host;
@@ -2179,12 +2218,12 @@ int filemap_fault(struct vm_area_struct *vma, struct vm_fault *vmf)
 		 * We found the page, so try async readahead before
 		 * waiting for the lock.
 		 */
-		do_async_mmap_readahead(vma, ra, file, page, offset);
+		do_async_mmap_readahead(vmf->vma, ra, file, page, offset);
 	} else if (!page) {
 		/* No page in the page cache at all */
-		do_sync_mmap_readahead(vma, ra, file, offset);
+		do_sync_mmap_readahead(vmf->vma, ra, file, offset);
 		count_vm_event(PGMAJFAULT);
-		mem_cgroup_count_vm_event(vma->vm_mm, PGMAJFAULT);
+		mem_cgroup_count_vm_event(vmf->vma->vm_mm, PGMAJFAULT);
 		ret = VM_FAULT_MAJOR;
 retry_find:
 		page = find_get_page(mapping, offset);
@@ -2192,7 +2231,7 @@ retry_find:
 			goto no_cached_page;
 	}
 
-	if (!lock_page_or_retry(page, vma->vm_mm, vmf->flags)) {
+	if (!lock_page_or_retry(page, vmf->vma->vm_mm, vmf->flags)) {
 		put_page(page);
 		return ret | VM_FAULT_RETRY;
 	}
@@ -2359,14 +2398,14 @@ next:
 }
 EXPORT_SYMBOL(filemap_map_pages);
 
-int filemap_page_mkwrite(struct vm_area_struct *vma, struct vm_fault *vmf)
+int filemap_page_mkwrite(struct vm_fault *vmf)
 {
 	struct page *page = vmf->page;
-	struct inode *inode = file_inode(vma->vm_file);
+	struct inode *inode = file_inode(vmf->vma->vm_file);
 	int ret = VM_FAULT_LOCKED;
 
 	sb_start_pagefault(inode->i_sb);
-	file_update_time(vma->vm_file);
+	file_update_time(vmf->vma->vm_file);
 	lock_page(page);
 	if (page->mapping != inode->i_mapping) {
 		unlock_page(page);