X-Git-Url: https://err.no/cgi-bin/gitweb.cgi?a=blobdiff_plain;f=fs%2Fbuffer.c;h=39ff14403d137be85dcd11161584abeabd9d7577;hb=a70e65df8812c52252fa07a2eb92a46451a4427f;hp=ddfdd2c80bf9ba22c20901e5a74f9cd449d80ccd;hpb=c523aef0f7284970463ebd77a54bca9069711d4a;p=linux-2.6

diff --git a/fs/buffer.c b/fs/buffer.c
index ddfdd2c80b..39ff14403d 100644
--- a/fs/buffer.c
+++ b/fs/buffer.c
@@ -1181,7 +1181,20 @@ __getblk_slow(struct block_device *bdev, sector_t block, int size)
 void mark_buffer_dirty(struct buffer_head *bh)
 {
 	WARN_ON_ONCE(!buffer_uptodate(bh));
-	if (!buffer_dirty(bh) && !test_set_buffer_dirty(bh))
+
+	/*
+	 * Very *carefully* optimize the it-is-already-dirty case.
+	 *
+	 * Don't let the final "is it dirty" escape to before we
+	 * perhaps modified the buffer.
+	 */
+	if (buffer_dirty(bh)) {
+		smp_mb();
+		if (buffer_dirty(bh))
+			return;
+	}
+
+	if (!test_set_buffer_dirty(bh))
 		__set_page_dirty(bh->b_page, page_mapping(bh->b_page), 0);
 }
 
@@ -2564,14 +2577,13 @@ int nobh_write_end(struct file *file, struct address_space *mapping,
 	struct inode *inode = page->mapping->host;
 	struct buffer_head *head = fsdata;
 	struct buffer_head *bh;
+	BUG_ON(fsdata != NULL && page_has_buffers(page));
 
-	if (!PageMappedToDisk(page)) {
-		if (unlikely(copied < len) && !page_has_buffers(page))
-			attach_nobh_buffers(page, head);
-		if (page_has_buffers(page))
-			return generic_write_end(file, mapping, pos, len,
-						copied, page, fsdata);
-	}
+	if (unlikely(copied < len) && !page_has_buffers(page))
+		attach_nobh_buffers(page, head);
+	if (page_has_buffers(page))
+		return generic_write_end(file, mapping, pos, len,
+					copied, page, fsdata);
 
 	SetPageUptodate(page);
 	set_page_dirty(page);
@@ -3213,7 +3225,7 @@ static int buffer_cpu_notify(struct notifier_block *self,
 }
 
 /**
- * bh_uptodate_or_lock: Test whether the buffer is uptodate
+ * bh_uptodate_or_lock - Test whether the buffer is uptodate
  * @bh: struct buffer_head
  *
  * Return true if the buffer is up-to-date and false,
@@ -3232,7 +3244,7 @@ int bh_uptodate_or_lock(struct buffer_head *bh)
 EXPORT_SYMBOL(bh_uptodate_or_lock);
 
 /**
- * bh_submit_read: Submit a locked buffer for reading
+ * bh_submit_read - Submit a locked buffer for reading
  * @bh: struct buffer_head
  *
  * Returns zero on success and -EIO on error.