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);
}
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);