Branch b1_6

Add some explanatory comments.

lustre/llite/rw.c

@@ -1446,7 +1446,9 @@ int ll_readpage(struct file *filp, struct page *page)
                 ras_update(ll_i2sbi(inode), inode, &fd->fd_ras, page->index,
                            llap->llap_defer_uptodate);
 
+
         if (llap->llap_defer_uptodate) {
+                /* This is the callpath if we got the page from a readahead */
                 llap->llap_ra_used = 1;
                 rc = ll_readahead(&fd->fd_ras, exp, page->mapping, oig,
                                   fd->fd_flags);
@@ -1462,7 +1464,8 @@ int ll_readpage(struct file *filp, struct page *page)
         if (likely((fd->fd_flags & LL_FILE_IGNORE_LOCK) == 0)) {
                 rc = ll_page_matches(page, fd->fd_flags);
                 if (rc < 0) {
-                        LL_CDEBUG_PAGE(D_ERROR, page, "lock match failed: rc %d\n", rc);
+                        LL_CDEBUG_PAGE(D_ERROR, page,
+                                       "lock match failed: rc %d\n", rc);
                         GOTO(out, rc);
                 }
 
@@ -1479,6 +1482,8 @@ int ll_readpage(struct file *filp, struct page *page)
                 GOTO(out, rc);
 
         LL_CDEBUG_PAGE(D_PAGE, page, "queued readpage\n");
+        /* We have just requested the actual page we want, see if we can tack
+         * on some readahead to that page's RPC before it is sent. */
         if (ll_i2sbi(inode)->ll_ra_info.ra_max_pages)
                 ll_readahead(&fd->fd_ras, exp, page->mapping, oig,
                              fd->fd_flags);