X-Git-Url: https://git.openpandora.org/cgi-bin/gitweb.cgi?a=blobdiff_plain;f=mm%2Fswap_state.c;h=7b3dadd136e16d6e76ed87ec93a6f09e2efe4e44;hb=e60dde1114399bbae104e49368b62cad6cb6b730;hp=46680461785bef647c3618bc7d493d1909aea80f;hpb=bc9bc72e2f9bb07384c00604d1a40d0b5f62be6c;p=pandora-kernel.git

diff --git a/mm/swap_state.c b/mm/swap_state.c
index 46680461785b..7b3dadd136e1 100644
--- a/mm/swap_state.c
+++ b/mm/swap_state.c
@@ -6,7 +6,6 @@
  *
  *  Rewritten to use page cache, (C) 1998 Stephen Tweedie
  */
-#include <linux/module.h>
 #include <linux/mm.h>
 #include <linux/gfp.h>
 #include <linux/kernel_stat.h>
@@ -28,7 +27,7 @@
  */
 static const struct address_space_operations swap_aops = {
 	.writepage	= swap_writepage,
-	.set_page_dirty	= __set_page_dirty_nobuffers,
+	.set_page_dirty	= __set_page_dirty_no_writeback,
 	.migratepage	= migrate_page,
 };
 
@@ -315,8 +314,24 @@ struct page *read_swap_cache_async(swp_entry_t entry, gfp_t gfp_mask,
 		 * Swap entry may have been freed since our caller observed it.
 		 */
 		err = swapcache_prepare(entry);
-		if (err == -EEXIST) {	/* seems racy */
+		if (err == -EEXIST) {
 			radix_tree_preload_end();
+			/*
+			 * We might race against get_swap_page() and stumble
+			 * across a SWAP_HAS_CACHE swap_map entry whose page
+			 * has not been brought into the swapcache yet, while
+			 * the other end is scheduled away waiting on discard
+			 * I/O completion at scan_swap_map().
+			 *
+			 * In order to avoid turning this transitory state
+			 * into a permanent loop around this -EEXIST case
+			 * if !CONFIG_PREEMPT and the I/O completion happens
+			 * to be waiting on the CPU waitqueue where we are now
+			 * busy looping, we just conditionally invoke the
+			 * scheduler here, if there are some more important
+			 * tasks to run.
+			 */
+			cond_resched();
 			continue;
 		}
 		if (err) {		/* swp entry is obsolete ? */