Re: [PATCH 7/7] page migration: Add new fallback function

[Christoph Lameter <clameter@sgi.com>]

Hmmm... We need to get rid of if(PageLocked())

This introduced another race condition since another process may have
locked the page. Simply relock the page after successfully calling
migratepages() and then retry.

Signed-off-by: Christoph Lameter <clameter@sgi.com>

Index: linux-2.6.17-rc2-mm1/mm/migrate.c
===================================================================
--- linux-2.6.17-rc2-mm1.orig/mm/migrate.c	2006-04-27 22:55:46.731119932 -0700
+++ linux-2.6.17-rc2-mm1/mm/migrate.c	2006-04-27 23:39:11.853319378 -0700
@@ -476,17 +476,20 @@
 			/* Someone else already triggered a write */
 			return -EAGAIN;
 
-		if (mapping->a_ops->writepage(page, &wbc) < 0)
+		rc = mapping->a_ops->writepage(page, &wbc);
+		if (rc < 0)
 			/* I/O Error writing */
 			return -EIO;
 
+		if (rc == AOP_WRITEPAGE_ACTIVATE)
+			return -EAGAIN;
+
+		lock_page(page);
 		/*
-		 * Retry if writepage() removed the lock or the page
-		 * is still dirty or undergoing writeback.
+		 * The lock was dropped by writepage() and so something
+		 * may have changed with the page.
 		 */
-		if (!PageLocked(page) ||
-			PageWriteback(page) || PageDirty(page))
-				return -EAGAIN;
+		return -EAGAIN;
 	}
 
 	/*
@@ -599,8 +602,7 @@
 
 		unlock_page(newpage);
 unlock_page:
-		if (PageLocked(page))	/* writepage() may unlock */
-			unlock_page(page);
+		unlock_page(page);
 
 next:
 		if (rc) {

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