From: Larry Woodman <lwoodman@redhat.com>
Subject: [RHEL5 patch] Fix for shmem_truncate_range() BUG_ON()
Date: Wed, 03 Jan 2007 16:17:44 -0500
Bugzilla: 219821
Message-Id: <459C1D78.8010609@redhat.com>
Changelog: mm: Fix for shmem_truncate_range() BUG_ON()


The following patch prevents the BUG_ON in shmem_truncate_range() when 
there are no
indirect blocks or it is punching a hole below indirect blocks. 

Fixes BZ 219821 and this patch was accepted upstream and committed into 
kernel 2.6.19



--- linux-2.6.18.noarch/mm/shmem.c.orig
+++ linux-2.6.18.noarch/mm/shmem.c
@@ -510,7 +510,11 @@ static void shmem_truncate_range(struct 
 			size = SHMEM_NR_DIRECT;
 		nr_swaps_freed = shmem_free_swp(ptr+idx, ptr+size);
 	}
-	if (!topdir)
+	/*
+	 * If there are no indirect blocks or we are punching a hole
+	 * below indirect blocks, nothing to be done.
+	 */
+	if (!topdir || (punch_hole && (limit <= SHMEM_NR_DIRECT)))
 		goto done2;
 
 	BUG_ON(limit <= SHMEM_NR_DIRECT);