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From: John Baldwin <jhb@FreeBSD.org>
Date: Tue, 8 Feb 2011 13:02:26 +0000 (UTC)
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Subject: svn commit: r218438 - head/sys/fs/ext2fs
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Author: jhb
Date: Tue Feb  8 13:02:25 2011
New Revision: 218438
URL: http://svn.freebsd.org/changeset/base/218438

Log:
  After reading a bitmap block for i-nodes or blocks, recheck the count of
  free i-nodes or blocks to handle a race where another thread might have
  allocated the last i-node or block while we were waiting for the buffer.
  
  Tested by:	dougb

Modified:
  head/sys/fs/ext2fs/ext2_alloc.c

Modified: head/sys/fs/ext2fs/ext2_alloc.c
==============================================================================
--- head/sys/fs/ext2fs/ext2_alloc.c	Tue Feb  8 12:51:54 2011	(r218437)
+++ head/sys/fs/ext2fs/ext2_alloc.c	Tue Feb  8 13:02:25 2011	(r218438)
@@ -650,6 +650,15 @@ ext2_alloccg(struct inode *ip, int cg, d
 		EXT2_LOCK(ump);
 		return (0);
 	}
+	if (fs->e2fs_gd[cg].ext2bgd_nbfree == 0) {
+		/*
+		 * Another thread allocated the last block in this
+		 * group while we were waiting for the buffer.
+		 */
+		brelse(bp);
+		EXT2_LOCK(ump);
+		return (0);
+	}
 	bbp = (char *)bp->b_data;
 
 	if (dtog(fs, bpref) != cg)
@@ -776,6 +785,15 @@ ext2_nodealloccg(struct inode *ip, int c
 		EXT2_LOCK(ump);
 		return (0);
 	}
+	if (fs->e2fs_gd[cg].ext2bgd_nifree == 0) {
+		/*
+		 * Another thread allocated the last i-node in this
+		 * group while we were waiting for the buffer.
+		 */
+		brelse(bp);
+		EXT2_LOCK(ump);
+		return (0);
+	}
 	ibp = (char *)bp->b_data;
 	if (ipref) {
 		ipref %= fs->e2fs->e2fs_ipg;