[PATCH] make inode reclaim synchronise with xfs_iflush_done()

[Lachlan McIlroy <lachlan@sgi.com>]

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On a forced shutdown, xfs_finish_reclaim() will skip flushing the inode.
If the inode flush lock is not already held and there is an outstanding
xfs_iflush_done() then we might free the inode prematurely.  By acquiring
and releasing the flush lock we will synchronise with xfs_iflush_done().

Alternatively we could take a hold on the inode when when issuing I/Os
with xfs_iflush_done() and release it in xfs_iflush_done().  Would this
be a better approach?

Lachlan

[-- Attachment #2: xfs_finish_reclaim.diff --]
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--- fs/xfs/xfs_vnodeops.c_1.726	2007-12-12 17:14:59.000000000 +1100
+++ fs/xfs/xfs_vnodeops.c	2007-12-12 17:15:42.000000000 +1100
@@ -3762,20 +3762,29 @@ xfs_finish_reclaim(
 				goto reclaim;
 			}
 			xfs_iflock(ip); /* synchronize with xfs_iflush_done */
+			xfs_ifunlock(ip);
 		}
 
 		ASSERT(ip->i_update_core == 0);
 		ASSERT(ip->i_itemp == NULL ||
 		       ip->i_itemp->ili_format.ilf_fields == 0);
 		xfs_iunlock(ip, XFS_ILOCK_EXCL);
-	} else if (locked) {
+	} else {
 		/*
 		 * We are not interested in doing an iflush if we're
 		 * in the process of shutting down the filesystem forcibly.
 		 * So, just reclaim the inode.
-		 */
-		xfs_ifunlock(ip);
-		xfs_iunlock(ip, XFS_ILOCK_EXCL);
+		 * 
+		 * If the flush lock is not already held then temporarily
+		 * acquire it to synchronize with xfs_iflush_done.
+		 */
+		if (locked) {
+			xfs_ifunlock(ip);
+			xfs_iunlock(ip, XFS_ILOCK_EXCL);
+		} else {
+			xfs_iflock(ip);
+			xfs_ifunlock(ip);
+		}
 	}
 
  reclaim: