[PATCH] fix ->setattr ATTR_SIZE locking for nfsd

[Christoph Hellwig <hch@lst.de>]

Since the big direct I/O rework do_truncate takes i_alloc_sem before
calling into ->setattr.  Unfortunately the other callers of ->setattr
with ATTR_SIZE, most notably nfsd don't take it.

The (out of tree) XFS dmapi code relies wants to release i_alloc_sem and
thus gets into problems like

	http://oss.sgi.com/bugzilla/show_bug.cgi?id=365

This patch moves acquiring and releasing i_alloc_sem into
notify_change() to make the locking behaviour consistant.


Index: fs/attr.c
===================================================================
RCS file: /cvs/linux-2.6-xfs/fs/attr.c,v
retrieving revision 1.2
diff -u -p -r1.2 attr.c
--- fs/attr.c	16 Aug 2004 03:52:41 -0000	1.2
+++ fs/attr.c	6 Jan 2005 04:55:14 -0000
@@ -167,6 +167,9 @@ int notify_change(struct dentry * dentry
 	if (!attr->ia_valid)
 		return 0;
 
+	if (ia_valid & ATTR_SIZE)
+		down_write(&dentry->d_inode->i_alloc_sem);
+
 	if (inode->i_op && inode->i_op->setattr) {
 		error = security_inode_setattr(dentry, attr);
 		if (!error)
@@ -183,6 +186,10 @@ int notify_change(struct dentry * dentry
 				error = inode_setattr(inode, attr);
 		}
 	}
+
+	if (ia_valid & ATTR_SIZE)
+		up_write(&dentry->d_inode->i_alloc_sem);
+
 	if (!error) {
 		unsigned long dn_mask = setattr_mask(ia_valid);
 		if (dn_mask)
Index: fs/open.c
===================================================================
RCS file: /cvs/linux-2.6-xfs/fs/open.c,v
retrieving revision 1.7
diff -u -p -r1.7 open.c
--- fs/open.c	16 Aug 2004 03:52:41 -0000	1.7
+++ fs/open.c	6 Jan 2005 04:55:15 -0000
@@ -202,10 +202,9 @@ int do_truncate(struct dentry *dentry, l
 
 	newattrs.ia_size = length;
 	newattrs.ia_valid = ATTR_SIZE | ATTR_CTIME;
+
 	down(&dentry->d_inode->i_sem);
-	down_write(&dentry->d_inode->i_alloc_sem);
 	err = notify_change(dentry, &newattrs);
-	up_write(&dentry->d_inode->i_alloc_sem);
 	up(&dentry->d_inode->i_sem);
 	return err;
 }