From mboxrd@z Thu Jan  1 00:00:00 1970
From: Dave Hansen <dave@linux.vnet.ibm.com>
Subject: [PATCH] update kvm's anon_inodes.c for r/o bind mounts
Date: Wed, 16 Jul 2008 23:45:56 -0700
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Cc: "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
	kvm-devel <kvm@vger.kernel.org>,
	"Anthony N. Liguori [imap]" <aliguori@us.ibm.com>
To: Avi Kivity <avi@qumranet.com>
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That also reminds me.  kvm somehow has an outdated copy of
anon_inodes.c.  It needs to be updated for the r/o bind mount patches to
add a proper mnt_want/drop_write().  Otherwise, you'll run into warnings
about imbalanced mount writer counts.  Something like this will do, but
it would be best to just stay up to date with mainline for this kind of
stuff.

diff --git a/kernel/anon_inodes.c b/kernel/anon_inodes.c
index 74630ea..a47bc55 100644
--- a/kernel/anon_inodes.c
+++ b/kernel/anon_inodes.c
@@ -90,9 +90,6 @@ int anon_inode_getfd(const char *name, const struct file_operations *fops,
 
 	if (IS_ERR(anon_inode_inode))
 		return -ENODEV;
-	file = get_empty_filp();
-	if (!file)
-		return -ENFILE;
 
 	inode = igrab(anon_inode_inode);
 	if (IS_ERR(inode)) {
@@ -121,14 +118,15 @@ int anon_inode_getfd(const char *name, const struct file_operations *fops,
 	dentry->d_flags &= ~DCACHE_UNHASHED;
 	d_instantiate(dentry, inode);
 
-	file->f_vfsmnt = mntget(anon_inode_mnt);
-	file->f_dentry = dentry;
-	file->f_mapping = inode->i_mapping;
+	file = alloc_file(anon_inode_mnt, dentry, FMODE_READ | FMODE_WRITE,
+			(struct file_operations *)fops);
+	if (!file) {
+		error = -ENFILE;
+		goto err_dput;
+	}
 
 	file->f_pos = 0;
 	file->f_flags = O_RDWR;
-	file->f_op = (struct file_operations *)fops;
-	file->f_mode = FMODE_READ | FMODE_WRITE;
 	file->f_version = 0;
 	file->private_data = priv;
 
@@ -136,12 +134,13 @@ int anon_inode_getfd(const char *name, const struct file_operations *fops,
 
 	return fd;
 
+err_dput:
+	dput(dentry);
 err_put_unused_fd:
 	put_unused_fd(fd);
 err_iput:
 	iput(inode);
 err_put_filp:
-	fput(file);
 	return error;
 }
 


-- Dave