[RFC][PATCH 1/5] get mount write in __dentry_open()

[Dave Hansen <haveblue@us.ibm.com>]

The first three patches here fix actual bugs.  I think
the last two will reduce the chance for any future bugs
to creep in.  RFC for now.

--

This is a bug fix for the r/o bind mount patch set.

We need to ensure taking a mnt write on the mnt
referenced by any new struct file.  

---

 lxc-dave/fs/open.c |   12 ++++++++++--
 1 file changed, 10 insertions(+), 2 deletions(-)

diff -puN fs/open.c~get-write-in-__dentry_open fs/open.c
--- lxc/fs/open.c~get-write-in-__dentry_open	2007-09-27 11:51:31.000000000 -0700
+++ lxc-dave/fs/open.c	2007-09-27 11:51:31.000000000 -0700
@@ -778,9 +778,15 @@ static struct file *__dentry_open(struct
 				FMODE_PREAD | FMODE_PWRITE;
 	inode = dentry->d_inode;
 	if (f->f_mode & FMODE_WRITE) {
-		error = get_write_access(inode);
+		error = mnt_want_write(mnt);
 		if (error)
 			goto cleanup_file;
+
+		error = get_write_access(inode);
+		if (error) {
+			mnt_drop_write(mnt);
+			goto cleanup_file;
+		}
 	}
 
 	f->f_mapping = inode->i_mapping;
@@ -820,8 +826,10 @@ static struct file *__dentry_open(struct
 
 cleanup_all:
 	fops_put(f->f_op);
-	if (f->f_mode & FMODE_WRITE)
+	if (f->f_mode & FMODE_WRITE) {
 		put_write_access(inode);
+		mnt_drop_write(mnt);
+	}
 	file_kill(f);
 	f->f_path.dentry = NULL;
 	f->f_path.mnt = NULL;
_