From ad775f5a8faa5845377f093ca11caf577404add9 Mon Sep 17 00:00:00 2001 From: Dave Hansen Date: Fri, 15 Feb 2008 14:38:01 -0800 Subject: [PATCH] r/o bind mounts: debugging for missed calls There have been a few oopses caused by 'struct file's with NULL f_vfsmnts. There was also a set of potentially missed mnt_want_write()s from dentry_open() calls. This patch provides a very simple debugging framework to catch these kinds of bugs. It will WARN_ON() them, but should stop us from having any oopses or mnt_writer count imbalances. I'm quite convinced that this is a good thing because it found bugs in the stuff I was working on as soon as I wrote it. [hch: made it conditional on a debug option. But it's still a little bit too ugly] [hch: merged forced remount r/o fix from Dave and akpm's fix for the fix] Signed-off-by: Dave Hansen Acked-by: Al Viro Signed-off-by: Christoph Hellwig Signed-off-by: Andrew Morton Signed-off-by: Al Viro --- fs/open.c | 12 +++++++++++- 1 file changed, 11 insertions(+), 1 deletion(-) (limited to 'fs/open.c') diff --git a/fs/open.c b/fs/open.c index e58382d57e72..b70e7666bb2c 100644 --- a/fs/open.c +++ b/fs/open.c @@ -806,6 +806,8 @@ static struct file *__dentry_open(struct dentry *dentry, struct vfsmount *mnt, error = __get_file_write_access(inode, mnt); if (error) goto cleanup_file; + if (!special_file(inode->i_mode)) + file_take_write(f); } f->f_mapping = inode->i_mapping; @@ -847,8 +849,16 @@ cleanup_all: fops_put(f->f_op); if (f->f_mode & FMODE_WRITE) { put_write_access(inode); - if (!special_file(inode->i_mode)) + if (!special_file(inode->i_mode)) { + /* + * We don't consider this a real + * mnt_want/drop_write() pair + * because it all happenend right + * here, so just reset the state. + */ + file_reset_write(f); mnt_drop_write(mnt); + } } file_kill(f); f->f_path.dentry = NULL; -- cgit v1.2.3-58-ga151