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/file_table.c | 11 +++++++++-- fs/open.c | 12 +++++++++++- fs/super.c | 3 +++ 3 files changed, 23 insertions(+), 3 deletions(-) (limited to 'fs') diff --git a/fs/file_table.c b/fs/file_table.c index 71efc700022..7a0a9b87225 100644 --- a/fs/file_table.c +++ b/fs/file_table.c @@ -42,6 +42,7 @@ static inline void file_free_rcu(struct rcu_head *head) static inline void file_free(struct file *f) { percpu_counter_dec(&nr_files); + file_check_state(f); call_rcu(&f->f_u.fu_rcuhead, file_free_rcu); } @@ -207,6 +208,7 @@ int init_file(struct file *file, struct vfsmount *mnt, struct dentry *dentry, * that we can do debugging checks at __fput() */ if ((mode & FMODE_WRITE) && !special_file(dentry->d_inode->i_mode)) { + file_take_write(file); error = mnt_want_write(mnt); WARN_ON(error); } @@ -237,8 +239,13 @@ void drop_file_write_access(struct file *file) struct inode *inode = dentry->d_inode; put_write_access(inode); - if (!special_file(inode->i_mode)) - mnt_drop_write(mnt); + + if (special_file(inode->i_mode)) + return; + if (file_check_writeable(file) != 0) + return; + mnt_drop_write(mnt); + file_release_write(file); } EXPORT_SYMBOL_GPL(drop_file_write_access); diff --git a/fs/open.c b/fs/open.c index e58382d57e7..b70e7666bb2 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; diff --git a/fs/super.c b/fs/super.c index 01d5c40e911..1f8f05ede43 100644 --- a/fs/super.c +++ b/fs/super.c @@ -579,6 +579,9 @@ retry: if (!(f->f_mode & FMODE_WRITE)) continue; f->f_mode &= ~FMODE_WRITE; + if (file_check_writeable(f) != 0) + continue; + file_release_write(f); mnt = mntget(f->f_path.mnt); file_list_unlock(); /* -- cgit v1.2.3