Re: [PATCH] int (*readpage)(struct file *, struct page *);

From: Jeff V. Merkey (jmerkey@timpanogas.com)
Date: Thu May 11 2000 - 11:36:58 EST


Trond Myklebust wrote:
>
> >>>>> " " == Jeff V Merkey <jmerkey@timpanogas.com> writes:
>
> > If I understand this correctly, then I am assuming that since
> > the struct file *file can be NULL, then the struct inode *inode
> > address will always be assumed to be available from
> > page->mapping->host instead of dentry->d_inode? Knowing that
> > callers may pass a NULL strut file * is useful to know.
>
> Stop it! This sort of thing should only be used by private code
> (i.e. the disk-specific stuff) where one knows that the file/dentry is
> not needed. If people want to document uses of that, then fine.
>
> The generic VM/VFS code should however never pass a NULL value for the
> file parameter, or similarly assume that we can 'make do' with
> page->mapping->host when calling readpage(), writepage() etc.

According to comments made in this thread, the proposed change stated
that FS's should handle a NULL case for file *. If this is so, I need
to know so I don't try to use the file->private_data field and
subsequently cause a NULL pointer dereference in kernel space.

Jeff

>
> Cheers,
> Trond

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