Messages in this thread | | | Date | Wed, 16 May 2007 10:32:19 +1000 | From | Nick Piggin <> | Subject | Re: [PATCH 2/2] AFS: Implement shared-writable mmap |
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David Howells wrote: > Implement shared-writable mmap for AFS. > > The key with which to access the file is obtained from the VMA at the point > where the PTE is made writable by the page_mkwrite() VMA op and cached in the > affected page. > > If there's an outstanding write on the page made with a different key, then > page_mkwrite() will flush it before attaching a record of the new key.
Good, will be nice to get a page_mkwrite() user in the tree.
> +/* > + * notification that a previously read-only page is about to become writable > + * - if it returns an error, the caller will deliver a bus error signal > + * > + * we use this to make a record of the key with which the writeback should be > + * performed and to flush any outstanding writes made with a different key > + * > + * the key to be used is attached to the file pinned by the VMA > + */ > +int afs_page_mkwrite(struct vm_area_struct *vma, struct page *page) > +{ > + struct afs_vnode *vnode = AFS_FS_I(vma->vm_file->f_mapping->host); > + struct key *key = vma->vm_file->private_data; > + int ret; > + > + _enter("{{%x:%u},%x},{%lx}", > + vnode->fid.vid, vnode->fid.vnode, key_serial(key), page->index); > + > + lock_page(page); > + ret = afs_prepare_write(vma->vm_file, page, 0, 0); > + unlock_page(page); > + > + _leave(" = %d", ret); > + return ret; > +}
By the looks of afs_prepare_write, it is going to go bang when the page gets truncated before lock_page.
Checking page->mapping after lock_page should do the trick.
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