lkml.org 
[lkml]   [2007]   [May]   [15]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
Date
From
SubjectRe: [PATCH 2/2] AFS: Implement shared-writable mmap
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.

--
SUSE Labs, Novell Inc.
-
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@vger.kernel.org
More majordomo info at http://vger.kernel.org/majordomo-info.html
Please read the FAQ at http://www.tux.org/lkml/

\
 
 \ /
  Last update: 2007-05-16 02:35    [W:1.924 / U:0.340 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site