On Tue, Dec 04, 2007 at 12:35:49PM +0100, Nick Piggin wrote:
> On Tue, Dec 04, 2007 at 03:26:20AM -0800, Andrew Morton wrote:
> > On Tue, 4 Dec 2007 12:21:00 +0100 Nick Piggin <[email protected]> wrote:
> >
> > > + *
> > > + * Cannot support XIP and highmem, because our ->direct_access
> > > + * routine for XIP must return memory that is always addressable.
> > > + * If XIP was reworked to use pfns and kmap throughout, this
> > > + * restriction might be able to be lifted.
> > > */
> > > + gfp_flags = GFP_NOIO | __GFP_ZERO;
> > > +#ifndef CONFIG_BLK_DEV_XIP
> > > + gfp_flags |= __GFP_HIGHMEM;
> > > +#endif
> >
> > A dubious tradeoff?
>
> On big highmem machines certainly. It may be somewhat useful on small
> memory systems... but having the config option there is nice for a VM
> developer without an s390 easily available ;)
>
> But don't apply these XIP patches yet -- after a bit more testing I'm
> seeing some data corruption, so I'll have to work out what's going
> wrong with that first.
Here we go. See, brd already found a bug ;)
Can you apply the ext2 XIP patch too? And I'll resend the brd XIP patch.
---
Writing to XIP files at a non-page-aligned offset results in data corruption
because the writes were always sent to the start of the page.
Signed-off-by: Nick Piggin <[email protected]>
---
Index: linux-2.6/mm/filemap_xip.c
===================================================================
--- linux-2.6.orig/mm/filemap_xip.c
+++ linux-2.6/mm/filemap_xip.c
@@ -314,7 +314,7 @@ __xip_file_write(struct file *filp, cons
fault_in_pages_readable(buf, bytes);
kaddr = kmap_atomic(page, KM_USER0);
copied = bytes -
- __copy_from_user_inatomic_nocache(kaddr, buf, bytes);
+ __copy_from_user_inatomic_nocache(kaddr + offset, buf, bytes);
kunmap_atomic(kaddr, KM_USER0);
flush_dcache_page(page);
--
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