On Tue, 24 Apr 2007 12:59:17 -0700 (PDT) Christoph Lameter <[EMAIL PROTECTED]>
wrote:
> On Tue, 24 Apr 2007, Andrew Morton wrote:
>
> > No, think of the following scenario:
> >
> > - file I/O causes a read of an ext2 file's bitmap. The bitmap is
> > brought into /dev/hda1's pagecache using !__GFP_HIGHMEM
> >
> > - references are released against that page and it's now just clean
> > reclaimable pagecache
> >
> > - someone (say, an online filesystem checker or something) mmaps
> > /dev/hda1 and reads that page.
> >
> > - migration comes alnog and migrates that page into highmem
> >
> > - file I/O causes a read of that bitmap again. We find it in
> > /dev/hda's pagecache.
>
> Read of the bitmap? How would that work? Page cache lookup right?
yup.
sb_bread
->__bread
->__getblk
->__find_get_block
->__find_get_block_slow
->find_get_page
> > Here's set_bh_page().
>
> A highmem page can have buffers???
yep. Take a 4k page which is stored in four discontiguous 1k disk blocks. The
data at page_buffers(page) is the sole way in which we track which parts of
the page belong to which blocks of the disk.
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