On Tue, 24 Apr 2007 13:12:42 -0700 (PDT) Christoph Lameter <[EMAIL PROTECTED]> wrote:
> On Tue, 24 Apr 2007, Andrew Morton wrote: > > > > 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. > > But I see no use of kmap for buffer access? The data is not accessible. > The kernel rarely has a need to actually read or write the page's contents with the CPU. On those occasions where it does, it will use kmap. Search for zero_user_page() and kmap in rc7-mm1's fs/buffer.c But that's file pagecache, which can be in highmem. File metadata is accessed within the filesystems without kmapping. This: box:/usr/src/linux-2.6.21-rc7> grep '[-]>b_data' fs/*/*.c | wc -l 1017 explains why that never got fixed. - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [EMAIL PROTECTED] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
