Messages in this thread | | | Date | Fri, 21 Apr 2006 21:57:26 +0100 (BST) | From | Hugh Dickins <> | Subject | Re: [PATCH] Shrink rbtree |
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On Fri, 21 Apr 2006, David Woodhouse wrote: > On Fri, 2006-04-21 at 23:06 +1000, Nick Piggin wrote: > > How do we know the pointers are always going to be aligned? IIRC > > struct address_space needed to be explicitly aligned when doing > > this trick in page->mapping because some platform byte aligned it. > > Really? I've been doing this kind of trick with the jffs2_raw_node_ref > for years. We always allocate sufficiently aligned objects.
} __attribute__((aligned(sizeof(long)))); /* * On most architectures that alignment is already the case; but * must be enforced here for CRIS, to let the least signficant bit * of struct page's "mapping" pointer be used for PAGE_MAPPING_ANON. */
You can often get away with it - I notice we never added the same alignment to struct anon_vma, which in theory needed it just as much. Some accident of how structures are packed into slabs on CRIS, I suppose.
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