On Wed, Nov 14, 2007 at 12:18:43PM +0000, David Howells wrote: > Nick Piggin <npiggin@xxxxxxx> wrote: > > > > The problem is that the code called assumes that the struct page * > > > argument points to a single page, not an array of pages as would > > > presumably be the case if PAGE_CACHE_SIZE > PAGE_SIZE. > > > > Incorrect. Christoph's patch for example does this by using compound pages. > > Now I personally don't like the patch or see the point in PAGE_CACHE_SIZE / > > PAGE_SIZE distinction, but I'm just telling you what the convention is. There > > is no point you arguing against it, that's simply how it is. > > No! You are wrong. I wrote the AFS code. I *know* it can only deal with No I'm talking about core code. In core code, the PAGE_CACHE_SIZE is for page cache struct pages. Single struct pages (not page arrays). Take a look at generic mapping read or something. There is nothing to deal with page arrays there either, but that's simply the convention. > > > So: you may not change the assertion unless you also fix the lower > > > functions. > > > > I won't change the assertion, because you haven't been following said > > convention, so just changing it in one place is stupider than not changing > > it at all, but not for the reason cited. > > The convention is not precisely clear. Just grep for PAGE_CACHE_SIZE in > Documentation/. It's only mentioned twice, and in neither case does it give > any information about what PAGE_CACHE_SIZE is, what it represents, or where it > applies. Therefore it's an ill-defined concept. > > If you look in Documentation/filesystems/vfs.txt, you'll see that it almost > always talks about 'pages'. It only mentions 'pagecache pages' once - in the > description of write_begin(), but it's not clear whether that means anything. Documentation is the opposite of convention ;) Look in mm/. > However, I've now noted that I need to fix my code, so just keep the assertion > for now and I'll fix my code to handle multipage blocks. I'm not saying you need to do that. Leave it at PAGE_SIZE, really it doesn't matter that much at present. This has just blown out of proportion. - To unsubscribe from this list: send the line "unsubscribe linux-fsdevel" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
