On Mon, Jun 25, 2007 at 05:41:58PM +1000, Nick Piggin wrote: > Neil Brown wrote: > >On Sunday June 24, npiggin@xxxxxxx wrote: > > > >> > >>+#define PG_blocks 20 /* Page has block mappings */ > >>+ > > > > > >I've only had a very quick look, but this line looks *very* wrong. > >You should be using PG_private. > > > >There should never be any confusion about whether ->private has > >buffers or blocks attached as the only routines that ever look in > >->private are address_space operations (or should be. I think 'NULL' > >is sometimes special cased, as in try_to_release_page. It would be > >good to do some preliminary work and tidy all that up). > > There is a lot of confusion, actually :) > But as you see in the patch, I added a couple more aops APIs, and > am working toward decoupling it as much as possible. It's pretty > close after the fsblock patch... however: > > > >Why do you think you need PG_blocks? > > Block device pagecache (buffer cache) has to be able to accept > attachment of either buffers or blocks for filesystem metadata, > and call into either buffer.c or fsblock.c based on that. > > If the page flag is really important, we can do some awful hack > like assuming the first long of the private data is flags, and > those flags will tell us whether the structure is a buffer_head > or fsblock ;) But for now it is just easier to use a page flag. The block device pagecache isn't special, and certainly isn't that much code. I would suggest keeping it buffer head specific and making a second variant that does only fsblocks. This is mostly to keep the semantics of PagePrivate sane, lets not fuzz the line. -chris - 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
