On Fri, 2009-12-18 at 19:24 +0900, FUJITA Tomonori wrote: > On Fri, 18 Dec 2009 11:01:29 +0100 > James Bottomley <James.Bottomley@xxxxxxx> wrote: > > > > Yeah, but now only XFS passes vmap'ed pages to the block layer. Isn't > > > it better to wait until we have real users of the API? > > > > XFS is a real user ... the XFS filesystem is our most trusted code base > > that can break the 8TB limit, which hard disks are already at. Ext4 may > > be ready, but it's not universally present in enterprise distros like > > XFS. > > XFS already has the own code to handle that, which works fine (with > your patchset except for 5/6 for the block layer). Not much motivation > for XFS to move to the generic API? Right, but it's for completeness. If we decide to allow vmap buffers, then only supporting them on certain paths is a recipe for confusion in a year's time when someone assumes we support vmap buffers on all block paths; a bit like the current confusion over what we support .... > > > > That would ensure the architecturally > > > > correct flushing of the aliases, and would satisfy the expectations of > > > > blk_rq_map_kern(). The down side is that vmap/vmalloc set up and clear > > > > page tables, which isn't necessary and might impact performance (xfs > > > > people?) > > > > > > btw, I'm not sure that the existing blk_rq_map_* API isn't fit well to > > > file systems since blk_rq_map_user and blk_rq_map_kern takes a request > > > structure. > > > > OK, so that was illustrative. The meat of the change is at the bio > > layer anyway (fss tend to speak bios). > > Yeah, I think so, it's up to Jens to add new APIs for vmap there. Agreed. James -- To unsubscribe from this list: send the line "unsubscribe linux-parisc" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
