On Wed, 2011-11-30 at 01:25 +0800, Peng Tao wrote: > On Wed, Nov 30, 2011 at 12:40 AM, Trond Myklebust > <Trond.Myklebust@xxxxxxxxxx> wrote: > > On Fri, 2011-12-02 at 20:52 -0800, Peng Tao wrote: > >> Asking for layout in pg_init will always make client ask for only 4KB > >> layout in every layoutget. This way, client drops the IO size information > >> that is meaningful for MDS in handing out layout. > >> > >> In stead, if layout is not find in cache, do not send layoutget > >> at once. Wait until before issuing IO in pnfs_do_multiple_reads/writes > >> because that is where we know the real size of current IO. By telling the > >> real IO size to MDS, MDS will have a better chance to give proper layout. > > > > Why can't you just split pnfs_update_layout() into 2 sub-functions > > instead of duplicating it in private block code? > Because I wanted to differentiate between no layout header and no > cached lseg, where the pnfs_update_layout() interface is not enough to > tell the difference. Of course I can put these all into generic layer. > I will update the patchset to do it. > > > > > Then call layoutget in your pg_doio() callback instead of adding a > > redundant pnfs_update_layout to > > pnfs_do_multiple_reads/pnfs_do_multiple_writes... > I have considered it before but using private pg_doio() means we will > have as much duplication of pnfs_generic_pg_read/writepages. Why? All you need to do is send the layoutget, and then call the existing pnfs_generic_pg_read/writepages? The difference here is that you're adding that step into pnfs_generic_pg_read/writepages in patch 3/4. Basically you are adding block-specific code into an otherwise generic function instead of doing it cleanly in the block-specific callbacks. -- Trond Myklebust Linux NFS client maintainer NetApp Trond.Myklebust@xxxxxxxxxx www.netapp.com -- To unsubscribe from this list: send the line "unsubscribe linux-nfs" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
