On Thu, Oct 09, 2008 at 10:39:23AM -0400, Chris Mason wrote: > On Thu, 2008-10-09 at 16:21 +0200, Nick Piggin wrote: > > On Thu, Oct 09, 2008 at 10:12:55AM -0400, Chris Mason wrote: > > > On Thu, 2008-10-09 at 15:55 +0200, Nick Piggin wrote: > > > > On Thu, Oct 09, 2008 at 09:35:58AM -0400, Chris Mason wrote: > > > > > On Thu, 2008-10-09 at 15:27 +0200, Nick Piggin wrote: > > > > > > > > > > I don't think do_sync_mapping_range is broken as is. It simply splits > > > > > the operations into different parts. The caller can request that we > > > > > wait for pending IO first. > > > > > > > > It is. Not because of it's whacky API, but because it uses WB_SYNC_NONE. > > > > > > > > > > > > > WB_SYNC_NONE none just means don't wait for IO in flight, and there are > > > > > valid uses for it that will slow down if you switch them all to > > > > > WB_SYNC_ALL. > > > > > > > > To write_cache_pages it means that, but further down the chain (eg. > > > > block_write_full_page) it also means not to wait on other stuff. > > > > > > > > It has broadly meant "don't worry about data integirty" for a long time > > > > AFAIKS. > > > > > > Sadly it has broadly meant different things to different people ;) > > > You're right, block_write_full_page is broken. > > > > Well, I really just think it is do_sync_mapping_range that is broken. > > Because __sync_single_inode treats WB_SYNC_NONE as a general "nowait", > > so does __writeback_single_inode. Weakest semantics define the API :) > > Unfortunately these things are using the flag differently > __sync_single_inode and __writeback_single_inode do different things > with the flag than people that end up directly calling the writepages > methods. Sure, but it's the "nowait" semantics that they want, right? And *they* eventually call into writepages. So they want similar semantics from writepages, presumably. The comment in WB_SYNC_NONE definition kind of suggests it meant don't wait for anything when it was written... > At the write_cache_pages level, WB_SYNC_NONE should only change the > waiting for IO in flight. Aside from do_sync_mapping_range, what are other reasons to enforce the same thing all up and down the writeout stack? If there are good reasons, let's add WB_SYNC_WRITEBACK? -- 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
