On Thu, Mar 15, 2007 at 01:54:32PM +0100, Jens Axboe wrote: > On Thu, Mar 15 2007, Nick Piggin wrote: > > On Thu, Mar 15, 2007 at 01:27:23PM +0100, Jens Axboe wrote: > > > On Thu, Mar 15 2007, Nick Piggin wrote: > > > > > > > > We should be able to allow for it with the new a_ops API I'm working > > > > on. > > > > > > "Should be" and in progress stuff, is it guarenteed to get there? > > > > Well considering that it is needed in order to solve 3 different deadlock > > scenarios in the core write(2) path without taking a big performance hit, > > I'd hope so ;) > > > > It isn't guaranteed, but I have only had positive feedback so far. Would > > take a while to actually get merged, though. > > It's not that I don't believe you, I'm just a little reluctant to rip > stuff out with a promise to fix it later when foo and bar are merged, > since things like that have a tendency not to get done because they are > forgotten :-)
Fair enough. The API side is trivial, all I need to do is set a single flag and make splice pass down the page, and set that flag when stealing. Filesystems might vary from trivial to impossible, but I think most should be OK. If the flag is there then they at least have the option. > Do you have a test case for stealing failures? What I'm really asking is > how critical is this? I guess you could fill a filesystem completely, and have a sparse file in it. Then steal a page and splice it in. The prepare_write should fail, but the page will still be in pagecache, until it gets reclaimed, then it will go back to zeroes. (no I don't have a test case ;)). You could do something like remove the page if prepare_write fails, but there is still a window where a read can see it. Basically I can't see a way that it can possibly work within our current prepare_write API, and it is a data corruption bug, so in my opinion it is a candidate for 2.6.21 + stable. - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [EMAIL PROTECTED] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
