On Thu, Apr 11, 2013 at 11:23:08AM -0400, Naoya Horiguchi wrote: > On Thu, Apr 11, 2013 at 03:49:16PM +0200, Andi Kleen wrote: > > > As a result, if the dirty cache includes user data, the data is lost, > > > and data corruption occurs if an application uses old data. > > > > The application cannot use old data, the kernel code kills it if it > > would do that. And if it's IO data there is an EIO triggered. > > > > iirc the only concern in the past was that the application may miss > > the asynchronous EIO because it's cleared on any fd access. > > > > This is a general problem not specific to memory error handling, > > as these asynchronous IO errors can happen due to other reason > > (bad disk etc.) > > > > If you're really concerned about this case I think the solution > > is to make the EIO more sticky so that there is a higher chance > > than it gets returned. This will make your data much more safe, > > as it will cover all kinds of IO errors, not just the obscure memory > > errors. > > I'm interested in this topic, and in previous discussion, what I was said > is that we can't expect user applications to change their behaviors when > they get EIO, so globally changing EIO's stickiness is not a great approach. Not sure. Some of the current behavior may be dubious and it may be possible to change it. But would need more analysis. I don't think we're concerned that much about "correct" applications, but more ones that do not check everything. So returning more errors should be safer. For example you could have a sysctl that enables always stick IO error -- that keeps erroring until it is closed. > I'm working on a new pagecache tag based mechanism to solve this. > But it needs time and more discussions. > So I guess Tanino-san suggests giving up on dirty pagecache errors > as a quick solution. A quick solution would be enabling panic for any asynchronous IO error. I don't think the memory error code is the right point to hook into. -Andi -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@xxxxxxxxx. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: <a href=mailto:"dont@xxxxxxxxx";> email@xxxxxxxxx </a>