On Fri, Jul 04, 2014 at 01:28:02PM +0200, David Jander wrote: > > Here is the output I am getting... AFAICS no problems on the raw device. Is > this sufficient testing, Ted? I'm not sure what theory Dmitry was trying to pursue when he requested that you run the fio test. Dmitry? Please note that at this point there may be multiple causes with similar symptoms that are showing up. So just because one person reports one set of data points, such as someone claiming they've seen this without a power drop to the storage device, that therefore all of the problems were caused by flaky I/O to the device. Right now, there are multiple theories floating around --- and it may be that more than one of them are true (i.e., there may be multiple bugs here). Some of the possibilities, which again, may not be mutually exclusive: 1) Some kind of eMMC driver bug, which is possibly causing the CACHE FLUSH command not to be sent. 2) Some kind of hardware problem involving flash translation layers not having durable transactions of their flash metadata across power failures. 3) Some kind of ext4/jbd2 bug, recently introduced, where we are modifying some ext4 metadata (either the block allocation bitmap or block group summary statistics) outside of a valid transaction handle. 4) Some other kind of hard-to-reproduce race or wild pointer which is sometimes corrupting fs data structures. If someone has a easy to reproduce failure case, the first step is to do a very rough bisection test. Does the easy-to-reproduce failure go away if you use 3.14? 3.12? Also, if you can describe in great detail your hardware and software configuration, and under what circumstances the problem reproduces, and when it doesn't, that would also be critical. Whether you are just doing reset or a power cycle if an unclean shutdown is involved, might also be important. And at this point, because I'm getting very suspicious that there may be more than one root cause, we should try to keep the debugging of one person's reproduction, such as David's, separate from another's, such as Matteo's. It may be that there ultimately have the same root cause, and so if one person is able to get an interesting reproduction result, it would be great for the other person to try running the same experiment on their hardware/software configuration. But what we must not do is assume that one person's experiment is automatically applicable to other circumstances. Cheers, - Ted -- To unsubscribe from this list: send the line "unsubscribe linux-ext4" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
