On 8/10/12 2:59 PM, Theodore Ts'o wrote: > On Fri, Aug 10, 2012 at 02:38:10PM -0500, Eric Sandeen wrote: >> >> Can the commit message also describe more about the problem: how bad >> it is, the root cause, and why it's so hard to fix properly? > > The use case is going to be fairly userspace specific, but one example > might be if the log reaper fails to run for whatever reason, and the > log directory then proceeds to grow without bound. And then when the > log repear *does* have a chance to run, if it happens to be in tight > memory cgroup, it then dies so the directory grows even larger, and > then when other processes try to access the directory, a readdir will > cause them to die because of their memory limitation, and hilarity > ensues. Oh, I thought this was papering over a scaling problem in ext4. The intent is to protect userspace from arbitrarily large readdir results? If that's the case, this should probably be proposed as a VFS level option, and see how it's received there... (Can you tell I'm not a huge fan of the idea?) ;) -Eric > You can fix this in other places in the software stack, but belt and > suspenders is good, and if there is no reason for directories to grow > larger than some set size, it's better to get a hard failure with an > ENOSPC rather than an funny failures caused by OOM's or slower and > slower performance. >> Please also update Documentation/filesystems/ext4.txt so people >> know for sure what the use & intent of this new knob is. > > Yes, I'll do that in the next spin of the patches. > > - 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
