On Wed, Jan 22, 2014 at 10:09:10PM -0800, Andrew Morton wrote: > > > > > > That being said, this could cause vma blowups for programs that are > > > actually using this thing. > > > > Hi Andy, indeed, this could happen. The easiest way is to ignore softdirty bit > > when we're trying to merge vmas and set it one new merged. I think this should > > be correct. Once I finish I'll send the patch. > > Hang on. We think the problem is that gimp is generating vmas which > *should* be merged, but for unknown reasons they differ in > VM_SOFTDIRTY, yes? Yes. One place where I forgot to set softdirty bit is setup_arg_pages. But it called once on elf load, so it can't cause such effect (but should be fixed too). Also there is do_brk where vmasoftdirty is missed too :/ Another problem is the potential scenario when we have a bunch of vmas and clear vma-softdirty bit on them, then we try to map new one, flags won't match and instead of extending old vma the new one will be created. I think (if only I'm not missing something) that vma-softdirty should be ignored in such case (ie inside is_mergeable_vma) and once vma extended it should be marked as dirty one. Again, I need to think and test more. > Shouldn't we work out where we're forgetting to set VM_SOFTDIRTY? > Putting bandaids over this error when we come to trying to merge the > vmas sounds very wrong? I'm looking into this as well. Cyrill -- 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>