Messages in this thread | | | Subject | Re: [BUG?] possible recursive locking detected | From | Anton Altaparmakov <> | Date | Thu, 27 Jul 2006 10:35:28 +0100 |
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On Thu, 2006-07-27 at 19:18 +1000, Nick Piggin wrote: > Anton Altaparmakov wrote: > > On Thu, 2006-07-27 at 00:38 -0700, Andrew Morton wrote: > > > >>On Thu, 27 Jul 2006 08:15:27 +0100 > >>Anton Altaparmakov <aia21@cam.ac.uk> wrote: > >> > >> > >>>>I'm surprised ext2 is allocating with __GFP_FS set, though. Would that > >>>>cause any problem? > >>> > >>>That is an ext2 bug IMO. > >> > >>There is no bug. > >> > >>What there is is an ill-defined set of rules. If we want to tighten these > >>rules we have a choice between > > > > > > I beg to differ. It is a bug. You cannot reenter the file system when > > the file system is trying to allocate memory. Otherwise you can never > > allocate memory with any locks held or you are bound to introduce an > > A->B B->A deadlock somewhere. > > I don't think it is a bug in general. It really depends on the allocation: > > - If it is a path that might be required in order to writeout a page, then > yes GFP_NOFS is going to help prevent deadlocks. > > - If it is a path where you'll take the same locks as page reclaim requires, > then again GFP_NOFS is required. > > For NTFS case, it seems like holding i_mutex on the write path falls foul > of the second problem. But I agree with Andrew that this is a critical case > where we do have to enter the fs. GFP_NOFS is too big a hammer to use. > > I guess you'd have to change NTFS to do something sane privately, or come > up with a nice general solution that doesn't harm the common filesystems > that apparently don't have a problem here... can you just add GFP_NOFS to > NTFS's mapping_gfp_mask to start with?
I don't think NTFS has a problem either. It is a theoretical problem with an extremely small chance of being hit. I am happy to have such a problem for now. There are more pressing problems to solve. The only thing that needs to happen is for the messages to stop so people stop complaining / getting worried about them...
Best regards,
Anton -- Anton Altaparmakov <aia21 at cam.ac.uk> (replace at with @) Unix Support, Computing Service, University of Cambridge, CB2 3QH, UK Linux NTFS maintainer / IRC: #ntfs on irc.freenode.net WWW: http://www.linux-ntfs.org/ & http://www-stu.christs.cam.ac.uk/~aia21/
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