lkml.org 
[lkml]   [2010]   [Jun]   [24]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
    /
    Date
    From
    SubjectRe: [patch 16/52] fs: dcache RCU for multi-step operaitons
    On Thu, Jun 24, 2010 at 09:58:10AM +0200, Peter Zijlstra wrote:
    > On Thu, 2010-06-24 at 13:02 +1000, npiggin@suse.de wrote:
    > > plain text document attachment (fs-dcache_lock-multi-step.patch)
    > > The remaining usages for dcache_lock is to allow atomic, multi-step read-side
    > > operations over the directory tree by excluding modifications to the tree.
    > > Also, to walk in the leaf->root direction in the tree where we don't have
    > > a natural d_lock ordering.
    > >
    > > This could be accomplished by taking every d_lock, but this would mean a
    > > huge number of locks and actually gets very tricky.
    > >
    > > Solve this instead by using the rename seqlock for multi-step read-side
    > > operations. Insert operations are not serialised. Delete operations are
    > > tricky when walking up the directory our parent might have been deleted
    > > when dropping locks so also need to check and retry for that.
    > >
    > > XXX: hmm, we could of course just take the rename lock if there is any worry
    > > about livelock. Most of these are slow paths.
    >
    >
    > Ah, does this address John's issue?

    This is where John's issue is introduced. I actually again couldn't
    see the problem (thought I saw a problem, then lost it!).

    Got to think about it and test more... I couldn't reproduce the problem
    mind you, but I was testing mainline wheras bug was seen on -rt.


    \
     
     \ /
      Last update: 2010-06-24 17:05    [W:2.548 / U:0.404 seconds]
    ©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site