> -----Original Message----- > From: Benny Halevy [mailto:bhalevy@xxxxxxxxxx] > Sent: Tuesday, September 13, 2011 4:32 AM > To: Peng Tao > Cc: Trond Myklebust; Peng, Tao; gusev.vitaliy@xxxxxxxxxxx; > gusev.vitaliy@xxxxxxxxx; linux-nfs@xxxxxxxxxxxxxxx > Subject: Re: [PATCH] nfs: fix inifinite loop at nfs4_layoutcommit_release > > On 2011-09-12 07:56, Peng Tao wrote: > > On Sat, Sep 10, 2011 at 3:14 PM, Benny Halevy <bhalevy@xxxxxxxxxx> wrote: > >> On 2011-09-09 11:20, Trond Myklebust wrote: > >>> On Thu, 2011-09-08 at 23:11 -0400, tao.peng@xxxxxxx wrote: > >>>> HI, Trond, > >>>> > >>>>> -----Original Message----- > >>>>> From: Myklebust, Trond [mailto:Trond.Myklebust@xxxxxxxxxx] > >>>>> Sent: Friday, September 09, 2011 1:05 AM > >>>>> To: Peng Tao > >>>>> Cc: Peng, Tao; gusev.vitaliy@xxxxxxxxxxx; gusev.vitaliy@xxxxxxxxx; > >>>>> linux-nfs@xxxxxxxxxxxxxxx > >>>>> Subject: RE: [PATCH] nfs: fix inifinite loop at nfs4_layoutcommit_release > >>>>> > >>>>>> -----Original Message----- > >>>>>> From: Peng Tao [mailto:bergwolf@xxxxxxxxx] > >>>>>> Sent: Thursday, September 08, 2011 11:00 AM > >>>>>> To: Myklebust, Trond > >>>>>> Cc: tao.peng@xxxxxxx; gusev.vitaliy@xxxxxxxxxxx; > >>>>>> gusev.vitaliy@xxxxxxxxx; linux-nfs@xxxxxxxxxxxxxxx > >>>>>> Subject: Re: [PATCH] nfs: fix inifinite loop at > >>>>>> nfs4_layoutcommit_release > >>>>>> > >>>>>> On Thu, Sep 8, 2011 at 8:01 PM, Myklebust, Trond > >>>>>> <Trond.Myklebust@xxxxxxxxxx> wrote: > >>>>>>>> -----Original Message----- > >>>>>> > >>>>>>> > >>>>>>> Yes, but as far as I can see, even in the blocks case there can be > >>>>>> multiple extents per layout segment. What if I write to one > >>>>>> uninitialised extent, layoutcommit, then write to another uninitialized > >>>>>> extent in the same layout segment and layoutcommit? In my reading of > >>>>>> the code, there is a chance that the second layoutcommit will fail to > >>>>>> pick up the layout segment, and so will fail to notify the MDS that the > >>>>>> second extent now contains data. > >>>>>> > >>>>>> blocklayout does not decide what to layoutcommit according to the lseg > >>>>>> list. Instead, it keeps track of each extent's state at the > >>>>>> granularity of blocksize, and encode whatever needs layoutcommitted in > >>>>>> the layoutcommit call. So in your above case, as long as the second > >>>>>> layoutcommit is issued, blocklayout will encode the newly written > >>>>>> extent in the second layoutcommit call, even if the lseg is not > >>>>>> attached to the second layoutcommit. > >>>>>> > >>>>>> But that leads to another two question: > >>>>>> 1. How do we protect against layoutrecall if lseg is not linked to > >>>>>> layoutcommit? For this one, can we just reject layoutrecall if there > >>>>>> is inflight layoutcommit? It will be less parallel but can guarantee > >>>>>> current implementation correctness. > >>>>>> 2. blocklayout ONLY: bl_committing may be overloaded by several > >>>>>> layoutcommit calls and we don't have information in > >>>>>> cleanup_layoutcommit() on how many entry should be removed from > >>>>>> bl_committing. Maybe we can add a (void*) to struct > >>>>>> nfs4_layoutcommit_data, so that LD can pass some private information > >>>>>> between encode_layoutcommit() and cleanup_layoutcommit()? > >>>>> > >>>>> 3. What is the purpose of pinning the layout segment at all if neither blocks, > nor > >>>>> objects nor files cares? > >>>> I believe it is for protecting against layoutrecall. But since we are seperating > lseg and LD specific layout information management, it is actually not working as > expected. > >>>> > >> > >> The layout segments are not really in use while in LAYOUTCOMMIT. > >> We only need to get the stateid right with respect to concurrent layout recalls. > > LAYOUTCOMMIT takes lseg reference to mark them as in use so that > > layoutrecall cannot free them. > > > > And if layoutrecall would have freed layout segments during layoutcommit, > what is your specific concern? In layoutcommit_release, blocklayout need to access the corresponding extents to convert their states. If the layout segments are freed by layoutrecall, it can cause problems. > > Benny -- To unsubscribe from this list: send the line "unsubscribe linux-nfs" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
