On 2014/10/30 17:23, Markus Armbruster wrote: > Michael Tokarev <m...@tls.msk.ru> writes: > >> 30.10.2014 10:10, Markus Armbruster wrote: >>> <arei.gong...@huawei.com> writes: >>> >>>> From: Gonglei <arei.gong...@huawei.com> >>>> >>>> After commit 4c7e251a (), when dump memory completed, >>>> the s->fd will be closed twice. We should return >>>> directly when dump completed. >>>> >>>> Using do/while block, make the badly chosen return >>>> values of get_next_block() more visible and fix >>>> this issue. >>>> >>>> Signed-off-by: Gonglei <arei.gong...@huawei.com> >>> >>> I'm afraid the commit message is a bit misleading. Let's examine what >>> exactly happens. >>> >>> dump_iterate() dumps blocks in a loop. Eventually, get_next_block() >>> returns "no more". We then call dump_completed(). But we neglect to >>> break the loop! Broken in commit 4c7e251a. >>> >>> Because of that, we dump the last block again. This attempts to write >>> to s->fd, which fails if we're lucky. The error makes dump_iterate() >>> return unsuccessfully. It's the only way it can ever return. >>> >>> Theoretical: if we're not so lucky, something else has opened something >>> for writing and got the same fd. dump_iterate() then keeps looping, >>> messing up the something else's output, until a write fails, or the >>> process mercifully terminates. >>> >>> Is this correct? >> >> Heh. I was starring at all this last 20 minutes, re-reading the >> original v1 patch and your (Marcus) followup suggestion, trying to >> match the commit description with the actual happening and with the >> "no return" case which was before this patch. Oh well. >> >> Yes, this looks correct indeed, we come to the same conclusion. >> But at this stage I really wonder if this is a -trivial material. > > Distinguished old math professor does a proof on the blackboard. At > some point he faces the audience and says "this is trivial". Faces > blackboard, pauses. "Is it trivial?" Pauses again. Storms out of the > classroom. After ten minutes, he comes back and exclaims "it *is* > trivial!" >
:) >> (I can apply it to -trivial because no maintainer is listed for >> this file and because after some digging it becomes obvious). > > Appreciated! Do I need to send v3 for changing commit message, or /mjt do it directly? Thanks Best regards, -Gonglei
