> From: Rick Jones [mailto:rick.jones2@xxxxxxx] > Sent: Tuesday, June 28, 2016 23:43 > To: Dexuan Cui <decui@xxxxxxxxxxxxx>; David Miller <davem@xxxxxxxxxxxxx> > Cc: gregkh@xxxxxxxxxxxxxxxxxxx; netdev@xxxxxxxxxxxxxxx; linux- > kernel@xxxxxxxxxxxxxxx; devel@xxxxxxxxxxxxxxxxxxxxxx; olaf@xxxxxxxxx; > apw@xxxxxxxxxxxxx; jasowang@xxxxxxxxxx; vkuznets@xxxxxxxxxx; > cavery@xxxxxxxxxx; KY Srinivasan <kys@xxxxxxxxxxxxx>; Haiyang Zhang > <haiyangz@xxxxxxxxxxxxx>; joe@xxxxxxxxxxx > Subject: Re: [PATCH v12 net-next 1/1] hv_sock: introduce Hyper-V Sockets > > On 06/28/2016 02:59 AM, Dexuan Cui wrote: > > The idea here is: IMO the syscalls sys_read()/write() shoudn't return > > -ENOMEM, so I have to make sure the buffer allocation succeeds? > > > > I tried to use kmalloc with __GFP_NOFAIL, but I hit a warning in > > in mm/page_alloc.c: > > WARN_ON_ONCE((gfp_flags & __GFP_NOFAIL) && (order > 1)); > > > > What error code do you think I should return? > > EAGAIN, ERESTARTSYS, or something else? > > > > May I have your suggestion? Thanks! > > What happens as far as errno is concerned when an application makes a > read() call against a (say TCP) socket associated with a connection > which has been reset? I suppose it is ECONNRESET (Connection reset by peer). > Is it limited to those errno values listed in the > read() manpage, or does it end-up getting an errno value from those > listed in the recv() manpage? Or, perhaps even one not (presently) > listed in either? > > rick jones Actually "man read/write" says "Other errors may occur, depending on the object connected to fd". "man send/recv" indeed lists ENOMEM. Considering AF_HYPERV is a new socket type, ENOMEM seems OK to me and I'm going to post a new version of the patch. In the long run, I think we should add a new API in the VMBus driver, allowing data copy from VMBus ringbuffer into user mode buffer directly. This way, we can even eliminate this temporary buffer. Thanks, -- Dexuan _______________________________________________ devel mailing list devel@xxxxxxxxxxxxxxxxxxxxxx http://driverdev.linuxdriverproject.org/mailman/listinfo/driverdev-devel
