Messages in this thread | | | Date | Mon, 11 Nov 2002 17:48:17 +0000 (GMT) | From | Hugh Dickins <> | Subject | Re: [PATCH] loop sendfile retval |
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On Mon, 11 Nov 2002, Linus Torvalds wrote: > On Mon, 11 Nov 2002, Hugh Dickins wrote: > > > > Buffer I/O error on device loop: its use of sendfile is (trivially) > > broken - retval is usually count done, only an error when negative. > > Hmm.. Sendfile can return other values than "count" (ie a partial read). > This return value change makes "do_lo_receive()" lose that information. As > such, the new do_lo_receive() is weaker than the old one.
True, with that patch it's passing back less info than 2.5.47 tried to do; but no less than 2.5.46 and earlier, which always returned desc.error and ignored the desc.written, desc.count coming back from do_generic_file_read. So it's not a regression, but of course you're right that it's weak.
> If fixing the loop code to handle partial IO is too nasty, then I would > suggest doing maybe something like > > if (ret > 0 && ret != bvec->bv_len) > ret = -EIO; > > which at least makes a partial IO an error instead of making it a success > case (the code as-is seems to think that any non-negative return value > means that the IO was fully successful). > > > Nearby spinlocking clearly bogus, delete instead of remarking on it. > > I'll apply the patch, it looks better than what is there now, but it might > be worth fixing this _right_.
Thanks, that gets it going again. I'll step aside and leave the correct partial handling to those who know loop much better than I - Adam?
Hugh
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