Messages in this thread | | | Date | Fri, 20 May 2022 14:43:22 +0200 | From | "Jason A. Donenfeld" <> | Subject | Re: [PATCHSET 0/2] Fix splice from random/urandom |
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Hi Jens,
On Thu, May 19, 2022 at 07:10:56PM -0600, Jens Axboe wrote: > On 5/19/22 7:00 PM, Jason A. Donenfeld wrote: > > Hi Jens, > > > > On Thu, May 19, 2022 at 06:56:12PM -0600, Jens Axboe wrote: > >> On 5/19/22 6:48 PM, Jason A. Donenfeld wrote: > >>> sendfile() returns -EINVAL even with your patches. Only splicing to pipes > >>> seems to work. > >> > >> Huh, that really should work. Are you trying to sendfile() to random? If > >> so, you need that last write_iter patch too, and add the splice_write as > >> I mentioned. > > > > No, I've only tried the read side so far. I made a little program: > > > > #include <sys/sendfile.h> > > #include <stdio.h> > > > > int main(int argc, char *argv[]) > > { > > ssize_t s = sendfile(1, 0, NULL, 0xffff); > > fprintf(stderr, "ret: %zd\n", s); > > return 0; > > } > > > > Then I ran `./a.out < /dev/urandom > /dev/null`. Fails. OTOH, if I > > replace /dev/urandom with an ordinary file, it succeeds. > > Here's why, it's limited to regular files or block devices: > > if (unlikely(!S_ISREG(i_mode) && !S_ISBLK(i_mode))) > return -EINVAL; > > in splice_direct_to_actor().
Indeed. Looks like that was your code from long long ago!
I posted https://lore.kernel.org/lkml/20220520095747.123748-1-Jason@zx2c4.com/ to fix it if you'd like to review.
Jason
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