Messages in this thread | | | Date | Thu, 19 May 2022 19:10:56 -0600 | Subject | Re: [PATCHSET 0/2] Fix splice from random/urandom | From | Jens Axboe <> |
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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().
-- Jens Axboe
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