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Message-ID: <8f890747-c37f-2fd4-2428-4a9ffc865cac@kernel.dk>
Date: Thu, 19 May 2022 19:05:57 -0600
From: Jens Axboe <axboe@...nel.dk>
To: "Jason A. Donenfeld" <Jason@...c4.com>
Cc: Theodore Ts'o <tytso@....edu>, Christoph Hellwig <hch@....de>,
LKML <linux-kernel@...r.kernel.org>
Subject: Re: [PATCHSET 0/2] Fix splice from random/urandom
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.
Yeah I reproduced the same, doing it the other way works fine. Curious
enough to see what it is, looking into it.
--
Jens Axboe
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