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From: Jens Axboe <[email protected]>
To: Stefan Metzmacher <[email protected]>, [email protected]
Cc: [email protected]
Subject: Re: [PATCH v2 1/1] io_uring: call req_set_fail_links() on short send[msg]()/recv[msg]() with MSG_WAITALL
Date: Sat, 20 Mar 2021 16:57:42 -0600	[thread overview]
Message-ID: <[email protected]> (raw)
In-Reply-To: <12efc18b6bef3955500080a238197e90ca6a402c.1616268538.git.metze@samba.org>

On 3/20/21 1:33 PM, Stefan Metzmacher wrote:
> Without that it's not safe to use them in a linked combination with
> others.
> 
> Now combinations like IORING_OP_SENDMSG followed by IORING_OP_SPLICE
> should be possible.
> 
> We already handle short reads and writes for the following opcodes:
> 
> - IORING_OP_READV
> - IORING_OP_READ_FIXED
> - IORING_OP_READ
> - IORING_OP_WRITEV
> - IORING_OP_WRITE_FIXED
> - IORING_OP_WRITE
> - IORING_OP_SPLICE
> - IORING_OP_TEE
> 
> Now we have it for these as well:
> 
> - IORING_OP_SENDMSG
> - IORING_OP_SEND
> - IORING_OP_RECVMSG
> - IORING_OP_RECV
> 
> For IORING_OP_RECVMSG we also check for the MSG_TRUNC and MSG_CTRUNC
> flags in order to call req_set_fail_links().
> 
> There might be applications arround depending on the behavior
> that even short send[msg]()/recv[msg]() retuns continue an
> IOSQE_IO_LINK chain.
> 
> It's very unlikely that such applications pass in MSG_WAITALL,
> which is only defined in 'man 2 recvmsg', but not in 'man 2 sendmsg'.
> 
> It's expected that the low level sock_sendmsg() call just ignores
> MSG_WAITALL, as MSG_ZEROCOPY is also ignored without explicitly set
> SO_ZEROCOPY.
> 
> We also expect the caller to know about the implicit truncation to
> MAX_RW_COUNT, which we don't detect.

Thanks, I do think this is much better and I feel comfortable getting
htis applied for 5.12 (and stable).

-- 
Jens Axboe


  reply	other threads:[~2021-03-20 22:58 UTC|newest]

Thread overview: 15+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-03-16 15:33 [PATCH 0/2] send[msg]()/recv[msg]() fixes/improvements Stefan Metzmacher
2021-03-16 15:33 ` [PATCH 1/2] io_uring: call req_set_fail_links() on short send[msg]()/recv[msg]() calls Stefan Metzmacher
2021-03-20 19:33   ` [PATCH v2 1/1] io_uring: call req_set_fail_links() on short send[msg]()/recv[msg]() with MSG_WAITALL Stefan Metzmacher
2021-03-20 22:57     ` Jens Axboe [this message]
2021-03-21 10:20       ` Stefan Metzmacher
2021-03-21 13:10         ` Jens Axboe
2021-03-16 15:33 ` [PATCH 2/2] io_uring: imply MSG_NOSIGNAL for send[msg]()/recv[msg]() calls Stefan Metzmacher
2021-03-17 22:36 ` [PATCH 0/2] send[msg]()/recv[msg]() fixes/improvements Jens Axboe
2021-03-17 23:07   ` Pavel Begunkov
2021-03-17 23:24     ` Jens Axboe
2021-03-17 23:26     ` Stefan Metzmacher
2021-03-17 23:39       ` Pavel Begunkov
2021-03-18  0:15         ` Stefan Metzmacher
2021-03-18 13:00           ` Pavel Begunkov
2021-03-18 13:08           ` Pavel Begunkov

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