From: Jens Axboe <axboe@kernel.dk> To: Kanchan Joshi <joshiiitr@gmail.com> Cc: Kanchan Joshi <joshi.k@samsung.com>, viro@zeniv.linux.org.uk, bcrl@kvack.org, Matthew Wilcox <willy@infradead.org>, Christoph Hellwig <hch@infradead.org>, Damien Le Moal <Damien.LeMoal@wdc.com>, asml.silence@gmail.com, linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org, linux-aio@kvack.org, io-uring@vger.kernel.org, linux-block@vger.kernel.org, linux-api@vger.kernel.org, SelvaKumar S <selvakuma.s1@samsung.com>, Nitesh Shetty <nj.shetty@samsung.com>, Javier Gonzalez <javier.gonz@samsung.com> Subject: Re: [PATCH v4 6/6] io_uring: add support for zone-append Date: Mon, 27 Jul 2020 14:34:28 -0600 Message-ID: <b0b7159d-ed10-08ad-b6c7-b85d45f60d16@kernel.dk> (raw) In-Reply-To: <CA+1E3rJAa3E2Ti0fvvQTzARP797qge619m4aYLjXeR3wxdFwWw@mail.gmail.com> On 7/27/20 1:16 PM, Kanchan Joshi wrote: > On Fri, Jul 24, 2020 at 10:00 PM Jens Axboe <axboe@kernel.dk> wrote: >> >> On 7/24/20 9:49 AM, Kanchan Joshi wrote: >>> diff --git a/fs/io_uring.c b/fs/io_uring.c >>> index 7809ab2..6510cf5 100644 >>> --- a/fs/io_uring.c >>> +++ b/fs/io_uring.c >>> @@ -1284,8 +1301,15 @@ static void __io_cqring_fill_event(struct io_kiocb *req, long res, long cflags) >>> cqe = io_get_cqring(ctx); >>> if (likely(cqe)) { >>> WRITE_ONCE(cqe->user_data, req->user_data); >>> - WRITE_ONCE(cqe->res, res); >>> - WRITE_ONCE(cqe->flags, cflags); >>> + if (unlikely(req->flags & REQ_F_ZONE_APPEND)) { >>> + if (likely(res > 0)) >>> + WRITE_ONCE(cqe->res64, req->rw.append_offset); >>> + else >>> + WRITE_ONCE(cqe->res64, res); >>> + } else { >>> + WRITE_ONCE(cqe->res, res); >>> + WRITE_ONCE(cqe->flags, cflags); >>> + } >> >> This would be nice to keep out of the fast path, if possible. > > I was thinking of keeping a function-pointer (in io_kiocb) during > submission. That would have avoided this check......but argument count > differs, so it did not add up. But that'd grow the io_kiocb just for this use case, which is arguably even worse. Unless you can keep it in the per-request private data, but there's no more room there for the regular read/write side. >>> diff --git a/include/uapi/linux/io_uring.h b/include/uapi/linux/io_uring.h >>> index 92c2269..2580d93 100644 >>> --- a/include/uapi/linux/io_uring.h >>> +++ b/include/uapi/linux/io_uring.h >>> @@ -156,8 +156,13 @@ enum { >>> */ >>> struct io_uring_cqe { >>> __u64 user_data; /* sqe->data submission passed back */ >>> - __s32 res; /* result code for this event */ >>> - __u32 flags; >>> + union { >>> + struct { >>> + __s32 res; /* result code for this event */ >>> + __u32 flags; >>> + }; >>> + __s64 res64; /* appending offset for zone append */ >>> + }; >>> }; >> >> Is this a compatible change, both for now but also going forward? You >> could randomly have IORING_CQE_F_BUFFER set, or any other future flags. > > Sorry, I didn't quite understand the concern. CQE_F_BUFFER is not > used/set for write currently, so it looked compatible at this point. Not worried about that, since we won't ever use that for writes. But it is a potential headache down the line for other flags, if they apply to normal writes. > Yes, no room for future flags for this operation. > Do you see any other way to enable this support in io-uring? Honestly I think the only viable option is as we discussed previously, pass in a pointer to a 64-bit type where we can copy the additional completion information to. >> Layout would also be different between big and little endian, so not >> even that easy to set aside a flag for this. But even if that was done, >> we'd still have this weird API where liburing or the app would need to >> distinguish this cqe from all others based on... the user_data? Hence >> liburing can't do it, only the app would be able to. >> >> Just seems like a hack to me. > > Yes, only user_data to distinguish. Do liburing helpers need to look > at cqe->res (and decide something) before returning the cqe to > application? They generally don't, outside of the internal timeout. But it's an issue for the API, as it forces applications to handle the CQEs a certain way. Normally there's flexibility. This makes the append writes behave differently than everything else, which is never a good idea. -- Jens Axboe
next prev parent reply index Thread overview: 52+ messages / expand[flat|nested] mbox.gz Atom feed top [not found] <CGME20200724155244epcas5p2902f57e36e490ee8772da19aa9408cdc@epcas5p2.samsung.com> 2020-07-24 15:49 ` [PATCH v4 0/6] zone-append support in io-uring and aio Kanchan Joshi [not found] ` <CGME20200724155258epcas5p1a75b926950a18cd1e6c8e7a047e6c589@epcas5p1.samsung.com> 2020-07-24 15:49 ` [PATCH v4 1/6] fs: introduce FMODE_ZONE_APPEND and IOCB_ZONE_APPEND Kanchan Joshi 2020-07-24 16:34 ` Jens Axboe 2020-07-26 15:18 ` Christoph Hellwig 2020-07-28 1:49 ` Matthew Wilcox 2020-07-28 7:26 ` Christoph Hellwig [not found] ` <CGME20200724155324epcas5p18e1d3b4402d1e4a8eca87d0b56a3fa9b@epcas5p1.samsung.com> 2020-07-24 15:49 ` [PATCH v4 2/6] fs: change ki_complete interface to support 64bit ret2 Kanchan Joshi 2020-07-26 15:18 ` Christoph Hellwig [not found] ` <CGME20200724155329epcas5p345ba6bad0b8fe18056bb4bcd26c10019@epcas5p3.samsung.com> 2020-07-24 15:49 ` [PATCH v4 3/6] uio: return status with iov truncation Kanchan Joshi [not found] ` <CGME20200724155341epcas5p15bfc55927f2abb60f19784270fe8e377@epcas5p1.samsung.com> 2020-07-24 15:49 ` [PATCH v4 4/6] block: add zone append handling for direct I/O path Kanchan Joshi 2020-07-26 15:19 ` Christoph Hellwig [not found] ` <CGME20200724155346epcas5p2cfb383fe9904a45280c6145f4c13e1b4@epcas5p2.samsung.com> 2020-07-24 15:49 ` [PATCH v4 5/6] block: enable zone-append for iov_iter of bvec type Kanchan Joshi 2020-07-26 15:20 ` Christoph Hellwig [not found] ` <CGME20200724155350epcas5p3b8f1d59eda7f8fbb38c828f692d42fd6@epcas5p3.samsung.com> 2020-07-24 15:49 ` [PATCH v4 6/6] io_uring: add support for zone-append Kanchan Joshi 2020-07-24 16:29 ` Jens Axboe 2020-07-27 19:16 ` Kanchan Joshi 2020-07-27 20:34 ` Jens Axboe [this message] 2020-07-30 16:08 ` Pavel Begunkov 2020-07-30 16:13 ` Jens Axboe 2020-07-30 16:26 ` Pavel Begunkov 2020-07-30 17:16 ` Jens Axboe 2020-07-30 17:38 ` Pavel Begunkov 2020-07-30 17:51 ` Kanchan Joshi 2020-07-30 17:54 ` Jens Axboe 2020-07-30 18:25 ` Kanchan Joshi 2020-07-31 6:42 ` Damien Le Moal 2020-07-31 6:45 ` hch 2020-07-31 6:59 ` Damien Le Moal 2020-07-31 7:58 ` Kanchan Joshi 2020-07-31 8:14 ` Damien Le Moal 2020-07-31 9:14 ` hch 2020-07-31 9:34 ` Damien Le Moal 2020-07-31 9:41 ` hch 2020-07-31 10:16 ` Damien Le Moal 2020-07-31 12:51 ` hch 2020-07-31 13:08 ` hch 2020-07-31 15:07 ` Kanchan Joshi 2020-08-05 7:35 ` Damien Le Moal 2020-08-14 8:14 ` hch 2020-08-14 8:27 ` Damien Le Moal 2020-08-14 12:04 ` hch 2020-08-14 12:20 ` Damien Le Moal 2020-09-07 7:01 ` Kanchan Joshi 2020-09-08 15:18 ` hch 2020-09-24 17:19 ` Kanchan Joshi 2020-09-25 2:52 ` Damien Le Moal 2020-09-28 18:58 ` Kanchan Joshi 2020-09-29 1:24 ` Damien Le Moal 2020-09-29 18:49 ` Kanchan Joshi 2020-07-31 9:38 ` Kanchan Joshi 2020-07-31 7:08 ` Kanchan Joshi 2020-07-30 15:57 ` Pavel Begunkov
Reply instructions: You may reply publicly to this message via plain-text email using any one of the following methods: * Save the following mbox file, import it into your mail client, and reply-to-all from there: mbox Avoid top-posting and favor interleaved quoting: https://en.wikipedia.org/wiki/Posting_style#Interleaved_style * Reply using the --to, --cc, and --in-reply-to switches of git-send-email(1): git send-email \ --in-reply-to=b0b7159d-ed10-08ad-b6c7-b85d45f60d16@kernel.dk \ --to=axboe@kernel.dk \ --cc=Damien.LeMoal@wdc.com \ --cc=asml.silence@gmail.com \ --cc=bcrl@kvack.org \ --cc=hch@infradead.org \ --cc=io-uring@vger.kernel.org \ --cc=javier.gonz@samsung.com \ --cc=joshi.k@samsung.com \ --cc=joshiiitr@gmail.com \ --cc=linux-aio@kvack.org \ --cc=linux-api@vger.kernel.org \ --cc=linux-block@vger.kernel.org \ --cc=linux-fsdevel@vger.kernel.org \ --cc=linux-kernel@vger.kernel.org \ --cc=nj.shetty@samsung.com \ --cc=selvakuma.s1@samsung.com \ --cc=viro@zeniv.linux.org.uk \ --cc=willy@infradead.org \ /path/to/YOUR_REPLY https://kernel.org/pub/software/scm/git/docs/git-send-email.html * If your mail client supports setting the In-Reply-To header via mailto: links, try the mailto: link
Linux-api Archive on lore.kernel.org Archives are clonable: git clone --mirror https://lore.kernel.org/linux-api/0 linux-api/git/0.git # If you have public-inbox 1.1+ installed, you may # initialize and index your mirror using the following commands: public-inbox-init -V2 linux-api linux-api/ https://lore.kernel.org/linux-api \ linux-api@vger.kernel.org public-inbox-index linux-api Example config snippet for mirrors Newsgroup available over NNTP: nntp://nntp.lore.kernel.org/org.kernel.vger.linux-api AGPL code for this site: git clone https://public-inbox.org/public-inbox.git