From: Bijan Mottahedeh <[email protected]>
To: Pavel Begunkov <[email protected]>,
[email protected], [email protected]
Subject: Re: [PATCH v3 08/13] io_uring: implement fixed buffers registration similar to fixed files
Date: Wed, 6 Jan 2021 11:46:47 -0800 [thread overview]
Message-ID: <[email protected]> (raw)
In-Reply-To: <[email protected]>
On 1/4/2021 6:43 PM, Pavel Begunkov wrote:
> On 18/12/2020 18:07, Bijan Mottahedeh wrote:
>> Apply fixed_rsrc functionality for fixed buffers support.
>
> git generated a pretty messy diff...
I had tried to break this up a few ways but it didn't work well because
I think most of the code changes depend on the io_uring structure
changes. I can look again or if you some idea of how you want to split
it, I can do that.
> Because it's do quiesce, fixed read/write access buffers from asynchronous
> contexts without synchronisation. That won't work anymore, so
>
> 1. either we save it in advance, that would require extra req_async
> allocation for linked fixed rw
>
> 2. or synchronise whenever async. But that would mean that a request
> may get and do IO on two different buffers, that's rotten.
>
> 3. do mixed -- lazy, but if do IO then alloc.
>
> 3.5 also "synchronise" there would mean uring_lock, that's not welcome,
> but we can probably do rcu.
Are you referring to a case where a fixed buffer request can be
submitted from async context while those buffers are being unregistered,
or something like that?
> Let me think of a patch...
Ok, will wait for it.
>> @@ -8373,7 +8433,13 @@ static bool headpage_already_acct(struct io_ring_ctx *ctx, struct page **pages,
>>
>> /* check previously registered pages */
>> for (i = 0; i < ctx->nr_user_bufs; i++) {
>> - struct io_mapped_ubuf *imu = &ctx->user_bufs[i];
>> + struct fixed_rsrc_table *table;
>> + struct io_mapped_ubuf *imu;
>> + unsigned int index;
>> +
>> + table = &ctx->buf_data->table[i >> IORING_BUF_TABLE_SHIFT];
>> + index = i & IORING_BUF_TABLE_MASK;
>> + imu = &table->bufs[index];
>
> io_buf_from_index() may tak buf_data, so can be reused.
Ok.
>> + for (i = 0; i < nr_tables; i++) {
>> + struct fixed_rsrc_table *table = &buf_data->table[i];
>> + unsigned int this_bufs;
>> +
>> + this_bufs = min(nr_bufs, IORING_MAX_BUFS_TABLE);
>> + table->bufs = kcalloc(this_bufs, sizeof(struct io_mapped_ubuf),
>> + GFP_KERNEL);
>> + if (!table->bufs)
>> + break;
>> + nr_bufs -= this_bufs;
>> + }
>> +
>> + if (i == nr_tables)
>> + return 0;
>> +
>> + io_free_buf_tables(buf_data, nr_tables);
>
> Would work because kcalloc() zeroed buf_data->table, but
>
> io_free_buf_tables(buf_data, __i__);
Ok.
>> ret = io_buffer_validate(&iov);
>> if (ret)
>> break;
>>
>> + table = &buf_data->table[i >> IORING_BUF_TABLE_SHIFT];
>
> same, io_buf_from_index() can be reused
>
>> + index = i & IORING_BUF_TABLE_MASK;
>> + imu = &table->bufs[index];
Ok.
>> @@ -9854,6 +10023,7 @@ static bool io_register_op_must_quiesce(int op)
>> switch (op) {
>> case IORING_UNREGISTER_FILES:
>> case IORING_REGISTER_FILES_UPDATE:
>> + case IORING_UNREGISTER_BUFFERS:
>
> what about REGISTER_BUFFERS?
I followed the FILES case, which deals with UNREGISTER and UPDATE only,
should I add REGISTER for buffers only?
next prev parent reply other threads:[~2021-01-06 19:47 UTC|newest]
Thread overview: 32+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-12-18 18:07 [PATCH v3 00/13] io_uring: buffer registration enhancements Bijan Mottahedeh
2020-12-18 18:07 ` [PATCH v3 01/13] io_uring: modularize io_sqe_buffer_register Bijan Mottahedeh
2021-01-04 21:54 ` Pavel Begunkov
2021-01-06 19:46 ` Bijan Mottahedeh
2020-12-18 18:07 ` [PATCH v3 02/13] io_uring: modularize io_sqe_buffers_register Bijan Mottahedeh
2021-01-04 21:48 ` Pavel Begunkov
2020-12-18 18:07 ` [PATCH v3 03/13] io_uring: rename file related variables to rsrc Bijan Mottahedeh
2021-01-05 1:53 ` Pavel Begunkov
2021-01-06 19:46 ` Bijan Mottahedeh
2020-12-18 18:07 ` [PATCH v3 04/13] io_uring: generalize io_queue_rsrc_removal Bijan Mottahedeh
2020-12-18 18:07 ` [PATCH v3 05/13] io_uring: separate ref_list from fixed_rsrc_data Bijan Mottahedeh
2020-12-18 18:07 ` [PATCH v3 06/13] io_uring: generalize fixed_file_ref_node functionality Bijan Mottahedeh
2020-12-18 18:07 ` [PATCH v3 07/13] io_uring: add rsrc_ref locking routines Bijan Mottahedeh
2020-12-18 18:07 ` [PATCH v3 08/13] io_uring: implement fixed buffers registration similar to fixed files Bijan Mottahedeh
2021-01-05 2:43 ` Pavel Begunkov
2021-01-06 19:46 ` Bijan Mottahedeh [this message]
2021-01-06 22:22 ` Pavel Begunkov
2021-01-07 2:37 ` Pavel Begunkov
2021-01-07 21:21 ` Bijan Mottahedeh
2021-01-07 21:37 ` Pavel Begunkov
2021-01-07 22:14 ` Bijan Mottahedeh
2021-01-07 22:33 ` Pavel Begunkov
2021-01-07 23:10 ` Pavel Begunkov
2021-01-08 1:53 ` Bijan Mottahedeh
2021-01-11 5:12 ` Pavel Begunkov
2021-01-08 0:17 ` Bijan Mottahedeh
2020-12-18 18:07 ` [PATCH v3 09/13] io_uring: create common fixed_rsrc_ref_node handling routines Bijan Mottahedeh
2020-12-18 18:07 ` [PATCH v3 10/13] io_uring: generalize files_update functionlity to rsrc_update Bijan Mottahedeh
2020-12-18 18:07 ` [PATCH v3 11/13] io_uring: support buffer registration updates Bijan Mottahedeh
2020-12-18 18:07 ` [PATCH v3 12/13] io_uring: create common fixed_rsrc_data allocation routines Bijan Mottahedeh
2020-12-18 18:07 ` [PATCH v3 13/13] io_uring: support buffer registration sharing Bijan Mottahedeh
2021-01-04 17:09 ` [PATCH v3 00/13] io_uring: buffer registration enhancements Bijan Mottahedeh
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