fs/io_uring.c stable additions

fs/io_uring.c stable additions

[Jens Axboe]

Hi,

I forgot to mark a few patches for io_uring as stable. In order
of how to apply, can you add the following commits for 5.2?

f7b76ac9d17e16e44feebb6d2749fec92bfd6dd4
c0e48f9dea9129aa11bec3ed13803bcc26e96e49
bd11b3a391e3df6fa958facbe4b3f9f4cca9bd49
36703247d5f52a679df9da51192b6950fe81689f

Thanks!

-- 
Jens Axboe

Re: fs/io_uring.c stable additions

[Greg Kroah-Hartman]

On Mon, Jul 29, 2019 at 12:08:28PM -0600, Jens Axboe wrote:
> Hi,
> 
> I forgot to mark a few patches for io_uring as stable. In order
> of how to apply, can you add the following commits for 5.2?
> 
> f7b76ac9d17e16e44feebb6d2749fec92bfd6dd4

Does not apply :(

> c0e48f9dea9129aa11bec3ed13803bcc26e96e49

Now queued up.

> bd11b3a391e3df6fa958facbe4b3f9f4cca9bd49

Does not apply :(

> 36703247d5f52a679df9da51192b6950fe81689f

Now queued up.

You are 2 out of 4 :)

Care to send backported versions of the 2 that did not apply?  I'll be
glad to queue them up then.

thanks,

greg k-h

Re: fs/io_uring.c stable additions

[Jens Axboe]

On 7/29/19 12:15 PM, Greg Kroah-Hartman wrote:
> On Mon, Jul 29, 2019 at 12:08:28PM -0600, Jens Axboe wrote:
>> Hi,
>>
>> I forgot to mark a few patches for io_uring as stable. In order
>> of how to apply, can you add the following commits for 5.2?
>>
>> f7b76ac9d17e16e44feebb6d2749fec92bfd6dd4
> 
> Does not apply :(
> 
>> c0e48f9dea9129aa11bec3ed13803bcc26e96e49
> 
> Now queued up.
> 
>> bd11b3a391e3df6fa958facbe4b3f9f4cca9bd49
> 
> Does not apply :(
> 
>> 36703247d5f52a679df9da51192b6950fe81689f
> 
> Now queued up.
> 
> You are 2 out of 4 :)
> 
> Care to send backported versions of the 2 that did not apply?  I'll be
> glad to queue them up then.

Huh strange, I applied them to our internal 5.2 tree without conflict.
Maybe I had backported more...

I'll send versions for 5.2 in a bit for you.

-- 
Jens Axboe

Re: fs/io_uring.c stable additions

[Jens Axboe]

[-- Attachment #1: Type: text/plain, Size: 1033 bytes --]

On 7/29/19 12:17 PM, Jens Axboe wrote:
> On 7/29/19 12:15 PM, Greg Kroah-Hartman wrote:
>> On Mon, Jul 29, 2019 at 12:08:28PM -0600, Jens Axboe wrote:
>>> Hi,
>>>
>>> I forgot to mark a few patches for io_uring as stable. In order
>>> of how to apply, can you add the following commits for 5.2?
>>>
>>> f7b76ac9d17e16e44feebb6d2749fec92bfd6dd4
>>0ef67e605d2b1e8300d04fd9134d283bbbf441b9
>> Does not apply :(
>>
>>> c0e48f9dea9129aa11bec3ed13803bcc26e96e49
>>
>> Now queued up.
>>
>>> bd11b3a391e3df6fa958facbe4b3f9f4cca9bd49
>>
>> Does not apply :(
>>
>>> 36703247d5f52a679df9da51192b6950fe81689f
>>
>> Now queued up.
>>
>> You are 2 out of 4 :)
>>
>> Care to send backported versions of the 2 that did not apply?  I'll be
>> glad to queue them up then.
> 
> Huh strange, I applied them to our internal 5.2 tree without conflict.
> Maybe I had backported more...
> 
> I'll send versions for 5.2 in a bit for you.

Here you go, those two on top of the others. Ran it through the
regressions tests here, works for me.

-- 
Jens Axboe


[-- Attachment #2: 0002-io_uring-don-t-use-iov_iter_advance-for-fixed-buffer.patch --]
[-- Type: text/x-patch, Size: 3245 bytes --]

From b00254467e0d2fa90a82b5ffb7d8e990f6fee8df Mon Sep 17 00:00:00 2001
From: Jens Axboe <axboe@kernel.dk>
Date: Sat, 20 Jul 2019 08:37:31 -0600
Subject: [PATCH 2/2] io_uring: don't use iov_iter_advance() for fixed buffers

Hrvoje reports that when a large fixed buffer is registered and IO is
being done to the latter pages of said buffer, the IO submission time
is much worse:

reading to the start of the buffer: 11238 ns
reading to the end of the buffer:   1039879 ns

In fact, it's worse by two orders of magnitude. The reason for that is
how io_uring figures out how to setup the iov_iter. We point the iter
at the first bvec, and then use iov_iter_advance() to fast-forward to
the offset within that buffer we need.

However, that is abysmally slow, as it entails iterating the bvecs
that we setup as part of buffer registration. There's really no need
to use this generic helper, as we know it's a BVEC type iterator, and
we also know that each bvec is PAGE_SIZE in size, apart from possibly
the first and last. Hence we can just use a shift on the offset to
find the right index, and then adjust the iov_iter appropriately.
After this fix, the timings are:

reading to the start of the buffer: 10135 ns
reading to the end of the buffer:   1377 ns

Or about an 755x improvement for the tail page.

Reported-by: Hrvoje Zeba <zeba.hrvoje@gmail.com>
Tested-by: Hrvoje Zeba <zeba.hrvoje@gmail.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
(cherry picked from commit bd11b3a391e3df6fa958facbe4b3f9f4cca9bd49)
---
 fs/io_uring.c | 39 +++++++++++++++++++++++++++++++++++++--
 1 file changed, 37 insertions(+), 2 deletions(-)

diff --git a/fs/io_uring.c b/fs/io_uring.c
index c47f6bca760f..15e264e57f6c 100644
--- a/fs/io_uring.c
+++ b/fs/io_uring.c
@@ -999,8 +999,43 @@ static int io_import_fixed(struct io_ring_ctx *ctx, int rw,
 	 */
 	offset = buf_addr - imu->ubuf;
 	iov_iter_bvec(iter, rw, imu->bvec, imu->nr_bvecs, offset + len);
-	if (offset)
-		iov_iter_advance(iter, offset);
+
+	if (offset) {
+		/*
+		 * Don't use iov_iter_advance() here, as it's really slow for
+		 * using the latter parts of a big fixed buffer - it iterates
+		 * over each segment manually. We can cheat a bit here, because
+		 * we know that:
+		 *
+		 * 1) it's a BVEC iter, we set it up
+		 * 2) all bvecs are PAGE_SIZE in size, except potentially the
+		 *    first and last bvec
+		 *
+		 * So just find our index, and adjust the iterator afterwards.
+		 * If the offset is within the first bvec (or the whole first
+		 * bvec, just use iov_iter_advance(). This makes it easier
+		 * since we can just skip the first segment, which may not
+		 * be PAGE_SIZE aligned.
+		 */
+		const struct bio_vec *bvec = imu->bvec;
+
+		if (offset <= bvec->bv_len) {
+			iov_iter_advance(iter, offset);
+		} else {
+			unsigned long seg_skip;
+
+			/* skip first vec */
+			offset -= bvec->bv_len;
+			seg_skip = 1 + (offset >> PAGE_SHIFT);
+
+			iter->bvec = bvec + seg_skip;
+			iter->nr_segs -= seg_skip;
+			iter->count -= (seg_skip << PAGE_SHIFT);
+			iter->iov_offset = offset & ~PAGE_MASK;
+			if (iter->iov_offset)
+				iter->count -= iter->iov_offset;
+		}
+	}
 
 	/* don't drop a reference to these pages */
 	iter->type |= ITER_BVEC_FLAG_NO_REF;
-- 
2.17.1


[-- Attachment #3: 0001-io_uring-fix-counter-inc-dec-mismatch-in-async_list.patch --]
[-- Type: text/x-patch, Size: 1897 bytes --]

From 879d1e652332740de25ecc6091e7c1b82e7a3b24 Mon Sep 17 00:00:00 2001
From: Zhengyuan Liu <liuzhengyuan@kylinos.cn>
Date: Tue, 16 Jul 2019 23:26:14 +0800
Subject: [PATCH 1/2] io_uring: fix counter inc/dec mismatch in async_list

We could queue a work for each req in defer and link list without
increasing async_list->cnt, so we shouldn't decrease it while exiting
from workqueue as well if we didn't process the req in async list.

Thanks to Jens Axboe <axboe@kernel.dk> for his guidance.

Fixes: 31b515106428 ("io_uring: allow workqueue item to handle multiple buffered requests")
Signed-off-by: Zhengyuan Liu <liuzhengyuan@kylinos.cn>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
(cherry picked from commit f7b76ac9d17e16e44feebb6d2749fec92bfd6dd4)
---
 fs/io_uring.c | 8 ++++++++
 1 file changed, 8 insertions(+)

diff --git a/fs/io_uring.c b/fs/io_uring.c
index c6598fb786c3..c47f6bca760f 100644
--- a/fs/io_uring.c
+++ b/fs/io_uring.c
@@ -330,6 +330,9 @@ struct io_kiocb {
 #define REQ_F_SEQ_PREV		8	/* sequential with previous */
 #define REQ_F_IO_DRAIN		16	/* drain existing IO first */
 #define REQ_F_IO_DRAINED	32	/* drain done */
+#define REQ_F_LINK		64	/* linked sqes */
+#define REQ_F_LINK_DONE		128	/* linked sqes done */
+#define REQ_F_FAIL_LINK		256	/* fail rest of links */
 	u64			user_data;
 	u32			error;	/* iopoll result from callback */
 	u32			sequence;
@@ -1696,6 +1699,10 @@ static void io_sq_wq_submit_work(struct work_struct *work)
 		/* async context always use a copy of the sqe */
 		kfree(sqe);
 
+		/* req from defer and link list needn't decrease async cnt */
+		if (req->flags & (REQ_F_IO_DRAINED | REQ_F_LINK_DONE))
+			goto out;
+
 		if (!async_list)
 			break;
 		if (!list_empty(&req_list)) {
@@ -1743,6 +1750,7 @@ static void io_sq_wq_submit_work(struct work_struct *work)
 		}
 	}
 
+out:
 	if (cur_mm) {
 		set_fs(old_fs);
 		unuse_mm(cur_mm);
-- 
2.17.1

Re: fs/io_uring.c stable additions

[Greg Kroah-Hartman]

On Mon, Jul 29, 2019 at 12:35:14PM -0600, Jens Axboe wrote:
> On 7/29/19 12:17 PM, Jens Axboe wrote:
> > On 7/29/19 12:15 PM, Greg Kroah-Hartman wrote:
> > > On Mon, Jul 29, 2019 at 12:08:28PM -0600, Jens Axboe wrote:
> > > > Hi,
> > > > 
> > > > I forgot to mark a few patches for io_uring as stable. In order
> > > > of how to apply, can you add the following commits for 5.2?
> > > > 
> > > > f7b76ac9d17e16e44feebb6d2749fec92bfd6dd4
> > > 0ef67e605d2b1e8300d04fd9134d283bbbf441b9
> > > Does not apply :(
> > > 
> > > > c0e48f9dea9129aa11bec3ed13803bcc26e96e49
> > > 
> > > Now queued up.
> > > 
> > > > bd11b3a391e3df6fa958facbe4b3f9f4cca9bd49
> > > 
> > > Does not apply :(
> > > 
> > > > 36703247d5f52a679df9da51192b6950fe81689f
> > > 
> > > Now queued up.
> > > 
> > > You are 2 out of 4 :)
> > > 
> > > Care to send backported versions of the 2 that did not apply?  I'll be
> > > glad to queue them up then.
> > 
> > Huh strange, I applied them to our internal 5.2 tree without conflict.
> > Maybe I had backported more...
> > 
> > I'll send versions for 5.2 in a bit for you.
> 
> Here you go, those two on top of the others. Ran it through the
> regressions tests here, works for me.

That worked, all now queued up, thanks!

greg k-h

Re: fs/io_uring.c stable additions

[Jens Axboe]

On 7/29/19 12:58 PM, Greg Kroah-Hartman wrote:
> On Mon, Jul 29, 2019 at 12:35:14PM -0600, Jens Axboe wrote:
>> On 7/29/19 12:17 PM, Jens Axboe wrote:
>>> On 7/29/19 12:15 PM, Greg Kroah-Hartman wrote:
>>>> On Mon, Jul 29, 2019 at 12:08:28PM -0600, Jens Axboe wrote:
>>>>> Hi,
>>>>>
>>>>> I forgot to mark a few patches for io_uring as stable. In order
>>>>> of how to apply, can you add the following commits for 5.2?
>>>>>
>>>>> f7b76ac9d17e16e44feebb6d2749fec92bfd6dd4
>>>> 0ef67e605d2b1e8300d04fd9134d283bbbf441b9
>>>> Does not apply :(
>>>>
>>>>> c0e48f9dea9129aa11bec3ed13803bcc26e96e49
>>>>
>>>> Now queued up.
>>>>
>>>>> bd11b3a391e3df6fa958facbe4b3f9f4cca9bd49
>>>>
>>>> Does not apply :(
>>>>
>>>>> 36703247d5f52a679df9da51192b6950fe81689f
>>>>
>>>> Now queued up.
>>>>
>>>> You are 2 out of 4 :)
>>>>
>>>> Care to send backported versions of the 2 that did not apply?  I'll be
>>>> glad to queue them up then.
>>>
>>> Huh strange, I applied them to our internal 5.2 tree without conflict.
>>> Maybe I had backported more...
>>>
>>> I'll send versions for 5.2 in a bit for you.
>>
>> Here you go, those two on top of the others. Ran it through the
>> regressions tests here, works for me.
> 
> That worked, all now queued up, thanks!

Great, thanks Greg!

-- 
Jens Axboe

fs/io_uring.c stable additions

[Jens Axboe]

Hi,

Round two of this show, I forget to add these stable tags sometimes
apparently... Can you add these four to 5.2 stable? Again listed
in order of how they should be applied.

a982eeb09b6030e567b8b815277c8c9197168040
500f9fbadef86466a435726192f4ca4df7d94236
a3a0e43fd77013819e4b6f55e37e0efe8e35d805
08f5439f1df25a6cf6cf4c72cf6c13025599ce67


Thanks!

-- 
Jens Axboe

Re: fs/io_uring.c stable additions

[Sasha Levin]

On Mon, Aug 26, 2019 at 02:39:28PM -0600, Jens Axboe wrote:
>Hi,
>
>Round two of this show, I forget to add these stable tags sometimes
>apparently... Can you add these four to 5.2 stable? Again listed
>in order of how they should be applied.
>
>a982eeb09b6030e567b8b815277c8c9197168040

This one seems to fix sqe links, which were only introduced in the 5.3
merge window?

>500f9fbadef86466a435726192f4ca4df7d94236
>a3a0e43fd77013819e4b6f55e37e0efe8e35d805
>08f5439f1df25a6cf6cf4c72cf6c13025599ce67

These 3 look okay, but I haven't queued them up as you were explicit
with ordering instructions, and as I can't take the first one I'm
playing it safe.

--
Thanks,
Sasha

Re: fs/io_uring.c stable additions

[Jens Axboe]

On 8/26/19 3:41 PM, Sasha Levin wrote:
> On Mon, Aug 26, 2019 at 02:39:28PM -0600, Jens Axboe wrote:
>> Hi,
>>
>> Round two of this show, I forget to add these stable tags sometimes
>> apparently... Can you add these four to 5.2 stable? Again listed
>> in order of how they should be applied.
>>
>> a982eeb09b6030e567b8b815277c8c9197168040
> 
> This one seems to fix sqe links, which were only introduced in the 5.3
> merge window?

Ah yes indeed, you can disregard that one!

>> 500f9fbadef86466a435726192f4ca4df7d94236
>> a3a0e43fd77013819e4b6f55e37e0efe8e35d805
>> 08f5439f1df25a6cf6cf4c72cf6c13025599ce67
> 
> These 3 look okay, but I haven't queued them up as you were explicit
> with ordering instructions, and as I can't take the first one I'm
> playing it safe.

Thanks for checking, just these three is what we need for 5.2.

-- 
Jens Axboe

Re: fs/io_uring.c stable additions

[Sasha Levin]

On Mon, Aug 26, 2019 at 03:56:27PM -0600, Jens Axboe wrote:
>On 8/26/19 3:41 PM, Sasha Levin wrote:
>> On Mon, Aug 26, 2019 at 02:39:28PM -0600, Jens Axboe wrote:
>>> 500f9fbadef86466a435726192f4ca4df7d94236
>>> a3a0e43fd77013819e4b6f55e37e0efe8e35d805
>>> 08f5439f1df25a6cf6cf4c72cf6c13025599ce67
>>
>> These 3 look okay, but I haven't queued them up as you were explicit
>> with ordering instructions, and as I can't take the first one I'm
>> playing it safe.
>
>Thanks for checking, just these three is what we need for 5.2.

Queued up for 5.2, thanks!

--
Thanks,
Sasha

Re: fs/io_uring.c stable additions

[Jens Axboe]

On 8/26/19 4:32 PM, Sasha Levin wrote:
> On Mon, Aug 26, 2019 at 03:56:27PM -0600, Jens Axboe wrote:
>> On 8/26/19 3:41 PM, Sasha Levin wrote:
>>> On Mon, Aug 26, 2019 at 02:39:28PM -0600, Jens Axboe wrote:
>>>> 500f9fbadef86466a435726192f4ca4df7d94236
>>>> a3a0e43fd77013819e4b6f55e37e0efe8e35d805
>>>> 08f5439f1df25a6cf6cf4c72cf6c13025599ce67
>>>
>>> These 3 look okay, but I haven't queued them up as you were explicit
>>> with ordering instructions, and as I can't take the first one I'm
>>> playing it safe.
>>
>> Thanks for checking, just these three is what we need for 5.2.
> 
> Queued up for 5.2, thanks!

Thanks!

-- 
Jens Axboe