[PATCH 0/6] random patches for 5.8

[PATCH 0/6] random patches for 5.8

[Pavel Begunkov]

Nothing insteresting in particular, just start flushing stashed patches.
Ones in this series are pretty easy and short.

Pavel Begunkov (6):
  io_uring: fix flush req->refs underflow
  io_uring: simplify io_timeout locking
  io_uring: don't re-read sqe->off in timeout_prep()
  io_uring: separate DRAIN flushing into a cold path
  io_uring: get rid of manual punting in io_close
  io_uring: let io_req_aux_free() handle fixed files

 fs/io_uring.c | 64 ++++++++++++++++++++-------------------------------
 1 file changed, 25 insertions(+), 39 deletions(-)

-- 
2.24.0

[PATCH 1/6] io_uring: fix flush req->refs underflow

[Pavel Begunkov]

In io_uring_cancel_files(), after refcount_sub_and_test() leaves 0
req->refs, it calls io_put_req(), which would also put a ref. Call
io_free_req() instead.

Signed-off-by: Pavel Begunkov <asml.silence@gmail.com>
---
 fs/io_uring.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/fs/io_uring.c b/fs/io_uring.c
index bf75ac753b9d..42b5603ee410 100644
--- a/fs/io_uring.c
+++ b/fs/io_uring.c
@@ -7534,7 +7534,7 @@ static void io_uring_cancel_files(struct io_ring_ctx *ctx,
 			 * all we had, then we're done with this request.
 			 */
 			if (refcount_sub_and_test(2, &cancel_req->refs)) {
-				io_put_req(cancel_req);
+				io_free_req(cancel_req);
 				finish_wait(&ctx->inflight_wait, &wait);
 				continue;
 			}
-- 
2.24.0

Re: [PATCH 1/6] io_uring: fix flush req->refs underflow

[Jens Axboe]

On 5/26/20 11:34 AM, Pavel Begunkov wrote:
> In io_uring_cancel_files(), after refcount_sub_and_test() leaves 0
> req->refs, it calls io_put_req(), which would also put a ref. Call
> io_free_req() instead.

Needs a:

Fixes: 2ca10259b418 ("io_uring: prune request from overflow list on flush")     

I added it.

-- 
Jens Axboe

[PATCH 2/6] io_uring: simplify io_timeout locking

[Pavel Begunkov]

Move spin_lock_irq() earlier to have only 1 call site of it in
io_timeout(). It makes the flow easier.

Signed-off-by: Pavel Begunkov <asml.silence@gmail.com>
---
 fs/io_uring.c | 3 +--
 1 file changed, 1 insertion(+), 2 deletions(-)

diff --git a/fs/io_uring.c b/fs/io_uring.c
index 42b5603ee410..e30fc17dd268 100644
--- a/fs/io_uring.c
+++ b/fs/io_uring.c
@@ -4845,6 +4845,7 @@ static int io_timeout(struct io_kiocb *req)
 	u32 seq = req->sequence;
 
 	data = &req->io->timeout;
+	spin_lock_irq(&ctx->completion_lock);
 
 	/*
 	 * sqe->off holds how many events that need to occur for this
@@ -4853,7 +4854,6 @@ static int io_timeout(struct io_kiocb *req)
 	 */
 	if (!count) {
 		req->flags |= REQ_F_TIMEOUT_NOSEQ;
-		spin_lock_irq(&ctx->completion_lock);
 		entry = ctx->timeout_list.prev;
 		goto add;
 	}
@@ -4864,7 +4864,6 @@ static int io_timeout(struct io_kiocb *req)
 	 * Insertion sort, ensuring the first entry in the list is always
 	 * the one we need first.
 	 */
-	spin_lock_irq(&ctx->completion_lock);
 	list_for_each_prev(entry, &ctx->timeout_list) {
 		struct io_kiocb *nxt = list_entry(entry, struct io_kiocb, list);
 		unsigned nxt_seq;
-- 
2.24.0

[PATCH 3/6] io_uring: don't re-read sqe->off in timeout_prep()

[Pavel Begunkov]

SQEs are user writable, don't read sqe->off twice in io_timeout_prep()

Signed-off-by: Pavel Begunkov <asml.silence@gmail.com>
---
 fs/io_uring.c | 5 +++--
 1 file changed, 3 insertions(+), 2 deletions(-)

diff --git a/fs/io_uring.c b/fs/io_uring.c
index e30fc17dd268..067ebdeb1ba4 100644
--- a/fs/io_uring.c
+++ b/fs/io_uring.c
@@ -4803,18 +4803,19 @@ static int io_timeout_prep(struct io_kiocb *req, const struct io_uring_sqe *sqe,
 {
 	struct io_timeout_data *data;
 	unsigned flags;
+	u32 off = READ_ONCE(sqe->off);
 
 	if (unlikely(req->ctx->flags & IORING_SETUP_IOPOLL))
 		return -EINVAL;
 	if (sqe->ioprio || sqe->buf_index || sqe->len != 1)
 		return -EINVAL;
-	if (sqe->off && is_timeout_link)
+	if (off && is_timeout_link)
 		return -EINVAL;
 	flags = READ_ONCE(sqe->timeout_flags);
 	if (flags & ~IORING_TIMEOUT_ABS)
 		return -EINVAL;
 
-	req->timeout.count = READ_ONCE(sqe->off);
+	req->timeout.count = off;
 
 	if (!req->io && io_alloc_async_ctx(req))
 		return -ENOMEM;
-- 
2.24.0

[PATCH 4/6] io_uring: separate DRAIN flushing into a cold path

[Pavel Begunkov]

io_commit_cqring() assembly doesn't look good with extra code handling
drained requests. IOSQE_IO_DRAIN is slow and discouraged to be used in
a hot path, so try to minimise its impact by putting it into a helper
and doing a fast check.

Signed-off-by: Pavel Begunkov <asml.silence@gmail.com>
---
 fs/io_uring.c | 30 +++++++++++++++---------------
 1 file changed, 15 insertions(+), 15 deletions(-)

diff --git a/fs/io_uring.c b/fs/io_uring.c
index 067ebdeb1ba4..acf6ce9eee68 100644
--- a/fs/io_uring.c
+++ b/fs/io_uring.c
@@ -982,19 +982,6 @@ static inline bool req_need_defer(struct io_kiocb *req)
 	return false;
 }
 
-static struct io_kiocb *io_get_deferred_req(struct io_ring_ctx *ctx)
-{
-	struct io_kiocb *req;
-
-	req = list_first_entry_or_null(&ctx->defer_list, struct io_kiocb, list);
-	if (req && !req_need_defer(req)) {
-		list_del_init(&req->list);
-		return req;
-	}
-
-	return NULL;
-}
-
 static struct io_kiocb *io_get_timeout_req(struct io_ring_ctx *ctx)
 {
 	struct io_kiocb *req;
@@ -1127,6 +1114,19 @@ static void io_kill_timeouts(struct io_ring_ctx *ctx)
 	spin_unlock_irq(&ctx->completion_lock);
 }
 
+static void __io_queue_deferred(struct io_ring_ctx *ctx)
+{
+	do {
+		struct io_kiocb *req = list_first_entry(&ctx->defer_list,
+							struct io_kiocb, list);
+
+		if (req_need_defer(req))
+			break;
+		list_del_init(&req->list);
+		io_queue_async_work(req);
+	} while (!list_empty(&ctx->defer_list));
+}
+
 static void io_commit_cqring(struct io_ring_ctx *ctx)
 {
 	struct io_kiocb *req;
@@ -1136,8 +1136,8 @@ static void io_commit_cqring(struct io_ring_ctx *ctx)
 
 	__io_commit_cqring(ctx);
 
-	while ((req = io_get_deferred_req(ctx)) != NULL)
-		io_queue_async_work(req);
+	if (unlikely(!list_empty(&ctx->defer_list)))
+		__io_queue_deferred(ctx);
 }
 
 static struct io_uring_cqe *io_get_cqring(struct io_ring_ctx *ctx)
-- 
2.24.0

[PATCH 5/6] io_uring: get rid of manual punting in io_close

[Pavel Begunkov]

io_close() was punting async manually to skip grabbing files. Use
REQ_F_NO_FILE_TABLE instead, and pass it through the generic path
with -EAGAIN.

Signed-off-by: Pavel Begunkov <asml.silence@gmail.com>
---
 fs/io_uring.c | 20 +++++---------------
 1 file changed, 5 insertions(+), 15 deletions(-)

diff --git a/fs/io_uring.c b/fs/io_uring.c
index acf6ce9eee68..ac1aa25f4a55 100644
--- a/fs/io_uring.c
+++ b/fs/io_uring.c
@@ -3492,25 +3492,15 @@ static int io_close(struct io_kiocb *req, bool force_nonblock)
 
 	req->close.put_file = NULL;
 	ret = __close_fd_get_file(req->close.fd, &req->close.put_file);
-	if (ret < 0) {
-		if (ret == -ENOENT)
-			ret = -EBADF;
-		return ret;
-	}
+	if (ret < 0)
+		return (ret == -ENOENT) ? -EBADF : ret;
 
 	/* if the file has a flush method, be safe and punt to async */
 	if (req->close.put_file->f_op->flush && force_nonblock) {
-		/* submission ref will be dropped, take it for async */
-		refcount_inc(&req->refs);
-
+		/* avoid grabbing files - we don't need the files */
+		req->flags |= REQ_F_NO_FILE_TABLE | REQ_F_MUST_PUNT;
 		req->work.func = io_close_finish;
-		/*
-		 * Do manual async queue here to avoid grabbing files - we don't
-		 * need the files, and it'll cause io_close_finish() to close
-		 * the file again and cause a double CQE entry for this request
-		 */
-		io_queue_async_work(req);
-		return 0;
+		return -EAGAIN;
 	}
 
 	/*
-- 
2.24.0

[PATCH 6/6] io_uring: let io_req_aux_free() handle fixed files

[Pavel Begunkov]

Remove duplicated code putting fixed files in io_free_req_many(),
__io_req_aux_free() does the same thing, let it handle them.

Signed-off-by: Pavel Begunkov <asml.silence@gmail.com>
---
 fs/io_uring.c | 4 ----
 1 file changed, 4 deletions(-)

diff --git a/fs/io_uring.c b/fs/io_uring.c
index ac1aa25f4a55..a3dbd5f40391 100644
--- a/fs/io_uring.c
+++ b/fs/io_uring.c
@@ -1413,10 +1413,6 @@ static void io_free_req_many(struct io_ring_ctx *ctx, struct req_batch *rb)
 		for (i = 0; i < rb->to_free; i++) {
 			struct io_kiocb *req = rb->reqs[i];
 
-			if (req->flags & REQ_F_FIXED_FILE) {
-				req->file = NULL;
-				percpu_ref_put(req->fixed_file_refs);
-			}
 			if (req->flags & REQ_F_INFLIGHT)
 				inflight++;
 			__io_req_aux_free(req);
-- 
2.24.0

Re: [PATCH 6/6] io_uring: let io_req_aux_free() handle fixed files

[Jens Axboe]

On 5/26/20 11:34 AM, Pavel Begunkov wrote:
> Remove duplicated code putting fixed files in io_free_req_many(),
> __io_req_aux_free() does the same thing, let it handle them.

This one is already changed in mainline:


> commit 9d9e88a24c1f20ebfc2f28b1762ce78c0b9e1cb3 (tag: io_uring-5.7-2020-05-15)
Author: Jens Axboe <axboe@kernel.dk>
Date:   Wed May 13 12:53:19 2020 -0600

    io_uring: polled fixed file must go through free iteration


-- 
Jens Axboe

Re: [PATCH 6/6] io_uring: let io_req_aux_free() handle fixed files

[Pavel Begunkov]

On 26/05/2020 21:03, Jens Axboe wrote:
> On 5/26/20 11:34 AM, Pavel Begunkov wrote:
>> Remove duplicated code putting fixed files in io_free_req_many(),
>> __io_req_aux_free() does the same thing, let it handle them.
> 
> This one is already changed in mainline:
> 
> 
>> commit 9d9e88a24c1f20ebfc2f28b1762ce78c0b9e1cb3 (tag: io_uring-5.7-2020-05-15)
> Author: Jens Axboe <axboe@kernel.dk>
> Date:   Wed May 13 12:53:19 2020 -0600
> 
>     io_uring: polled fixed file must go through free iteration
> 

I see, missed it.

And thanks for adding the fixes tag for the other one.

-- 
Pavel Begunkov

Re: [PATCH 0/6] random patches for 5.8

[Jens Axboe]

On 5/26/20 11:34 AM, Pavel Begunkov wrote:
> Nothing insteresting in particular, just start flushing stashed patches.
> Ones in this series are pretty easy and short.
> 
> Pavel Begunkov (6):
>   io_uring: fix flush req->refs underflow
>   io_uring: simplify io_timeout locking
>   io_uring: don't re-read sqe->off in timeout_prep()
>   io_uring: separate DRAIN flushing into a cold path
>   io_uring: get rid of manual punting in io_close
>   io_uring: let io_req_aux_free() handle fixed files
> 
>  fs/io_uring.c | 64 ++++++++++++++++++++-------------------------------
>  1 file changed, 25 insertions(+), 39 deletions(-)

Applied 1-5, thanks.

-- 
Jens Axboe