[PATCH for-5.9 0/4] moving grab_env() later before punt

[PATCH for-5.9 0/4] moving grab_env() later before punt

[Pavel Begunkov]

This is a first part of patches cleaning up after recent link/tast_work
quick fixes. The main idea intention here is to make io_steal_work()
functional again. That's done in [4/4], others are preps.

[4/4] may have its dragons, and even though I tested it
long enough, would love someone to take a closer look / test as well.

note: on top of "cleanup for req_free/find_next"

Pavel Begunkov (4):
  io_uring: don't pass def into io_req_work_grab_env
  io_uring: do init work in grab_env()
  io_uring: factor out grab_env() from defer_prep()
  io_uring: do grab_env() just before punting

 fs/io_uring.c | 73 +++++++++++++++++++++++++++------------------------
 1 file changed, 38 insertions(+), 35 deletions(-)

-- 
2.24.0

[PATCH 1/4] io_uring: don't pass def into io_req_work_grab_env

[Pavel Begunkov]

Remove struct io_op_def *def parameter from io_req_work_grab_env(),
it's trivially deducible from req->opcode and fast. The API is
cleaner this way, and also helps the complier to understand
that it's a real constant and could be register-cached.

Signed-off-by: Pavel Begunkov <asml.silence@gmail.com>
---
 fs/io_uring.c | 9 +++++----
 1 file changed, 5 insertions(+), 4 deletions(-)

diff --git a/fs/io_uring.c b/fs/io_uring.c
index 013f31e35e78..ecee44a97c29 100644
--- a/fs/io_uring.c
+++ b/fs/io_uring.c
@@ -1101,9 +1101,10 @@ static void __io_commit_cqring(struct io_ring_ctx *ctx)
 	}
 }
 
-static inline void io_req_work_grab_env(struct io_kiocb *req,
-					const struct io_op_def *def)
+static inline void io_req_work_grab_env(struct io_kiocb *req)
 {
+	const struct io_op_def *def = &io_op_defs[req->opcode];
+
 	if (!req->work.mm && def->needs_mm) {
 		mmgrab(current->mm);
 		req->work.mm = current->mm;
@@ -1161,7 +1162,7 @@ static inline void io_prep_async_work(struct io_kiocb *req,
 	}
 
 	io_req_init_async(req);
-	io_req_work_grab_env(req, def);
+	io_req_work_grab_env(req);
 
 	*link = io_prep_linked_timeout(req);
 }
@@ -5232,7 +5233,7 @@ static int io_req_defer_prep(struct io_kiocb *req,
 
 	if (for_async || (req->flags & REQ_F_WORK_INITIALIZED)) {
 		io_req_init_async(req);
-		io_req_work_grab_env(req, &io_op_defs[req->opcode]);
+		io_req_work_grab_env(req);
 	}
 
 	switch (req->opcode) {
-- 
2.24.0

[PATCH 2/4] io_uring: do init work in grab_env()

[Pavel Begunkov]

Place io_req_init_async() in io_req_work_grab_env() so it won't be
forgotten.

Signed-off-by: Pavel Begunkov <asml.silence@gmail.com>
---
 fs/io_uring.c | 8 +++-----
 1 file changed, 3 insertions(+), 5 deletions(-)

diff --git a/fs/io_uring.c b/fs/io_uring.c
index ecee44a97c29..4a05bc519134 100644
--- a/fs/io_uring.c
+++ b/fs/io_uring.c
@@ -1105,6 +1105,8 @@ static inline void io_req_work_grab_env(struct io_kiocb *req)
 {
 	const struct io_op_def *def = &io_op_defs[req->opcode];
 
+	io_req_init_async(req);
+
 	if (!req->work.mm && def->needs_mm) {
 		mmgrab(current->mm);
 		req->work.mm = current->mm;
@@ -1161,9 +1163,7 @@ static inline void io_prep_async_work(struct io_kiocb *req,
 			req->work.flags |= IO_WQ_WORK_UNBOUND;
 	}
 
-	io_req_init_async(req);
 	io_req_work_grab_env(req);
-
 	*link = io_prep_linked_timeout(req);
 }
 
@@ -5231,10 +5231,8 @@ static int io_req_defer_prep(struct io_kiocb *req,
 			return ret;
 	}
 
-	if (for_async || (req->flags & REQ_F_WORK_INITIALIZED)) {
-		io_req_init_async(req);
+	if (for_async || (req->flags & REQ_F_WORK_INITIALIZED))
 		io_req_work_grab_env(req);
-	}
 
 	switch (req->opcode) {
 	case IORING_OP_NOP:
-- 
2.24.0

[PATCH 3/4] io_uring: factor out grab_env() from defer_prep()

[Pavel Begunkov]

Remove io_req_work_grab_env() call from io_req_defer_prep(), just call
it when neccessary.

Signed-off-by: Pavel Begunkov <asml.silence@gmail.com>
---
 fs/io_uring.c | 15 +++++++--------
 1 file changed, 7 insertions(+), 8 deletions(-)

diff --git a/fs/io_uring.c b/fs/io_uring.c
index 4a05bc519134..2dcdc2c09e8c 100644
--- a/fs/io_uring.c
+++ b/fs/io_uring.c
@@ -5217,7 +5217,7 @@ static int io_files_update(struct io_kiocb *req, bool force_nonblock,
 }
 
 static int io_req_defer_prep(struct io_kiocb *req,
-			     const struct io_uring_sqe *sqe, bool for_async)
+			     const struct io_uring_sqe *sqe)
 {
 	ssize_t ret = 0;
 
@@ -5231,9 +5231,6 @@ static int io_req_defer_prep(struct io_kiocb *req,
 			return ret;
 	}
 
-	if (for_async || (req->flags & REQ_F_WORK_INITIALIZED))
-		io_req_work_grab_env(req);
-
 	switch (req->opcode) {
 	case IORING_OP_NOP:
 		break;
@@ -5346,9 +5343,10 @@ static int io_req_defer(struct io_kiocb *req, const struct io_uring_sqe *sqe)
 	if (!req->io) {
 		if (io_alloc_async_ctx(req))
 			return -EAGAIN;
-		ret = io_req_defer_prep(req, sqe, true);
+		ret = io_req_defer_prep(req, sqe);
 		if (ret < 0)
 			return ret;
+		io_req_work_grab_env(req);
 	}
 
 	spin_lock_irq(&ctx->completion_lock);
@@ -5960,9 +5958,10 @@ static void io_queue_sqe(struct io_kiocb *req, const struct io_uring_sqe *sqe,
 			ret = -EAGAIN;
 			if (io_alloc_async_ctx(req))
 				goto fail_req;
-			ret = io_req_defer_prep(req, sqe, true);
+			ret = io_req_defer_prep(req, sqe);
 			if (unlikely(ret < 0))
 				goto fail_req;
+			io_req_work_grab_env(req);
 		}
 
 		/*
@@ -6016,7 +6015,7 @@ static int io_submit_sqe(struct io_kiocb *req, const struct io_uring_sqe *sqe,
 		if (io_alloc_async_ctx(req))
 			return -EAGAIN;
 
-		ret = io_req_defer_prep(req, sqe, false);
+		ret = io_req_defer_prep(req, sqe);
 		if (ret) {
 			/* fail even hard links since we don't submit */
 			head->flags |= REQ_F_FAIL_LINK;
@@ -6043,7 +6042,7 @@ static int io_submit_sqe(struct io_kiocb *req, const struct io_uring_sqe *sqe,
 			if (io_alloc_async_ctx(req))
 				return -EAGAIN;
 
-			ret = io_req_defer_prep(req, sqe, false);
+			ret = io_req_defer_prep(req, sqe);
 			if (ret)
 				req->flags |= REQ_F_FAIL_LINK;
 			*link = req;
-- 
2.24.0

[PATCH 4/4] io_uring: do grab_env() just before punting

[Pavel Begunkov]

Currently io_steal_work() is disabled, and every linked request should
go through task_work for initialisation. Do io_req_work_grab_env()
just before io-wq punting and for the whole link, so any request
reachable by io_steal_work() is prepared.

This is also interesting for another reason -- it localises
io_req_work_grab_env() into one place just before io-wq punting, helping
to to better manage req->work lifetime and add some neat
cleanup/optimisations later.

Signed-off-by: Pavel Begunkov <asml.silence@gmail.com>
---
 fs/io_uring.c | 53 ++++++++++++++++++++++++++++-----------------------
 1 file changed, 29 insertions(+), 24 deletions(-)

diff --git a/fs/io_uring.c b/fs/io_uring.c
index 2dcdc2c09e8c..5928404acb17 100644
--- a/fs/io_uring.c
+++ b/fs/io_uring.c
@@ -1101,7 +1101,7 @@ static void __io_commit_cqring(struct io_ring_ctx *ctx)
 	}
 }
 
-static inline void io_req_work_grab_env(struct io_kiocb *req)
+static void io_req_work_grab_env(struct io_kiocb *req)
 {
 	const struct io_op_def *def = &io_op_defs[req->opcode];
 
@@ -1150,8 +1150,7 @@ static inline void io_req_work_drop_env(struct io_kiocb *req)
 	}
 }
 
-static inline void io_prep_async_work(struct io_kiocb *req,
-				      struct io_kiocb **link)
+static void io_prep_async_work(struct io_kiocb *req)
 {
 	const struct io_op_def *def = &io_op_defs[req->opcode];
 
@@ -1164,15 +1163,22 @@ static inline void io_prep_async_work(struct io_kiocb *req,
 	}
 
 	io_req_work_grab_env(req);
-	*link = io_prep_linked_timeout(req);
 }
 
-static inline void io_queue_async_work(struct io_kiocb *req)
+static void io_prep_async_link(struct io_kiocb *req)
 {
-	struct io_ring_ctx *ctx = req->ctx;
-	struct io_kiocb *link;
+	struct io_kiocb *cur;
 
-	io_prep_async_work(req, &link);
+	io_prep_async_work(req);
+	if (req->flags & REQ_F_LINK_HEAD)
+		list_for_each_entry(cur, &req->link_list, link_list)
+			io_prep_async_work(cur);
+}
+
+static void __io_queue_async_work(struct io_kiocb *req)
+{
+	struct io_ring_ctx *ctx = req->ctx;
+	struct io_kiocb *link = io_prep_linked_timeout(req);
 
 	trace_io_uring_queue_async_work(ctx, io_wq_is_hashed(&req->work), req,
 					&req->work, req->flags);
@@ -1182,6 +1188,13 @@ static inline void io_queue_async_work(struct io_kiocb *req)
 		io_queue_linked_timeout(link);
 }
 
+static void io_queue_async_work(struct io_kiocb *req)
+{
+	/* init ->work of the whole link before punting */
+	io_prep_async_link(req);
+	__io_queue_async_work(req);
+}
+
 static void io_kill_timeout(struct io_kiocb *req)
 {
 	int ret;
@@ -1215,7 +1228,8 @@ static void __io_queue_deferred(struct io_ring_ctx *ctx)
 		if (req_need_defer(req))
 			break;
 		list_del_init(&req->list);
-		io_queue_async_work(req);
+		/* punt-init is done before queueing for defer */
+		__io_queue_async_work(req);
 	} while (!list_empty(&ctx->defer_list));
 }
 
@@ -1774,7 +1788,7 @@ static void io_put_req(struct io_kiocb *req)
 
 static struct io_wq_work *io_steal_work(struct io_kiocb *req)
 {
-	struct io_kiocb *nxt = NULL;
+	struct io_kiocb *timeout, *nxt = NULL;
 
 	/*
 	 * A ref is owned by io-wq in which context we're. So, if that's the
@@ -1788,18 +1802,10 @@ static struct io_wq_work *io_steal_work(struct io_kiocb *req)
 	if (!nxt)
 		return NULL;
 
-	if ((nxt->flags & REQ_F_ISREG) && io_op_defs[nxt->opcode].hash_reg_file)
-		io_wq_hash_work(&nxt->work, file_inode(nxt->file));
-
-	io_req_task_queue(nxt);
-	/*
-	 * If we're going to return actual work, here should be timeout prep:
-	 *
-	 * link = io_prep_linked_timeout(nxt);
-	 * if (link)
-	 *	nxt->flags |= REQ_F_QUEUE_TIMEOUT;
-	 */
-	return NULL;
+	timeout = io_prep_linked_timeout(nxt);
+	if (timeout)
+		nxt->flags |= REQ_F_QUEUE_TIMEOUT;
+	return &nxt->work;
 }
 
 /*
@@ -5346,8 +5352,8 @@ static int io_req_defer(struct io_kiocb *req, const struct io_uring_sqe *sqe)
 		ret = io_req_defer_prep(req, sqe);
 		if (ret < 0)
 			return ret;
-		io_req_work_grab_env(req);
 	}
+	io_prep_async_link(req);
 
 	spin_lock_irq(&ctx->completion_lock);
 	if (!req_need_defer(req) && list_empty(&ctx->defer_list)) {
@@ -5961,7 +5967,6 @@ static void io_queue_sqe(struct io_kiocb *req, const struct io_uring_sqe *sqe,
 			ret = io_req_defer_prep(req, sqe);
 			if (unlikely(ret < 0))
 				goto fail_req;
-			io_req_work_grab_env(req);
 		}
 
 		/*
-- 
2.24.0

Re: [PATCH for-5.9 0/4] moving grab_env() later before punt

[Jens Axboe]

On 6/29/20 10:18 AM, Pavel Begunkov wrote:
> This is a first part of patches cleaning up after recent link/tast_work
> quick fixes. The main idea intention here is to make io_steal_work()
> functional again. That's done in [4/4], others are preps.
> 
> [4/4] may have its dragons, and even though I tested it
> long enough, would love someone to take a closer look / test as well.

1-3 are straight forward, but I also didn't find any issues with 4
both reviewing it and also testing it. So I'll apply this series,
thanks!

-- 
Jens Axboe