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From: Jens Axboe <[email protected]>
To: [email protected]
Cc: Jens Axboe <[email protected]>
Subject: [PATCH 17/18] io_uring: assign new io_identity for task if members have changed
Date: Fri, 16 Oct 2020 10:02:23 -0600	[thread overview]
Message-ID: <[email protected]> (raw)
In-Reply-To: <[email protected]>

This avoids doing a copy for each new async IO, if some parts of the
io_identity has changed. We avoid reference counting for the normal
fast path of nothing ever changing.

Signed-off-by: Jens Axboe <[email protected]>
---
 fs/io_uring.c            | 19 +++++++++++++++----
 include/linux/io_uring.h |  3 ++-
 2 files changed, 17 insertions(+), 5 deletions(-)

diff --git a/fs/io_uring.c b/fs/io_uring.c
index bc16327a6481..5af6dafcc669 100644
--- a/fs/io_uring.c
+++ b/fs/io_uring.c
@@ -1066,12 +1066,18 @@ static void io_init_identity(struct io_identity *id)
  */
 static inline void io_req_init_async(struct io_kiocb *req)
 {
+	struct io_uring_task *tctx = current->io_uring;
+
 	if (req->flags & REQ_F_WORK_INITIALIZED)
 		return;
 
 	memset(&req->work, 0, sizeof(req->work));
 	req->flags |= REQ_F_WORK_INITIALIZED;
-	req->work.identity = &current->io_uring->identity;
+
+	/* Grab a ref if this isn't our static identity */
+	req->work.identity = tctx->identity;
+	if (tctx->identity != &tctx->__identity)
+		refcount_inc(&req->work.identity->count);
 }
 
 static inline bool io_async_submit(struct io_ring_ctx *ctx)
@@ -1179,7 +1185,7 @@ static void __io_commit_cqring(struct io_ring_ctx *ctx)
 
 static void io_put_identity(struct io_uring_task *tctx, struct io_kiocb *req)
 {
-	if (req->work.identity == &tctx->identity)
+	if (req->work.identity == &tctx->__identity)
 		return;
 	if (refcount_dec_and_test(&req->work.identity->count))
 		kfree(req->work.identity);
@@ -1254,11 +1260,12 @@ static bool io_identity_cow(struct io_kiocb *req)
 	refcount_inc(&id->count);
 
 	/* drop old identity, assign new one. one ref for req, one for tctx */
-	if (req->work.identity != &tctx->identity &&
+	if (req->work.identity != tctx->identity &&
 	    refcount_sub_and_test(2, &req->work.identity->count))
 		kfree(req->work.identity);
 
 	req->work.identity = id;
+	tctx->identity = id;
 	return true;
 }
 
@@ -7684,7 +7691,8 @@ static int io_uring_alloc_task_context(struct task_struct *task)
 	tctx->in_idle = 0;
 	atomic_long_set(&tctx->req_issue, 0);
 	atomic_long_set(&tctx->req_complete, 0);
-	io_init_identity(&tctx->identity);
+	io_init_identity(&tctx->__identity);
+	tctx->identity = &tctx->__identity;
 	task->io_uring = tctx;
 	return 0;
 }
@@ -7694,6 +7702,9 @@ void __io_uring_free(struct task_struct *tsk)
 	struct io_uring_task *tctx = tsk->io_uring;
 
 	WARN_ON_ONCE(!xa_empty(&tctx->xa));
+	WARN_ON_ONCE(refcount_read(&tctx->identity->count) != 1);
+	if (tctx->identity != &tctx->__identity)
+		kfree(tctx->identity);
 	kfree(tctx);
 	tsk->io_uring = NULL;
 }
diff --git a/include/linux/io_uring.h b/include/linux/io_uring.h
index bd3346194bca..607d14f61132 100644
--- a/include/linux/io_uring.h
+++ b/include/linux/io_uring.h
@@ -24,7 +24,8 @@ struct io_uring_task {
 	struct wait_queue_head	wait;
 	struct file		*last;
 	atomic_long_t		req_issue;
-	struct io_identity	identity;
+	struct io_identity	__identity;
+	struct io_identity	*identity;
 
 	/* completion side */
 	bool			in_idle ____cacheline_aligned_in_smp;
-- 
2.28.0


  parent reply	other threads:[~2020-10-16 16:02 UTC|newest]

Thread overview: 19+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-10-16 16:02 [PATCHES 0/10] Fixes queued up for 5.10 Jens Axboe
2020-10-16 16:02 ` [PATCH 01/18] io_uring: Fix sizeof() mismatch Jens Axboe
2020-10-16 16:02 ` [PATCH 02/18] readahead: use limited read-ahead to satisfy read Jens Axboe
2020-10-16 16:02 ` [PATCH 03/18] io_uring: don't clear IOCB_NOWAIT for async buffered retry Jens Axboe
2020-10-16 16:02 ` [PATCH 04/18] io_uring: don't set COMP_LOCKED if won't put Jens Axboe
2020-10-16 16:02 ` [PATCH 05/18] io_uring: don't unnecessarily clear F_LINK_TIMEOUT Jens Axboe
2020-10-16 16:02 ` [PATCH 06/18] io_uring: don't put a poll req under spinlock Jens Axboe
2020-10-16 16:02 ` [PATCH 07/18] io_uring: dig out COMP_LOCK from deep call chain Jens Axboe
2020-10-16 16:02 ` [PATCH 08/18] io_uring: fix REQ_F_COMP_LOCKED by killing it Jens Axboe
2020-10-16 16:02 ` [PATCH 09/18] Revert "io_uring: mark io_uring_fops/io_op_defs as __read_mostly" Jens Axboe
2020-10-16 16:02 ` [PATCH 10/18] io_uring: fix error path cleanup in io_sqe_files_register() Jens Axboe
2020-10-16 16:02 ` [PATCH 11/18] io-wq: assign NUMA node locality if appropriate Jens Axboe
2020-10-16 16:02 ` [PATCH 12/18] io_uring: pass required context in as flags Jens Axboe
2020-10-16 16:02 ` [PATCH 13/18] io_uring: rely solely on work flags to determine personality Jens Axboe
2020-10-16 16:02 ` [PATCH 14/18] io_uring: move io identity items into separate struct Jens Axboe
2020-10-16 16:02 ` [PATCH 15/18] io_uring: COW io_identity on mismatch Jens Axboe
2020-10-16 16:02 ` [PATCH 16/18] io_uring: store io_identity in io_uring_task Jens Axboe
2020-10-16 16:02 ` Jens Axboe [this message]
2020-10-16 16:02 ` [PATCH 18/18] io_uring: use percpu counters to track inflight requests Jens Axboe

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