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From: Pavel Begunkov <[email protected]>
To: Jens Axboe <[email protected]>, [email protected]
Subject: [PATCH v2 4/6] io_uring: don't take task ring-file notes
Date: Fri,  5 Mar 2021 04:18:22 +0000	[thread overview]
Message-ID: <5c394abd70bf5c3b21437c5a3dfd3f9ddfbc7ab3.1614917790.git.asml.silence@gmail.com> (raw)
In-Reply-To: <[email protected]>

With ->flush() gone we're now leaving all uring file notes until the
task dies/execs, so the ctx will not be freed until all tasks that have
ever submit a request die. It was nicer with flush but not much, we
could have locked as described ctx in many cases.

Now we guarantee that ctx outlives all tctx in a sense that
io_ring_exit_work() waits for all tctxs to drop their corresponding
enties in ->xa, and ctx won't go away until then. Hence, additional
io_uring file reference (a.k.a. task file notes) are not needed anymore.

Signed-off-by: Pavel Begunkov <[email protected]>
---
 fs/io_uring.c | 5 ++---
 1 file changed, 2 insertions(+), 3 deletions(-)

diff --git a/fs/io_uring.c b/fs/io_uring.c
index 9865b2c708c2..d819d389f4ee 100644
--- a/fs/io_uring.c
+++ b/fs/io_uring.c
@@ -8815,11 +8815,9 @@ static int io_uring_add_task_file(struct io_ring_ctx *ctx, struct file *file)
 			node->file = file;
 			node->task = current;
 
-			get_file(file);
 			ret = xa_err(xa_store(&tctx->xa, (unsigned long)file,
 						node, GFP_KERNEL));
 			if (ret) {
-				fput(file);
 				kfree(node);
 				return ret;
 			}
@@ -8850,6 +8848,8 @@ static void io_uring_del_task_file(unsigned long index)
 	struct io_uring_task *tctx = current->io_uring;
 	struct io_tctx_node *node;
 
+	if (!tctx)
+		return;
 	node = xa_erase(&tctx->xa, index);
 	if (!node)
 		return;
@@ -8863,7 +8863,6 @@ static void io_uring_del_task_file(unsigned long index)
 
 	if (tctx->last == node->file)
 		tctx->last = NULL;
-	fput(node->file);
 	kfree(node);
 }
 
-- 
2.24.0


  parent reply	other threads:[~2021-03-05  4:22 UTC|newest]

Thread overview: 7+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-03-05  4:18 [PATCH v2 5.12 0/6] remove task file notes Pavel Begunkov
2021-03-05  4:18 ` [PATCH v2 1/6] io_uring: make del_task_file more forgiving Pavel Begunkov
2021-03-05  4:18 ` [PATCH v2 2/6] io_uring: introduce ctx to tctx back map Pavel Begunkov
2021-03-05  4:18 ` [PATCH v2 3/6] io_uring: do ctx initiated file note removal Pavel Begunkov
2021-03-05  4:18 ` Pavel Begunkov [this message]
2021-03-05  4:18 ` [PATCH v2 5/6] io_uring: index io_uring->xa by ctx not file Pavel Begunkov
2021-03-05  4:18 ` [PATCH v2 6/6] io_uring: warn when ring exit takes too long Pavel Begunkov

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