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From: Nadav Amit <[email protected]>
To: [email protected]
Cc: Nadav Amit <[email protected]>, Jens Axboe <[email protected]>,
	Andrea Arcangeli <[email protected]>,
	Peter Xu <[email protected]>,
	Alexander Viro <[email protected]>,
	[email protected], [email protected],
	[email protected]
Subject: [RFC PATCH 04/13] fs/userfaultfd: simplify locks in userfaultfd_ctx_read
Date: Sat, 28 Nov 2020 16:45:39 -0800	[thread overview]
Message-ID: <[email protected]> (raw)
In-Reply-To: <[email protected]>

From: Nadav Amit <[email protected]>

Small refactoring to reduce the number of locations in which locks are
released in userfaultfd_ctx_read(), as this makes the understanding of
the code and its changes harder.

No functional change intended.

Cc: Jens Axboe <[email protected]>
Cc: Andrea Arcangeli <[email protected]>
Cc: Peter Xu <[email protected]>
Cc: Alexander Viro <[email protected]>
Cc: [email protected]
Cc: [email protected]
Cc: [email protected]
Cc: [email protected]
Signed-off-by: Nadav Amit <[email protected]>
---
 fs/userfaultfd.c | 16 +++++++---------
 1 file changed, 7 insertions(+), 9 deletions(-)

diff --git a/fs/userfaultfd.c b/fs/userfaultfd.c
index 4fe07c1a44c6..fedf7c1615d5 100644
--- a/fs/userfaultfd.c
+++ b/fs/userfaultfd.c
@@ -1039,6 +1039,7 @@ static ssize_t userfaultfd_ctx_read(struct userfaultfd_ctx *ctx, int no_wait,
 		set_current_state(TASK_INTERRUPTIBLE);
 		spin_lock(&ctx->fault_pending_wqh.lock);
 		uwq = find_userfault(ctx);
+		ret = -EAGAIN;
 		if (uwq) {
 			/*
 			 * Use a seqcount to repeat the lockless check
@@ -1077,11 +1078,11 @@ static ssize_t userfaultfd_ctx_read(struct userfaultfd_ctx *ctx, int no_wait,
 
 			/* careful to always initialize msg if ret == 0 */
 			*msg = uwq->msg;
-			spin_unlock(&ctx->fault_pending_wqh.lock);
 			ret = 0;
-			break;
 		}
 		spin_unlock(&ctx->fault_pending_wqh.lock);
+		if (!ret)
+			break;
 
 		spin_lock(&ctx->event_wqh.lock);
 		uwq = find_userfault_evt(ctx);
@@ -1099,17 +1100,14 @@ static ssize_t userfaultfd_ctx_read(struct userfaultfd_ctx *ctx, int no_wait,
 				 * reference on it.
 				 */
 				userfaultfd_ctx_get(fork_nctx);
-				spin_unlock(&ctx->event_wqh.lock);
-				ret = 0;
-				break;
+			} else {
+				userfaultfd_event_complete(ctx, uwq);
 			}
-
-			userfaultfd_event_complete(ctx, uwq);
-			spin_unlock(&ctx->event_wqh.lock);
 			ret = 0;
-			break;
 		}
 		spin_unlock(&ctx->event_wqh.lock);
+		if (!ret)
+			break;
 
 		if (signal_pending(current)) {
 			ret = -ERESTARTSYS;
-- 
2.25.1


  parent reply	other threads:[~2020-11-29  0:50 UTC|newest]

Thread overview: 24+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-11-29  0:45 [RFC PATCH 00/13] fs/userfaultfd: support iouring and polling Nadav Amit
2020-11-29  0:45 ` [RFC PATCH 01/13] fs/userfaultfd: fix wrong error code on WP & !VM_MAYWRITE Nadav Amit
2020-12-01 21:22   ` Mike Kravetz
2020-12-21 19:01     ` Peter Xu
2020-11-29  0:45 ` [RFC PATCH 02/13] fs/userfaultfd: fix wrong file usage with iouring Nadav Amit
2020-11-29  0:45 ` [RFC PATCH 03/13] selftests/vm/userfaultfd: wake after copy failure Nadav Amit
2020-12-21 19:28   ` Peter Xu
2020-12-21 19:51     ` Nadav Amit
2020-12-21 20:52       ` Peter Xu
2020-12-21 20:54         ` Nadav Amit
2020-11-29  0:45 ` Nadav Amit [this message]
2020-11-29  0:45 ` [RFC PATCH 05/13] fs/userfaultfd: introduce UFFD_FEATURE_POLL Nadav Amit
2020-11-29  0:45 ` [RFC PATCH 06/13] iov_iter: support atomic copy_page_from_iter_iovec() Nadav Amit
2020-11-29  0:45 ` [RFC PATCH 07/13] fs/userfaultfd: support read_iter to use io_uring Nadav Amit
2020-11-30 18:20   ` Jens Axboe
2020-11-30 19:23     ` Nadav Amit
2020-11-29  0:45 ` [RFC PATCH 08/13] fs/userfaultfd: complete reads asynchronously Nadav Amit
2020-11-29  0:45 ` [RFC PATCH 09/13] fs/userfaultfd: use iov_iter for copy/zero Nadav Amit
2020-11-29  0:45 ` [RFC PATCH 10/13] fs/userfaultfd: add write_iter() interface Nadav Amit
2020-11-29  0:45 ` [RFC PATCH 11/13] fs/userfaultfd: complete write asynchronously Nadav Amit
2020-12-02  7:12   ` Nadav Amit
2020-11-29  0:45 ` [RFC PATCH 12/13] fs/userfaultfd: kmem-cache for wait-queue objects Nadav Amit
2020-11-30 19:51   ` Nadav Amit
2020-11-29  0:45 ` [RFC PATCH 13/13] selftests/vm/userfaultfd: iouring and polling tests Nadav Amit

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