linux-kernel - [PATCH 1/3] aio_ring_remap: turn the ctx->dead check into WARN

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Message-ID: <20150616230426.GA15790@redhat.com>
Date:	Wed, 17 Jun 2015 01:04:26 +0200
From:	Oleg Nesterov <oleg@...hat.com>
To:	Al Viro <viro@...IV.linux.org.uk>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Benjamin LaHaise <bcrl@...ck.org>,
	Jeff Moyer <jmoyer@...hat.com>
Cc:	linux-aio@...ck.org, linux-kernel@...r.kernel.org
Subject: [PATCH 1/3] aio_ring_remap: turn the ctx->dead check into WARN_ON()

atomic_read(&ctx->dead) in aio_ring_remap() looks confusing.
kill_ioctx() sets ctx->dead and removes ctx from ->ioctx_table
"atomically" under mm->ioctx_lock, so aio_ring_remap() can never
see a dead ctx.

If we really want this check, we should put it under WARN_ON()
and it should not depend on aio_ring_file == file.

Signed-off-by: Oleg Nesterov <oleg@...hat.com>
---
 fs/aio.c |   16 ++++++++--------
 1 files changed, 8 insertions(+), 8 deletions(-)

diff --git a/fs/aio.c b/fs/aio.c
index 480440f..0693333 100644
--- a/fs/aio.c
+++ b/fs/aio.c
@@ -325,14 +325,14 @@ static int aio_ring_remap(struct file *file, struct vm_area_struct *vma)
 	rcu_read_lock();
 	table = rcu_dereference(mm->ioctx_table);
 	for (i = 0; i < table->nr; i++) {
-		struct kioctx *ctx;
-
-		ctx = table->table[i];
-		if (ctx && ctx->aio_ring_file == file) {
-			if (!atomic_read(&ctx->dead)) {
-				ctx->user_id = ctx->mmap_base = vma->vm_start;
-				res = 0;
-			}
+		struct kioctx *ctx = table->table[i];
+
+		if (!ctx || WARN_ON(atomic_read(&ctx->dead)))
+			continue;
+
+		if (ctx->aio_ring_file == file) {
+			ctx->user_id = ctx->mmap_base = vma->vm_start;
+			res = 0;
 			break;
 		}
 	}
-- 
1.5.5.1

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