linux-kernel - [PATCH 4.4 4.9 4.14] loop: Add LOOP_SET_DIRECT

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Message-Id: <20191023171736.161697-1-balsini@android.com>
Date:   Wed, 23 Oct 2019 18:17:36 +0100
From:   Alessio Balsini <balsini@...roid.com>
To:     gregkh@...uxfoundation.org
Cc:     stable@...r.kernel.org, linux-kernel@...r.kernel.org,
        kernel-team@...roid.com, Alessio Balsini <balsini@...roid.com>,
        Jens Axboe <axboe@...nel.dk>, Sasha Levin <sashal@...nel.org>
Subject: [PATCH 4.4 4.9 4.14] loop: Add LOOP_SET_DIRECT_IO to compat ioctl

[ Upstream commit fdbe4eeeb1aac219b14f10c0ed31ae5d1123e9b8 ]

Enabling Direct I/O with loop devices helps reducing memory usage by
avoiding double caching.  32 bit applications running on 64 bits systems
are currently not able to request direct I/O because is missing from the
lo_compat_ioctl.

This patch fixes the compatibility issue mentioned above by exporting
LOOP_SET_DIRECT_IO as additional lo_compat_ioctl() entry.
The input argument for this ioctl is a single long converted to a 1-bit
boolean, so compatibility is preserved.

Cc: Jens Axboe <axboe@...nel.dk>
Signed-off-by: Alessio Balsini <balsini@...roid.com>
Signed-off-by: Jens Axboe <axboe@...nel.dk>
Signed-off-by: Sasha Levin <sashal@...nel.org>
---
 drivers/block/loop.c | 1 +
 1 file changed, 1 insertion(+)

diff --git a/drivers/block/loop.c b/drivers/block/loop.c
index da3902ac16c86..8aadd4d0c3a88 100644
--- a/drivers/block/loop.c
+++ b/drivers/block/loop.c
@@ -1557,6 +1557,7 @@ static int lo_compat_ioctl(struct block_device *bdev, fmode_t mode,
 		arg = (unsigned long) compat_ptr(arg);
 	case LOOP_SET_FD:
 	case LOOP_CHANGE_FD:
+	case LOOP_SET_DIRECT_IO:
 		err = lo_ioctl(bdev, mode, cmd, arg);
 		break;
 	default:
-- 
2.23.0.866.gb869b98d4c-goog