linux-kernel - [PATCH 4.4 12/41] loop: Add LOOP_SET_DIRECT

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Message-Id: <20191027203110.371349330@linuxfoundation.org>
Date:   Sun, 27 Oct 2019 22:00:50 +0100
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org, Jens Axboe <axboe@...nel.dk>,
        Alessio Balsini <balsini@...roid.com>,
        Sasha Levin <sashal@...nel.org>
Subject: [PATCH 4.4 12/41] loop: Add LOOP_SET_DIRECT_IO to compat ioctl

From: Alessio Balsini <balsini@...roid.com>

[ 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(+)

--- a/drivers/block/loop.c
+++ b/drivers/block/loop.c
@@ -1557,6 +1557,7 @@ static int lo_compat_ioctl(struct block_
 		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: