linux-kernel - [PATCH v2] loop: Add LOOP_SET_DIRECT

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Message-Id: <20190807004828.28059-1-balsini@android.com>
Date:   Wed,  7 Aug 2019 01:48:28 +0100
From:   Alessio Balsini <balsini@...roid.com>
To:     linux-block@...r.kernel.org
Cc:     linux-kernel@...r.kernel.org, axboe@...nel.dk, dvander@...il.com,
        elsk@...gle.com, gregkh@...uxfoundation.org, joelaf@...gle.com,
        kernel-team@...roid.com
Subject: [PATCH v2] loop: Add LOOP_SET_DIRECT_IO to compat ioctl

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>
---
 drivers/block/loop.c | 1 +
 1 file changed, 1 insertion(+)

diff --git a/drivers/block/loop.c b/drivers/block/loop.c
index 44c9985f352ab..2e2193f754ab0 100644
--- a/drivers/block/loop.c
+++ b/drivers/block/loop.c
@@ -1753,6 +1753,7 @@ static int lo_compat_ioctl(struct block_device *bdev, fmode_t mode,
 	case LOOP_SET_FD:
 	case LOOP_CHANGE_FD:
 	case LOOP_SET_BLOCK_SIZE:
+	case LOOP_SET_DIRECT_IO:
 		err = lo_ioctl(bdev, mode, cmd, arg);
 		break;
 	default:
-- 
2.23.0.rc1.153.gdeed80330f-goog