linux-kernel - [PATCH v1 3/3] block: set partition read/write policy according to write-protection status

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Date:   Wed, 4 Mar 2020 10:51:14 +0800
From:   <light.hsieh@...iatek.com>
To:     <ulf.hansson@...aro.org>
CC:     <linux-mediatek@...ts.infradead.org>, <axboe@...nel.dk>,
        <linux-block@...r.kernel.org>, <linux-kernel@...r.kernel.org>,
        <kuohong.wang@...iatek.com>, <stanley.chu@...iatek.com>,
        Light Hsieh <light.hsieh@...iatek.com>
Subject: [PATCH v1 3/3] block: set partition read/write policy according to write-protection status

From: Light Hsieh <light.hsieh@...iatek.com>

For storage device with write-protection support, e.g. eMMC, register
check_disk_range_wp() in struct block_device_operations for checking
write-protection status. When creating block device for a partition, set
read/write policy according to result of check_disk_range_wp() operation
(if registered).

Without this patch, ro attribute is not set for created block device of
write-protected partition. User perform asynchronous buffered write to
such partition won't get immediate error and therefore he won't be awared
that write is not actually performed.
With this patch, ro attribute is set for created block device of
write-protected partition. User perform asynchronous buffered write to
such partition will get immediate error and therefore he will be awared.

Signed-off-by: Light Hsieh <light.hsieh@...iatek.com>
---
 block/partition-generic.c | 10 ++++++++++
 drivers/mmc/core/block.c  |  1 +
 include/linux/blkdev.h    |  1 +
 3 files changed, 12 insertions(+)

diff --git a/block/partition-generic.c b/block/partition-generic.c
index 564fae7..69088e8 100644
--- a/block/partition-generic.c
+++ b/block/partition-generic.c
@@ -394,6 +394,16 @@ struct hd_struct *add_partition(struct gendisk *disk, int partno,
 		goto out_free_info;
 	pdev->devt = devt;
 
+	if (!p->policy) {
+		if (disk->fops->check_disk_range_wp) {
+			err = disk->fops->check_disk_range_wp(disk, start, len);
+			if (err > 0)
+				p->policy = 1;
+			else if (err != 0)
+				goto out_free_info;
+		}
+	}
+
 	/* delay uevent until 'holders' subdir is created */
 	dev_set_uevent_suppress(pdev, 1);
 	err = device_add(pdev);
diff --git a/drivers/mmc/core/block.c b/drivers/mmc/core/block.c
index ee85abf..af81311 100644
--- a/drivers/mmc/core/block.c
+++ b/drivers/mmc/core/block.c
@@ -1047,6 +1047,7 @@ static int mmc_blk_compat_ioctl(struct block_device *bdev, fmode_t mode,
 #ifdef CONFIG_COMPAT
 	.compat_ioctl		= mmc_blk_compat_ioctl,
 #endif
+	.check_disk_range_wp	= mmc_blk_check_disk_range_wp,
 };
 
 static int mmc_blk_part_switch_pre(struct mmc_card *card,
diff --git a/include/linux/blkdev.h b/include/linux/blkdev.h
index 053ea4b..7814290 100644
--- a/include/linux/blkdev.h
+++ b/include/linux/blkdev.h
@@ -1707,6 +1707,7 @@ struct block_device_operations {
 	void (*swap_slot_free_notify) (struct block_device *, unsigned long);
 	int (*report_zones)(struct gendisk *, sector_t sector,
 			unsigned int nr_zones, report_zones_cb cb, void *data);
+	int (*check_disk_range_wp)(struct gendisk *d, sector_t s, sector_t l);
 	struct module *owner;
 	const struct pr_ops *pr_ops;
 };
-- 
1.8.1.1.dirty