From e5113505904ea1c1c0e1f92c1cfa91fbf4da1694 Mon Sep 17 00:00:00 2001
From: Shin'ichiro Kawasaki <shinichiro.kawasaki@wdc.com>
Date: Thu, 11 Mar 2021 16:25:46 +0900
Subject: [PATCH] block: Discard page cache of zone reset target range
Git-commit: e5113505904ea1c1c0e1f92c1cfa91fbf4da1694
Patch-mainline: v5.12-rc3
References: bsc#1187402

When zone reset ioctl and data read race for a same zone on zoned block
devices, the data read leaves stale page cache even though the zone
reset ioctl zero clears all the zone data on the device. To avoid
non-zero data read from the stale page cache after zone reset, discard
page cache of reset target zones in blkdev_zone_mgmt_ioctl(). Introduce
the helper function blkdev_truncate_zone_range() to discard the page
cache. Ensure the page cache discarded by calling the helper function
before and after zone reset in same manner as fallocate does.

This patch can be applied back to the stable kernel version v5.10.y.
Rework is needed for older stable kernels.

Signed-off-by: Shin'ichiro Kawasaki <shinichiro.kawasaki@wdc.com>
Fixes: 3ed05a987e0f ("blk-zoned: implement ioctls")
Cc: <stable@vger.kernel.org> # 5.10+
Reviewed-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Johannes Thumshirn <johannes.thumshirn@wdc.com>
Link: https://lore.kernel.org/r/20210311072546.678999-1-shinichiro.kawasaki@wdc.com
Signed-off-by: Jens Axboe <axboe@kernel.dk>
Acked-by: Jan Kara <jack@suse.cz>

---
 block/blk-zoned.c |   38 ++++++++++++++++++++++++++++++++++++--
 1 file changed, 36 insertions(+), 2 deletions(-)

--- a/block/blk-zoned.c
+++ b/block/blk-zoned.c
@@ -388,6 +388,23 @@ int blkdev_report_zones_ioctl(struct blo
 	return ret;
 }
 
+static int blkdev_truncate_zone_range(struct block_device *bdev, fmode_t mode,
+				      const struct blk_zone_range *zrange)
+{
+	loff_t start, end;
+
+	if (zrange->sector + zrange->nr_sectors <= zrange->sector ||
+	    zrange->sector + zrange->nr_sectors > get_capacity(bdev->bd_disk))
+		/* Out of range */
+		return -EINVAL;
+
+	start = zrange->sector << SECTOR_SHIFT;
+	end = ((zrange->sector + zrange->nr_sectors) << SECTOR_SHIFT) - 1;
+
+	truncate_inode_pages_range(bdev->bd_inode->i_mapping, start, end);
+	return 0;
+}
+
 /*
  * BLKRESETZONE ioctl processing.
  * Called from blkdev_ioctl.
@@ -398,6 +415,7 @@ int blkdev_reset_zones_ioctl(struct bloc
 	void __user *argp = (void __user *)arg;
 	struct request_queue *q;
 	struct blk_zone_range zrange;
+	int ret;
 
 	if (!argp)
 		return -EINVAL;
@@ -418,6 +436,22 @@ int blkdev_reset_zones_ioctl(struct bloc
 	if (copy_from_user(&zrange, argp, sizeof(struct blk_zone_range)))
 		return -EFAULT;
 
-	return blkdev_reset_zones(bdev, zrange.sector, zrange.nr_sectors,
-				  GFP_KERNEL);
+	/* Invalidate the page cache, including dirty pages. */
+	ret = blkdev_truncate_zone_range(bdev, mode, &zrange);
+	if (ret)
+		return ret;
+
+	ret = blkdev_reset_zones(bdev, zrange.sector, zrange.nr_sectors,
+				 GFP_KERNEL);
+	/*
+	 * Invalidate the page cache again for zone reset: writes can only be
+	 * direct for zoned devices so concurrent writes would not add any page
+	 * to the page cache after/during reset. The page cache may be filled
+	 * again due to concurrent reads though and dropping the pages for
+	 * these is fine.
+	 */
+	if (!ret)
+		ret = blkdev_truncate_zone_range(bdev, mode, &zrange);
+
+	return ret;
 }