[patch 016/158] mm, swap: disallow swapon() on zoned block devices

[akpm@linux-foundation.org]

From: Naohiro Aota <naohiro.aota@wdc.com>
Subject: mm, swap: disallow swapon() on zoned block devices

A zoned block device consists of a number of zones.  Zones are either
conventional and accepting random writes or sequential and requiring that
writes be issued in LBA order from each zone write pointer position.  For
the write restriction, zoned block devices are not suitable for a swap
device.  Disallow swapon on them.

[akpm@linux-foundation.org: reflow and reword comment, per Christoph]
Link: http://lkml.kernel.org/r/20191015085814.637837-1-naohiro.aota@wdc.com
Signed-off-by: Naohiro Aota <naohiro.aota@wdc.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Cc: Matthew Wilcox <willy@infradead.org>
Cc: "Theodore Y. Ts'o" <tytso@mit.edu>
Cc: Hannes Reinecke <hare@suse.de>
Cc: Hugh Dickins <hughd@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
---

 mm/swapfile.c |    7 +++++++
 1 file changed, 7 insertions(+)

--- a/mm/swapfile.c~mm-swap-disallow-swapon-on-zoned-block-devices
+++ a/mm/swapfile.c
@@ -2887,6 +2887,13 @@ static int claim_swapfile(struct swap_in
 		error = set_blocksize(p->bdev, PAGE_SIZE);
 		if (error < 0)
 			return error;
+		/*
+		 * Zoned block devices contain zones that have a sequential
+		 * write only restriction.  Hence zoned block devices are not
+		 * suitable for swapping.  Disallow them here.
+		 */
+		if (blk_queue_is_zoned(p->bdev->bd_queue))
+			return -EINVAL;
 		p->flags |= SWP_BLKDEV;
 	} else if (S_ISREG(inode->i_mode)) {
 		p->bdev = inode->i_sb->s_bdev;
_