From a14e5ec66a7a66e57b24e2469f9212a78460207e Mon Sep 17 00:00:00 2001
From: Mikulas Patocka <mpatocka@redhat.com>
Date: Tue, 23 Feb 2021 21:21:20 +0100
Subject: [PATCH] dm bufio: subtract the number of initial sectors in
 dm_bufio_get_device_size
Git-commit: a14e5ec66a7a66e57b24e2469f9212a78460207e
Patch-mainline: v5.12-rc2
References: git-fixes

dm_bufio_get_device_size returns the device size in blocks. Before
returning the value, we must subtract the nubmer of starting
sectors. The number of starting sectors may not be divisible by block
size.

Note that currently, no target is using dm_bufio_set_sector_offset and
dm_bufio_get_device_size simultaneously, so this change has no effect.
However, an upcoming dm-verity-fec fix needs this change.

Signed-off-by: Mikulas Patocka <mpatocka@redhat.com>
Reviewed-by: Milan Broz <gmazyland@gmail.com>
Cc: stable@vger.kernel.org
Signed-off-by: Mike Snitzer <snitzer@redhat.com>
Signed-off-by: Coly Li <colyli@suse.de>

---
 drivers/md/dm-bufio.c | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/drivers/md/dm-bufio.c b/drivers/md/dm-bufio.c
index fce4cbf9529d..50f3e673729c 100644
--- a/drivers/md/dm-bufio.c
+++ b/drivers/md/dm-bufio.c
@@ -1526,6 +1526,10 @@ EXPORT_SYMBOL_GPL(dm_bufio_get_block_size);
 sector_t dm_bufio_get_device_size(struct dm_bufio_client *c)
 {
 	sector_t s = i_size_read(c->bdev->bd_inode) >> SECTOR_SHIFT;
+	if (s >= c->start)
+		s -= c->start;
+	else
+		s = 0;
 	if (likely(c->sectors_per_block_bits >= 0))
 		s >>= c->sectors_per_block_bits;
 	else
-- 
2.35.3