dm writecache: fix writing beyond end of underlying device when shrinking

stable inclusion
from linux-4.19.199
commit 797b950e8aaec3fc30312bb9a44d702c6cc9d25e

--------------------------------

commit 4134455f upstream.

Do not attempt to write any data beyond the end of the underlying data
device while shrinking it.

The DM writecache device must be suspended when the underlying data
device is shrunk.
Signed-off-by: NMikulas Patocka <mpatocka@redhat.com>
Cc: stable@vger.kernel.org
Signed-off-by: NMike Snitzer <snitzer@redhat.com>
Signed-off-by: NGreg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: NYang Yingliang <yangyingliang@huawei.com>

drivers/md/dm-writecache.c

@@ -142,6 +142,7 @@ struct dm_writecache {
 	size_t metadata_sectors;
 	size_t n_blocks;
 	uint64_t seq_count;
+	sector_t data_device_sectors;
 	void *block_start;
 	struct wc_entry *entries;
 	unsigned block_size;
@@ -929,6 +930,8 @@ static void writecache_resume(struct dm_target *ti)
 
 	wc_lock(wc);
 
+	wc->data_device_sectors = i_size_read(wc->dev->bdev->bd_inode) >> SECTOR_SHIFT;
+
 	if (WC_MODE_PMEM(wc)) {
 		persistent_memory_invalidate_cache(wc->memory_map, wc->memory_map_size);
 	} else {
@@ -1499,6 +1502,10 @@ static bool wc_add_block(struct writeback_struct *wb, struct wc_entry *e, gfp_t
 	void *address = memory_data(wc, e);
 
 	persistent_memory_flush_cache(address, block_size);
+
+	if (unlikely(bio_end_sector(&wb->bio) >= wc->data_device_sectors))
+		return true;
+
 	return bio_add_page(&wb->bio, persistent_memory_page(address),
 			    block_size, persistent_memory_page_offset(address)) != 0;
 }
@@ -1571,6 +1578,9 @@ static void __writecache_writeback_pmem(struct dm_writecache *wc, struct writeba
 		if (writecache_has_error(wc)) {
 			bio->bi_status = BLK_STS_IOERR;
 			bio_endio(&wb->bio);
+		} else if (unlikely(!bio_sectors(&wb->bio))) {
+			bio->bi_status = BLK_STS_OK;
+			bio_endio(&wb->bio);
 		} else {
 			submit_bio(&wb->bio);
 		}
@@ -1614,6 +1624,14 @@ static void __writecache_writeback_ssd(struct dm_writecache *wc, struct writebac
 			e = f;
 		}
 
+		if (unlikely(to.sector + to.count > wc->data_device_sectors)) {
+			if (to.sector >= wc->data_device_sectors) {
+				writecache_copy_endio(0, 0, c);
+				continue;
+			}
+			from.count = to.count = wc->data_device_sectors - to.sector;
+		}
+
 		dm_kcopyd_copy(wc->dm_kcopyd, &from, 1, &to, 0, writecache_copy_endio, c);
 
 		__writeback_throttle(wc, wbl);