nbd: move the task_recv check into nbd_size_update

mainline inclusion
from mainline-v5.11-rc1
commit 92f93c3a
category: bugfix
bugzilla: 187706,,https://gitee.com/openeuler/kernel/issues/I5XEBX
CVE: NA

Reference: https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=92f93c3a1bf9dc73181dc6566497d16b690cb576

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

nbd_size_update is about to acquire a few more callers, so lift the check
into the function.
Signed-off-by: NChristoph Hellwig <hch@lst.de>
Reviewed-by: NJosef Bacik <josef@toxicpanda.com>
Signed-off-by: NJens Axboe <axboe@kernel.dk>

Conflicts:
	drivers/block/nbd.c
[0c98057b ("nbd: Fix use-after-free in pid_show") include first]
Signed-off-by: NZhong Jinghua <zhongjinghua@huawei.com>
Reviewed-by: NJason Yan <yanaijie@huawei.com>
Reviewed-by: NYu Kuai <yukuai3@huawei.com>
Signed-off-by: NZheng Zengkai <zhengzengkai@huawei.com>

drivers/block/nbd.c

@@ -304,8 +304,11 @@ static void nbd_size_clear(struct nbd_device *nbd)
 static void nbd_size_update(struct nbd_device *nbd)
 {
 	struct nbd_config *config = nbd->config;
-	struct block_device *bdev = bdget_disk(nbd->disk, 0);
 	sector_t nr_sectors = config->bytesize >> 9;
+	struct block_device *bdev;
+
+	if (!nbd->pid)
+		return;
 
 	if (config->flags & NBD_FLAG_SEND_TRIM) {
 		nbd->disk->queue->limits.discard_granularity = config->blksize;
@@ -314,7 +317,9 @@ static void nbd_size_update(struct nbd_device *nbd)
 	}
 	blk_queue_logical_block_size(nbd->disk->queue, config->blksize);
 	blk_queue_physical_block_size(nbd->disk->queue, config->blksize);
+
 	set_capacity(nbd->disk, nr_sectors);
+	bdev = bdget_disk(nbd->disk, 0);
 	if (bdev) {
 		if (bdev->bd_disk)
 			bd_set_nr_sectors(bdev, nr_sectors);
@@ -331,7 +336,6 @@ static void nbd_size_set(struct nbd_device *nbd, loff_t blocksize,
 	struct nbd_config *config = nbd->config;
 	config->blksize = blocksize;
 	config->bytesize = blocksize * nr_blocks;
-	if (nbd->pid)
 	nbd_size_update(nbd);
 }