loop: Only change blocksize when needed.

Return early in loop_set_block_size() if the requested block size is
identical to the one we already have; this avoids expensive calls to
freeze the block queue.

Reviewed-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Martijn Coenen <maco@android.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>

diff --git a/drivers/block/loop.c b/drivers/block/loop.c
index 739b372a51128be568740ff448ef3c2c1e10f454..93b8d6047c14e3515fc45aabf34156cbc9609018 100644 (file)
--- a/drivers/block/loop.c
+++ b/drivers/block/loop.c
@@ -1539,16 +1539,16 @@ static int loop_set_block_size(struct loop_device *lo, unsigned long arg)
        if (arg < 512 || arg > PAGE_SIZE || !is_power_of_2(arg))
                return -EINVAL;
 
-       if (lo->lo_queue->limits.logical_block_size != arg) {
-               sync_blockdev(lo->lo_device);
-               kill_bdev(lo->lo_device);
-       }
+       if (lo->lo_queue->limits.logical_block_size == arg)
+               return 0;
+
+       sync_blockdev(lo->lo_device);
+       kill_bdev(lo->lo_device);
 
        blk_mq_freeze_queue(lo->lo_queue);
 
        /* kill_bdev should have truncated all the pages */
-       if (lo->lo_queue->limits.logical_block_size != arg &&
-                       lo->lo_device->bd_inode->i_mapping->nrpages) {
+       if (lo->lo_device->bd_inode->i_mapping->nrpages) {
                err = -EAGAIN;
                pr_warn("%s: loop%d (%s) has still dirty pages (nrpages=%lu)\n",
                        __func__, lo->lo_number, lo->lo_file_name,