loop: change queue block size to match when using DIO

The loop driver assumes that if the passed in fd is opened with
O_DIRECT, the caller wants to use direct I/O on the loop device.
However, if the underlying block device has a different block size than
the loop block queue, direct I/O can't be enabled. Instead of requiring
userspace to manually change the blocksize and re-enable direct I/O,
just change the queue block sizes to match, as well as the io_min size.

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 1410fa89365389a62f42782b3ef89dfb23fa1600..f6f77eaa7217e0df51b51047ca3c734a001d0479 100644 (file)
--- a/drivers/block/loop.c
+++ b/drivers/block/loop.c
@@ -994,6 +994,16 @@ static int loop_set_fd(struct loop_device *lo, fmode_t mode,
        if (!(lo_flags & LO_FLAGS_READ_ONLY) && file->f_op->fsync)
                blk_queue_write_cache(lo->lo_queue, true, false);
 
+       if (io_is_direct(lo->lo_backing_file) && inode->i_sb->s_bdev) {
+               /* In case of direct I/O, match underlying block size */
+               unsigned short bsize = bdev_logical_block_size(
+                       inode->i_sb->s_bdev);
+
+               blk_queue_logical_block_size(lo->lo_queue, bsize);
+               blk_queue_physical_block_size(lo->lo_queue, bsize);
+               blk_queue_io_min(lo->lo_queue, bsize);
+       }
+
        loop_update_rotational(lo);
        loop_update_dio(lo);
        set_capacity(lo->lo_disk, size);