block: pass iov_iter to the BLOCK_PC mapping functions

Make use of a new interface provided by iov_iter, backed by
scatter-gather list of iovec, instead of the old interface based on
sg_iovec. Also use iov_iter_advance() instead of manual iteration.

This commit should contain only literal replacements, without
functional changes.

Cc: Christoph Hellwig <hch@infradead.org>
Cc: Jens Axboe <axboe@kernel.dk>
Cc: Doug Gilbert <dgilbert@interlog.com>
Cc: "James E.J. Bottomley" <JBottomley@parallels.com>
Signed-off-by: Kent Overstreet <kmo@daterainc.com>
[dpark: add more description in commit message]
Signed-off-by: Dongsu Park <dongsu.park@profitbricks.com>
[hch: fixed to do a deep clone of the iov_iter, and to properly use
      the iov_iter direction]
Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Ming Lei <tom.leiming@gmail.com>
Signed-off-by: Jens Axboe <axboe@fb.com>

1 files changed, 4 insertions, 13 deletions

diff --git a/block/scsi_ioctl.c b/block/scsi_ioctl.c
index 28163fad3c5d..e1f71c396193 100644
--- a/block/scsi_ioctl.c
+++ b/block/scsi_ioctl.c
@@ -332,7 +332,7 @@ static int sg_io(struct request_queue *q, struct gendisk *bd_disk,
 
         ret = 0;
         if (hdr->iovec_count) {
-                size_t iov_data_len;
+                struct iov_iter i;
                 struct iovec *iov = NULL;
 
                 ret = rw_copy_check_uvector(-1, hdr->dxferp, hdr->iovec_count,
@@ -342,20 +342,11 @@ static int sg_io(struct request_queue *q, struct gendisk *bd_disk,
                         goto out_free_cdb;
                 }
 
-                iov_data_len = ret;
-                ret = 0;
-
                 /* SG_IO howto says that the shorter of the two wins */
-                if (hdr->dxfer_len < iov_data_len) {
-                        hdr->iovec_count = iov_shorten(iov,
-                                                       hdr->iovec_count,
-                                                       hdr->dxfer_len);
-                        iov_data_len = hdr->dxfer_len;
-                }
+                iov_iter_init(&i, rq_data_dir(rq), iov, hdr->iovec_count,
+                              min_t(unsigned, ret, hdr->dxfer_len));
 
-                ret = blk_rq_map_user_iov(q, rq, NULL, (struct sg_iovec *) iov,
-                                          hdr->iovec_count,
-                                          iov_data_len, GFP_KERNEL);
+                ret = blk_rq_map_user_iov(q, rq, NULL, &i, GFP_KERNEL);
                 kfree(iov);
         } else if (hdr->dxfer_len)
                 ret = blk_rq_map_user(q, rq, NULL, hdr->dxferp, hdr->dxfer_len,