On Mon, 29 Jun 2009 13:41:20 +0200
Douglas Gilbert <dgilbert@xxxxxxxxxxxx> wrote:
> The semantics of SG_DXFER_TO_FROM_DEV were:
> - copy user space buffer to kernel (LLD) buffer
> - do SCSI command which is assumed to be of the DATA_IN
> (data from device) variety. This would overwrite
> some or all of the kernel buffer
> - copy kernel (LLD) buffer back to the user space.
>
> The idea was to detect short reads by filling the original
> user space buffer with some marker bytes ("0xec" it would
> seem in this report). The "resid" value is a better way
> of detecting short reads but that was only added this century
> and requires co-operation from the LLD.
>
> There were major plumbing changes in the sg driver around
> lk 2.6.28 and it looks like the above nuance was lost.
> Perhaps the block layer does support the above "double
> shuffle".
Sorry, I overlooked SG_DXFER_TO_FROM_DEV.
Does this patch work?
diff --git a/drivers/scsi/sg.c b/drivers/scsi/sg.c
index 8201387..8df3b6a 100644
--- a/drivers/scsi/sg.c
+++ b/drivers/scsi/sg.c
@@ -1658,6 +1658,10 @@ static int sg_start_req(Sg_request *srp, unsigned char *cmd)
md->nr_entries = req_schp->k_use_sg;
md->offset = 0;
md->null_mapped = hp->dxferp ? 0 : 1;
+ if (dxfer_dir == SG_DXFER_TO_FROM_DEV)
+ md->from_user = 1;
+ else
+ md->from_user = 0;
}
if (iov_count) {
diff --git a/fs/bio.c b/fs/bio.c
index 24c9140..e467dd8 100644
--- a/fs/bio.c
+++ b/fs/bio.c
@@ -705,14 +705,13 @@ static struct bio_map_data *bio_alloc_map_data(int nr_segs, int iov_count,
}
static int __bio_copy_iov(struct bio *bio, struct bio_vec *iovecs,
- struct sg_iovec *iov, int iov_count, int uncopy,
- int do_free_page)
+ struct sg_iovec *iov, int iov_count,
+ int to_user, int from_user, int do_free_page)
{
int ret = 0, i;
struct bio_vec *bvec;
int iov_idx = 0;
unsigned int iov_off = 0;
- int read = bio_data_dir(bio) == READ;
__bio_for_each_segment(bvec, bio, i, 0) {
char *bv_addr = page_address(bvec->bv_page);
@@ -727,13 +726,14 @@ static int __bio_copy_iov(struct bio *bio, struct bio_vec *iovecs,
iov_addr = iov[iov_idx].iov_base + iov_off;
if (!ret) {
- if (!read && !uncopy)
- ret = copy_from_user(bv_addr, iov_addr,
- bytes);
- if (read && uncopy)
+ if (to_user)
ret = copy_to_user(iov_addr, bv_addr,
bytes);
+ if (from_user)
+ ret = copy_from_user(bv_addr, iov_addr,
+ bytes);
+
if (ret)
ret = -EFAULT;
}
@@ -770,7 +770,8 @@ int bio_uncopy_user(struct bio *bio)
if (!bio_flagged(bio, BIO_NULL_MAPPED))
ret = __bio_copy_iov(bio, bmd->iovecs, bmd->sgvecs,
- bmd->nr_sgvecs, 1, bmd->is_our_pages);
+ bmd->nr_sgvecs, bio_data_dir(bio) == READ,
+ 0, bmd->is_our_pages);
bio_free_map_data(bmd);
bio_put(bio);
return ret;
@@ -875,8 +876,9 @@ struct bio *bio_copy_user_iov(struct request_queue *q,
/*
* success
*/
- if (!write_to_vm && (!map_data || !map_data->null_mapped)) {
- ret = __bio_copy_iov(bio, bio->bi_io_vec, iov, iov_count, 0, 0);
+ if ((!write_to_vm && (!map_data || !map_data->null_mapped)) ||
+ (map_data && map_data->from_user)) {
+ ret = __bio_copy_iov(bio, bio->bi_io_vec, iov, iov_count, 0, 1, 0);
if (ret)
goto cleanup;
}
diff --git a/include/linux/blkdev.h b/include/linux/blkdev.h
index 8963d91..36c5ff8 100644
--- a/include/linux/blkdev.h
+++ b/include/linux/blkdev.h
@@ -730,6 +730,7 @@ struct rq_map_data {
int nr_entries;
unsigned long offset;
int null_mapped;
+ int from_user;
};
struct req_iterator {
--
To unsubscribe from this list: send the line "unsubscribe linux-scsi" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at http://vger.kernel.org/majordomo-info.html
