Support vectored IO as in SGv3. The iovec structure uses explicit
sizes to avoid the need for compat conversion.
Signed-off-by: Pete Wyckoff <pw@xxxxxxx>
---
My application definitely can take advantage of scatter/gather IO,
which is supported in sgv3 but not in the bsg implementation of sgv4.
I understand Tomo's concerns about code bloat and the need for
32/64 compat translations, but this will make things much easier on
users of bsg who read or write out of multiple buffers in a single
SCSI operation.
Clearly we want to avoid doing the compat work that sg.c has to do
now, so I went with __u64 for the addresses in the structures that
userspace sees. But to interface with existing bio structures, that
must be converted back to 32-bit pointers in sg_iovec (only on
32-bit architectures). In the long run, maybe we should have a
bio_map_user_iov() that works on the constant-sized sg_io_v4_vec
proposed here?
-- Pete
block/bsg.c | 132 ++++++++++++++++++++++++++++++++++++++++++---------
include/linux/bsg.h | 16 ++++++
2 files changed, 125 insertions(+), 23 deletions(-)
diff --git a/block/bsg.c b/block/bsg.c
index c85d961..8e3d6c7 100644
--- a/block/bsg.c
+++ b/block/bsg.c
@@ -280,6 +280,95 @@ bsg_validate_sgv4_hdr(request_queue_t *q, struct sg_io_v4 *hdr, int *rw)
}
/*
+ * Sits around blk_rq_map_user_iov so we can use an iovec type that
+ * does not require compat manipulations. For now we just clumsily
+ * remap the entire iovec if the types do not match. Later consider
+ * changing the bio map function.
+ */
+static int bsg_map_user_iovec(request_queue_t *q, struct request *rq,
+ struct sg_io_v4_vec *vec, int numvec,
+ size_t tot_len, enum dma_data_direction dir)
+{
+ struct bio *bio;
+ struct sg_iovec *iov;
+ int write_to_vm = (dir == DMA_FROM_DEVICE ? 1 : 0);
+ int must_copy_iovec = (sizeof(*iov) != sizeof(*vec));
+
+ /*
+ * For 64-bit everywhere, sg_io_v4_vec using __u64 is same as sg_iovec
+ * using void *. For 64-bit kernel with 32-bit userspace, also no
+ * translation needed as userspace is forced to use __u64. Only in the
+ * all 32-bit case will sg_iovec use 32-bit pointers and hence we
+ * must shrink our 64-bit pointers down into it.
+ */
+ if (must_copy_iovec) {
+ int i;
+ iov = kmalloc(numvec * sizeof(*iov), GFP_KERNEL);
+ for (i=0; i<numvec; i++) {
+ iov[i].iov_base = (void __user *) vec[i].iov_base;
+ iov[i].iov_len = vec[i].iov_len;
+ }
+ } else {
+ iov = (struct sg_iovec *) vec;
+ }
+
+ bio = bio_map_user_iov(q, NULL, iov, numvec, write_to_vm);
+
+ if (must_copy_iovec)
+ kfree(iov);
+
+ if (IS_ERR(bio)) {
+ dprintk("bio_map_user_iov err\n");
+ return PTR_ERR(bio);
+ }
+
+ if (bio->bi_size != tot_len) {
+ dprintk("bio->bi_size %u != len %lu\n", bio->bi_size, tot_len);
+ bio_endio(bio, bio->bi_size, 0);
+ bio_unmap_user(bio);
+ return -EINVAL;
+ }
+
+ bio_get(bio);
+ blk_rq_bio_prep_bidi(q, rq, bio, dir);
+ rq->buffer = rq->data = NULL;
+ return 0;
+}
+
+/*
+ * Map either the in or out bufs.
+ */
+static int bsg_map_data(struct request_queue *q, struct request *rq,
+ __u64 uaddr, __u32 tot_len, __u32 numiov,
+ enum dma_data_direction dir)
+{
+ int ret;
+ void __user *ubuf = (void __user *) (unsigned long) uaddr;
+
+ if (numiov) {
+ struct sg_io_v4_vec *vec;
+ size_t len = numiov * sizeof(*vec);
+
+ vec = kmalloc(len, GFP_KERNEL);
+ if (vec == NULL) {
+ ret = -ENOMEM;
+ goto out;
+ }
+ if (copy_from_user(vec, ubuf, len)) {
+ ret = -EFAULT;
+ kfree(vec);
+ goto out;
+ }
+ ret = bsg_map_user_iovec(q, rq, vec, numiov, tot_len, dir);
+ kfree(vec);
+ } else
+ ret = blk_rq_map_user(q, rq, ubuf, tot_len);
+
+out:
+ return ret;
+}
+
+/*
* map sg_io_v4 to a request.
*/
static struct request *
@@ -288,12 +377,10 @@ bsg_map_hdr(struct bsg_device *bd, struct sg_io_v4 *hdr)
request_queue_t *q = bd->queue;
struct request *rq;
int ret, rw = 0; /* shut up gcc */
- unsigned int dxfer_len;
- void *dxferp = NULL;
- dprintk("map hdr %llx/%u %llx/%u\n", (unsigned long long) hdr->dout_xferp,
- hdr->dout_xfer_len, (unsigned long long) hdr->din_xferp,
- hdr->din_xfer_len);
+ dprintk("map hdr %llx/%u %llx/%u\n",
+ (unsigned long long) hdr->dout_xferp, hdr->dout_xfer_len,
+ (unsigned long long) hdr->din_xferp, hdr->din_xfer_len);
ret = bsg_validate_sgv4_hdr(q, hdr, &rw);
if (ret)
@@ -305,29 +392,28 @@ bsg_map_hdr(struct bsg_device *bd, struct sg_io_v4 *hdr)
rq = blk_get_request(q, rw, GFP_KERNEL);
ret = blk_fill_sgv4_hdr_rq(q, rq, hdr, test_bit(BSG_F_WRITE_PERM,
&bd->flags));
- if (ret) {
- blk_put_request(rq);
- return ERR_PTR(ret);
- }
+ if (ret)
+ goto errout;
if (hdr->dout_xfer_len) {
- dxfer_len = hdr->dout_xfer_len;
- dxferp = (void*)(unsigned long)hdr->dout_xferp;
+ ret = bsg_map_data(q, rq, hdr->dout_xferp, hdr->dout_xfer_len,
+ hdr->dout_iovec_count, DMA_TO_DEVICE);
+ if (ret)
+ goto errout;
} else if (hdr->din_xfer_len) {
- dxfer_len = hdr->din_xfer_len;
- dxferp = (void*)(unsigned long)hdr->din_xferp;
- } else
- dxfer_len = 0;
-
- if (dxfer_len) {
- ret = blk_rq_map_user(q, rq, dxferp, dxfer_len);
- if (ret) {
- dprintk("failed map at %d\n", ret);
- blk_put_request(rq);
- rq = ERR_PTR(ret);
- }
+ ret = bsg_map_data(q, rq, hdr->din_xferp, hdr->din_xfer_len,
+ hdr->din_iovec_count, DMA_FROM_DEVICE);
+ if (ret)
+ goto errout;
}
+ goto out;
+
+errout:
+ blk_put_request(rq);
+ rq = ERR_PTR(ret);
+
+out:
return rq;
}
diff --git a/include/linux/bsg.h b/include/linux/bsg.h
index 2154a6d..3580921 100644
--- a/include/linux/bsg.h
+++ b/include/linux/bsg.h
@@ -16,6 +16,8 @@ struct sg_io_v4 {
__u64 response; /* [i], [*o] {SCSI: (auto)sense data} */
/* "din_" for data in (from device); "dout_" for data out (to device) */
+ __u32 dout_iovec_count; /* [i] =0 -> "flat" data transfer */
+ __u32 din_iovec_count; /* [i] */
__u32 dout_xfer_len; /* [i] bytes to be transferred to device */
__u32 din_xfer_len; /* [i] bytes to be transferred from device */
__u64 dout_xferp; /* [i], [*i] */
@@ -40,6 +42,20 @@ struct sg_io_v4 {
__u32 padding;
};
+/*
+ * Vector of address/length pairs, used when dout_iovec_count (or din_)
+ * is non-zero. In that case, dout_xferp is a list of struct sg_io_v4_vec
+ * and dout_iovec_count is the number of entries in that list. dout_xfer_len
+ * is the total length of the list. Note the use of u64 instead of a
+ * native pointer to avoid compat issues, and padding to avoid structure
+ * alignment problems.
+ */
+struct sg_io_v4_vec {
+ __u64 iov_base;
+ __u32 iov_len;
+ __u32 __pad1;
+};
+
#ifdef __KERNEL__
#if defined(CONFIG_BLK_DEV_BSG)
--
1.5.0.2
-
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
