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Subject[PATCH 2/5] block: fix SG_IO vector request data length handling
Date
Impact: fix SG_IO behavior such that it matches the documentation

SG_IO howto says that if ->dxfer_len and sum of iovec disagress, the
shorter one wins. However, the current implementation returns -EINVAL
for such cases. Trim iovc if it's longer than ->dxfer_len.

This patch uses iov_*() helpers which take struct iovec * by casting
struct sg_iovec * to it. sg_iovec is always identical to iovec and
this will be further cleaned up with later patches.

Signed-off-by: Tejun Heo <tj@kernel.org>
---
block/scsi_ioctl.c | 13 ++++++++++++-
1 files changed, 12 insertions(+), 1 deletions(-)
diff --git a/block/scsi_ioctl.c b/block/scsi_ioctl.c
index 84b7f87..82a0ca2 100644
--- a/block/scsi_ioctl.c
+++ b/block/scsi_ioctl.c
@@ -290,6 +290,7 @@ static int sg_io(struct request_queue *q, struct gendisk *bd_disk,

if (hdr->iovec_count) {
const int size = sizeof(struct sg_iovec) * hdr->iovec_count;
+ size_t iov_data_len;
struct sg_iovec *iov;

iov = kmalloc(size, GFP_KERNEL);
@@ -304,8 +305,18 @@ static int sg_io(struct request_queue *q, struct gendisk *bd_disk,
goto out;
}

+ /* SG_IO howto says that the shorter of the two wins */
+ iov_data_len = iov_length((struct iovec *)iov,
+ hdr->iovec_count);
+ if (hdr->dxfer_len < iov_data_len) {
+ hdr->iovec_count = iov_shorten((struct iovec *)iov,
+ hdr->iovec_count,
+ hdr->dxfer_len);
+ iov_data_len = hdr->dxfer_len;
+ }
+
ret = blk_rq_map_user_iov(q, rq, NULL, iov, hdr->iovec_count,
- hdr->dxfer_len, GFP_KERNEL);
+ iov_data_len, GFP_KERNEL);
kfree(iov);
} else if (hdr->dxfer_len)
ret = blk_rq_map_user(q, rq, NULL, hdr->dxferp, hdr->dxfer_len,
--
1.6.0.2


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