[SCSI] fix write buffer length in scsi_req_map_sg()

sg's may have setup a the buffer with a different length than
the transfer length so we should be using the bufflen passed
in as the request's data len.

Signed-off-by: Mike Christie <michaelc@cs.wisc.edu>
Signed-off-by: James Bottomley <James.Bottomley@SteelEye.com>

1 files changed, 10 insertions, 4 deletions

diff --git a/drivers/scsi/scsi_lib.c b/drivers/scsi/scsi_lib.c
index a417a6ff9f97..277f1b64e9ac 100644
--- a/drivers/scsi/scsi_lib.c
+++ b/drivers/scsi/scsi_lib.c
@@ -301,7 +301,7 @@ static int scsi_req_map_sg(struct request *rq, struct scatterlist *sgl,
 {
         struct request_queue *q = rq->q;
         int nr_pages = (bufflen + sgl[0].offset + PAGE_SIZE - 1) >> PAGE_SHIFT;
-        unsigned int data_len = 0, len, bytes, off;
+        unsigned int data_len = bufflen, len, bytes, off;
         struct page *page;
         struct bio *bio = NULL;
         int i, err, nr_vecs = 0;
@@ -310,10 +310,15 @@ static int scsi_req_map_sg(struct request *rq, struct scatterlist *sgl,
                 page = sgl[i].page;
                 off = sgl[i].offset;
                 len = sgl[i].length;
-                data_len += len;
 
-                while (len > 0) {
+                while (len > 0 && data_len > 0) {
+                        /*
+                         * sg sends a scatterlist that is larger than
+                         * the data_len it wants transferred for certain
+                         * IO sizes
+                         */
                         bytes = min_t(unsigned int, len, PAGE_SIZE - off);
+                        bytes = min(bytes, data_len);
 
                         if (!bio) {
                                 nr_vecs = min_t(int, BIO_MAX_PAGES, nr_pages);
@@ -345,12 +350,13 @@ static int scsi_req_map_sg(struct request *rq, struct scatterlist *sgl,
 
                         page++;
                         len -= bytes;
+                        data_len -=bytes;
                         off = 0;
                 }
         }
 
         rq->buffer = rq->data = NULL;
-        rq->data_len = data_len;
+        rq->data_len = bufflen;
         return 0;
 
 free_bios: