libata sg chaining support fix

Signed-off-by: FUJITA Tomonori <fujita.tomonori@lab.ntt.co.jp>
Signed-off-by: Jens Axboe <jens.axboe@oracle.com>

1 files changed, 6 insertions, 1 deletions

diff --git a/drivers/ata/libata-core.c b/drivers/ata/libata-core.c
index e52c33180e42..bbaa545ea999 100644
--- a/drivers/ata/libata-core.c
+++ b/drivers/ata/libata-core.c
@@ -4952,16 +4952,18 @@ static void __atapi_pio_bytes(struct ata_queued_cmd *qc, unsigned int bytes)
 {
         int do_write = (qc->tf.flags & ATA_TFLAG_WRITE);
         struct scatterlist *sg = qc->__sg;
+        struct scatterlist *lsg = sg_last(qc->__sg, qc->n_elem);
         struct ata_port *ap = qc->ap;
         struct page *page;
         unsigned char *buf;
         unsigned int offset, count;
+        int no_more_sg = 0;
 
         if (qc->curbytes + bytes >= qc->nbytes)
                 ap->hsm_task_state = HSM_ST_LAST;
 
 next_sg:
-        if (unlikely(qc->cursg == sg_last(qc->__sg, qc->n_elem))) {
+        if (unlikely(no_more_sg)) {
                 /*
                  * The end of qc->sg is reached and the device expects
                  * more data to transfer. In order not to overrun qc->sg
@@ -5023,6 +5025,9 @@ next_sg:
         qc->cursg_ofs += count;
 
         if (qc->cursg_ofs == sg->length) {
+                if (qc->cursg == lsg)
+                        no_more_sg = 1;
+
                 qc->cursg = sg_next(qc->cursg);
                 qc->cursg_ofs = 0;
         }