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>

diff --git a/drivers/ata/libata-core.c b/drivers/ata/libata-core.c
index e52c331..bbaa545 100644 (file)
--- 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;
        }