From: Tejun Heo <htejun@gmail.com>
Date: Mon, 20 Feb 2006 14:48:38 +0000 (+0900)
Subject: [PATCH] libata: fix qc->n_elem == 0 case handling in ata_qc_next_sg
X-Git-Tag: v2.6.16-rc5~67^2~1
X-Git-Url: https://err.no/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=cc1887f3d8ae8ea61efa1a75af8ec0467b9dd546;p=linux-2.6

[PATCH] libata: fix qc->n_elem == 0 case handling in ata_qc_next_sg

This patch makes ata_for_each_sg() start with pad_sgent when
qc->n_elem is zero.  Previously, ata_for_each_sg() unconditionally
started with qc->__sg, handling the first sg to fill_sg() routines
even when the entry was invalid.  And while at it, unwind ?: in
ata_qc_next_sg() into if statement.

Signed-off-by: Tejun Heo <htejun@gmail.com>
Signed-off-by: Jeff Garzik <jgarzik@pobox.com>
---

diff --git a/include/linux/libata.h b/include/linux/libata.h
index 9e5db2949c..c91be5e64e 100644
--- a/include/linux/libata.h
+++ b/include/linux/libata.h
@@ -556,6 +556,16 @@ ata_sg_is_last(struct scatterlist *sg, struct ata_queued_cmd *qc)
 	return 0;
 }
 
+static inline struct scatterlist *
+ata_qc_first_sg(struct ata_queued_cmd *qc)
+{
+	if (qc->n_elem)
+		return qc->__sg;
+	if (qc->pad_len)
+		return &qc->pad_sgent;
+	return NULL;
+}
+
 static inline struct scatterlist *
 ata_qc_next_sg(struct scatterlist *sg, struct ata_queued_cmd *qc)
 {
@@ -563,11 +573,13 @@ ata_qc_next_sg(struct scatterlist *sg, struct ata_queued_cmd *qc)
 		return NULL;
 	if (++sg - qc->__sg < qc->n_elem)
 		return sg;
-	return qc->pad_len ? &qc->pad_sgent : NULL;
+	if (qc->pad_len)
+		return &qc->pad_sgent;
+	return NULL;
 }
 
 #define ata_for_each_sg(sg, qc) \
-	for (sg = qc->__sg; sg; sg = ata_qc_next_sg(sg, qc))
+	for (sg = ata_qc_first_sg(qc); sg; sg = ata_qc_next_sg(sg, qc))
 
 static inline unsigned int ata_tag_valid(unsigned int tag)
 {