---

yaml
---
r: 107770
b: refs/heads/master
c: 1835107
h: refs/heads/master
v: v3

[refs]

@@ -1,2 +1,2 @@
 ---
-refs/heads/master: e63e03273b89f7248baa56cf242474f661e776e1
+refs/heads/master: 18351070b86d155713cf790b26af4f21b1fd0b29

trunk/drivers/scsi/sd.c

@@ -375,6 +375,7 @@ static int sd_prep_fn(struct request_queue *q, struct request *rq)
 	struct gendisk *disk = rq->rq_disk;
 	struct scsi_disk *sdkp;
 	sector_t block = rq->sector;
+	sector_t threshold;
 	unsigned int this_count = rq->nr_sectors;
 	unsigned int timeout = sdp->timeout;
 	int ret;
@@ -422,13 +423,21 @@ static int sd_prep_fn(struct request_queue *q, struct request *rq)
 	}
 
 	/*
-	 * Some devices (some sdcards for one) don't like it if the
-	 * last sector gets read in a larger then 1 sector read.
+	 * Some SD card readers can't handle multi-sector accesses which touch
+	 * the last one or two hardware sectors.  Split accesses as needed.
 	 */
-	if (unlikely(sdp->last_sector_bug &&
-	    rq->nr_sectors > sdp->sector_size / 512 &&
-	    block + this_count == get_capacity(disk)))
-		this_count -= sdp->sector_size / 512;
+	threshold = get_capacity(disk) - SD_LAST_BUGGY_SECTORS *
+		(sdp->sector_size / 512);
+
+	if (unlikely(sdp->last_sector_bug && block + this_count > threshold)) {
+		if (block < threshold) {
+			/* Access up to the threshold but not beyond */
+			this_count = threshold - block;
+		} else {
+			/* Access only a single hardware sector */
+			this_count = sdp->sector_size / 512;
+		}
+	}
 
 	SCSI_LOG_HLQUEUE(2, scmd_printk(KERN_INFO, SCpnt, "block=%llu\n",
 					(unsigned long long)block));

trunk/drivers/scsi/sd.h

@@ -31,6 +31,12 @@
  */
 #define SD_BUF_SIZE		512
 
+/*
+ * Number of sectors at the end of the device to avoid multi-sector
+ * accesses to in the case of last_sector_bug
+ */
+#define SD_LAST_BUGGY_SECTORS	8
+
 struct scsi_disk {
 	struct scsi_driver *driver;	/* always &sd_template */
 	struct scsi_device *device;

trunk/include/scsi/scsi_device.h

@@ -140,7 +140,8 @@ struct scsi_device {
 	unsigned fix_capacity:1;	/* READ_CAPACITY is too high by 1 */
 	unsigned guess_capacity:1;	/* READ_CAPACITY might be too high by 1 */
 	unsigned retry_hwerror:1;	/* Retry HARDWARE_ERROR */
-	unsigned last_sector_bug:1;	/* Always read last sector in a 1 sector read */
+	unsigned last_sector_bug:1;	/* do not use multisector accesses on
+					   SD_LAST_BUGGY_SECTORS */
 
 	DECLARE_BITMAP(supported_events, SDEV_EVT_MAXBITS); /* supported events */
 	struct list_head event_list;	/* asserted events */