Revert "[SCSI] extend the last_sector_bug flag to cover more sectors"

This reverts commit 2b142900784c6e38c8d39fa57d5f95ef08e735d8, since it
seems to break some other USB storage devices (at least a JMicron USB to
ATA bridge).  As such, while it apparently fixes some cardreaders, it
would need to be made conditional on the exact reader it fixes in order
to avoid causing regressions.

Cc: Alan Jenkins <alan-jenkins@tuffmail.co.uk>
Cc: James Bottomley <James.Bottomley@HansenPartnership.com>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

diff --git a/drivers/scsi/sd.c b/drivers/scsi/sd.c
index e5e7d78564545543925fc6136c6e7c7fc994c028..8e08d51a0f0531d8bf661dc0d3bf8f822d35c357 100644 (file)
--- a/drivers/scsi/sd.c
+++ b/drivers/scsi/sd.c
@@ -375,7 +375,6 @@ 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;
@@ -423,21 +422,13 @@ static int sd_prep_fn(struct request_queue *q, struct request *rq)
        }
 
        /*
-        * Some SD card readers can't handle multi-sector accesses which touch
-        * the last one or two hardware sectors.  Split accesses as needed.
+        * Some devices (some sdcards for one) don't like it if the
+        * last sector gets read in a larger then 1 sector read.
         */
-       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;
-               }
-       }
+       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;
 
        SCSI_LOG_HLQUEUE(2, scmd_printk(KERN_INFO, SCpnt, "block=%llu\n",
                                        (unsigned long long)block));

diff --git a/drivers/scsi/sd.h b/drivers/scsi/sd.h
index 95b9f06534d579bf72797c20ecd5546970f4b190..550b2f70a1f8330f93fea284c19f13554297ef86 100644 (file)
--- a/drivers/scsi/sd.h
+++ b/drivers/scsi/sd.h
@@ -31,12 +31,6 @@
  */
 #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;

diff --git a/include/scsi/scsi_device.h b/include/scsi/scsi_device.h
index 291d56a19167db9b8688dbbba446d051daae3b17..9cecc409f0f8418cea3e547447e210d8304f4178 100644 (file)
--- a/include/scsi/scsi_device.h
+++ b/include/scsi/scsi_device.h
@@ -140,8 +140,7 @@ 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;     /* do not use multisector accesses on
-                                          SD_LAST_BUGGY_SECTORS */
+       unsigned last_sector_bug:1;     /* Always read last sector in a 1 sector read */
 
        DECLARE_BITMAP(supported_events, SDEV_EVT_MAXBITS); /* supported events */
        struct list_head event_list;    /* asserted events */