On 15-12-16 05:53 PM, Martin K. Petersen wrote:
Eryu Guan reported that loading scsi_debug would fail. This turned out
to be caused by scsi_debug reporting an optimal I/O size of 32KB which
is smaller than the 64KB page size on the PowerPC system in question.
Add a check to ensure that we only use the device-reported OPTIMAL
TRANSFER LENGTH if it is bigger than or equal to the page cache size.
Reported-by: Eryu Guan <guane...@gmail.com>
Reported-by: Ming Lei <tom.leim...@gmail.com>
Signed-off-by: Martin K. Petersen <martin.peter...@oracle.com>
---
drivers/scsi/sd.c | 9 ++++++---
1 file changed, 6 insertions(+), 3 deletions(-)
diff --git a/drivers/scsi/sd.c b/drivers/scsi/sd.c
index 3d22fc3e3c1a..4e08d1cd704d 100644
--- a/drivers/scsi/sd.c
+++ b/drivers/scsi/sd.c
@@ -2885,10 +2885,13 @@ static int sd_revalidate_disk(struct gendisk *disk)
/*
* Use the device's preferred I/O size for reads and writes
- * unless the reported value is unreasonably large (or garbage).
+ * unless the reported value is unreasonably small, large, or
+ * garbage.
*/
- if (sdkp->opt_xfer_blocks && sdkp->opt_xfer_blocks <= dev_max &&
- sdkp->opt_xfer_blocks <= SD_DEF_XFER_BLOCKS)
+ if (sdkp->opt_xfer_blocks &&
+ sdkp->opt_xfer_blocks <= dev_max &&
+ sdkp->opt_xfer_blocks <= SD_DEF_XFER_BLOCKS &&
+ sdkp->opt_xfer_blocks * sdp->sector_size >= PAGE_CACHE_SIZE)
rw_max = q->limits.io_opt =
logical_to_sectors(sdp, sdkp->opt_xfer_blocks);
else
and following that 'else' is:
rw_max = BLK_DEF_MAX_SECTORS;
and blkdev.h says:
enum blk_default_limits {
BLK_MAX_SEGMENTS = 128,
BLK_SAFE_MAX_SECTORS = 255,
BLK_DEF_MAX_SECTORS = 2560,
BLK_MAX_SEGMENT_SIZE = 65536,
BLK_SEG_BOUNDARY_MASK = 0xFFFFFFFFUL,
};
Reviewed-by: Douglas Gilbert <dgilb...@interlog.com>
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