[PATCH 3.18 09/39] sd: Fix max transfer length for 4k disks

From: Greg Kroah-Hartman
Date: Mon Feb 09 2015 - 03:37:29 EST

3.18-stable review patch. If anyone has any objections, please let me know.


From: Brian King <brking@xxxxxxxxxxxxxxxxxx>

commit 3a9794d32984b67a6d8992226918618f0e51e5d5 upstream.

The following patch fixes an issue observed with 4k sector disks
where the max_hw_sectors attribute was getting set too large in
sd_revalidate_disk. Since sdkp->max_xfer_blocks is in units
of SCSI logical blocks and queue_max_hw_sectors is in units of
512 byte blocks, on a 4k sector disk, every time we went through
sd_revalidate_disk, we were taking the current value of
queue_max_hw_sectors and increasing it by a factor of 8. Fix
this by only shifting sdkp->max_xfer_blocks.

Signed-off-by: Brian King <brking@xxxxxxxxxxxxxxxxxx>
Reviewed-by: Paolo Bonzini <pbonzini@xxxxxxxxxx>
Reviewed-by: Martin K. Petersen <martin.petersen@xxxxxxxxxx>
Signed-off-by: Christoph Hellwig <hch@xxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>

drivers/scsi/sd.c | 6 ++++--
1 file changed, 4 insertions(+), 2 deletions(-)

--- a/drivers/scsi/sd.c
+++ b/drivers/scsi/sd.c
@@ -2818,9 +2818,11 @@ static int sd_revalidate_disk(struct gen

- max_xfer = min_not_zero(queue_max_hw_sectors(sdkp->disk->queue),
- sdkp->max_xfer_blocks);
+ max_xfer = sdkp->max_xfer_blocks;
max_xfer <<= ilog2(sdp->sector_size) - 9;
+ max_xfer = min_not_zero(queue_max_hw_sectors(sdkp->disk->queue),
+ max_xfer);
blk_queue_max_hw_sectors(sdkp->disk->queue, max_xfer);
set_capacity(disk, sdkp->capacity);

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