Commit 4f258a46 authored by Martin K. Petersen's avatar Martin K. Petersen Committed by James Bottomley

sd: Fix maximum I/O size for BLOCK_PC requests

Commit bcdb247c ("sd: Limit transfer length") clamped the maximum
size of an I/O request to the MAXIMUM TRANSFER LENGTH field in the BLOCK
LIMITS VPD. This had the unfortunate effect of also limiting the maximum
size of non-filesystem requests sent to the device through sg/bsg.

Avoid using blk_queue_max_hw_sectors() and set the max_sectors queue
limit directly.

Also update the comment in blk_limits_max_hw_sectors() to clarify that
max_hw_sectors defines the limit for the I/O controller only.
Signed-off-by: default avatarMartin K. Petersen <>
Reported-by: default avatarBrian King <>
Tested-by: default avatarBrian King <>
Cc: # 3.17+
Signed-off-by: default avatarJames Bottomley <>
parent 8f2777f5
......@@ -241,8 +241,8 @@ EXPORT_SYMBOL(blk_queue_bounce_limit);
* Description:
* Enables a low level driver to set a hard upper limit,
* max_hw_sectors, on the size of requests. max_hw_sectors is set by
* the device driver based upon the combined capabilities of I/O
* controller and storage device.
* the device driver based upon the capabilities of the I/O
* controller.
* max_sectors is a soft limit imposed by the block layer for
* filesystem type requests. This value can be overridden on a
......@@ -2770,9 +2770,9 @@ static int sd_revalidate_disk(struct gendisk *disk)
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),
blk_queue_max_hw_sectors(sdkp->disk->queue, max_xfer);
sdkp->disk->queue->limits.max_sectors =
min_not_zero(queue_max_hw_sectors(sdkp->disk->queue), max_xfer);
set_capacity(disk, sdkp->capacity);
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