On 01/08/2018 12:51 PM, Ilya Dryomov wrote:
> Commit d3834fefcfe5 ("rbd: bump queue_max_segments") bumped
> max_segments (unsigned short) to max_hw_sectors (unsigned int).
> max_hw_sectors is set to the number of 512-byte sectors in an object
> and overflows unsigned short for 32M (largest possible) objects, making
> the block layer resort to handing us single segment (i.e. single page
> or even smaller) bios in that case.
>
> Cc: stable@xxxxxxxxxxxxxxx
> Fixes: d3834fefcfe5 ("rbd: bump queue_max_segments")
> Signed-off-by: Ilya Dryomov <idryomov@xxxxxxxxx>
Is it OK for max_segments to be bigger than max_hw_sectors?
I didn't investigate but the question occurred to me, since you're
fixing max_segments regardless of segment size, but not doing that
to the other limits being set.
If that is not a problem:
Reviewed-by: Alex Elder <elder@xxxxxxxxxx>
> ---
> drivers/block/rbd.c | 2 +-
> 1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/drivers/block/rbd.c b/drivers/block/rbd.c
> index f40050c97bb3..0bda823a90ca 100644
> --- a/drivers/block/rbd.c
> +++ b/drivers/block/rbd.c
> @@ -4381,7 +4381,7 @@ static int rbd_init_disk(struct rbd_device *rbd_dev)
> segment_size = rbd_obj_bytes(&rbd_dev->header);
> blk_queue_max_hw_sectors(q, segment_size / SECTOR_SIZE);
> q->limits.max_sectors = queue_max_hw_sectors(q);
> - blk_queue_max_segments(q, segment_size / SECTOR_SIZE);
> + blk_queue_max_segments(q, USHRT_MAX);
> blk_queue_max_segment_size(q, segment_size);
> blk_queue_io_min(q, segment_size);
> blk_queue_io_opt(q, segment_size);
>
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