On Thu, Dec 22, 2022 at 09:52:04AM -0800, Keith Busch wrote:
> From: Keith Busch <kbusch@xxxxxxxxxx>
>
> The user can set the max_sectors limit to any valid value via sysfs
> /sys/block/<dev>/queue/max_sectors_kb attribute. If the device limits
> are ever rescanned, though, the limit reverts back to the kernel defined
> BLK_DEF_MAX_SECTORS limit.
>
> Preserve the user's setting for the max_sectors limit as long as it's
> valid. The user can reset back to defaults by writing 0 to the sysfs
> file.
>
> Signed-off-by: Keith Busch <kbusch@xxxxxxxxxx>
> ---
> block/blk-settings.c | 9 +++++++--
> block/blk-sysfs.c | 10 +++++++++-
> include/linux/blkdev.h | 1 +
> 3 files changed, 17 insertions(+), 3 deletions(-)
>
> diff --git a/block/blk-settings.c b/block/blk-settings.c
> index 0477c4d527fee..e75304f853bd5 100644
> --- a/block/blk-settings.c
> +++ b/block/blk-settings.c
> @@ -40,7 +40,7 @@ void blk_set_default_limits(struct queue_limits *lim)
> lim->virt_boundary_mask = 0;
> lim->max_segment_size = BLK_MAX_SEGMENT_SIZE;
> lim->max_sectors = lim->max_hw_sectors = BLK_SAFE_MAX_SECTORS;
> - lim->max_dev_sectors = 0;
> + lim->max_user_sectors = lim->max_dev_sectors = 0;
> lim->chunk_sectors = 0;
> lim->max_write_zeroes_sectors = 0;
> lim->max_zone_append_sectors = 0;
> @@ -135,7 +135,12 @@ void blk_queue_max_hw_sectors(struct request_queue *q, unsigned int max_hw_secto
> limits->max_hw_sectors = max_hw_sectors;
>
> max_sectors = min_not_zero(max_hw_sectors, limits->max_dev_sectors);
> - max_sectors = min_t(unsigned int, max_sectors, BLK_DEF_MAX_SECTORS);
> +
> + if (limits->max_user_sectors)
> + max_sectors = min_not_zero(max_sectors, limits->max_user_sectors);
I don't think the min_not_zero here makes sense, as you just checked
max_user_sectors for zero above, and max_sectors better not be zero.
> + else
> + max_sectors = min_t(unsigned int, max_sectors, BLK_DEF_MAX_SECTORS);
And please make BLK_DEF_MAX_SECTORS an unsigned constant as it should be
and drop the min_t here. Instead of working around type mismatches
just avoid them from the beginning..
> + if (max_sectors_kb == 0) {
> + q->limits.max_user_sectors = 0;
> + max_sectors_kb = min_t(unsigned int, max_hw_sectors_kb,
> + BLK_DEF_MAX_SECTORS >> 1);
.. which will also pay off here.
> + } else if (max_sectors_kb > max_hw_sectors_kb ||
> + max_sectors_kb < page_kb) {
> return -EINVAL;
And this check should probably move above the old one to keep the
sanity checks first.
> + } else {
> + q->limits.max_user_sectors = max_sectors_kb << 1;
> + }
i.e.
if (max_sectors_kb > max_hw_sectors_kb || max_sectors_kb < page_kb)
return -EINVAL;
q->limits.max_user_sectors = max_sectors_kb << 1;
/* reset to default when the user clears max_sectors_kb: */
if (max_sectors_kb == 0) {
max_sectors_kb =
min(max_hw_sectors_kb, BLK_DEF_MAX_SECTORS >> 1);
}
