| Message ID | 20201111051648.635300-4-damien.lemoal@wdc.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | null_blk fixes, improvements and cleanup | expand |
On Wed, Nov 11, 2020 at 02:16:42PM +0900, Damien Le Moal wrote: > null_blk always uses the default BLK_SAFE_MAX_SECTORS value for the > max_hw_sectors and max_sectors queue limits resulting in a maximum > request size of 127 sectors. When the blocksize setting is larger than > the default 512B, this maximum request size is not aligned to the > block size. To emulate a real device more accurately, fix this by > setting the max_hw_sectors and max_sectors queue limits to a value > that is aligned to the block size. Shouldn't we fix this in the block layer instead of individual drivers?
On 2020/11/11 17:07, Christoph Hellwig wrote: > On Wed, Nov 11, 2020 at 02:16:42PM +0900, Damien Le Moal wrote: >> null_blk always uses the default BLK_SAFE_MAX_SECTORS value for the >> max_hw_sectors and max_sectors queue limits resulting in a maximum >> request size of 127 sectors. When the blocksize setting is larger than >> the default 512B, this maximum request size is not aligned to the >> block size. To emulate a real device more accurately, fix this by >> setting the max_hw_sectors and max_sectors queue limits to a value >> that is aligned to the block size. > > Shouldn't we fix this in the block layer instead of individual drivers? > Yes, I wondered about that too. Probably a good idea to have that generic but that will require changing both blk_queue_logical_block_size() and blk_queue_max_hw_sectors() since drivers may call these in different order. Jens, thoughts ?
diff --git a/drivers/block/null_blk_main.c b/drivers/block/null_blk_main.c index 4685ea401d5b..b77a506a4ae4 100644 --- a/drivers/block/null_blk_main.c +++ b/drivers/block/null_blk_main.c @@ -1866,6 +1866,9 @@ static int null_add_dev(struct nullb_device *dev) blk_queue_logical_block_size(nullb->q, dev->blocksize); blk_queue_physical_block_size(nullb->q, dev->blocksize); + blk_queue_max_hw_sectors(nullb->q, + round_down(queue_max_hw_sectors(nullb->q), + dev->blocksize >> SECTOR_SHIFT)); null_config_discard(nullb);
null_blk always uses the default BLK_SAFE_MAX_SECTORS value for the max_hw_sectors and max_sectors queue limits resulting in a maximum request size of 127 sectors. When the blocksize setting is larger than the default 512B, this maximum request size is not aligned to the block size. To emulate a real device more accurately, fix this by setting the max_hw_sectors and max_sectors queue limits to a value that is aligned to the block size. Signed-off-by: Damien Le Moal <damien.lemoal@wdc.com> --- drivers/block/null_blk_main.c | 3 +++ 1 file changed, 3 insertions(+)