Re: [PATCH v7 2/3] ufs: set QUEUE_FLAG_LIMIT_BIO_SIZE
From: Bart Van Assche <bvanassche@acm.org>
Date: 2021-04-13 16:14:09
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On 4/12/21 7:55 PM, Changheun Lee wrote:
quoted hunk ↗ jump to hunk
Set QUEUE_FLAG_LIMIT_BIO_SIZE queue flag to limit bio max size to queue max sectors size for UFS device. Signed-off-by: Changheun Lee <redacted> --- drivers/scsi/scsi_lib.c | 2 ++ drivers/scsi/ufs/ufshcd.c | 1 + include/scsi/scsi_host.h | 2 ++ 3 files changed, 5 insertions(+)diff --git a/drivers/scsi/scsi_lib.c b/drivers/scsi/scsi_lib.c index 7d52a11e1b61..73ce6ba7903a 100644 --- a/drivers/scsi/scsi_lib.c +++ b/drivers/scsi/scsi_lib.c@@ -1838,6 +1838,8 @@ void __scsi_init_queue(struct Scsi_Host *shost, struct request_queue *q) * Devices that require a bigger alignment can increase it later. */ blk_queue_dma_alignment(q, max(4, dma_get_cache_alignment()) - 1); + + blk_queue_set_limit_bio_size(q, shost->limit_bio_size); } EXPORT_SYMBOL_GPL(__scsi_init_queue);diff --git a/drivers/scsi/ufs/ufshcd.c b/drivers/scsi/ufs/ufshcd.c index d3d05e997c13..000eb5ab022e 100644 --- a/drivers/scsi/ufs/ufshcd.c +++ b/drivers/scsi/ufs/ufshcd.c@@ -9313,6 +9313,7 @@ int ufshcd_init(struct ufs_hba *hba, void __iomem *mmio_base, unsigned int irq) host->max_channel = UFSHCD_MAX_CHANNEL; host->unique_id = host->host_no; host->max_cmd_len = UFS_CDB_SIZE; + host->limit_bio_size = true; hba->max_pwr_info.is_valid = false;diff --git a/include/scsi/scsi_host.h b/include/scsi/scsi_host.h index e30fd963b97d..486f61588717 100644 --- a/include/scsi/scsi_host.h +++ b/include/scsi/scsi_host.h@@ -607,6 +607,8 @@ struct Scsi_Host { unsigned int max_segment_size; unsigned long dma_boundary; unsigned long virt_boundary_mask; + unsigned int limit_bio_size; + /* * In scsi-mq mode, the number of hardware queues supported by the LLD. *
This patch should have been split into one patch for the SCSI core and another patch for the UFS driver. I see an issue with this patch: a new attribute has been introduced in struct Scsi_Host but it is not used by the SCSI core. That seems weird to me. Another comment I have about this patch is why to restrict the BIO size (blk_queue_set_limit_bio_size(q, shost->limit_bio_size)) only for UFS devices? Aren't all block devices, including NVMe devices, expected to benefit from limiting the BIO size if no stacking is involved? How about the following approach? * In blk_queue_max_hw_sectors(), set the maximum BIO size to max_hw_sectors. As you may know blk_queue_max_hw_sectors() may be called by any block driver (stacking and non-stacking). * In blk_stack_limits(), set the maximum BIO size to UINT_MAX. Stacking block drivers must call blk_stack_limits(). Thanks, Bart.