From: Jens Axboe <axboe@kernel.dk>
To: Ming Lei <ming.lei@redhat.com>,
"linux-block@vger.kernel.org" <linux-block@vger.kernel.org>
Subject: [PATCH] ublk_drv: set DMA alignment mask to 3
Date: Sat, 11 May 2024 08:40:57 -0600 [thread overview]
Message-ID: <379b841f-210f-41dc-a44c-f1dc3197e10f@kernel.dk> (raw)
By default, this will be 511, as that's the block layer default. But
drivers these days can support memory alignments that aren't tied to
the sector sizes, instead just being limited by what the DMA engine
supports. An example is NVMe, where it's generally set to a 32-bit or
64-bit boundary. As ublk itself doesn't really care, just set it low
enough that we don't run into issues with NVMe where the required
O_DIRECT memory alignment is now more restrictive on ublk than it is
on the underlying device.
This was triggered by spurious -EINVAL returns on O_DIRECT IO on a
setup with ublk managing NVMe devices, which previously worked just
fine on the NVMe device itself. With the alignment relaxed, the test
works fine.
Signed-off-by: Jens Axboe <axboe@kernel.dk>
---
diff --git a/drivers/block/ublk_drv.c b/drivers/block/ublk_drv.c
index 851c78913de2..292fa2bdd77d 100644
--- a/drivers/block/ublk_drv.c
+++ b/drivers/block/ublk_drv.c
@@ -2176,6 +2176,7 @@ static int ublk_ctrl_start_dev(struct ublk_device *ub, struct io_uring_cmd *cmd)
.max_hw_sectors = p->max_sectors,
.chunk_sectors = p->chunk_sectors,
.virt_boundary_mask = p->virt_boundary_mask,
+ .dma_alignment = 3,
};
struct gendisk *disk;
--
Jens Axboe
next reply other threads:[~2024-05-11 14:40 UTC|newest]
Thread overview: 2+ messages / expand[flat|nested] mbox.gz Atom feed top
2024-05-11 14:40 Jens Axboe [this message]
2024-05-11 15:04 ` [PATCH] ublk_drv: set DMA alignment mask to 3 Ming Lei
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