From: sashiko-bot@kernel.org
To: "Mykola Marzhan" <mykola@meshstor.io>
Cc: yukuai@fygo.io, linux-raid@vger.kernel.org, linux-pci@vger.kernel.org
Subject: Re: [PATCH v3 4/8] md/raid1: don't use write-behind for P2PDMA bios
Date: Tue, 21 Jul 2026 17:54:44 +0000 [thread overview]
Message-ID: <20260721175444.F12681F00A3D@smtp.kernel.org> (raw)
In-Reply-To: <20260721174502.111503-5-mykola@meshstor.io>
> alloc_behind_master_bio() copies the bio's data with bio_copy_data(),
> a CPU copy. P2PDMA pages are peer device (BAR) memory; generic code
> must not assume CPU load/store access to them is safe or fast on
> every architecture, and bouncing peer memory through the CPU defeats
> the point of a peer-to-peer transfer.
>
> Skip write-behind for P2PDMA bios: they are written directly to all
> members, including write-mostly ones. Ordering against write-behind
> I/O in flight to overlapping sectors is preserved: the non-behind
> clone path serializes on CollisionCheck rdevs (see the preceding
> fix), which covers these bios like any other write that bypasses
> write-behind.
>
> Fixes: 02666132403a ("md: propagate BLK_FEAT_PCI_P2PDMA from member devices to RAID device")
> Assisted-by: Claude:claude-opus-4-8
> Signed-off-by: Mykola Marzhan <mykola@meshstor.io>
Sashiko has reviewed this patch and found no issues. It looks great!
--
Sashiko AI review · https://sashiko.dev/#/patchset/20260721174502.111503-1-mykola@meshstor.io?part=4
next prev parent reply other threads:[~2026-07-21 17:54 UTC|newest]
Thread overview: 17+ messages / expand[flat|nested] mbox.gz Atom feed top
2026-07-21 17:44 [PATCH v3 0/8] block,md,nvme: correct handling of unsupported P2PDMA transfers Mykola Marzhan
2026-07-21 17:44 ` [PATCH v3 1/8] blk-mq-dma: restore BLK_STS_TARGET for unsupported P2P transfers Mykola Marzhan
2026-07-21 18:00 ` sashiko-bot
2026-07-21 17:44 ` [PATCH v3 2/8] md: ensure REQ_NOMERGE is set on P2PDMA bios Mykola Marzhan
2026-07-21 17:54 ` sashiko-bot
2026-07-21 17:44 ` [PATCH v3 3/8] md/raid1: serialize non-write-behind writes on CollisionCheck rdevs Mykola Marzhan
2026-07-21 18:04 ` sashiko-bot
2026-07-21 17:44 ` [PATCH v3 4/8] md/raid1: don't use write-behind for P2PDMA bios Mykola Marzhan
2026-07-21 17:54 ` sashiko-bot [this message]
2026-07-21 17:44 ` [PATCH v3 5/8] md/raid1,raid10: keep REQ_NOMERGE on narrow_write_error() retry clones Mykola Marzhan
2026-07-21 18:05 ` sashiko-bot
2026-07-21 17:45 ` [PATCH v3 6/8] md/raid1: skip futile retries on P2PDMA mapping failures Mykola Marzhan
2026-07-21 18:02 ` sashiko-bot
2026-07-21 17:45 ` [PATCH v3 7/8] md/raid10: " Mykola Marzhan
2026-07-21 18:01 ` sashiko-bot
2026-07-21 17:45 ` [PATCH v3 8/8] nvme-rdma: return BLK_STS_TARGET for unsupported P2P transfers Mykola Marzhan
2026-07-21 18:13 ` sashiko-bot
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