From: sashiko-bot@kernel.org
To: "Mykola Marzhan" <mykola@meshstor.io>
Cc: yukuai@fygo.io, linux-pci@vger.kernel.org, linux-raid@vger.kernel.org
Subject: Re: [PATCH v2 4/7] md/raid1: don't use write-behind for P2PDMA bios
Date: Sun, 19 Jul 2026 11:05:13 +0000 [thread overview]
Message-ID: <20260719110513.9B8DB1F000E9@smtp.kernel.org> (raw)
In-Reply-To: <20260719105327.864949-5-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/20260719105327.864949-1-mykola@meshstor.io?part=4
next prev parent reply other threads:[~2026-07-19 11:05 UTC|newest]
Thread overview: 23+ messages / expand[flat|nested] mbox.gz Atom feed top
2026-07-19 10:53 [PATCH v2 0/7] block,md,nvme: correct handling of unsupported P2PDMA transfers Mykola Marzhan
2026-07-19 10:53 ` [PATCH v2 1/7] blk-mq-dma: restore BLK_STS_TARGET for unsupported P2P transfers Mykola Marzhan
2026-07-19 11:01 ` sashiko-bot
2026-07-20 14:49 ` Christoph Hellwig
[not found] ` <CAPzsNDv6hUV3gHdaxuwjRcr4couUKq_M5DKObFNaYqCHnm7ZMw@mail.gmail.com>
2026-07-20 18:42 ` Logan Gunthorpe
2026-07-20 18:49 ` Logan Gunthorpe
2026-07-21 17:49 ` Mykola Marzhan
2026-07-19 10:53 ` [PATCH v2 2/7] md: ensure REQ_NOMERGE is set on P2PDMA bios Mykola Marzhan
2026-07-19 11:02 ` sashiko-bot
2026-07-19 10:53 ` [PATCH v2 3/7] md/raid1: serialize non-write-behind writes on CollisionCheck rdevs Mykola Marzhan
2026-07-19 11:08 ` sashiko-bot
2026-07-19 10:53 ` [PATCH v2 4/7] md/raid1: don't use write-behind for P2PDMA bios Mykola Marzhan
2026-07-19 11:05 ` sashiko-bot [this message]
2026-07-20 16:31 ` Logan Gunthorpe
2026-07-19 10:53 ` [PATCH v2 5/7] md/raid1,raid10: keep REQ_NOMERGE on narrow_write_error() retry clones Mykola Marzhan
2026-07-19 11:20 ` sashiko-bot
2026-07-20 16:32 ` Logan Gunthorpe
2026-07-19 10:53 ` [PATCH v2 6/7] md/raid1,raid10: skip futile retries on P2PDMA mapping failures Mykola Marzhan
2026-07-19 11:11 ` sashiko-bot
2026-07-20 16:49 ` Logan Gunthorpe
2026-07-21 17:50 ` Mykola Marzhan
2026-07-19 10:53 ` [PATCH v2 7/7] nvme-rdma: return BLK_STS_TARGET for unsupported P2P transfers Mykola Marzhan
2026-07-19 11:17 ` sashiko-bot
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