Re: [PATCH v6 04/12] md/raid1: don't use write-behind for P2PDMA bios
From: sashiko-bot@kernel.org
Date: 2026-07-26 12:01:12
Also in:
linux-pci
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 <redacted>Sashiko has reviewed this patch and found no issues. It looks great! -- Sashiko AI review · https://sashiko.dev/#/patchset/20260726113229.2154269-1-mykola@meshstor.io?part=4