From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 0E97D3859E0 for ; Fri, 1 May 2026 11:07:51 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=10.30.226.201 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1777633672; cv=none; b=OS44yH2soJKuBfJfHshUd+3IWpSeOJSh3CCZfvfOmlx9jJ2n0nb8ID6/o//nPnAeyf/VHQfzeHtE5jFBAWuFu6EOoZysJRCPPRG+reNMrJNzZDqvg8LNC5mBD8/hD4PGUdvPJ9dGCgcGvI23J1S4OxtKBH0yUaV2h1zc5PvLK3w= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1777633672; c=relaxed/simple; bh=0E4DV+A7gFt/FeBuMvqLOFGwgX9RvJnVpFIdOzPSivY=; h=Subject:To:Cc:From:Date:Message-ID:MIME-Version:Content-Type; b=mohnrG9P9f3ueV0vk7ii2+lA3BqxEHKfMQchVUKw0GFWPiTqhewaGkWwFG8osQB+lFL66J35mEzh0EkgsRx3XwE8/ODNFZRD2UhBhjXok4ytlENdKgPttXBvzELB7l/2jlCvkU5IFDLHvmRK/zW2V88fjljPtNgGpdiviEx7B/k= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b=akjMua3m; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b="akjMua3m" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 774DBC2BCB4; Fri, 1 May 2026 11:07:51 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1777633671; bh=0E4DV+A7gFt/FeBuMvqLOFGwgX9RvJnVpFIdOzPSivY=; h=Subject:To:Cc:From:Date:From; b=akjMua3mZbIqaYo3S2AWyy9C5oTgGqtiXmFU9hnuxzo+OvyQh4+XKkTg1Y1124AMl 3yfxXfaKXhPlkVkKQe7ApW4WP98E5Ts6+rWtZtTv/C03xOq1q5MUHMairAL3HmdOhJ yeVRuL7N7wFt6X9Y7X7lb7+XoSbGo6/62BYVIArE= Subject: FAILED: patch "[PATCH] block: relax pgmap check in bio_add_page for compatible zone" failed to apply to 6.12-stable tree To: namjain@linux.microsoft.com,axboe@kernel.dk,hch@lst.de Cc: From: Date: Fri, 01 May 2026 13:07:49 +0200 Message-ID: <2026050149-moonlike-issue-7246@gregkh> Precedence: bulk X-Mailing-List: stable@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=ANSI_X3.4-1968 Content-Transfer-Encoding: 8bit The patch below does not apply to the 6.12-stable tree. If someone wants it applied there, or to any other stable or longterm tree, then please email the backport, including the original git commit id to . To reproduce the conflict and resubmit, you may use the following commands: git fetch https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/ linux-6.12.y git checkout FETCH_HEAD git cherry-pick -x 41c665aae2b5dbecddddcc8ace344caf630cc7a4 # git commit -s git send-email --to '' --in-reply-to '2026050149-moonlike-issue-7246@gregkh' --subject-prefix 'PATCH 6.12.y' HEAD^.. Possible dependencies: thanks, greg k-h ------------------ original commit in Linus's tree ------------------ >From 41c665aae2b5dbecddddcc8ace344caf630cc7a4 Mon Sep 17 00:00:00 2001 From: Naman Jain Date: Fri, 10 Apr 2026 15:34:14 +0000 Subject: [PATCH] block: relax pgmap check in bio_add_page for compatible zone device pages bio_add_page() and bio_integrity_add_page() reject pages from different dev_pagemaps entirely, returning 0 even when those pages have compatible DMA mapping requirements. This forces callers to start a new bio when buffers span pgmap boundaries, even though the pages could safely coexist as separate bvec entries. This matters for guests where memory is registered through devm_memremap_pages() with MEMORY_DEVICE_GENERIC in multiple calls, creating separate dev_pagemaps for each chunk. When a direct I/O buffer spans two such chunks, bio_add_page() rejects the second page, forcing an unnecessary bio split or I/O failure. Introduce zone_device_pages_compatible() in blk.h to check whether two pages can coexist in the same bio as separate bvec entries. The block DMA iterator (blk_dma_map_iter_start) caches the P2PDMA mapping state from the first segment and applies it to all others, so P2PDMA pages from different pgmaps must not be mixed, and neither must P2PDMA and non-P2PDMA pages. All other combinations (MEMORY_DEVICE_GENERIC pages from different pgmaps, or MEMORY_DEVICE_GENERIC with normal RAM) use the same dma_map_phys path and are safe. Replace the blanket zone_device_pages_have_same_pgmap() rejection with zone_device_pages_compatible(), while keeping zone_device_pages_have_same_pgmap() as a merge guard. Pages from different pgmaps can be added as separate bvec entries but must not be coalesced into the same segment, as that would make it impossible to recover the correct pgmap via page_pgmap(). Fixes: 49580e690755 ("block: add check when merging zone device pages") Cc: stable@vger.kernel.org Signed-off-by: Naman Jain Reviewed-by: Christoph Hellwig Link: https://patch.msgid.link/20260410153414.4159050-3-namjain@linux.microsoft.com Signed-off-by: Jens Axboe diff --git a/block/bio-integrity.c b/block/bio-integrity.c index e79eaf047794..e54c6e06e1cb 100644 --- a/block/bio-integrity.c +++ b/block/bio-integrity.c @@ -231,10 +231,10 @@ int bio_integrity_add_page(struct bio *bio, struct page *page, if (bip->bip_vcnt > 0) { struct bio_vec *bv = &bip->bip_vec[bip->bip_vcnt - 1]; - if (!zone_device_pages_have_same_pgmap(bv->bv_page, page)) + if (!zone_device_pages_compatible(bv->bv_page, page)) return 0; - - if (bvec_try_merge_hw_page(q, bv, page, len, offset)) { + if (zone_device_pages_have_same_pgmap(bv->bv_page, page) && + bvec_try_merge_hw_page(q, bv, page, len, offset)) { bip->bip_iter.bi_size += len; return len; } diff --git a/block/bio.c b/block/bio.c index 641ef0928d73..c52a0bd1e899 100644 --- a/block/bio.c +++ b/block/bio.c @@ -1048,10 +1048,10 @@ int bio_add_page(struct bio *bio, struct page *page, if (bio->bi_vcnt > 0) { struct bio_vec *bv = &bio->bi_io_vec[bio->bi_vcnt - 1]; - if (!zone_device_pages_have_same_pgmap(bv->bv_page, page)) + if (!zone_device_pages_compatible(bv->bv_page, page)) return 0; - - if (bvec_try_merge_page(bv, page, len, offset)) { + if (zone_device_pages_have_same_pgmap(bv->bv_page, page) && + bvec_try_merge_page(bv, page, len, offset)) { bio->bi_iter.bi_size += len; return len; } diff --git a/block/blk.h b/block/blk.h index 50a41db03913..b998a7761faf 100644 --- a/block/blk.h +++ b/block/blk.h @@ -136,6 +136,25 @@ static inline bool biovec_phys_mergeable(struct request_queue *q, return true; } +/* + * Check if two pages from potentially different zone device pgmaps can + * coexist as separate bvec entries in the same bio. + * + * The block DMA iterator (blk_dma_map_iter_start) caches the P2PDMA mapping + * state from the first segment and applies it to all subsequent segments, so + * P2PDMA pages from different pgmaps must not be mixed in the same bio. + * + * Other zone device types (FS_DAX, GENERIC) use the same dma_map_phys() path + * as normal RAM. PRIVATE and COHERENT pages never appear in bios. + */ +static inline bool zone_device_pages_compatible(const struct page *a, + const struct page *b) +{ + if (is_pci_p2pdma_page(a) || is_pci_p2pdma_page(b)) + return zone_device_pages_have_same_pgmap(a, b); + return true; +} + static inline bool __bvec_gap_to_prev(const struct queue_limits *lim, struct bio_vec *bprv, unsigned int offset) {