FAILED: patch "[PATCH] block: relax pgmap check in bio_add_page for compatible zone" failed to apply to 6.6-stable tree

PATCH New [email protected] 2 participants 2 messages May 1 – May 2

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[email protected]

author maintainer

2026-05-01 11:08 UTC #0 lore raw

The patch below does not apply to the 6.6-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 <[email protected]>.

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-6.6.y
git checkout FETCH_HEAD
git cherry-pick -x 41c665aae2b5dbecddddcc8ace344caf630cc7a4
# <resolve conflicts, build, test, etc.>
git commit -s
git send-email --to '<[email protected]>' --in-reply-to '2026050150-reheat-spinout-eedf@gregkh' --subject-prefix 'PATCH 6.6.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 <[email protected]>
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 [email protected]

Signed-off-by Naman Jain <[email protected]>

Reviewed-by Christoph Hellwig <[email protected]>

Link https://patch.msgid.link/[email protected] open here

Signed-off-by Jens Axboe <[email protected]>

block/bio-integrity.c +3 -3

index e79eaf047794..e54c6e06e1cb 100644
@@ -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;
 		}

block/bio.c +3 -3

index 641ef0928d73..c52a0bd1e899 100644
@@ -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;
 		}

block/blk.h +19 -0

index 50a41db03913..b998a7761faf 100644
@@ -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)
 {

Sasha Levin

maintainer

2026-05-02 23:58 UTC #1 lore raw

PATCH 1/1 block: relax pgmap check in bio_add_page for compatible zone device pages

From: Naman Jain <[email protected]>

[ Upstream commit 41c665aae2b5dbecddddcc8ace344caf630cc7a4 ]

Fixes 49580e690755 ("block: add check when merging zone device pages")

Cc [email protected]

Signed-off-by Naman Jain <[email protected]>

Reviewed-by Christoph Hellwig <[email protected]>

Link https://patch.msgid.link/[email protected] open here

Signed-off-by Jens Axboe <[email protected]>

[ restructured combined `if` into explicit `bv` block ]

Signed-off-by Sasha Levin <[email protected]>

---
 block/bio-integrity.c |  2 ++
 block/bio.c           | 14 +++++++++-----
 block/blk.h           | 19 +++++++++++++++++++
 3 files changed, 30 insertions(+), 5 deletions(-)

block/bio-integrity.c +2 -0

index 15e444b2fcc12..dc6a9b0fab369 100644
@@ -134,6 +134,8 @@ int bio_integrity_add_page(struct bio *bio, struct page *page,
 		struct bio_vec *bv = &bip->bip_vec[bip->bip_vcnt - 1];
 		bool same_page = false;
 
+		if (!zone_device_pages_compatible(bv->bv_page, page))
+			return 0;
 		if (bvec_try_merge_hw_page(q, bv, page, len, offset,
 					   &same_page)) {
 			bip->bip_iter.bi_size += len;

block/bio.c +9 -5

index b197abbaebc46..14aefb1905454 100644
@@ -1098,11 +1098,15 @@ int bio_add_page(struct bio *bio, struct page *page,
 	if (bio->bi_iter.bi_size > UINT_MAX - len)
 		return 0;
 
-	if (bio->bi_vcnt > 0 &&
-	    bvec_try_merge_page(&bio->bi_io_vec[bio->bi_vcnt - 1],
-				page, len, offset, &same_page)) {
-		bio->bi_iter.bi_size += len;
-		return len;
+	if (bio->bi_vcnt > 0) {
+		struct bio_vec *bv = &bio->bi_io_vec[bio->bi_vcnt - 1];
+
+		if (!zone_device_pages_compatible(bv->bv_page, page))
+			return 0;
+		if (bvec_try_merge_page(bv, page, len, offset, &same_page)) {
+			bio->bi_iter.bi_size += len;
+			return len;
+		}
 	}
 
 	if (bio->bi_vcnt >= bio->bi_max_vecs)

block/blk.h +19 -0

index 67915b04b3c17..676c91c19940d 100644
@@ -102,6 +102,25 @@ 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)
 {

Signature · 1 line

2.53.0