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block: fix pgmap handling for zone device pages in bio merge paths #712

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block: fix pgmap handling for zone device pages in bio merge paths #712

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f693fd6
block: add pgmap check to biovec_phys_mergeable
Apr 10, 2026
f341413
block: relax pgmap check in bio_add_page for compatible zone device p…
Apr 10, 2026
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6 changes: 3 additions & 3 deletions block/bio-integrity.c
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Original file line number Diff line number Diff line change
Expand Up @@ -167,10 +167,10 @@ 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;
}
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6 changes: 3 additions & 3 deletions block/bio.c
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Original file line number Diff line number Diff line change
Expand Up @@ -1070,10 +1070,10 @@ 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;
}
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21 changes: 21 additions & 0 deletions block/blk.h
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Original file line number Diff line number Diff line change
Expand Up @@ -132,13 +132,34 @@ static inline bool biovec_phys_mergeable(struct request_queue *q,

if (addr1 + vec1->bv_len != addr2)
return false;
if (!zone_device_pages_have_same_pgmap(vec1->bv_page, vec2->bv_page))
return false;
if (xen_domain() && !xen_biovec_phys_mergeable(vec1, vec2->bv_page))
return false;
if ((addr1 | mask) != ((addr2 + vec2->bv_len - 1) | mask))
return false;
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)
{
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