linux-kernel - [PATCH v2] block, scsi: sd_zbc: Respect bio vector limits for report zones buffer

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Message-ID: <20250502193554.113928-1-ssiwinski@atto.com>
Date: Fri,  2 May 2025 15:35:54 -0400
From: Steve Siwinski <stevensiwinski@...il.com>
To: hch@...radead.org
Cc: James.Bottomley@...senpartnership.com,
	bgrove@...o.com,
	dlemoal@...nel.org,
	linux-kernel@...r.kernel.org,
	linux-scsi@...r.kernel.org,
	martin.petersen@...cle.com,
	ssiwinski@...o.com,
	stevensiwinski@...il.com,
	axboe@...nel.dk,
	tdoedline@...o.com,
	linux-block@...r.kernel.org
Subject: [PATCH v2] block, scsi: sd_zbc: Respect bio vector limits for report zones buffer

The report zones buffer size is currently limited by the HBA's
maximum segment count to ensure the buffer can be mapped. However,
the block layer further limits the number of iovec entries to
1024 when allocating a bio.

To avoid allocation of buffers too large to be mapped, further
restrict the maximum buffer size to BIO_MAX_INLINE_VECS.

Replace the UIO_MAXIOV symbolic name with the more contextually
appropriate BIO_MAX_INLINE_VECS.

Signed-off-by: Steve Siwinski <ssiwinski@...o.com>
---
 block/bio.c           | 2 +-
 drivers/scsi/sd_zbc.c | 3 +++
 include/linux/bio.h   | 2 ++
 3 files changed, 6 insertions(+), 1 deletion(-)

diff --git a/block/bio.c b/block/bio.c
index 4e6c85a33d74..4be592d37fb6 100644
--- a/block/bio.c
+++ b/block/bio.c
@@ -611,7 +611,7 @@ struct bio *bio_kmalloc(unsigned short nr_vecs, gfp_t gfp_mask)
 {
 	struct bio *bio;
 
-	if (nr_vecs > UIO_MAXIOV)
+	if (nr_vecs > BIO_MAX_INLINE_VECS)
 		return NULL;
 	return kmalloc(struct_size(bio, bi_inline_vecs, nr_vecs), gfp_mask);
 }
diff --git a/drivers/scsi/sd_zbc.c b/drivers/scsi/sd_zbc.c
index 7a447ff600d2..a5364fdc2824 100644
--- a/drivers/scsi/sd_zbc.c
+++ b/drivers/scsi/sd_zbc.c
@@ -180,12 +180,15 @@ static void *sd_zbc_alloc_report_buffer(struct scsi_disk *sdkp,
 	 * Furthermore, since the report zone command cannot be split, make
 	 * sure that the allocated buffer can always be mapped by limiting the
 	 * number of pages allocated to the HBA max segments limit.
+	 * Since max segments can be larger than the max inline bio vectors,
+	 * further limit the allocated buffer to BIO_MAX_INLINE_VECS.
 	 */
 	nr_zones = min(nr_zones, sdkp->zone_info.nr_zones);
 	bufsize = roundup((nr_zones + 1) * 64, SECTOR_SIZE);
 	bufsize = min_t(size_t, bufsize,
 			queue_max_hw_sectors(q) << SECTOR_SHIFT);
 	bufsize = min_t(size_t, bufsize, queue_max_segments(q) << PAGE_SHIFT);
+	bufsize = min_t(size_t, bufsize, BIO_MAX_INLINE_VECS << PAGE_SHIFT);
 
 	while (bufsize >= SECTOR_SIZE) {
 		buf = kvzalloc(bufsize, GFP_KERNEL | __GFP_NORETRY);
diff --git a/include/linux/bio.h b/include/linux/bio.h
index cafc7c215de8..7cf9506a6c36 100644
--- a/include/linux/bio.h
+++ b/include/linux/bio.h
@@ -11,6 +11,8 @@
 #include <linux/uio.h>
 
 #define BIO_MAX_VECS		256U
+/* BIO_MAX_INLINE_VECS must be at most the size of UIO_MAXIOV */
+#define BIO_MAX_INLINE_VECS	1024
 
 struct queue_limits;
 
-- 
2.43.5