scsi: sd_zbc: block: 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.

Fixes: b091ac6 ("sd_zbc: Fix report zones buffer allocation")
Cc: stable@vger.kernel.org
Signed-off-by: Steve Siwinski <ssiwinski@atto.com>
Link: https://lore.kernel.org/r/20250508200122.243129-1-ssiwinski@atto.com
Reviewed-by: Damien Le Moal <dlemoal@kernel.org>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>

Author: ssiwinski-atto

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);
 }

drivers/scsi/sd_zbc.c

@@ -169,6 +169,7 @@ static void *sd_zbc_alloc_report_buffer(struct scsi_disk *sdkp,
 					unsigned int nr_zones, size_t *buflen)
 {
 	struct request_queue *q = sdkp->disk->queue;
+	unsigned int max_segments;
 	size_t bufsize;
 	void *buf;
 
@@ -180,12 +181,15 @@ 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);
+	max_segments = min(BIO_MAX_INLINE_VECS, queue_max_segments(q));
+	bufsize = min_t(size_t, bufsize, max_segments << PAGE_SHIFT);
 
 	while (bufsize >= SECTOR_SIZE) {
 		buf = kvzalloc(bufsize, GFP_KERNEL | __GFP_NORETRY);

include/linux/bio.h

@@ -11,6 +11,7 @@
 #include <linux/uio.h>
 
 #define BIO_MAX_VECS		256U
+#define BIO_MAX_INLINE_VECS	UIO_MAXIOV
 
 struct queue_limits;