Commit 414a4c93 authored by Christoph Hellwig's avatar Christoph Hellwig
Browse files

nvme-pci: derive and better document max segments limits 



Redefine the max segments and max integrity limits based on the limiting
factors.  This keeps exactly the same values for 4k PAGE_SIZE systems,
but increases the number of segments for larger page size as it properly
derives the scatterlist allocation based limit for them instead of
assuming a 4k PAGE_SIZE.

Signed-off-by: default avatarChristoph Hellwig <hch@lst.de>
Reviewed-by: default avatarKeith Busch <kbusch@kernel.org>
parent de65e642

drivers/nvme/host/pci.c

+16 −6
Original line number Diff line number Diff line
@@ -35,8 +35,6 @@ 
#define SQ_SIZE(q)	((q)->q_depth << (q)->sqes)

#define CQ_SIZE(q)	((q)->q_depth * sizeof(struct nvme_completion))



#define SGES_PER_PAGE	(NVME_CTRL_PAGE_SIZE / sizeof(struct nvme_sgl_desc))



/* Optimisation for I/Os between 4k and 128k */

#define NVME_SMALL_POOL_SIZE	256
@@ -45,10 +43,24 @@ 
 * require an sg allocation that needs more than a page of data.

 */

#define NVME_MAX_KB_SZ	8192

#define NVME_MAX_SEGS	128

#define NVME_MAX_META_SEGS 15

#define NVME_MAX_NR_DESCRIPTORS	5



/*

 * For data SGLs we support a single descriptors worth of SGL entries, but for

 * now we also limit it to avoid an allocation larger than PAGE_SIZE for the

 * scatterlist.

 */

#define NVME_MAX_SEGS \

	min(NVME_CTRL_PAGE_SIZE / sizeof(struct nvme_sgl_desc), \

	    (PAGE_SIZE / sizeof(struct scatterlist)))



/*

 * For metadata SGLs, only the small descriptor is supported, and the first

 * entry is the segment descriptor, which for the data pointer sits in the SQE.

 */

#define NVME_MAX_META_SEGS \

	((NVME_SMALL_POOL_SIZE / sizeof(struct nvme_sgl_desc)) - 1)



static int use_threaded_interrupts;

module_param(use_threaded_interrupts, int, 0444);
@@ -3829,8 +3841,6 @@ static int __init nvme_init(void) 
	BUILD_BUG_ON(sizeof(struct nvme_create_sq) != 64);

	BUILD_BUG_ON(sizeof(struct nvme_delete_queue) != 64);

	BUILD_BUG_ON(IRQ_AFFINITY_MAX_SETS < 2);

	BUILD_BUG_ON(NVME_MAX_SEGS > SGES_PER_PAGE);

	BUILD_BUG_ON(sizeof(struct scatterlist) * NVME_MAX_SEGS > PAGE_SIZE);

	BUILD_BUG_ON(nvme_pci_npages_prp() > NVME_MAX_NR_DESCRIPTORS);



	return pci_register_driver(&nvme_driver);