Re: [PATCH 03/14] bcache: add initial data structures for nvm pages

[Hannes Reinecke <hare@suse.de>]

On 6/15/21 7:49 AM, Coly Li wrote:
> This patch initializes the prototype data structures for nvm pages
> allocator,
> 
> - struct bch_nvm_pages_sb
> This is the super block allocated on each nvdimm namespace. A nvdimm
> set may have multiple namespaces, bch_nvm_pages_sb->set_uuid is used
> to mark which nvdimm set this name space belongs to. Normally we will
> use the bcache's cache set UUID to initialize this uuid, to connect this
> nvdimm set to a specified bcache cache set.
> 
> - struct bch_owner_list_head
> This is a table for all heads of all owner lists. A owner list records
> which page(s) allocated to which owner. After reboot from power failure,
> the ownwer may find all its requested and allocated pages from the owner

owner

> list by a handler which is converted by a UUID.
> 
> - struct bch_nvm_pages_owner_head
> This is a head of an owner list. Each owner only has one owner list,
> and a nvm page only belongs to an specific owner. uuid[] will be set to
> owner's uuid, for bcache it is the bcache's cache set uuid. label is not
> mandatory, it is a human-readable string for debug purpose. The pointer
> *recs references to separated nvm page which hold the table of struct
> bch_nvm_pgalloc_rec.
> 
> - struct bch_nvm_pgalloc_recs
> This struct occupies a whole page, owner_uuid should match the uuid
> in struct bch_nvm_pages_owner_head. recs[] is the real table contains all
> allocated records.
> 
> - struct bch_nvm_pgalloc_rec
> Each structure records a range of allocated nvm pages.
>   - Bits  0 - 51: is pages offset of the allocated pages.
>   - Bits 52 - 57: allocaed size in page_size * order-of-2
>   - Bits 58 - 63: reserved.
> Since each of the allocated nvm pages are power of 2, using 6 bits to
> represent allocated size can have (1<<(1<<64) - 1) * PAGE_SIZE maximum
> value. It can be a 76 bits width range size in byte for 4KB page size,
> which is large enough currently.
> 
> Signed-off-by: Coly Li <colyli@suse.de>
> Cc: Jianpeng Ma <jianpeng.ma@intel.com>
> Cc: Qiaowei Ren <qiaowei.ren@intel.com>
> ---
>  include/uapi/linux/bcache-nvm.h | 200 ++++++++++++++++++++++++++++++++
>  1 file changed, 200 insertions(+)
>  create mode 100644 include/uapi/linux/bcache-nvm.h
> 
> diff --git a/include/uapi/linux/bcache-nvm.h b/include/uapi/linux/bcache-nvm.h
> new file mode 100644
> index 000000000000..5094a6797679
> --- /dev/null
> +++ b/include/uapi/linux/bcache-nvm.h
> @@ -0,0 +1,200 @@
> +/* SPDX-License-Identifier: GPL-2.0 WITH Linux-syscall-note */
> +
> +#ifndef _UAPI_BCACHE_NVM_H
> +#define _UAPI_BCACHE_NVM_H
> +
> +#if (__BITS_PER_LONG == 64)
> +/*
> + * Bcache on NVDIMM data structures
> + */
> +
> +/*
> + * - struct bch_nvm_pages_sb
> + *   This is the super block allocated on each nvdimm namespace. A nvdimm
> + * set may have multiple namespaces, bch_nvm_pages_sb->set_uuid is used to mark
> + * which nvdimm set this name space belongs to. Normally we will use the
> + * bcache's cache set UUID to initialize this uuid, to connect this nvdimm
> + * set to a specified bcache cache set.
> + *
> + * - struct bch_owner_list_head
> + *   This is a table for all heads of all owner lists. A owner list records
> + * which page(s) allocated to which owner. After reboot from power failure,
> + * the ownwer may find all its requested and allocated pages from the owner
> + * list by a handler which is converted by a UUID.
> + *
> + * - struct bch_nvm_pages_owner_head
> + *   This is a head of an owner list. Each owner only has one owner list,
> + * and a nvm page only belongs to an specific owner. uuid[] will be set to
> + * owner's uuid, for bcache it is the bcache's cache set uuid. label is not
> + * mandatory, it is a human-readable string for debug purpose. The pointer
> + * recs references to separated nvm page which hold the table of struct
> + * bch_pgalloc_rec.
> + *
> + *- struct bch_nvm_pgalloc_recs
> + *  This structure occupies a whole page, owner_uuid should match the uuid
> + * in struct bch_nvm_pages_owner_head. recs[] is the real table contains all
> + * allocated records.
> + *
> + * - struct bch_pgalloc_rec
> + *   Each structure records a range of allocated nvm pages. pgoff is offset
> + * in unit of page size of this allocated nvm page range. The adjoint page
> + * ranges of same owner can be merged into a larger one, therefore pages_nr
> + * is NOT always power of 2.
> + *
> + *
> + * Memory layout on nvdimm namespace 0
> + *
> + *    0 +---------------------------------+
> + *      |                                 |
> + *  4KB +---------------------------------+
> + *      |         bch_nvm_pages_sb        |
> + *  8KB +---------------------------------+ <--- bch_nvm_pages_sb.bch_owner_list_head
> + *      |       bch_owner_list_head       |
> + *      |                                 |
> + * 16KB +---------------------------------+ <--- bch_owner_list_head.heads[0].recs[0]
> + *      |       bch_nvm_pgalloc_recs      |
> + *      |  (nvm pages internal usage)     |
> + * 24KB +---------------------------------+
> + *      |                                 |
> + *      |                                 |
> + * 16MB  +---------------------------------+
> + *      |      allocable nvm pages        |
> + *      |      for buddy allocator        |
> + * end  +---------------------------------+
> + *
> + *
> + *
> + * Memory layout on nvdimm namespace N
> + * (doesn't have owner list)
> + *
> + *    0 +---------------------------------+
> + *      |                                 |
> + *  4KB +---------------------------------+
> + *      |         bch_nvm_pages_sb        |
> + *  8KB +---------------------------------+
> + *      |                                 |
> + *      |                                 |
> + *      |                                 |
> + *      |                                 |
> + *      |                                 |
> + *      |                                 |
> + * 16MB  +---------------------------------+
> + *      |      allocable nvm pages        |
> + *      |      for buddy allocator        |
> + * end  +---------------------------------+
> + *
> + */
> +
> +#include <linux/types.h>
> +
> +/* In sectors */
> +#define BCH_NVM_PAGES_SB_OFFSET			4096
> +#define BCH_NVM_PAGES_OFFSET			(16 << 20)
> +
> +#define BCH_NVM_PAGES_LABEL_SIZE		32
> +#define BCH_NVM_PAGES_NAMESPACES_MAX		8
> +
> +#define BCH_NVM_PAGES_OWNER_LIST_HEAD_OFFSET	(8<<10)
> +#define BCH_NVM_PAGES_SYS_RECS_HEAD_OFFSET	(16<<10)
> +
> +#define BCH_NVM_PAGES_SB_VERSION		0
> +#define BCH_NVM_PAGES_SB_VERSION_MAX		0
> +
> +static const unsigned char bch_nvm_pages_magic[] = {
> +	0x17, 0xbd, 0x53, 0x7f, 0x1b, 0x23, 0xd6, 0x83,
> +	0x46, 0xa4, 0xf8, 0x28, 0x17, 0xda, 0xec, 0xa9 };
> +static const unsigned char bch_nvm_pages_pgalloc_magic[] = {
> +	0x39, 0x25, 0x3f, 0xf7, 0x27, 0x17, 0xd0, 0xb9,
> +	0x10, 0xe6, 0xd2, 0xda, 0x38, 0x68, 0x26, 0xae };
> +
> +/* takes 64bit width */
> +struct bch_pgalloc_rec {
> +	__u64	pgoff:52;
> +	__u64	order:6;
> +	__u64	reserved:6;
> +};
> +
> +struct bch_nvm_pgalloc_recs {
> +union {

Indentation.

> +	struct {
> +		struct bch_nvm_pages_owner_head	*owner;
> +		struct bch_nvm_pgalloc_recs	*next;
> +		unsigned char			magic[16];
> +		unsigned char			owner_uuid[16];
> +		unsigned int			size;
> +		unsigned int			used;
> +		unsigned long			_pad[4];
> +		struct bch_pgalloc_rec		recs[];
> +	};
> +	unsigned char				pad[8192];
> +};
> +};
> +

Consider using __u64 and friends when specifying a structure with a
fixed alignment; that also removes the need of the BITS_PER_LONG ifdef
at the top.

> +#define BCH_MAX_RECS					\
> +	((sizeof(struct bch_nvm_pgalloc_recs) -		\
> +	 offsetof(struct bch_nvm_pgalloc_recs, recs)) /	\
> +	 sizeof(struct bch_pgalloc_rec))
> +

What _are_ you doing here?
You're not seriously using the 'pad' field as a placeholder to size the
structure accordingly?
Also, what is the size of the 'bch_nvm_pgalloc_recs' structure?
8k + header size?
That is very awkward, as the page allocator won't be able to handle it
efficiently.
Please size it to either 8k or 16k overall.
And if you do that you can simplify this define.

> +struct bch_nvm_pages_owner_head {
> +	unsigned char			uuid[16];
> +	unsigned char			label[BCH_NVM_PAGES_LABEL_SIZE];
> +	/* Per-namespace own lists */
> +	struct bch_nvm_pgalloc_recs	*recs[BCH_NVM_PAGES_NAMESPACES_MAX];
> +};
> +
> +/* heads[0] is always for nvm_pages internal usage */
> +struct bch_owner_list_head {
> +union {
> +	struct {
> +		unsigned int			size;
> +		unsigned int			used;
> +		unsigned long			_pad[4];
> +		struct bch_nvm_pages_owner_head	heads[];
> +	};
> +	unsigned char				pad[8192];
> +};
> +};
> +#define BCH_MAX_OWNER_LIST				\
> +	((sizeof(struct bch_owner_list_head) -		\
> +	 offsetof(struct bch_owner_list_head, heads)) /	\
> +	 sizeof(struct bch_nvm_pages_owner_head))
> +

Same here.
Please size it that the 'bch_owner_list_head' structure fits into either
8k or 16k.

> +/* The on-media bit order is local CPU order */
> +struct bch_nvm_pages_sb {
> +	unsigned long				csum;
> +	unsigned long				ns_start;
> +	unsigned long				sb_offset;
> +	unsigned long				version;
> +	unsigned char				magic[16];
> +	unsigned char				uuid[16];
> +	unsigned int				page_size;
> +	unsigned int				total_namespaces_nr;
> +	unsigned int				this_namespace_nr;
> +	union {
> +		unsigned char			set_uuid[16];
> +		unsigned long			set_magic;
> +	};
> +
> +	unsigned long				flags;
> +	unsigned long				seq;
> +
> +	unsigned long				feature_compat;
> +	unsigned long				feature_incompat;
> +	unsigned long				feature_ro_compat;
> +
> +	/* For allocable nvm pages from buddy systems */
> +	unsigned long				pages_offset;
> +	unsigned long				pages_total;
> +
> +	unsigned long				pad[8];
> +
> +	/* Only on the first name space */
> +	struct bch_owner_list_head		*owner_list_head;
> +
> +	/* Just for csum_set() */
> +	unsigned int				keys;
> +	unsigned long				d[0];
> +};

And also here, use __u64 and friends.

Cheers,

Hannes
-- 
Dr. Hannes Reinecke		           Kernel Storage Architect
hare@suse.de			                  +49 911 74053 688
SUSE Software Solutions Germany GmbH, Maxfeldstr. 5, 90409 Nürnberg
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