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linux-next/drivers/block/xen-blkback/common.h
Roger Pau Monne 3f3aad5e66 xen-blkback: implement LRU mechanism for persistent grants 
This mechanism allows blkback to change the number of grants
persistently mapped at run time.

The algorithm uses a simple LRU mechanism that removes (if needed) the
persistent grants that have not been used since the last LRU run, or
if all grants have been used it removes the first grants in the list
(that are not in use).

The algorithm allows the user to change the maximum number of
persistent grants, by changing max_persistent_grants in sysfs.

Since we are storing the persistent grants used inside the request
struct (to be able to mark them as "unused" when unmapping), we no
longer need the bitmap (unmap_seg).

Signed-off-by: Roger Pau Monné <roger.pau@citrix.com>
Cc: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
Cc: xen-devel@lists.xen.org
Signed-off-by: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
2013-04-18 09:29:23 -04:00

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/*
* This program is free software; you can redistribute it and/or
* modify it under the terms of the GNU General Public License version 2
* as published by the Free Software Foundation; or, when distributed
* separately from the Linux kernel or incorporated into other
* software packages, subject to the following license:
*
* Permission is hereby granted, free of charge, to any person obtaining a copy
* of this source file (the "Software"), to deal in the Software without
* restriction, including without limitation the rights to use, copy, modify,
* merge, publish, distribute, sublicense, and/or sell copies of the Software,
* and to permit persons to whom the Software is furnished to do so, subject to
* the following conditions:
*
* The above copyright notice and this permission notice shall be included in
* all copies or substantial portions of the Software.
*
* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
* IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
* FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
* AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
* LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
* FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS
* IN THE SOFTWARE.
*/
#ifndef __XEN_BLKIF__BACKEND__COMMON_H__
#define __XEN_BLKIF__BACKEND__COMMON_H__
#include <linux/module.h>
#include <linux/interrupt.h>
#include <linux/slab.h>
#include <linux/blkdev.h>
#include <linux/vmalloc.h>
#include <linux/wait.h>
#include <linux/io.h>
#include <linux/rbtree.h>
#include <asm/setup.h>
#include <asm/pgalloc.h>
#include <asm/hypervisor.h>
#include <xen/grant_table.h>
#include <xen/xenbus.h>
#include <xen/interface/io/ring.h>
#include <xen/interface/io/blkif.h>
#include <xen/interface/io/protocols.h>
#define DRV_PFX "xen-blkback:"
#define DPRINTK(fmt, args...) \
pr_debug(DRV_PFX "(%s:%d) " fmt ".\n", \
__func__, __LINE__, ##args)
/* Not a real protocol. Used to generate ring structs which contain
* the elements common to all protocols only. This way we get a
* compiler-checkable way to use common struct elements, so we can
* avoid using switch(protocol) in a number of places. */
struct blkif_common_request {
char dummy;
};
struct blkif_common_response {
char dummy;
};
struct blkif_x86_32_request_rw {
uint8_t nr_segments; /* number of segments */
blkif_vdev_t handle; /* only for read/write requests */
uint64_t id; /* private guest value, echoed in resp */
blkif_sector_t sector_number;/* start sector idx on disk (r/w only) */
struct blkif_request_segment seg[BLKIF_MAX_SEGMENTS_PER_REQUEST];
} __attribute__((__packed__));
struct blkif_x86_32_request_discard {
uint8_t flag; /* BLKIF_DISCARD_SECURE or zero */
blkif_vdev_t _pad1; /* was "handle" for read/write requests */
uint64_t id; /* private guest value, echoed in resp */
blkif_sector_t sector_number;/* start sector idx on disk (r/w only) */
uint64_t nr_sectors;
} __attribute__((__packed__));
struct blkif_x86_32_request_other {
uint8_t _pad1;
blkif_vdev_t _pad2;
uint64_t id; /* private guest value, echoed in resp */
} __attribute__((__packed__));
struct blkif_x86_32_request {
uint8_t operation; /* BLKIF_OP_??? */
union {
struct blkif_x86_32_request_rw rw;
struct blkif_x86_32_request_discard discard;
struct blkif_x86_32_request_other other;
} u;
} __attribute__((__packed__));
/* i386 protocol version */
#pragma pack(push, 4)
struct blkif_x86_32_response {
uint64_t id; /* copied from request */
uint8_t operation; /* copied from request */
int16_t status; /* BLKIF_RSP_??? */
};
#pragma pack(pop)
/* x86_64 protocol version */
struct blkif_x86_64_request_rw {
uint8_t nr_segments; /* number of segments */
blkif_vdev_t handle; /* only for read/write requests */
uint32_t _pad1; /* offsetof(blkif_reqest..,u.rw.id)==8 */
uint64_t id;
blkif_sector_t sector_number;/* start sector idx on disk (r/w only) */
struct blkif_request_segment seg[BLKIF_MAX_SEGMENTS_PER_REQUEST];
} __attribute__((__packed__));
struct blkif_x86_64_request_discard {
uint8_t flag; /* BLKIF_DISCARD_SECURE or zero */
blkif_vdev_t _pad1; /* was "handle" for read/write requests */
uint32_t _pad2; /* offsetof(blkif_..,u.discard.id)==8 */
uint64_t id;
blkif_sector_t sector_number;/* start sector idx on disk (r/w only) */
uint64_t nr_sectors;
} __attribute__((__packed__));
struct blkif_x86_64_request_other {
uint8_t _pad1;
blkif_vdev_t _pad2;
uint32_t _pad3; /* offsetof(blkif_..,u.discard.id)==8 */
uint64_t id; /* private guest value, echoed in resp */
} __attribute__((__packed__));
struct blkif_x86_64_request {
uint8_t operation; /* BLKIF_OP_??? */
union {
struct blkif_x86_64_request_rw rw;
struct blkif_x86_64_request_discard discard;
struct blkif_x86_64_request_other other;
} u;
} __attribute__((__packed__));
struct blkif_x86_64_response {
uint64_t __attribute__((__aligned__(8))) id;
uint8_t operation; /* copied from request */
int16_t status; /* BLKIF_RSP_??? */
};
DEFINE_RING_TYPES(blkif_common, struct blkif_common_request,
struct blkif_common_response);
DEFINE_RING_TYPES(blkif_x86_32, struct blkif_x86_32_request,
struct blkif_x86_32_response);
DEFINE_RING_TYPES(blkif_x86_64, struct blkif_x86_64_request,
struct blkif_x86_64_response);
union blkif_back_rings {
struct blkif_back_ring native;
struct blkif_common_back_ring common;
struct blkif_x86_32_back_ring x86_32;
struct blkif_x86_64_back_ring x86_64;
};
enum blkif_protocol {
BLKIF_PROTOCOL_NATIVE = 1,
BLKIF_PROTOCOL_X86_32 = 2,
BLKIF_PROTOCOL_X86_64 = 3,
};
struct xen_vbd {
/* What the domain refers to this vbd as. */
blkif_vdev_t handle;
/* Non-zero -> read-only */
unsigned char readonly;
/* VDISK_xxx */
unsigned char type;
/* phys device that this vbd maps to. */
u32 pdevice;
struct block_device *bdev;
/* Cached size parameter. */
sector_t size;
unsigned int flush_support:1;
unsigned int discard_secure:1;
unsigned int feature_gnt_persistent:1;
unsigned int overflow_max_grants:1;
};
struct backend_info;
/* Number of available flags */
#define PERSISTENT_GNT_FLAGS_SIZE 2
/* This persistent grant is currently in use */
#define PERSISTENT_GNT_ACTIVE 0
/*
* This persistent grant has been used, this flag is set when we remove the
* PERSISTENT_GNT_ACTIVE, to know that this grant has been used recently.
*/
#define PERSISTENT_GNT_WAS_ACTIVE 1
struct persistent_gnt {
struct page *page;
grant_ref_t gnt;
grant_handle_t handle;
DECLARE_BITMAP(flags, PERSISTENT_GNT_FLAGS_SIZE);
struct rb_node node;
struct list_head remove_node;
};
struct xen_blkif {
/* Unique identifier for this interface. */
domid_t domid;
unsigned int handle;
/* Physical parameters of the comms window. */
unsigned int irq;
/* Comms information. */
enum blkif_protocol blk_protocol;
union blkif_back_rings blk_rings;
void *blk_ring;
/* The VBD attached to this interface. */
struct xen_vbd vbd;
/* Back pointer to the backend_info. */
struct backend_info *be;
/* Private fields. */
spinlock_t blk_ring_lock;
atomic_t refcnt;
wait_queue_head_t wq;
/* for barrier (drain) requests */
struct completion drain_complete;
atomic_t drain;
/* One thread per one blkif. */
struct task_struct *xenblkd;
unsigned int waiting_reqs;
/* tree to store persistent grants */
struct rb_root persistent_gnts;
unsigned int persistent_gnt_c;
atomic_t persistent_gnt_in_use;
unsigned long next_lru;
/* used by the kworker that offload work from the persistent purge */
struct list_head persistent_purge_list;
struct work_struct persistent_purge_work;
/* buffer of free pages to map grant refs */
spinlock_t free_pages_lock;
int free_pages_num;
struct list_head free_pages;
/* statistics */
unsigned long st_print;
unsigned long long st_rd_req;
unsigned long long st_wr_req;
unsigned long long st_oo_req;
unsigned long long st_f_req;
unsigned long long st_ds_req;
unsigned long long st_rd_sect;
unsigned long long st_wr_sect;
wait_queue_head_t waiting_to_free;
};
#define vbd_sz(_v) ((_v)->bdev->bd_part ? \
(_v)->bdev->bd_part->nr_sects : \
get_capacity((_v)->bdev->bd_disk))
#define xen_blkif_get(_b) (atomic_inc(&(_b)->refcnt))
#define xen_blkif_put(_b) \
do { \
if (atomic_dec_and_test(&(_b)->refcnt)) \
wake_up(&(_b)->waiting_to_free);\
} while (0)
struct phys_req {
unsigned short dev;
blkif_sector_t nr_sects;
struct block_device *bdev;
blkif_sector_t sector_number;
};
int xen_blkif_interface_init(void);
int xen_blkif_xenbus_init(void);
irqreturn_t xen_blkif_be_int(int irq, void *dev_id);
int xen_blkif_schedule(void *arg);
int xen_blkif_purge_persistent(void *arg);
int xen_blkbk_flush_diskcache(struct xenbus_transaction xbt,
struct backend_info *be, int state);
int xen_blkbk_barrier(struct xenbus_transaction xbt,
struct backend_info *be, int state);
struct xenbus_device *xen_blkbk_xenbus(struct backend_info *be);
static inline void blkif_get_x86_32_req(struct blkif_request *dst,
struct blkif_x86_32_request *src)
{
int i, n = BLKIF_MAX_SEGMENTS_PER_REQUEST;
dst->operation = src->operation;
switch (src->operation) {
case BLKIF_OP_READ:
case BLKIF_OP_WRITE:
case BLKIF_OP_WRITE_BARRIER:
case BLKIF_OP_FLUSH_DISKCACHE:
dst->u.rw.nr_segments = src->u.rw.nr_segments;
dst->u.rw.handle = src->u.rw.handle;
dst->u.rw.id = src->u.rw.id;
dst->u.rw.sector_number = src->u.rw.sector_number;
barrier();
if (n > dst->u.rw.nr_segments)
n = dst->u.rw.nr_segments;
for (i = 0; i < n; i++)
dst->u.rw.seg[i] = src->u.rw.seg[i];
break;
case BLKIF_OP_DISCARD:
dst->u.discard.flag = src->u.discard.flag;
dst->u.discard.id = src->u.discard.id;
dst->u.discard.sector_number = src->u.discard.sector_number;
dst->u.discard.nr_sectors = src->u.discard.nr_sectors;
break;
default:
/*
* Don't know how to translate this op. Only get the
* ID so failure can be reported to the frontend.
*/
dst->u.other.id = src->u.other.id;
break;
}
}
static inline void blkif_get_x86_64_req(struct blkif_request *dst,
struct blkif_x86_64_request *src)
{
int i, n = BLKIF_MAX_SEGMENTS_PER_REQUEST;
dst->operation = src->operation;
switch (src->operation) {
case BLKIF_OP_READ:
case BLKIF_OP_WRITE:
case BLKIF_OP_WRITE_BARRIER:
case BLKIF_OP_FLUSH_DISKCACHE:
dst->u.rw.nr_segments = src->u.rw.nr_segments;
dst->u.rw.handle = src->u.rw.handle;
dst->u.rw.id = src->u.rw.id;
dst->u.rw.sector_number = src->u.rw.sector_number;
barrier();
if (n > dst->u.rw.nr_segments)
n = dst->u.rw.nr_segments;
for (i = 0; i < n; i++)
dst->u.rw.seg[i] = src->u.rw.seg[i];
break;
case BLKIF_OP_DISCARD:
dst->u.discard.flag = src->u.discard.flag;
dst->u.discard.id = src->u.discard.id;
dst->u.discard.sector_number = src->u.discard.sector_number;
dst->u.discard.nr_sectors = src->u.discard.nr_sectors;
break;
default:
/*
* Don't know how to translate this op. Only get the
* ID so failure can be reported to the frontend.
*/
dst->u.other.id = src->u.other.id;
break;
}
}
#endif /* __XEN_BLKIF__BACKEND__COMMON_H__ */
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