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/*
* Copyright (c) 2023-2024 Ian Marco Moffett and the Osmora Team.
* All rights reserved.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions are met:
*
* 1. Redistributions of source code must retain the above copyright notice,
* this list of conditions and the following disclaimer.
* 2. Redistributions in binary form must reproduce the above copyright
* notice, this list of conditions and the following disclaimer in the
* documentation and/or other materials provided with the distribution.
* 3. Neither the name of Hyra nor the names of its
* contributors may be used to endorse or promote products derived from
* this software without specific prior written permission.
*
* THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
* AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
* IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
* ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE
* LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
* CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
* SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
* INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
* CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
* ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
* POSSIBILITY OF SUCH DAMAGE.
*/
#include <sys/vnode.h>
#include <sys/errno.h>
#include <sys/types.h>
#include <sys/cdefs.h>
#include <sys/sysctl.h>
#include <sys/syslog.h>
#include <sys/panic.h>
#include <sys/spinlock.h>
#include <vm/dynalloc.h>
#include <string.h>
#define VCACHE_SIZE 64
#define pr_trace(fmt, ...) kprintf("vcache: " fmt, ##__VA_ARGS__)
struct vcache {
TAILQ_HEAD(vcache_head, vnode) q;
ssize_t size; /* In entries (-1 not set up) */
} vcache = { .size = -1 };
/*
* Our vcache will be here if our caching type is
* global.
*/
static int vcache_type = VCACHE_TYPE_NONE;
__cacheline_aligned static struct spinlock vcache_lock;
/*
* Pull a vnode from the head of the global
* vcache. Returns NULL if none are found.
*
* XXX: Caller must acquire vcache_lock.
*/
static struct vnode *
vcache_global_pull(void)
{
struct vnode *vp;
if (vcache.size <= 0) {
return NULL;
}
vp = TAILQ_FIRST(&vcache.q);
TAILQ_REMOVE(&vcache.q, vp, vcache_link);
--vcache.size;
return vp;
}
/*
* Add a new entry to the global vcache
*
* XXX: Caller must acquire vcache_lock.
* @vp: New vnode to add.
*/
static int
vcache_global_add(struct vnode *vp)
{
struct vnode *tmp;
/*
* Do some checks on the vcache size, should be >= 0
* but if it is -1 then we just need to initialize the
* queue. However, if it is less than -1... Then shit,
* good luck debugging I suppose.
*
* The global vcache naturally behaves as an LRU cache.
* If we need more space, the tail of the queue is evicted.
*/
if (vcache.size < 0) {
TAILQ_INIT(&vcache.q);
vcache.size = 0;
} else if (vcache.size < -1) {
panic("vcache_global_add: Bad vcache size, catching fire\n");
} else if (vcache.size == VCACHE_SIZE) {
/* Evict the tail */
tmp = TAILQ_LAST(&vcache.q, vcache_head);
TAILQ_REMOVE(&vcache.q, tmp, vcache_link);
dynfree(tmp);
--vcache.size;
}
TAILQ_INSERT_TAIL(&vcache.q, vp, vcache_link);
++vcache.size;
return 0;
}
/*
* Migrate the vnode cache (vcache) from one mode
* (e.g., global, proc, none) to another. This transition
* is done without an extreme performance impact through a
* process called lazy vcache migration (LZVM). For example,
* if we update the vcache type to be "proc" from an initial
* type of "global", the global vcache is made read-only until
* all entries are eventually invalidated naturally. In other
* words, both the global vcache and per-process vcaches will
* be checked during the migration process, however once the
* global vcache becomes empty it will no longer be checked.
*/
int
vfs_vcache_migrate(int newtype)
{
char *sysctl_val;
struct sysctl_args args;
int retval, name = KERN_VCACHE_TYPE;
switch (newtype) {
case VCACHE_TYPE_NONE:
sysctl_val = "none";
break;
case VCACHE_TYPE_PROC:
sysctl_val = "proc";
break;
case VCACHE_TYPE_GLOBAL:
sysctl_val = "global";
break;
default:
return -EINVAL;
}
/* Prepare the sysctl args */
args.name = &name;
args.nlen = 1;
args.oldp = NULL;
args.oldlenp = NULL;
args.newp = sysctl_val;
args.newlen = strlen(sysctl_val);
if ((retval = sysctl(&args)) != 0) {
return retval;
}
vcache_type = newtype;
return 0;
}
/*
* Add a vnode to vcache.
*
* @vp: Pointer of vnode to add.
*/
int
vfs_vcache_enter(struct vnode *vp)
{
int retval = 0;
switch (vcache_type) {
case VCACHE_TYPE_NONE:
break;
case VCACHE_TYPE_PROC:
/* TODO */
pr_trace("warn: proc vcache not supported, using global...\n");
vcache_type = VCACHE_TYPE_GLOBAL;
/* - FALL THROUGH - */
case VCACHE_TYPE_GLOBAL:
spinlock_acquire(&vcache_lock);
retval = vcache_global_add(vp);
spinlock_release(&vcache_lock);
break;
default:
pr_trace("warn: Bad vcache type, falling back to none\n");
vcache_type = VCACHE_TYPE_NONE;
break;
}
return retval;
}
/*
* Pull a random vnode from the vcache to
* recycle.
*/
struct vnode *
vfs_recycle_vnode(void)
{
struct vnode *vp = NULL;
switch (vcache_type) {
case VCACHE_TYPE_NONE:
break;
case VCACHE_TYPE_PROC:
/* TODO */
pr_trace("warn: proc vcache not supported, using global...\n");
vcache_type = VCACHE_TYPE_GLOBAL;
/* - FALL THROUGH - */
case VCACHE_TYPE_GLOBAL:
spinlock_acquire(&vcache_lock);
vp = vcache_global_pull();
spinlock_release(&vcache_lock);
break;
default:
pr_trace("warn: Bad vcache type, falling back to none\n");
vcache_type = VCACHE_TYPE_NONE;
break;
}
return vp;
}
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