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提交 3a2a1212 创建 作者: Nickolai Zeldovich's avatar Nickolai Zeldovich
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avoid bumping inode refcounts, use rcu instead, with a mostly-unimplemented

plan for eviction.
上级 07cad277
隐藏空白字符变更
内嵌 并排
正在显示 包含 52 行增加 和 76 行删除
include/kernel.hh
浏览文件 @ 3a2a1212
......@@ -91,6 +91,7 @@ struct inode* ialloc(u32, short);
struct inode* namei(inode *cwd, const char*);
void iput(struct inode*);
struct inode* iget(u32 dev, u32 inum);
struct inode* igetnoref(u32 dev, u32 inum);
void ilock(struct inode*, int writer);
void iunlockput(struct inode*);
void iupdate(struct inode*);
......
kernel/fs.cc
浏览文件 @ 3a2a1212
......@@ -10,6 +10,22 @@
// routines. The (higher-level) system call implementations
// are in sysfile.c.
/*
* inode cache will be RCU-managed:
*
* - to evict, mark inode as a victim
* - lookups that encounter a victim inode must return an error (-E_RETRY)
* - E_RETRY rolls back to the beginning of syscall/pagefault and retries
* - out-of-memory error should be treated like -E_RETRY
* - once an inode is marked as victim, it can be gc_delayed()
* - the do_gc() method should remove inode from the namespace & free it
*
* - inodes have a refcount that lasts beyond a GC epoch
* - to bump refcount, first bump, then check victim flag
* - if victim flag is set, reduce the refcount and -E_RETRY
*
*/
#include "types.h"
#include "stat.h"
#include "mmu.h"
......@@ -239,72 +255,36 @@ inode::~inode()
struct inode*
iget(u32 dev, u32 inum)
{
struct inode *ip;
struct inode *ip = igetnoref(dev, inum);
if (ip)
idup(ip);
return ip;
}
struct inode*
igetnoref(u32 dev, u32 inum)
{
retry:
// Try for cached inode.
gc_begin_epoch();
ip = ins->lookup(mkpair(dev, inum));
if (ip) {
// tricky: first bump ref, then check free flag
ip->ref++;
if (ip->flags & I_FREE) {
gc_end_epoch();
ip->ref--;
goto retry;
}
gc_end_epoch();
if (!(ip->flags & I_VALID)) {
acquire(&ip->lock);
while((ip->flags & I_VALID) == 0)
cv_sleep(&ip->cv, &ip->lock);
release(&ip->lock);
}
{
scoped_gc_epoch e;
struct inode *ip = ins->lookup(mkpair(dev, inum));
if (ip) {
if (!(ip->flags & I_VALID)) {
acquire(&ip->lock);
while((ip->flags & I_VALID) == 0)
cv_sleep(&ip->cv, &ip->lock);
release(&ip->lock);
}
return ip;
}
gc_end_epoch();
// Allocate fresh inode cache slot.
retry_evict:
(void) 0;
u32 cur_free = icache_free[mycpu()->id].x;
if (cur_free == 0) {
struct inode *victim = 0;
ins->enumerate([&victim](const pair<u32, u32>&, inode* eip)->bool{
if (eip->ref || eip->type == T_DIR)
return false;
acquire(&eip->lock);
if (eip->ref == 0 && eip->type != T_DIR &&
!(eip->flags & (I_FREE | I_BUSYR | I_BUSYW))) {
victim = eip;
return true;
}
release(&eip->lock);
return false;
});
if (!victim)
panic("iget out of space");
// tricky: first flag as free, then check refcnt, then remove from ns
victim->flags |= I_FREE;
if (victim->ref > 0) {
victim->flags &= ~(I_FREE);
release(&victim->lock);
goto retry_evict;
}
release(&victim->lock);
ins->remove(mkpair(victim->dev, victim->inum), &victim);
gc_delayed(victim);
} else {
if (!cmpxch(&icache_free[mycpu()->id].x, cur_free, cur_free-1))
goto retry_evict;
}
ip = new inode();
// Allocate fresh inode cache slot.
struct inode *ip = new inode();
ip->dev = dev;
ip->inum = inum;
ip->ref = 1;
ip->ref = 0;
ip->flags = I_BUSYR | I_BUSYW;
ip->readbusy = 1;
snprintf(ip->lockname, sizeof(ip->lockname), "cv:ino:%d", ip->inum);
......@@ -366,7 +346,7 @@ ilock(struct inode *ip, int writer)
void
iunlock(struct inode *ip)
{
if(ip == 0 || !(ip->flags & (I_BUSYR | I_BUSYW)) || ip->ref < 1)
if(ip == 0 || !(ip->flags & (I_BUSYR | I_BUSYW)))
panic("iunlock");
acquire(&ip->lock);
......@@ -407,6 +387,9 @@ iput(struct inode *ip)
ip->flags |= (I_BUSYR | I_BUSYW);
ip->readbusy++;
// XXX: use gc_delayed() to truncate the inode later.
// flag it as a victim in the meantime.
release(&ip->lock);
itrunc(ip);
......@@ -751,12 +734,12 @@ namex(inode *cwd, const char *path, int nameiparent, char *name)
{
struct inode *ip, *next;
int r;
scoped_gc_epoch e;
gc_begin_epoch();
if(*path == '/')
ip = iget(ROOTDEV, ROOTINO);
ip = igetnoref(ROOTDEV, ROOTINO);
else
ip = idup(cwd);
ip = cwd;
while((r = skipelem(&path, name)) == 1){
// XXX Doing this here requires some annoying reasoning about all
......@@ -773,32 +756,24 @@ namex(inode *cwd, const char *path, int nameiparent, char *name)
if(next == 0){
if(ip->type == 0)
panic("namex");
if(ip->type != T_DIR){
iput(ip);
gc_end_epoch();
if(ip->type != T_DIR)
return 0;
}
if(nameiparent && *path == '\0'){
// Stop one level early.
gc_end_epoch();
idup(ip);
return ip;
}
if((next = dirlookup(ip, name)) == 0){
iput(ip);
gc_end_epoch();
if((next = dirlookup(ip, name)) == 0)
return 0;
}
iput(ip);
}
ip = next;
}
if(r == -1 || nameiparent){
iput(ip);
gc_end_epoch();
if(r == -1 || nameiparent)
return 0;
}
mtreadavar("inode:%x.%x", ip->dev, ip->inum);
gc_end_epoch();
idup(ip);
return ip;
}
......
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