inode cache

2010-03-19 08:35:33 132 阅读 AI 写同款 · GEO 优化AI 选题数据监测一键分发 ›

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linux kernel 1.0 中__iget 实现如下：

struct inode * __iget(struct super_block * sb, int nr, int crossmntp)
{
static struct wait_queue * update_wait = NULL;
struct inode_hash_entry * h;
struct inode * inode;
struct inode * empty = NULL;

if (!sb)
panic("VFS: iget with sb==NULL");
h = hash(sb->s_dev, nr);
repeat:
for (inode = h->inode; inode ; inode = inode->i_hash_next)
if (inode->i_dev == sb->s_dev && inode->i_ino == nr)
goto found_it;
if (!empty) {
h->updating++;
empty = get_empty_inode();
if (!--h->updating)
wake_up(&update_wait);
if (empty)
goto repeat;
return (NULL);
}
inode = empty;
inode->i_sb = sb;
inode->i_dev = sb->s_dev;
inode->i_ino = nr;
inode->i_flags = sb->s_flags;
put_last_free(inode);
insert_inode_hash(inode);
read_inode(inode);
goto return_it;

found_it:
if (!inode->i_count)
nr_free_inodes--;
inode->i_count++;
wait_on_inode(inode);
if (inode->i_dev != sb->s_dev || inode->i_ino != nr) {
printk("Whee.. inode changed from under us. Tell Linus\n");
iput(inode);
goto repeat;
}
if (crossmntp && inode->i_mount) {
struct inode * tmp = inode->i_mount;
tmp->i_count++;
iput(inode);
inode = tmp;
wait_on_inode(inode);
}
if (empty)
iput(empty);

return_it:
while (h->updating)
sleep_on(&update_wait);
return inode;
}

请问其中的update_wait是什么作用？如何起作用的? 谢谢~

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