Root/fs/coda/cache.c

1/*
2 * Cache operations for Coda.
3 * For Linux 2.1: (C) 1997 Carnegie Mellon University
4 * For Linux 2.3: (C) 2000 Carnegie Mellon University
5 *
6 * Carnegie Mellon encourages users of this code to contribute improvements
7 * to the Coda project http://www.coda.cs.cmu.edu/ <coda@cs.cmu.edu>.
8 */
9
10#include <linux/types.h>
11#include <linux/kernel.h>
12#include <linux/time.h>
13#include <linux/fs.h>
14#include <linux/stat.h>
15#include <linux/errno.h>
16#include <asm/uaccess.h>
17#include <linux/string.h>
18#include <linux/list.h>
19#include <linux/sched.h>
20#include <linux/spinlock.h>
21
22#include <linux/coda.h>
23#include <linux/coda_psdev.h>
24#include "coda_linux.h"
25#include "coda_cache.h"
26
27static atomic_t permission_epoch = ATOMIC_INIT(0);
28
29/* replace or extend an acl cache hit */
30void coda_cache_enter(struct inode *inode, int mask)
31{
32    struct coda_inode_info *cii = ITOC(inode);
33
34    spin_lock(&cii->c_lock);
35    cii->c_cached_epoch = atomic_read(&permission_epoch);
36    if (cii->c_uid != current_fsuid()) {
37        cii->c_uid = current_fsuid();
38                cii->c_cached_perm = mask;
39        } else
40                cii->c_cached_perm |= mask;
41    spin_unlock(&cii->c_lock);
42}
43
44/* remove cached acl from an inode */
45void coda_cache_clear_inode(struct inode *inode)
46{
47    struct coda_inode_info *cii = ITOC(inode);
48    spin_lock(&cii->c_lock);
49    cii->c_cached_epoch = atomic_read(&permission_epoch) - 1;
50    spin_unlock(&cii->c_lock);
51}
52
53/* remove all acl caches */
54void coda_cache_clear_all(struct super_block *sb)
55{
56    atomic_inc(&permission_epoch);
57}
58
59
60/* check if the mask has been matched against the acl already */
61int coda_cache_check(struct inode *inode, int mask)
62{
63    struct coda_inode_info *cii = ITOC(inode);
64    int hit;
65    
66    spin_lock(&cii->c_lock);
67    hit = (mask & cii->c_cached_perm) == mask &&
68        cii->c_uid == current_fsuid() &&
69        cii->c_cached_epoch == atomic_read(&permission_epoch);
70    spin_unlock(&cii->c_lock);
71
72    return hit;
73}
74
75
76/* Purging dentries and children */
77/* The following routines drop dentries which are not
78   in use and flag dentries which are in use to be
79   zapped later.
80
81   The flags are detected by:
82   - coda_dentry_revalidate (for lookups) if the flag is C_PURGE
83   - coda_dentry_delete: to remove dentry from the cache when d_count
84     falls to zero
85   - an inode method coda_revalidate (for attributes) if the
86     flag is C_VATTR
87*/
88
89/* this won't do any harm: just flag all children */
90static void coda_flag_children(struct dentry *parent, int flag)
91{
92    struct list_head *child;
93    struct dentry *de;
94
95    spin_lock(&parent->d_lock);
96    list_for_each(child, &parent->d_subdirs)
97    {
98        de = list_entry(child, struct dentry, d_u.d_child);
99        /* don't know what to do with negative dentries */
100        if ( ! de->d_inode )
101            continue;
102        coda_flag_inode(de->d_inode, flag);
103    }
104    spin_unlock(&parent->d_lock);
105    return;
106}
107
108void coda_flag_inode_children(struct inode *inode, int flag)
109{
110    struct dentry *alias_de;
111
112    if ( !inode || !S_ISDIR(inode->i_mode))
113        return;
114
115    alias_de = d_find_alias(inode);
116    if (!alias_de)
117        return;
118    coda_flag_children(alias_de, flag);
119    shrink_dcache_parent(alias_de);
120    dput(alias_de);
121}
122
123

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