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
  27 static atomic_t permission_epoch = ATOMIC_INIT(0);
  28
  29 /* replace or extend an acl cache hit */
  30 void 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 */
  45 void 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 */
  54 void 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 */
  61 int 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 */
  90 static 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
 108 void 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