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
  21 #include <linux/coda.h>
  22 #include <linux/coda_linux.h>
  23 #include <linux/coda_psdev.h>
  24 #include <linux/coda_fs_i.h>
  25 #include <linux/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         cii->c_cached_epoch = atomic_read(&permission_epoch);
  35         if (cii->c_uid != current_fsuid()) {
  36                 cii->c_uid = current_fsuid();
  37                 cii->c_cached_perm = mask;
  38         } else
  39                 cii->c_cached_perm |= mask;
  40 }
  41
  42 /* remove cached acl from an inode */
  43 void coda_cache_clear_inode(struct inode *inode)
  44 {
  45         struct coda_inode_info *cii = ITOC(inode);
  46         cii->c_cached_epoch = atomic_read(&permission_epoch) - 1;
  47 }
  48
  49 /* remove all acl caches */
  50 void coda_cache_clear_all(struct super_block *sb)
  51 {
  52         atomic_inc(&permission_epoch);
  53 }
  54
  55
  56 /* check if the mask has been matched against the acl already */
  57 int coda_cache_check(struct inode *inode, int mask)
  58 {
  59         struct coda_inode_info *cii = ITOC(inode);
  60         int hit;
  61
  62         hit = (mask & cii->c_cached_perm) == mask &&
  63                 cii->c_uid == current_fsuid() &&
  64                 cii->c_cached_epoch == atomic_read(&permission_epoch);
  65
  66         return hit;
  67 }
  68
  69
  70 /* Purging dentries and children */
  71 /* The following routines drop dentries which are not
  72    in use and flag dentries which are in use to be
  73    zapped later.
  74
  75    The flags are detected by:
  76    - coda_dentry_revalidate (for lookups) if the flag is C_PURGE
  77    - coda_dentry_delete: to remove dentry from the cache when d_count
  78      falls to zero
  79    - an inode method coda_revalidate (for attributes) if the
  80      flag is C_VATTR
  81 */
  82
  83 /* this won't do any harm: just flag all children */
  84 static void coda_flag_children(struct dentry *parent, int flag)
  85 {
  86         struct list_head *child;
  87         struct dentry *de;
  88
  89         spin_lock(&dcache_lock);
  90         list_for_each(child, &parent->d_subdirs)
  91         {
  92                 de = list_entry(child, struct dentry, d_u.d_child);
  93                 /* don't know what to do with negative dentries */
  94                 if ( ! de->d_inode )
  95                         continue;
  96                 coda_flag_inode(de->d_inode, flag);
  97         }
  98         spin_unlock(&dcache_lock);
  99         return;
 100 }
 101
 102 void coda_flag_inode_children(struct inode *inode, int flag)
 103 {
 104         struct dentry *alias_de;
 105
 106         if ( !inode || !S_ISDIR(inode->i_mode))
 107                 return;
 108
 109         alias_de = d_find_alias(inode);
 110         if (!alias_de)
 111                 return;
 112         coda_flag_children(alias_de, flag);
 113         shrink_dcache_parent(alias_de);
 114         dput(alias_de);
 115 }
 116