fs/coda/cache.c

   1 // SPDX-License-Identifier: GPL-2.0
   2 /*
   3  * Cache operations for Coda.
   4  * For Linux 2.1: (C) 1997 Carnegie Mellon University
   5  * For Linux 2.3: (C) 2000 Carnegie Mellon University
   6  *
   7  * Carnegie Mellon encourages users of this code to contribute improvements
   8  * to the Coda project http://www.coda.cs.cmu.edu/ <coda@cs.cmu.edu>.
   9  */
  10
  11 #include <linux/types.h>
  12 #include <linux/kernel.h>
  13 #include <linux/time.h>
  14 #include <linux/fs.h>
  15 #include <linux/stat.h>
  16 #include <linux/errno.h>
  17 #include <linux/uaccess.h>
  18 #include <linux/string.h>
  19 #include <linux/list.h>
  20 #include <linux/sched.h>
  21 #include <linux/spinlock.h>
  22
  23 #include <linux/coda.h>
  24 #include "coda_psdev.h"
  25 #include "coda_linux.h"
  26 #include "coda_cache.h"
  27
  28 static atomic_t permission_epoch = ATOMIC_INIT(0);
  29
  30 /* replace or extend an acl cache hit */
  31 void coda_cache_enter(struct inode *inode, int mask)
  32 {
  33         struct coda_inode_info *cii = ITOC(inode);
  34
  35         spin_lock(&cii->c_lock);
  36         cii->c_cached_epoch = atomic_read(&permission_epoch);
  37         if (!uid_eq(cii->c_uid, current_fsuid())) {
  38                 cii->c_uid = current_fsuid();
  39                 cii->c_cached_perm = mask;
  40         } else
  41                 cii->c_cached_perm |= mask;
  42         spin_unlock(&cii->c_lock);
  43 }
  44
  45 /* remove cached acl from an inode */
  46 void coda_cache_clear_inode(struct inode *inode)
  47 {
  48         struct coda_inode_info *cii = ITOC(inode);
  49         spin_lock(&cii->c_lock);
  50         cii->c_cached_epoch = atomic_read(&permission_epoch) - 1;
  51         spin_unlock(&cii->c_lock);
  52 }
  53
  54 /* remove all acl caches */
  55 void coda_cache_clear_all(struct super_block *sb)
  56 {
  57         atomic_inc(&permission_epoch);
  58 }
  59
  60
  61 /* check if the mask has been matched against the acl already */
  62 int coda_cache_check(struct inode *inode, int mask)
  63 {
  64         struct coda_inode_info *cii = ITOC(inode);
  65         int hit;
  66
  67         spin_lock(&cii->c_lock);
  68         hit = (mask & cii->c_cached_perm) == mask &&
  69             uid_eq(cii->c_uid, current_fsuid()) &&
  70             cii->c_cached_epoch == atomic_read(&permission_epoch);
  71         spin_unlock(&cii->c_lock);
  72
  73         return hit;
  74 }
  75
  76
  77 /* Purging dentries and children */
  78 /* The following routines drop dentries which are not
  79    in use and flag dentries which are in use to be
  80    zapped later.
  81
  82    The flags are detected by:
  83    - coda_dentry_revalidate (for lookups) if the flag is C_PURGE
  84    - coda_dentry_delete: to remove dentry from the cache when d_count
  85      falls to zero
  86    - an inode method coda_revalidate (for attributes) if the
  87      flag is C_VATTR
  88 */
  89
  90 /* this won't do any harm: just flag all children */
  91 static void coda_flag_children(struct dentry *parent, int flag)
  92 {
  93         struct dentry *de;
  94
  95         spin_lock(&parent->d_lock);
  96         list_for_each_entry(de, &parent->d_subdirs, d_child) {
  97                 /* don't know what to do with negative dentries */
  98                 if (d_inode(de) )
  99                         coda_flag_inode(d_inode(de), flag);
 100         }
 101         spin_unlock(&parent->d_lock);
 102         return;
 103 }
 104
 105 void coda_flag_inode_children(struct inode *inode, int flag)
 106 {
 107         struct dentry *alias_de;
 108
 109         if ( !inode || !S_ISDIR(inode->i_mode))
 110                 return;
 111
 112         alias_de = d_find_alias(inode);
 113         if (!alias_de)
 114                 return;
 115         coda_flag_children(alias_de, flag);
 116         shrink_dcache_parent(alias_de);
 117         dput(alias_de);
 118 }
 119