mirror of
https://github.com/torvalds/linux
synced 2024-11-05 18:23:50 +00:00
b5ce1d83a6
We mostly need it to protect cached user permissions. The c_flags field is advisory, reading the wrong value is harmless and in the worst case we hit a slow path where we have to make an extra upcall to the userspace cache manager when revalidating a dentry or inode. Signed-off-by: Yoshihisa Abe <yoshiabe@cs.cmu.edu> Signed-off-by: Jan Harkes <jaharkes@cs.cmu.edu> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
123 lines
3.1 KiB
C
123 lines
3.1 KiB
C
/*
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* Cache operations for Coda.
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* For Linux 2.1: (C) 1997 Carnegie Mellon University
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* For Linux 2.3: (C) 2000 Carnegie Mellon University
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*
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* Carnegie Mellon encourages users of this code to contribute improvements
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* to the Coda project http://www.coda.cs.cmu.edu/ <coda@cs.cmu.edu>.
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*/
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#include <linux/types.h>
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#include <linux/kernel.h>
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#include <linux/time.h>
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#include <linux/fs.h>
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#include <linux/stat.h>
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#include <linux/errno.h>
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#include <asm/uaccess.h>
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#include <linux/string.h>
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#include <linux/list.h>
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#include <linux/sched.h>
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#include <linux/spinlock.h>
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#include <linux/coda.h>
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#include <linux/coda_linux.h>
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#include <linux/coda_psdev.h>
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#include <linux/coda_fs_i.h>
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#include <linux/coda_cache.h>
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static atomic_t permission_epoch = ATOMIC_INIT(0);
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/* replace or extend an acl cache hit */
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void coda_cache_enter(struct inode *inode, int mask)
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{
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struct coda_inode_info *cii = ITOC(inode);
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spin_lock(&cii->c_lock);
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cii->c_cached_epoch = atomic_read(&permission_epoch);
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if (cii->c_uid != current_fsuid()) {
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cii->c_uid = current_fsuid();
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cii->c_cached_perm = mask;
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} else
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cii->c_cached_perm |= mask;
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spin_unlock(&cii->c_lock);
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}
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/* remove cached acl from an inode */
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void coda_cache_clear_inode(struct inode *inode)
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{
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struct coda_inode_info *cii = ITOC(inode);
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spin_lock(&cii->c_lock);
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cii->c_cached_epoch = atomic_read(&permission_epoch) - 1;
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spin_unlock(&cii->c_lock);
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}
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/* remove all acl caches */
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void coda_cache_clear_all(struct super_block *sb)
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{
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atomic_inc(&permission_epoch);
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}
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/* check if the mask has been matched against the acl already */
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int coda_cache_check(struct inode *inode, int mask)
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{
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struct coda_inode_info *cii = ITOC(inode);
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int hit;
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spin_lock(&cii->c_lock);
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hit = (mask & cii->c_cached_perm) == mask &&
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cii->c_uid == current_fsuid() &&
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cii->c_cached_epoch == atomic_read(&permission_epoch);
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spin_unlock(&cii->c_lock);
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return hit;
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}
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/* Purging dentries and children */
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/* The following routines drop dentries which are not
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in use and flag dentries which are in use to be
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zapped later.
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The flags are detected by:
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- coda_dentry_revalidate (for lookups) if the flag is C_PURGE
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- coda_dentry_delete: to remove dentry from the cache when d_count
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falls to zero
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- an inode method coda_revalidate (for attributes) if the
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flag is C_VATTR
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*/
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/* this won't do any harm: just flag all children */
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static void coda_flag_children(struct dentry *parent, int flag)
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{
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struct list_head *child;
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struct dentry *de;
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spin_lock(&dcache_lock);
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list_for_each(child, &parent->d_subdirs)
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{
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de = list_entry(child, struct dentry, d_u.d_child);
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/* don't know what to do with negative dentries */
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if ( ! de->d_inode )
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continue;
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coda_flag_inode(de->d_inode, flag);
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}
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spin_unlock(&dcache_lock);
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return;
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}
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void coda_flag_inode_children(struct inode *inode, int flag)
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{
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struct dentry *alias_de;
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if ( !inode || !S_ISDIR(inode->i_mode))
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return;
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alias_de = d_find_alias(inode);
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if (!alias_de)
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return;
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coda_flag_children(alias_de, flag);
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shrink_dcache_parent(alias_de);
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dput(alias_de);
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}
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