diff options
Diffstat (limited to 'fs/namei.c')
| -rw-r--r-- | fs/namei.c | 114 |
1 files changed, 84 insertions, 30 deletions
@@ -179,19 +179,14 @@ static int check_acl(struct inode *inode, int mask) #ifdef CONFIG_FS_POSIX_ACL struct posix_acl *acl; - /* - * Under RCU walk, we cannot even do a "get_cached_acl()", - * because that involves locking and getting a refcount on - * a cached ACL. - * - * So the only case we handle during RCU walking is the - * case of a cached "no ACL at all", which needs no locks - * or refcounts. - */ if (mask & MAY_NOT_BLOCK) { - if (negative_cached_acl(inode, ACL_TYPE_ACCESS)) + acl = get_cached_acl_rcu(inode, ACL_TYPE_ACCESS); + if (!acl) return -EAGAIN; - return -ECHILD; + /* no ->get_acl() calls in RCU mode... */ + if (acl == ACL_NOT_CACHED) + return -ECHILD; + return posix_acl_permission(inode, acl, mask & ~MAY_NOT_BLOCK); } acl = get_cached_acl(inode, ACL_TYPE_ACCESS); @@ -313,6 +308,26 @@ int generic_permission(struct inode *inode, int mask) return -EACCES; } +/* + * We _really_ want to just do "generic_permission()" without + * even looking at the inode->i_op values. So we keep a cache + * flag in inode->i_opflags, that says "this has not special + * permission function, use the fast case". + */ +static inline int do_inode_permission(struct inode *inode, int mask) +{ + if (unlikely(!(inode->i_opflags & IOP_FASTPERM))) { + if (likely(inode->i_op->permission)) + return inode->i_op->permission(inode, mask); + + /* This gets set once for the inode lifetime */ + spin_lock(&inode->i_lock); + inode->i_opflags |= IOP_FASTPERM; + spin_unlock(&inode->i_lock); + } + return generic_permission(inode, mask); +} + /** * inode_permission - check for access rights to a given inode * @inode: inode to check permission on @@ -327,7 +342,7 @@ int inode_permission(struct inode *inode, int mask) { int retval; - if (mask & MAY_WRITE) { + if (unlikely(mask & MAY_WRITE)) { umode_t mode = inode->i_mode; /* @@ -344,11 +359,7 @@ int inode_permission(struct inode *inode, int mask) return -EACCES; } - if (inode->i_op->permission) - retval = inode->i_op->permission(inode, mask); - else - retval = generic_permission(inode, mask); - + retval = do_inode_permission(inode, mask); if (retval) return retval; @@ -716,17 +727,20 @@ static int follow_automount(struct path *path, unsigned flags, if ((flags & LOOKUP_NO_AUTOMOUNT) && !(flags & LOOKUP_PARENT)) return -EISDIR; /* we actually want to stop here */ - /* We want to mount if someone is trying to open/create a file of any - * type under the mountpoint, wants to traverse through the mountpoint - * or wants to open the mounted directory. + /* We don't want to mount if someone's just doing a stat - + * unless they're stat'ing a directory and appended a '/' to + * the name. * - * We don't want to mount if someone's just doing a stat and they've - * set AT_SYMLINK_NOFOLLOW - unless they're stat'ing a directory and - * appended a '/' to the name. + * We do, however, want to mount if someone wants to open or + * create a file of any type under the mountpoint, wants to + * traverse through the mountpoint or wants to open the + * mounted directory. Also, autofs may mark negative dentries + * as being automount points. These will need the attentions + * of the daemon to instantiate them before they can be used. */ - if (!(flags & LOOKUP_FOLLOW) && - !(flags & (LOOKUP_PARENT | LOOKUP_DIRECTORY | - LOOKUP_OPEN | LOOKUP_CREATE))) + if (!(flags & (LOOKUP_PARENT | LOOKUP_DIRECTORY | + LOOKUP_OPEN | LOOKUP_CREATE)) && + path->dentry->d_inode) return -EISDIR; current->total_link_count++; @@ -1244,6 +1258,26 @@ static void terminate_walk(struct nameidata *nd) } } +/* + * Do we need to follow links? We _really_ want to be able + * to do this check without having to look at inode->i_op, + * so we keep a cache of "no, this doesn't need follow_link" + * for the common case. + */ +static inline int should_follow_link(struct inode *inode, int follow) +{ + if (unlikely(!(inode->i_opflags & IOP_NOFOLLOW))) { + if (likely(inode->i_op->follow_link)) + return follow; + + /* This gets set once for the inode lifetime */ + spin_lock(&inode->i_lock); + inode->i_opflags |= IOP_NOFOLLOW; + spin_unlock(&inode->i_lock); + } + return 0; +} + static inline int walk_component(struct nameidata *nd, struct path *path, struct qstr *name, int type, int follow) { @@ -1266,7 +1300,7 @@ static inline int walk_component(struct nameidata *nd, struct path *path, terminate_walk(nd); return -ENOENT; } - if (unlikely(inode->i_op->follow_link) && follow) { + if (should_follow_link(inode, follow)) { if (nd->flags & LOOKUP_RCU) { if (unlikely(unlazy_walk(nd, path->dentry))) { terminate_walk(nd); @@ -1319,6 +1353,26 @@ static inline int nested_symlink(struct path *path, struct nameidata *nd) } /* + * We really don't want to look at inode->i_op->lookup + * when we don't have to. So we keep a cache bit in + * the inode ->i_opflags field that says "yes, we can + * do lookup on this inode". + */ +static inline int can_lookup(struct inode *inode) +{ + if (likely(inode->i_opflags & IOP_LOOKUP)) + return 1; + if (likely(!inode->i_op->lookup)) + return 0; + + /* We do this once for the lifetime of the inode */ + spin_lock(&inode->i_lock); + inode->i_opflags |= IOP_LOOKUP; + spin_unlock(&inode->i_lock); + return 1; +} + +/* * Name resolution. * This is the basic name resolution function, turning a pathname into * the final dentry. We expect 'base' to be positive and a directory. @@ -1397,10 +1451,10 @@ static int link_path_walk(const char *name, struct nameidata *nd) if (err) return err; } + if (can_lookup(nd->inode)) + continue; err = -ENOTDIR; - if (!nd->inode->i_op->lookup) - break; - continue; + break; /* here ends the main loop */ last_component: |