/**************************************************************************** * fs/dirent/fs_opendir.c * * Copyright (C) 2007-2009, 2011, 2013-2014, 2017 Gregory Nutt. All rights reserved. * Author: Gregory Nutt * * Redistribution and use in source and binary forms, with or without * modification, are permitted provided that the following conditions * are met: * * 1. Redistributions of source code must retain the above copyright * notice, this list of conditions and the following disclaimer. * 2. Redistributions in binary form must reproduce the above copyright * notice, this list of conditions and the following disclaimer in * the documentation and/or other materials provided with the * distribution. * 3. Neither the name NuttX nor the names of its contributors may be * used to endorse or promote products derived from this software * without specific prior written permission. * * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS * FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE * COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, * BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS * OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED * AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN * ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE * POSSIBILITY OF SUCH DAMAGE. * ****************************************************************************/ /**************************************************************************** * Included Files ****************************************************************************/ #include #include #include #include #include #include #include #include #include #include "inode/inode.h" /**************************************************************************** * Private Functions ****************************************************************************/ /**************************************************************************** * Name: open_mountpoint * * Description: * Handle the case where the inode to be opened is within a mountpoint. * * Inputs: * inode -- the inode of the mountpoint to open * relpath -- the relative path within the mountpoint to open * dir -- the dirent structure to be initialized * * Return: * On success, OK is returned; Otherwise, a positive errno is returned. * ****************************************************************************/ #ifndef CONFIG_DISABLE_MOUNTPOINT static inline int open_mountpoint(FAR struct inode *inode, FAR const char *relpath, FAR struct fs_dirent_s *dir) { int ret; /* The inode itself as the 'root' of mounted volume. The actually * directory is at relpath into the* mounted filesystem. * * Verify that the mountpoint inode supports the opendir() method */ if (!inode->u.i_mops || !inode->u.i_mops->opendir) { return ENOSYS; } /* Take reference to the mountpoint inode. Note that we do not use * inode_addref() because we already hold the tree semaphore. */ inode->i_crefs++; /* Perform the opendir() operation */ ret = inode->u.i_mops->opendir(inode, relpath, dir); if (ret < 0) { /* We now need to back off our reference to the inode. We can't * call inode_release() to do that unless we release the tree * semaphore. The following should be safe because: (1) after the * reference count was incremented above it should be >=1 so it should * not decrement below zero, and (2) we hold the tree semaphore so no * other thread should be able to change the reference count. */ inode->i_crefs--; DEBUGASSERT(inode->i_crefs >= 0); /* Negate the error value so that it can be used to set errno */ return -ret; } return OK; } #endif /**************************************************************************** * Name: open_pseudodir * * Description: * Handle the case where the inode to be opened is within the top-level * pseudo-file system. * * Inputs: * inode -- the inode of the mountpoint to open * dir -- the dirent structure to be initialized * * Return: * None * ****************************************************************************/ static void open_pseudodir(FAR struct inode *inode, FAR struct fs_dirent_s *dir) { /* We have a valid pseudo-filesystem node. Take two references on the * inode -- one for the parent (fd_root) and one for the child (fd_next). * Note that we do not call inode_addref because we are holding the tree * semaphore and that would result in deadlock. */ inode->i_crefs += 2; dir->fd_root = inode; /* Save the inode where we start */ dir->u.pseudo.fd_next = inode; /* This is the next node to use for readdir() */ /* Flag the inode as belonging to the pseudo-filesystem */ #ifndef CONFIG_DISABLE_MOUNTPOINT DIRENT_SETPSEUDONODE(dir->fd_flags); #endif } /**************************************************************************** * Name: open_emptydir * * Description: * Handle the case where the inode to be opened is an empty, directory node * within the top-level pseudo-file system. That is, it has no operations * and, therefore, it must be a directory node. But is has no children * to be enumerated either. * * Inputs: * dir -- the dirent structure to be initialized * * Return: * None * ****************************************************************************/ static inline void open_emptydir(FAR struct fs_dirent_s *dir) { /* We have a valid, but empty pseudo-filesystem node. fd_next is NULL * meaning that we are already at the end of the list of its children. * fd_root is NULL so that if the directory is rewound, it will still be * at the end of the list. */ #if 0 /* Already nullified by kumm_zalloc */ dir->fd_root = NULL; /* Save the inode where we start */ dir->u.pseudo.fd_next = NULL; /* We are at the end of the list */ #endif /* Flag the inode as belonging to the pseudo-filesystem */ #ifndef CONFIG_DISABLE_MOUNTPOINT DIRENT_SETPSEUDONODE(dir->fd_flags); #endif } /**************************************************************************** * Public Functions ****************************************************************************/ /**************************************************************************** * Name: opendir * * Description: * The opendir() function opens a directory stream corresponding to the * directory name, and returns a pointer to the directory stream. The * stream is positioned at the first entry in the directory. * * Inputs: * path -- the directory to open * * Return: * The opendir() function returns a pointer to the directory stream. On * error, NULL is returned, and errno is set appropriately. * * EACCES - Permission denied. * EMFILE - Too many file descriptors in use by process. * ENFILE - Too many files are currently open in the * system. * ENOENT - Directory does not exist, or name is an empty * string. * ENOMEM - Insufficient memory to complete the operation. * ENOTDIR - 'path' is not a directory. * ****************************************************************************/ FAR DIR *opendir(FAR const char *path) { FAR struct inode *inode = NULL; FAR struct fs_dirent_s *dir; struct inode_search_s desc; #ifndef CONFIG_DISABLE_MOUNTPOINT FAR const char *relpath = NULL; #endif bool isroot = false; int ret; /* If we are given 'nothing' then we will interpret this as * request for the root inode. */ SETUP_SEARCH(&desc, path, false); inode_semtake(); if (path == NULL || *path == '\0' || strcmp(path, "/") == 0) { inode = g_root_inode; isroot = true; } else { /* We don't know what to do with relative pathes */ if (*path != '/') { ret = -ENOTDIR; goto errout_with_semaphore; } /* Find the node matching the path. */ ret = inode_search(&desc); if (ret >= 0) { inode = desc.node; DEBUGASSERT(inode != NULL); #ifndef CONFIG_DISABLE_MOUNTPOINT relpath = desc.relpath; #endif } } /* Did we get an inode? */ if (inode == NULL) { /* Inode for 'path' does not exist. */ ret = ENOTDIR; goto errout_with_semaphore; } /* Allocate a type DIR -- which is little more than an inode * container. */ dir = (FAR struct fs_dirent_s *)kumm_zalloc(sizeof(struct fs_dirent_s)); if (!dir) { /* Insufficient memory to complete the operation. */ ret = ENOMEM; goto errout_with_semaphore; } /* Populate the DIR structure and return it to the caller. The way that * we do this depends on whenever this is a "normal" pseudo-file-system * inode or a file system mountpoint. */ dir->fd_position = 0; /* This is the position in the read stream */ /* First, handle the special case of the root inode. This must be * special-cased here because the root inode might ALSO be a mountpoint. */ if (isroot) { /* Whatever payload the root inode carries, the root inode is always * a directory inode in the pseudo-file system */ open_pseudodir(inode, dir); } /* Is this a node in the pseudo filesystem? Or a mountpoint? If the node * is the root (isroot == TRUE), then this is a special case. */ #ifndef CONFIG_DISABLE_MOUNTPOINT else if (INODE_IS_MOUNTPT(inode)) { /* Yes, the node is a file system mountpoint */ dir->fd_root = inode; /* Save the inode where we start */ /* Open the directory at the relative path */ ret = open_mountpoint(inode, relpath, dir); if (ret != OK) { goto errout_with_direntry; } } #endif else { /* The node is part of the root pseudo file system. Does the inode * have a child? If so that the child would be the 'root' of a list * of nodes under the directory. */ FAR struct inode *child = inode->i_child; if (child != NULL) { /* It looks we have a valid pseudo-filesystem directory node. */ open_pseudodir(child, dir); } else if (!inode->u.i_ops) { /* This is a dangling node with no children and no operations. Set * up to enumerate an empty directory. */ open_emptydir(dir); } else { ret = ENOTDIR; goto errout_with_direntry; } } RELEASE_SEARCH(&desc); inode_semgive(); return ((FAR DIR *)dir); /* Nasty goto's make error handling simpler */ errout_with_direntry: kumm_free(dir); errout_with_semaphore: RELEASE_SEARCH(&desc); inode_semgive(); set_errno(ret); return NULL; }