/**************************************************************************** * fs/fs_inode.c * * Copyright (C) 2007-2009, 2011-2012 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 "fs_internal.h" /**************************************************************************** * Pre-processor Definitions ****************************************************************************/ #define NO_HOLDER (pid_t)-1; /**************************************************************************** * Private Types ****************************************************************************/ /* Implements a re-entrant mutex for inode access. This must be re-entrant * because there can be cycles. For example, it may be necessary to destroy * a block driver inode on umount() after a removable block device has been * removed. In that case umount() hold the inode semaphore, but the block * driver may callback to unregister_blockdriver() after the un-mount, * requiring the seamphore again. */ struct inode_sem_s { sem_t sem; /* The semaphore */ pid_t holder; /* The current holder of the semaphore */ int16_t count; /* Number of counts held */ }; /**************************************************************************** * Private Variables ****************************************************************************/ static struct inode_sem_s g_inode_sem; /**************************************************************************** * Public Variables ****************************************************************************/ FAR struct inode *root_inode = NULL; /**************************************************************************** * Private Functions ****************************************************************************/ /**************************************************************************** * Name: _inode_compare * * Description: * Compare two inode names * ****************************************************************************/ static int _inode_compare(FAR const char *fname, FAR struct inode *node) { char *nname = node->i_name; if (!nname) { return 1; } if (!fname) { return -1; } for (;;) { /* At end of node name? */ if (!*nname) { /* Yes.. also end of find name? */ if (!*fname || *fname == '/') { /* Yes.. return match */ return 0; } else { /* No... return find name > node name */ return 1; } } /* At end of find name?*/ else if (!*fname || *fname == '/') { /* Yes... return find name < node name */ return -1; } /* Check for non-matching characters */ else if (*fname > *nname) { return 1; } else if (*fname < *nname) { return -1; } /* Not at the end of either string and all of the * characters still match. keep looking. */ else { fname++; nname++; } } } /**************************************************************************** * Public Functions ****************************************************************************/ /**************************************************************************** * Name: fs_initialize * * Description: * This is called from the OS initialization logic to configure the file * system. * ****************************************************************************/ void fs_initialize(void) { /* Initialize the semaphore to one (to support one-at- * a-time access to the inode tree). */ (void)sem_init(&g_inode_sem.sem, 0, 1); g_inode_sem.holder = NO_HOLDER; g_inode_sem.count = 0; /* Initialize files array (if it is used) */ #ifdef CONFIG_HAVE_WEAKFUNCTIONS if (files_initialize != NULL) #endif { files_initialize(); } } /**************************************************************************** * Name: inode_semtake * * Description: * Get exclusive access to the in-memory inode tree (g_inode_sem). * ****************************************************************************/ void inode_semtake(void) { pid_t me; /* Do we already hold the semaphore? */ me = getpid(); if (me == g_inode_sem.holder) { /* Yes... just increment the count */ g_inode_sem.count++; DEBUGASSERT(g_inode_sem.count > 0); } /* Take the semaphore (perhaps waiting) */ else { while (sem_wait(&g_inode_sem.sem) != 0) { /* The only case that an error should occr here is if * the wait was awakened by a signal. */ ASSERT(get_errno() == EINTR); } /* No we hold the semaphore */ g_inode_sem.holder = me; g_inode_sem.count = 1; } } /**************************************************************************** * Name: inode_semgive * * Description: * Relinquish exclusive access to the in-memory inode tree (g_inode_sem). * ****************************************************************************/ void inode_semgive(void) { DEBUGASSERT(g_inode_sem.holder == getpid()); /* Is this our last count on the semaphore? */ if (g_inode_sem.count > 1) { /* No.. just decrement the count */ g_inode_sem.count--; } /* Yes.. then we can really release the semaphore */ else { g_inode_sem.holder = NO_HOLDER; g_inode_sem.count = 0; sem_post(&g_inode_sem.sem); } } /**************************************************************************** * Name: inode_search * * Description: * Find the inode associated with 'path' returning the inode references * and references to its companion nodes. * * Assumptions: * The caller holds the g_inode_sem semaphore * ****************************************************************************/ FAR struct inode *inode_search(const char **path, FAR struct inode **peer, FAR struct inode **parent, const char **relpath) { const char *name = *path + 1; /* Skip over leading '/' */ FAR struct inode *node = root_inode; FAR struct inode *left = NULL; FAR struct inode *above = NULL; while (node) { int result = _inode_compare(name, node); /* Case 1: The name is less than the name of the node. * Since the names are ordered, these means that there * is no peer node with this name and that there can be * no match in the fileystem. */ if (result < 0) { node = NULL; break; } /* Case 2: the name is greater than the name of the node. * In this case, the name may still be in the list to the * "right" */ else if (result > 0) { left = node; node = node->i_peer; } /* The names match */ else { /* Now there are three more possibilities: * (1) This is the node that we are looking for or, * (2) The node we are looking for is "below" this one. * (3) This node is a mountpoint and will absorb all request * below this one */ name = inode_nextname(name); if (!*name || INODE_IS_MOUNTPT(node)) { /* Either (1) we are at the end of the path, so this must be the * node we are looking for or else (2) this node is a mountpoint * and will handle the remaining part of the pathname */ if (relpath) { *relpath = name; } break; } else { /* More to go, keep looking at the next level "down" */ above = node; left = NULL; node = node->i_child; } } } /* node is null. This can happen in one of four cases: * With node = NULL * (1) We went left past the final peer: The new node * name is larger than any existing node name at * that level. * (2) We broke out in the middle of the list of peers * because the name was not found in the ordered * list. * (3) We went down past the final parent: The new node * name is "deeper" than anything that we currently * have in the tree. * with node != NULL * (4) When the node matching the full path is found */ if (peer) { *peer = left; } if (parent) { *parent = above; } *path = name; return node; } /**************************************************************************** * Name: inode_free * * Description: * Free resources used by an inode * ****************************************************************************/ void inode_free(FAR struct inode *node) { if (node) { inode_free(node->i_peer); inode_free(node->i_child); kfree(node); } } /**************************************************************************** * Name: inode_nextname * * Description: * Given a path with node names separated by '/', return the next node * name. * ****************************************************************************/ FAR const char *inode_nextname(FAR const char *name) { /* Search for the '/' delimiter or the NUL terminator at the end of the * string. */ while (*name && *name != '/') { name++; } /* If we found the '/' delimiter, then the path segment we want begins at * the next character (which might also be the NUL terminator). */ if (*name) { name++; } return name; }