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nuttx/fs/inode/fs_inodesearch.c

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/****************************************************************************
* fs/inode/fs_inodesearch.c
*
* Copyright (C) 2007-2009, 2011-2012, 2016-2017 Gregory Nutt. All rights reserved.
* Author: Gregory Nutt <gnutt@nuttx.org>
*
* 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 <nuttx/config.h>
#include <limits.h>
#include <string.h>
#include <assert.h>
#include <errno.h>
#include <nuttx/fs/fs.h>
#include "inode/inode.h"
/****************************************************************************
* Public Data
****************************************************************************/
FAR struct inode *g_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++;
}
}
}
/****************************************************************************
* Name: inode_linktarget
*
* Description:
* If the inode is a soft link, then (1) get the name of the full path of
* the soft link, (2) recursively look-up the inode referenced by the soft
* link, and (3) return the inode referenced by the soft link.
*
* Assumptions:
* The caller holds the g_inode_sem semaphore
*
****************************************************************************/
#ifdef CONFIG_PSEUDOFS_SOFTLINKS
static int inode_linktarget(FAR struct inode *node,
FAR struct inode_search_s *desc)
{
unsigned int count = 0;
int ret = -ENOENT;
DEBUGASSERT(desc != NULL && node != NULL);
/* An infinite loop is avoided only by the loop count.
*
* REVISIT: The ELOOP error should be reported to the application in that
* case but there is no simple mechanism to do that.
*/
while (INODE_IS_SOFTLINK(node))
{
/* Now, look-up the inode associated with the target path */
memset(desc, 0, sizeof(struct inode_search_s));
desc->path = (FAR const char *)node->u.i_link;
/* Look up the target of the symbolic link */
ret = inode_search_nofollow(desc);
if (ret < 0)
{
break;
}
/* Limit the number of symbolic links that we pass through */
if (++count > SYMLOOP_MAX)
{
ret = -ELOOP;
break;
}
/* Set up for the next time through the loop */
node = desc->node;
}
return ret;
}
#endif
/****************************************************************************
* Public Functions
****************************************************************************/
/****************************************************************************
* Name: inode_search and inode_search_nofollow
*
* Description:
* Find the inode associated with 'path' returning the inode references
* and references to its companion nodes.
*
* Both versions will follow soft links in path leading up to the terminal
* node. inode_search() will deference that terminal node,
* inode_search_nofollow will not.
*
* If a soft link is encountered that is not the terminal node in the path,
* that that WILL be deferenced and the mountpoint inode will be returned.
*
* Assumptions:
* The caller holds the g_inode_sem semaphore
*
****************************************************************************/
#ifdef CONFIG_PSEUDOFS_SOFTLINKS
int inode_search_nofollow(FAR struct inode_search_s *desc)
#else
int inode_search(FAR struct inode_search_s *desc)
#endif
{
FAR const char *name;
FAR struct inode *node = g_root_inode;
FAR struct inode *left = NULL;
FAR struct inode *above = NULL;
FAR const char *relpath = NULL;
int ret = -ENOENT;
/* Get the search path, skipping over the leading '/'. The leading '/' is
* mandatory because only absolte paths are expected in this context.
*/
DEBUGASSERT(desc != NULL && desc->path != NULL);
name = desc->path;
DEBUGASSERT(*name == '/');
if (*name != '/')
{
return -EINVAL;
}
name++; /* Skip over the leading '/' */
/* Traverse the pseudo file system node tree until either (1) all nodes
* have been examined without finding the matching node, or (2) the
* matching node is found.
*/
while (node != NULL)
{
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)
{
/* Continue looking to the "right" of this inode. */
left = node;
node = node->i_peer;
}
/* The names match */
else
{
/* Now there are three remaining possibilities:
* (1) This is the node that we are looking for.
* (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 == '\0' || 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
*/
relpath = name;
#ifdef CONFIG_PSEUDOFS_SOFTLINKS
/* NOTE that if the terminal inode is a soft link, it is not
* deferenced in this case. The raw inode is returned.
*
* In that case a wrapper function will perform that operation.
*/
#endif
ret = OK;
break;
}
else
{
/* More nodes to be examined in the path "below" this one. */
#ifdef CONFIG_PSEUDOFS_SOFTLINKS
/* Was the node a soft link? If so, then we need need to
* continue below the target of the link, not the link itself.
*/
if (INODE_IS_SOFTLINK(node))
{
int status;
/* If this intermediate inode in the is a soft link, then
* (1) get the name of the full path of the soft link, (2)
* recursively look-up the inode referenced by the soft
* link, and (3) continue searching with that inode instead.
*/
status = inode_linktarget(node, desc);
if (status < 0)
{
/* Probably means that the the target of the symbolic
* link does not exist.
*/
ret = status;
break;
}
else
{
FAR struct inode *newnode = desc->node;
if (newnode != node)
{
/* The node was a valid symbolic link and we have
* jumped to a different, spot in the the pseudo
* file system tree.
*
* Continue from this new inode.
*/
node = newnode;
/* Check if this took us to a mountpoint. */
if (INODE_IS_MOUNTPT(node))
{
/* Yes.. return the mountpoint information.
* REVISIT: The relpath is incorrect in this case.
* It is relative to symbolic link, not to the
* root of the mount.
*/
relpath = name;
above = NULL;
left = NULL;
ret = OK;
break;
}
}
}
}
#endif
/* 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
*/
desc->path = name;
desc->node = node;
desc->peer = left;
desc->parent = above;
desc->relpath = relpath;
return ret;
}
#ifdef CONFIG_PSEUDOFS_SOFTLINKS
int inode_search(FAR struct inode_search_s *desc)
{
int ret;
/* Lookup the terminal inode */
ret = inode_search_nofollow(desc);
/* Did we find it? inode_search_nofollow() will terminate in one of
* three ways:
*
* 1. With an error (node == NULL)
* 2. With node referring to the terminal inode which may be a symbolic
* link, or
* 3. with node referring to an intermediate MOUNTPOINT inode with the
* residual path in relpath.
*
* REVISIT: The relpath is incorrect in the final case. It will be relative
* to symbolic link, not to the root of the mount.
*/
if (ret >= 0)
{
/* Sucessfully found inode */
FAR struct inode *node = desc->node;
DEBUGASSERT(node != NULL);
/* Is the terminal node a softlink? */
if (INODE_IS_SOFTLINK(node))
{
/* The terminating inode is a valid soft link: Return the inode,
* corresponding to link target.
*/
ret = inode_linktarget(node, desc);
}
}
return ret;
}
#endif
/****************************************************************************
* Name: inode_nextname
*
* Description:
* Given a path with node names separated by '/', return the next path
* segment name.
*
****************************************************************************/
FAR const char *inode_nextname(FAR const char *name)
{
/* Search for the '/' delimiter or the NUL terminator at the end of the
* path segment.
*/
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;
}
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