161 lines
4.6 KiB
C
161 lines
4.6 KiB
C
/****************************************************************************
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* fs/inode/fs_inode.c
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*
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* Licensed to the Apache Software Foundation (ASF) under one or more
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* contributor license agreements. See the NOTICE file distributed with
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* this work for additional information regarding copyright ownership. The
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* ASF licenses this file to you under the Apache License, Version 2.0 (the
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* "License"); you may not use this file except in compliance with the
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* License. You may obtain a copy of the License at
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*
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* http://www.apache.org/licenses/LICENSE-2.0
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*
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* Unless required by applicable law or agreed to in writing, software
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* distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
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* WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
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* License for the specific language governing permissions and limitations
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* under the License.
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*
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****************************************************************************/
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/****************************************************************************
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* Included Files
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****************************************************************************/
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#include <nuttx/config.h>
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#include <unistd.h>
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#include <assert.h>
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#include <errno.h>
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#include <nuttx/fs/fs.h>
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#include <nuttx/semaphore.h>
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#include "inode/inode.h"
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/****************************************************************************
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* Pre-processor Definitions
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****************************************************************************/
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#define NO_HOLDER (INVALID_PROCESS_ID)
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/****************************************************************************
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* Private Types
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****************************************************************************/
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/* Implements a re-entrant mutex for inode access. This must be re-entrant
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* because there can be cycles. For example, it may be necessary to destroy
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* a block driver inode on umount() after a removable block device has been
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* removed. In that case umount() holds the inode semaphore, but the block
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* driver may callback to unregister_blockdriver() after the un-mount,
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* requiring the semaphore again.
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*/
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struct inode_sem_s
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{
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sem_t sem; /* The semaphore */
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pid_t holder; /* The current holder of the semaphore */
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int16_t count; /* Number of counts held */
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};
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/****************************************************************************
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* Private Data
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****************************************************************************/
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static struct inode_sem_s g_inode_sem =
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{
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SEM_INITIALIZER(1), NO_HOLDER, 0
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};
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/****************************************************************************
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* Public Functions
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****************************************************************************/
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/****************************************************************************
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* Name: inode_initialize
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*
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* Description:
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* This is called from the OS initialization logic to configure the file
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* system.
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*
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****************************************************************************/
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void inode_initialize(void)
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{
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/* Reserve the root node */
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inode_root_reserve();
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}
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/****************************************************************************
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* Name: inode_semtake
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*
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* Description:
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* Get exclusive access to the in-memory inode tree (g_inode_sem).
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*
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****************************************************************************/
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int inode_semtake(void)
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{
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pid_t me;
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int ret = OK;
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/* Do we already hold the semaphore? */
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me = getpid();
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if (me == g_inode_sem.holder)
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{
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/* Yes... just increment the count */
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g_inode_sem.count++;
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DEBUGASSERT(g_inode_sem.count > 0);
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}
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/* Take the semaphore (perhaps waiting) */
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else
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{
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ret = nxsem_wait_uninterruptible(&g_inode_sem.sem);
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if (ret >= 0)
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{
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/* No we hold the semaphore */
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g_inode_sem.holder = me;
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g_inode_sem.count = 1;
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}
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}
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return ret;
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}
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/****************************************************************************
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* Name: inode_semgive
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*
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* Description:
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* Relinquish exclusive access to the in-memory inode tree (g_inode_sem).
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*
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****************************************************************************/
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void inode_semgive(void)
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{
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DEBUGASSERT(g_inode_sem.holder == getpid());
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/* Is this our last count on the semaphore? */
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if (g_inode_sem.count > 1)
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{
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/* No.. just decrement the count */
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g_inode_sem.count--;
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}
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/* Yes.. then we can really release the semaphore */
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else
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{
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g_inode_sem.holder = NO_HOLDER;
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g_inode_sem.count = 0;
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nxsem_post(&g_inode_sem.sem);
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}
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}
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