src/cache_inode/cache_inode_readlink.c

/*
 * Copyright CEA/DAM/DIF  (2008)
 * contributeur : Philippe DENIEL   philippe.deniel@cea.fr
 *                Thomas LEIBOVICI  thomas.leibovici@cea.fr
 *
 *
 * This program is free software; you can redistribute it and/or
 * modify it under the terms of the GNU Lesser General Public
 * License as published by the Free Software Foundation; either
 * version 3 of the License, or (at your option) any later version.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
 * Lesser General Public License for more details.
 *
 * You should have received a copy of the GNU Lesser General Public
 * License along with this library; if not, write to the Free Software
 * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA
 * 02110-1301 USA
 *
 * ---------------------------------------
 */

/**
 * @addtogroup cache_inode
 * @{
 */

/**
 * @file    cache_inode_readlink.c
 * @brief   Reads a symlink.
 */

#include "config.h"
#include "abstract_atomic.h"
#include "log.h"
#include "hashtable.h"
#include "fsal.h"
#include "cache_inode.h"

#include <unistd.h>
#include <sys/types.h>
#include <sys/param.h>
#include <time.h>
#include <pthread.h>
#include <assert.h>

/**
 * @brief Read the target of a symlink
 *
 * Call the FSAL to allocate a buffer and pass back the contents of
 * the symbolic link.  The buffer must be allocated with gsh_malloc
 * and freed by the core.
 *
 * @param[in]  entry        The link to read
 * @param[out] link_content The location into which to write the
 *                          target
 *
 * @return CACHE_INODE_SUCCESS on success, other things on failure.
 */

cache_inode_status_t
cache_inode_readlink(cache_entry_t *entry,
		     struct gsh_buffdesc *link_content)
{
	cache_inode_status_t status = CACHE_INODE_SUCCESS;
	fsal_status_t fsal_status = { ERR_FSAL_NO_ERROR, 0 };
	bool refresh = false;

	if (entry->type != SYMBOLIC_LINK) {
		status = CACHE_INODE_BAD_TYPE;
		return status;
	}

	PTHREAD_RWLOCK_rdlock(&entry->content_lock);
	if (!(entry->flags & CACHE_INODE_TRUST_CONTENT)) {
		/* Our data are stale.  Drop the lock, get a
		   write-lock, load in new data, and copy it out to
		   the caller. */
		PTHREAD_RWLOCK_unlock(&entry->content_lock);
		PTHREAD_RWLOCK_wrlock(&entry->content_lock);
		/* Make sure nobody updated the content while we were
		   waiting. */
		refresh = !(entry->flags & CACHE_INODE_TRUST_CONTENT);
	}
	fsal_status =
	    entry->obj_handle->obj_ops.readlink(entry->obj_handle,
					     link_content, refresh);
	if (refresh && !(FSAL_IS_ERROR(fsal_status)))
		atomic_set_uint32_t_bits(&entry->flags,
					 CACHE_INODE_TRUST_CONTENT);

	PTHREAD_RWLOCK_unlock(&entry->content_lock);

	if (FSAL_IS_ERROR(fsal_status)) {
		status = cache_inode_error_convert(fsal_status);
		if (fsal_status.major == ERR_FSAL_STALE) {
			LogEvent(COMPONENT_CACHE_INODE,
				 "FSAL returned STALE from readlink");
			cache_inode_kill_entry(entry);
		}
		return status;
	}

	return status;
}

/** @} */