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incubator-nuttx/drivers/loop/losetup.c

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/****************************************************************************
* drivers/loop/losetup.c
*
* Licensed to the Apache Software Foundation (ASF) under one or more
* contributor license agreements. See the NOTICE file distributed with
* this work for additional information regarding copyright ownership. The
* ASF licenses this file to you under the Apache License, Version 2.0 (the
* "License"); you may not use this file except in compliance with the
* License. You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
* WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
* License for the specific language governing permissions and limitations
* under the License.
*
****************************************************************************/
/****************************************************************************
* Included Files
****************************************************************************/
#include <nuttx/config.h>
#include <sys/types.h>
#include <sys/stat.h>
#include <sys/types.h>
#include <sys/ioctl.h>
#include <sys/mount.h>
#include <stdint.h>
#include <stdbool.h>
#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
#include <string.h>
#include <fcntl.h>
#include <debug.h>
#include <errno.h>
#include <nuttx/kmalloc.h>
#include <nuttx/fs/fs.h>
#include <nuttx/fs/loop.h>
#include <nuttx/semaphore.h>
/****************************************************************************
* Pre-processor Definitions
****************************************************************************/
#define loop_semgive(d) nxsem_post(&(d)->sem) /* To match loop_semtake */
#define MAX_OPENCNT (255) /* Limit of uint8_t */
/****************************************************************************
* Private Types
****************************************************************************/
struct loop_struct_s
{
sem_t sem; /* For safe read-modify-write operations */
uint32_t nsectors; /* Number of sectors on device */
off_t offset; /* Offset (in bytes) to the first sector */
uint16_t sectsize; /* The size of one sector */
uint8_t opencnt; /* Count of open references to the loop device */
bool writeenabled; /* true: can write to device */
struct file devfile; /* File struct of char device/file */
};
/****************************************************************************
* Private Function Prototypes
****************************************************************************/
static int loop_semtake(FAR struct loop_struct_s *dev);
static int loop_open(FAR struct inode *inode);
static int loop_close(FAR struct inode *inode);
static ssize_t loop_read(FAR struct inode *inode, FAR unsigned char *buffer,
size_t start_sector, unsigned int nsectors);
static ssize_t loop_write(FAR struct inode *inode,
FAR const unsigned char *buffer,
size_t start_sector, unsigned int nsectors);
static int loop_geometry(FAR struct inode *inode,
FAR struct geometry *geometry);
/****************************************************************************
* Private Data
****************************************************************************/
static const struct block_operations g_bops =
{
loop_open, /* open */
loop_close, /* close */
loop_read, /* read */
loop_write, /* write */
loop_geometry, /* geometry */
NULL /* ioctl */
#ifndef CONFIG_DISABLE_PSEUDOFS_OPERATIONS
, NULL /* unlink */
#endif
};
/****************************************************************************
* Private Functions
****************************************************************************/
/****************************************************************************
* Name: loop_semtake
****************************************************************************/
static int loop_semtake(FAR struct loop_struct_s *dev)
{
return nxsem_wait(&dev->sem);
}
/****************************************************************************
* Name: loop_open
*
* Description: Open the block device
*
****************************************************************************/
static int loop_open(FAR struct inode *inode)
{
FAR struct loop_struct_s *dev;
int ret;
DEBUGASSERT(inode && inode->i_private);
dev = (FAR struct loop_struct_s *)inode->i_private;
/* Make sure we have exclusive access to the state structure */
ret = loop_semtake(dev);
if (ret == OK)
{
if (dev->opencnt == MAX_OPENCNT)
{
ret = -EMFILE;
}
else
{
/* Increment the open count */
dev->opencnt++;
}
loop_semgive(dev);
}
return ret;
}
/****************************************************************************
* Name: loop_close
*
* Description: close the block device
*
****************************************************************************/
static int loop_close(FAR struct inode *inode)
{
FAR struct loop_struct_s *dev;
int ret;
DEBUGASSERT(inode && inode->i_private);
dev = (FAR struct loop_struct_s *)inode->i_private;
/* Make sure we have exclusive access to the state structure */
ret = loop_semtake(dev);
if (ret == OK)
{
if (dev->opencnt == 0)
{
ret = -EIO;
}
else
{
/* Decrement the open count */
dev->opencnt--;
}
loop_semgive(dev);
}
return ret;
}
/****************************************************************************
* Name: loop_read
*
* Description: Read the specified number of sectors
*
****************************************************************************/
static ssize_t loop_read(FAR struct inode *inode, FAR unsigned char *buffer,
size_t start_sector, unsigned int nsectors)
{
FAR struct loop_struct_s *dev;
ssize_t nbytesread;
off_t offset;
off_t ret;
DEBUGASSERT(inode && inode->i_private);
dev = (FAR struct loop_struct_s *)inode->i_private;
if (start_sector + nsectors > dev->nsectors)
{
ferr("ERROR: Read past end of file\n");
return -EIO;
}
/* Calculate the offset to read the sectors and seek to the position */
offset = start_sector * dev->sectsize + dev->offset;
ret = file_seek(&dev->devfile, offset, SEEK_SET);
if (ret < 0)
{
ferr("ERROR: Seek failed for offset=%d: %d\n", (int)offset, (int)ret);
return -EIO;
}
/* Then read the requested number of sectors from that position */
do
{
nbytesread = file_read(&dev->devfile, buffer,
nsectors * dev->sectsize);
if (nbytesread < 0 && nbytesread != -EINTR)
{
ferr("ERROR: Read failed: %d\n", nbytesread);
return (int)nbytesread;
}
}
while (nbytesread < 0);
/* Return the number of sectors read */
return nbytesread / dev->sectsize;
}
/****************************************************************************
* Name: loop_write
*
* Description: Write the specified number of sectors
*
****************************************************************************/
static ssize_t loop_write(FAR struct inode *inode,
FAR const unsigned char *buffer,
size_t start_sector, unsigned int nsectors)
{
FAR struct loop_struct_s *dev;
ssize_t nbyteswritten;
off_t offset;
off_t ret;
DEBUGASSERT(inode && inode->i_private);
dev = (FAR struct loop_struct_s *)inode->i_private;
/* Calculate the offset to write the sectors and seek to the position */
offset = start_sector * dev->sectsize + dev->offset;
ret = file_seek(&dev->devfile, offset, SEEK_SET);
if (ret < 0)
{
ferr("ERROR: Seek failed for offset=%d: %d\n", (int)offset, (int)ret);
}
/* Then write the requested number of sectors to that position */
do
{
nbyteswritten = file_write(&dev->devfile, buffer,
nsectors * dev->sectsize);
if (nbyteswritten < 0 && nbyteswritten != -EINTR)
{
ferr("ERROR: nx_write failed: %d\n", nbyteswritten);
return nbyteswritten;
}
}
while (nbyteswritten < 0);
/* Return the number of sectors written */
return nbyteswritten / dev->sectsize;
}
/****************************************************************************
* Name: loop_geometry
*
* Description: Return device geometry
*
****************************************************************************/
static int loop_geometry(FAR struct inode *inode,
FAR struct geometry *geometry)
{
FAR struct loop_struct_s *dev;
DEBUGASSERT(inode);
if (geometry)
{
dev = (FAR struct loop_struct_s *)inode->i_private;
geometry->geo_available = true;
geometry->geo_mediachanged = false;
geometry->geo_writeenabled = dev->writeenabled;
geometry->geo_nsectors = dev->nsectors;
geometry->geo_sectorsize = dev->sectsize;
return OK;
}
return -EINVAL;
}
/****************************************************************************
* Public Functions
****************************************************************************/
/****************************************************************************
* Name: losetup
*
* Description:
* Setup the loop device so that it exports the file referenced by
* 'filename' as a block device.
*
****************************************************************************/
int losetup(FAR const char *devname, FAR const char *filename,
uint16_t sectsize, off_t offset, bool readonly)
{
FAR struct loop_struct_s *dev;
struct stat sb;
int ret;
/* Sanity check */
#ifdef CONFIG_DEBUG_FEATURES
if (devname == NULL || filename == NULL || sectsize == 0)
{
return -EINVAL;
}
#endif
/* Get the size of the file */
ret = stat(filename, &sb);
if (ret < 0)
{
ferr("ERROR: Failed to stat %s: %d\n", filename, get_errno());
return -get_errno();
}
/* Check if the file system is big enough for one block */
if (sb.st_size - offset < sectsize)
{
ferr("ERROR: File is too small for blocksize\n");
return -ERANGE;
}
/* Allocate a loop device structure */
dev = (FAR struct loop_struct_s *)
kmm_zalloc(sizeof(struct loop_struct_s));
if (dev == NULL)
{
return -ENOMEM;
}
/* Initialize the loop device structure. */
nxsem_init(&dev->sem, 0, 1);
dev->nsectors = (sb.st_size - offset) / sectsize;
dev->sectsize = sectsize;
dev->offset = offset;
/* Open the file. */
/* First try to open the device R/W access (unless we are asked
* to open it readonly).
*/
ret = -ENOSYS;
if (!readonly)
{
ret = file_open(&dev->devfile, filename, O_RDWR);
}
if (ret >= 0)
{
dev->writeenabled = true; /* Success */
}
else
{
/* If that fails, then try to open the device read-only */
ret = file_open(&dev->devfile, filename, O_RDONLY);
if (ret < 0)
{
ferr("ERROR: Failed to open %s: %d\n", filename, ret);
goto errout_with_dev;
}
}
/* Inode private data will be reference to the loop device structure */
ret = register_blockdriver(devname, &g_bops, 0, dev);
if (ret < 0)
{
ferr("ERROR: register_blockdriver failed: %d\n", -ret);
goto errout_with_file;
}
return OK;
errout_with_file:
file_close(&dev->devfile);
errout_with_dev:
kmm_free(dev);
return ret;
}
/****************************************************************************
* Name: loteardown
*
* Description:
* Undo the setup performed by losetup
*
****************************************************************************/
int loteardown(FAR const char *devname)
{
FAR struct loop_struct_s *dev;
FAR struct inode *inode;
int ret;
/* Sanity check */
#ifdef CONFIG_DEBUG_FEATURES
if (devname == NULL)
{
return -EINVAL;
}
#endif
/* Open the block driver associated with devname so that we can get the
* inode reference.
*/
ret = open_blockdriver(devname, MS_RDONLY, &inode);
if (ret < 0)
{
ferr("ERROR: Failed to open %s: %d\n", devname, -ret);
return ret;
}
/* Inode private data is a reference to the loop device structure */
dev = (FAR struct loop_struct_s *)inode->i_private;
close_blockdriver(inode);
DEBUGASSERT(dev != NULL);
/* Are there still open references to the device */
if (dev->opencnt > 0)
{
return -EBUSY;
}
/* Otherwise, unregister the block device */
ret = unregister_blockdriver(devname);
/* Release the device structure */
if (dev->devfile.f_inode != NULL)
{
file_close(&dev->devfile);
}
kmm_free(dev);
return ret;
}
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