/* -*- C -*-
* main.c -- the bare scullp char module
*
* Copyright (C) 2001 Alessandro Rubini and Jonathan Corbet
* Copyright (C) 2001 O'Reilly & Associates
*
* The source code in this file can be freely used, adapted,
* and redistributed in source or binary form, so long as an
* acknowledgment appears in derived source files. The citation
* should list that the code comes from the book "Linux Device
* Drivers" by Alessandro Rubini and Jonathan Corbet, published
* by O'Reilly & Associates. No warranty is attached;
* we cannot take responsibility for errors or fitness for use.
*
* $Id: _main.c.in,v 1.21 2004/10/14 20:11:39 corbet Exp $
*/
#include <linux/config.h>
#include <linux/module.h>
#include <linux/moduleparam.h>
#include <linux/init.h>
#include <linux/kernel.h> /* printk() */
#include <linux/slab.h> /* kmalloc() */
#include <linux/fs.h> /* everything... */
#include <linux/errno.h> /* error codes */
#include <linux/types.h> /* size_t */
#include <linux/proc_fs.h>
#include <linux/fcntl.h> /* O_ACCMODE */
#include <linux/aio.h>
#include <asm/uaccess.h>
#include "scullp.h" /* local definitions */
int scullp_major = SCULLP_MAJOR;
int scullp_devs = SCULLP_DEVS; /* number of bare scullp devices */
int scullp_qset = SCULLP_QSET;
int scullp_order = SCULLP_ORDER;
module_param(scullp_major, int, 0);
module_param(scullp_devs, int, 0);
module_param(scullp_qset, int, 0);
module_param(scullp_order, int, 0);
MODULE_AUTHOR("Alessandro Rubini");
MODULE_LICENSE("Dual BSD/GPL");
struct scullp_dev *scullp_devices; /* allocated in scullp_init */
int scullp_trim(struct scullp_dev *dev);
void scullp_cleanup(void);
#ifdef SCULLP_USE_PROC /* don't waste space if unused */
/*
* The proc filesystem: function to read and entry
*/
void scullp_proc_offset(char *buf, char **start, off_t *offset, int *len)
{
if (*offset == 0)
return;
if (*offset >= *len) {
/* Not there yet */
*offset -= *len;
*len = 0;
} else {
/* We're into the interesting stuff now */
*start = buf + *offset;
*offset = 0;
}
}
/* FIXME: Do we need this here?? It be ugly */
int scullp_read_procmem(char *buf, char **start, off_t offset,
int count, int *eof, void *data)
{
int i, j, order, qset, len = 0;
int limit = count - 80; /* Don't print more than this */
struct scullp_dev *d;
*start = buf;
for(i = 0; i < scullp_devs; i++) {
d = &scullp_devices[i];
if (down_interruptible (&d->sem))
return -ERESTARTSYS;
qset = d->qset; /* retrieve the features of each device */
order = d->order;
len += sprintf(buf+len,"\nDevice %i: qset %i, order %i, sz %li\n",
i, qset, order, (long)(d->size));
for (; d; d = d->next) { /* scan the list */
len += sprintf(buf+len," item at %p, qset at %p\n",d,d->data);
scullp_proc_offset (buf, start, &offset, &len);
if (len > limit)
goto out;
if (d->data && !d->next) /* dump only the last item - save space */
for (j = 0; j < qset; j++) {
if (d->data[j])
len += sprintf(buf+len," % 4i:%8p\n",j,d->data[j]);
scullp_proc_offset (buf, start, &offset, &len);
if (len > limit)
goto out;
}
}
out:
up (&scullp_devices[i].sem);
if (len > limit)
break;
}
*eof = 1;
return len;
}
#endif /* SCULLP_USE_PROC */
/*
* Open and close
*/
int scullp_open (struct inode *inode, struct file *filp)
{
struct scullp_dev *dev; /* device information */
/* Find the device */
dev = container_of(inode->i_cdev, struct scullp_dev, cdev);
/* now trim to 0 the length of the device if open was write-only */
if ( (filp->f_flags & O_ACCMODE) == O_WRONLY) {
if (down_interruptible (&dev->sem))
return -ERESTARTSYS;
scullp_trim(dev); /* ignore errors */
up (&dev->sem);
}
/* and use filp->private_data to point to the device data */
filp->private_data = dev;
return 0; /* success */
}
int scullp_release (struct inode *inode, struct file *filp)
{
return 0;
}
/*
* Follow the list
*/
struct scullp_dev *scullp_follow(struct scullp_dev *dev, int n)
{
while (n--) {
if (!dev->next) {
dev->next = kmalloc(sizeof(struct scullp_dev), GFP_KERNEL);
memset(dev->next, 0, sizeof(struct scullp_dev));
}
dev = dev->next;
continue;
}
return dev;
}
/*
* Data management: read and write
*/
ssize_t scullp_read (struct file *filp, char __user *buf, size_t count,
loff_t *f_pos)
{
struct scullp_dev *dev = filp->private_data; /* the first listitem */
struct scullp_dev *dptr;
int quantum = PAGE_SIZE << dev->order;
int qset = dev->qset;
int itemsize = quantum * qset; /* how many bytes in the listitem */
int item, s_pos, q_pos, rest;
ssize_t retval = 0;
if (down_interruptible (&dev->sem))
return -ERESTARTSYS;
if (*f_pos > dev->size)
goto nothing;
if (*f_pos + count > dev->size)
count = dev->size - *f_pos;
/* find listitem, qset index, and offset in the quantum */
item = ((long) *f_pos) / itemsize;
rest = ((long) *f_pos) % itemsize;
s_pos = rest / quantum; q_pos = rest % quantum;
/* follow the list up to the right position (defined elsewhere) */
dptr = scullp_follow(dev, item);
if (!dptr->data)
goto nothing; /* don't fill holes */
if (!dptr->data[s_pos])
goto nothing;
if (count > quantum - q_pos)
count = quantum - q_pos; /* read only up to the end of this quantum */
if (copy_to_user (buf, dptr->data[s_pos]+q_pos, count)) {
retval = -EFAULT;
goto nothing;
}
up (&dev->sem);
*f_pos += count;
return count;
nothing:
up (&dev->sem);
return retval;
}
ssize_t scullp_write (struct file *filp, const char __user *buf, size_t count,
loff_t *f_pos)
{
struct scullp_dev *dev = filp->private_data;
struct scullp_dev *dptr;
int quantum = PAGE_SIZE << dev->order;
int qset = dev->qset;
int itemsize = quantum * qset;
int item, s_pos, q_pos, rest;
ssize_t retval = -ENOMEM; /* our most likely error */
if (down_interruptible (&dev->sem))
return -ERESTARTSYS;
/* find listitem, qset index and offset in the quantum */
item = ((long) *f_pos) / itemsize;
rest = ((long) *f_pos) % itemsize;
s_pos = rest / quantum; q_pos = rest % quantum;
/* follow the list up to the right position */
dptr = scullp_follow(dev, item);
if (!dptr->data) {
dptr->data = kmalloc(qset * sizeof(void *), GFP_KERNEL);
if (!dptr->data)
goto nomem;
memset(dptr->data, 0, qset * sizeof(char *));
}
/* Here's the allocation of a single quantum */
if (!dptr->data[s_pos]) {
dptr->data[s_pos] =
(void *)__get_free_pages(GFP_KERNEL, dptr->order);
if (!dptr->data[s_pos])
goto nomem;
memset(dptr->data[s_pos], 0, PAGE_SIZE << dptr->order);
}
if (count > quantum - q_pos)
count = quantum - q_pos; /* write only up to the end of this quantum */
if (copy_from_user (dptr->data[s_pos]+q_pos, buf, count)) {
retval = -EFAULT;
goto nomem;
}
*f_pos += count;
/* update the size */
if (dev->size < *f_pos)
dev->size = *f_pos;
up (&dev->sem);
return count;
nomem:
up (&dev->sem);
return retval;
}
/*
* The ioctl() implementation
*/
int scullp_ioctl (struct inode *inode, struct file *filp,
unsigned int cmd, unsigned long arg)
{
int err = 0, ret = 0, tmp;
/* don't even decode wrong cmds: better returning ENOTTY than EFAULT */
if (_IOC_TYPE(cmd) != SCULLP_IOC_MAGIC) return -ENOTTY;
if (_IOC_NR(cmd) > SCULLP_IOC_MAXNR) return -ENOTTY;
/*
* the type is a bitmask, and VERIFY_WRITE catches R/W
* transfers. Note that the type is user-oriented, while
* verify_area is kernel-oriented, so the concept of "read" and
* "write" is reversed
*/
if (_IOC_DIR(cmd) & _IOC_READ)
err = !access_ok(VERIFY_WRITE, (void __user *)arg, _IOC_SIZE(cmd));
else if (_IOC_DIR(cmd) & _IOC_WRITE)
err = !access_ok(VERIFY_READ, (void __user *)arg, _IOC_SIZE(cmd));
if (err)
return -EFAULT;
switch(cmd) {
case SCULLP_IOCRESET:
scullp_qset = SCULLP_QSET;
scullp_order = SCULLP_ORDER;
break;
case SCULLP_IOCSORDER: /* Set: arg points to the value */
ret = __get_user(scullp_order, (int __user *) arg);
break;
case SCULLP_IOCTORDER: /* Tell: arg is the value */
scullp_order = arg;
break;
case SCULLP_IOCGORDER: /* Get: arg is pointer to result */
ret = __put_user (scullp_order, (int __user *) arg);
break;
case SCULLP_IOCQORDER: /* Query: return it (it's positive) */
return scullp_order;
case SCULLP_IOCXORDER: /* eXchange: use arg as pointer */
tmp = scullp_order;
ret = __get_user(scullp_order, (int __user *) arg);
if (ret == 0)
ret = __put_user(tmp, (int __user *) arg);
break;
case SCULLP_IOCHORDER: /* sHift: like Tell + Query */
tmp = scullp_order;
scullp_order = arg;
return tmp;
case SCULLP_IOCSQSET:
ret = __get_user(scullp_qset, (int __user *) arg);
break;
case SCULLP_IOCTQSET:
scullp_qset = arg;
break;
case SCULLP_IOCGQSET:
ret = __put_user(scullp_qset, (int __user *)arg);
break;
case SCULLP_IOCQQSET:
return scullp_qset;
case SCULLP_IOCXQSET:
tmp = scullp_qset;
ret = __get_user(scullp_qset, (int __user *)arg);
if (ret == 0)
ret = __put_user(tmp, (int __user *)arg);
break;
case SCULLP_IOCHQSET:
tmp = scullp_qset;
scullp_qset = arg;
return tmp;
default: /* redundant, as cmd was checked against MAXNR */
return -ENOTTY;
}
return ret;
}
/*
* The "extended" operations
*/
loff_t scullp_llseek (struct file *filp, loff_t off, int whence)
{
struct scullp_dev *dev = filp->private_data;
long newpos;
switch(whence) {
case 0: /* SEEK_SET */
newpos = off;
break;
case 1: /* SEEK_CUR */
newpos = filp->f_pos + off;
break;
case 2: /* SEEK_END */
newpos = dev->size + off;
break;
default: /* can't happen */
return -EINVAL;
}
if (newpos<0) return -EINVAL;
filp->f_pos = newpos;
return newpos;
}
/*
* A simple asynchronous I/O implementation.
*/
struct async_work {
struct kiocb *iocb;
int result;
struct work_struct work;
};
/*
* "Complete" an asynchronous operation.
*/
static void scullp_do_deferred_op(void *p)
{
struct async_work *stuff = (struct async_work *) p;
aio_complete(stuff->iocb, stuff->result, 0);
kfree(stuff);
}
static int scullp_defer_op(int write, struct kiocb *iocb, char __user *buf,
size_t count, loff_t pos)
{
struct async_work *stuff;
int result;
/* Copy now while we can access the buffer */
if (write)
result = scullp_write(iocb->ki_filp, buf, count, &pos);
else
result = scullp_read(iocb->ki_filp, buf, count, &pos);
/* If this is a synchronous IOCB, we return our status now. */
if (is_sync_kiocb(iocb))
return result;
/* Otherwise defer the completion for a few milliseconds. */
stuff = kmalloc (sizeof (*stuff), GFP_KERNEL);
if (stuff == NULL)
return result; /* No memory, just complete now */
stuff->iocb = iocb;
stuff->result = result;
INIT_WORK(&stuff->work, scullp_do_deferred_op, stuff);
schedule_delayed_work(&stuff->work, HZ/100);
return -EIOCBQUEUED;
}
static ssize_t scullp_aio_read(struct kiocb *iocb, char __user *buf, size_t count,
loff_t pos)
{
return scullp_defer_op(0, iocb, buf, count, pos);
}
static ssize_t scullp_aio_write(struct kiocb *iocb, const char __user *buf,
size_t count, loff_t pos)
{
return scullp_defer_op(1, iocb, (char __user *) buf, count, pos);
}
/*
* Mmap *is* available, but confined in a different file
*/
extern int scullp_mmap(struct file *filp, struct vm_area_struct *vma);
/*
* The fops
*/
struct file_operations scullp_fops = {
.owner = THIS_MODULE,
.llseek = scullp_llseek,
.read = scullp_read,
.write = scullp_write,
.ioctl = scullp_ioctl,
.mmap = scullp_mmap,
.open = scullp_open,
.release = scullp_release,
.aio_read = scullp_aio_read,
.aio_write = scullp_aio_write,
};
int scullp_trim(struct scullp_dev *dev)
{
struct scullp_dev *next, *dptr;
int qset = dev->qset; /* "dev" is not-null */
int i;
if (dev->vmas) /* don't trim: there are active mappings */
return -EBUSY;
for (dptr = dev; dptr; dptr = next) { /* all the list items */
if (dptr->data) {
/* This code frees a whole quantum-set */
for (i = 0; i < qset; i++)
if (dptr->data[i])
free_pages((unsigned long)(dptr->data[i]),
dptr->order);
kfree(dptr->data);
dptr->data=NULL;
}
next=dptr->next;
if (dptr != dev) kfree(dptr); /* all of them but the first */
}
dev->size = 0;
dev->qset = scullp_qset;
dev->order = scullp_order;
dev->next = NULL;
return 0;
}
static void scullp_setup_cdev(struct scullp_dev *dev, int index)
{
int err, devno = MKDEV(scullp_major, index);
cdev_init(&dev->cdev, &scullp_fops);
dev->cdev.owner = THIS_MODULE;
dev->cdev.ops = &scullp_fops;
err = cdev_add (&dev->cdev, devno, 1);
/* Fail gracefully if need be */
if (err)
printk(KERN_NOTICE "Error %d adding scull%d", err, index);
}
/*
* Finally, the module stuff
*/
int scullp_init(void)
{
int result, i;
dev_t dev = MKDEV(scullp_major, 0);
/*
* Register your major, and accept a dynamic number.
*/
if (scullp_major)
result = register_chrdev_region(dev, scullp_devs, "scullp");
else {
result = alloc_chrdev_region(&dev, 0, scullp_devs, "scullp");
scullp_major = MAJOR(dev);
}
if (result < 0)
return result;
/*
* allocate the devices -- we can't have them static, as the number
* can be specified at load time
*/
scullp_devices = kmalloc(scullp_devs*sizeof (struct scullp_dev), GFP_KERNEL);
if (!scullp_devices) {
result = -ENOMEM;
goto fail_malloc;
}
memset(scullp_devices, 0, scullp_devs*sizeof (struct scullp_dev));
for (i = 0; i < scullp_devs; i++) {
scullp_devices[i].order = scullp_order;
scullp_devices[i].qset = scullp_qset;
sema_init (&scullp_devices[i].sem, 1);
scullp_setup_cdev(scullp_devices + i, i);
}
#ifdef SCULLP_USE_PROC /* only when available */
create_proc_read_entry("scullpmem", 0, NULL, scullp_read_procmem, NULL);
#endif
return 0; /* succeed */
fail_malloc:
unregister_chrdev_region(dev, scullp_devs);
return result;
}
void scullp_cleanup(void)
{
int i;
#ifdef SCULLP_USE_PROC
remove_proc_entry("scullpmem", NULL);
#endif
for (i = 0; i < scullp_devs; i++) {
cdev_del(&scullp_devices[i].cdev);
scullp_trim(scullp_devices + i);
}
kfree(scullp_devices);
unregister_chrdev_region(MKDEV (scullp_major, 0), scullp_devs);
}
module_init(scullp_init);
module_exit(scullp_cleanup);详细说一下这个文件里的异步IO机制
了解如何通过READ_ONLY_OPEN_DELAYED参数调整，让只读表空间在实际需求时才访问数据，避免数据库打开时的延迟。特别适用于大量存储于慢速设备的读-only数据，设置为true可提升数据库打开速度。
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