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Code for: [Un]Register filesystem, [un]mount simplefs, Superblock placeholder

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Sankar சங்கர் 2013-03-16 14:47:45 +05:30
parent 1b67698838
commit 24df8c8c44
2 changed files with 140 additions and 4 deletions
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37
README
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@ -6,4 +6,39 @@ The source files are licensed under Creative Commons Zero License.
More information at: http://creativecommons.org/publicdomain/zero/1.0/
Full license text at: http://creativecommons.org/publicdomain/zero/1.0/legalcode
To compile, install linux kernel sources and run make from the checkedout directory.
To compile:
------------
install linux kernel sources and run make from the checkedout directory.
To test:
---------
One-time-activity:
linux-okb0:/home/psankar/src/simplefs > dd bs=1M count=100 if=/dev/zero of=image
linux-okb0:/home/psankar/src/simplefs > mkdir mount
Repeat everytime after making changes to the source:
linux-okb0:/home/psankar/src/simplefs > make
linux-okb0:/home/psankar/src/simplefs > su - ; # switch to root user if not already, or use sudo
linux-okb0:/home/psankar/src/simplefs # dmesg
linux-okb0:/home/psankar/src/simplefs # insmod simplefs.ko
linux-okb0:/home/psankar/src/simplefs # dmesg
[ 7467.426112] Sucessfully registered simplefs
linux-okb0:/home/psankar/src/simplefs # mount -o loop -t simplefs image /home/psankar/src/simplefs/mount/
linux-okb0:/home/psankar/src/simplefs # dmesg
[ 7467.426112] Sucessfully registered simplefs
[ 7478.223432] simplefs is succesfully mounted on [/dev/loop1]
linux-okb0:/home/psankar/src/simplefs # umount /home/psankar/src/simplefs/mount/
linux-okb0:/home/psankar/src/simplefs # dmesg
[ 7467.426112] Sucessfully registered simplefs
[ 7478.223432] simplefs is succesfully mounted on [/dev/loop1]
[ 7498.889439] simplefs superblock is destroyed. Unmount succesful.
linux-okb0:/home/psankar/src/simplefs # rmmod simplefs.ko
linux-okb0:/home/psankar/src/simplefs # dmesg
[ 7467.426112] Sucessfully registered simplefs
[ 7478.223432] simplefs is succesfully mounted on [/dev/loop1]
[ 7498.889439] simplefs superblock is destroyed. Unmount succesful.
[ 7506.906067] Sucessfully unregistered simplefs
linux-okb0:/home/psankar/src/simplefs #

107
simple.c
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@ -7,16 +7,117 @@
#include <linux/init.h>
#include <linux/module.h>
#include <linux/fs.h>
/* This function creates, configures and returns an inode,
* for the asked file (or) directory (differentiated by the mode param),
* under the directory specified by the dir param
* on the device dev, managed by the superblock sb param) */
struct inode *simplefs_get_inode(struct super_block *sb,
const struct inode *dir, umode_t mode,
dev_t dev)
{
struct inode *inode = new_inode(sb);
if (inode) {
inode->i_ino = get_next_ino();
inode_init_owner(inode, dir, mode);
inode->i_atime = inode->i_mtime = inode->i_ctime = CURRENT_TIME;
switch (mode & S_IFMT) {
case S_IFDIR:
/* i_nlink will be initialized to 1 in the inode_init_always function
* (that gets called inside the new_inode function),
* We change it to 2 for directories, for covering the "." entry */
inc_nlink(inode);
break;
case S_IFREG:
case S_IFLNK:
default:
printk(KERN_ERR
"simplefs can create meaningful inode for only root directory at the moment\n");
return NULL;
break;
}
}
return inode;
}
/* This function, as the name implies, Makes the super_block valid and
* fills filesystem specific information in the super block */
int simplefs_fill_super(struct super_block *sb, void *data, int silent)
{
struct inode *inode;
/* A magic number that uniquely identifies our filesystem type */
sb->s_magic = 0x10032013;
inode = simplefs_get_inode(sb, NULL, S_IFDIR, 0);
sb->s_root = d_make_root(inode);
if (!sb->s_root)
return -ENOMEM;
return 0;
}
static struct dentry *simplefs_mount(struct file_system_type *fs_type,
int flags, const char *dev_name,
void *data)
{
struct dentry *ret;
ret = mount_bdev(fs_type, flags, dev_name, data, simplefs_fill_super);
if (unlikely(IS_ERR(ret)))
printk(KERN_ERR "Error mounting simplefs");
else
printk(KERN_INFO "simplefs is succesfully mounted on [%s]\n",
dev_name);
return ret;
}
static void simplefs_kill_superblock(struct super_block *s)
{
printk(KERN_INFO
"simplefs superblock is destroyed. Unmount succesful.\n");
/* This is just a dummy function as of now. As our filesystem gets matured,
* we will do more meaningful operations here */
return;
}
struct file_system_type simplefs_fs_type = {
.owner = THIS_MODULE,
.name = "simplefs",
.mount = simplefs_mount,
.kill_sb = simplefs_kill_superblock,
};
static int simplefs_init(void)
{
printk(KERN_ALERT "Hello World\n");
return 0;
int ret;
ret = register_filesystem(&simplefs_fs_type);
if (likely(ret == 0))
printk(KERN_INFO "Sucessfully registered simplefs\n");
else
printk(KERN_ERR "Failed to register simplefs. Error:[%d]", ret);
return ret;
}
static void simplefs_exit(void)
{
printk(KERN_ALERT "Goodbye World\n");
int ret;
ret = unregister_filesystem(&simplefs_fs_type);
if (likely(ret == 0))
printk(KERN_INFO "Sucessfully unregistered simplefs\n");
else
printk(KERN_ERR "Failed to unregister simplefs. Error:[%d]",
ret);
}
module_init(simplefs_init);