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read support for existing files

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Sankar சங்கர் 2013-07-24 17:29:50 +05:30
parent a96e3142dd
commit 356bceb273
3 changed files with 87 additions and 29 deletions
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59
README
View File

@ -14,12 +14,14 @@ To test:
---------
~/src/simplefs> make
~/src/simplefs> dd bs=4096 count=100 if=/dev/zero of=image
psankar@linux-9dni:~/src/simplefs> make
psankar@linux-9dni:~/src/simplefs> dd bs=4096 count=100 if=/dev/zero of=image
100+0 records in
100+0 records out
409600 bytes (410 kB) copied, 0.00175839 s, 233 MB/s
~/src/simplefs> ./mkfs-simplefs image
409600 bytes (410 kB) copied, 0.00106026 s, 386 MB/s
psankar@linux-9dni:~/src/simplefs> ./mkfs-simplefs image
Super block written succesfully
root directory inode written succesfully
welcomefile inode written succesfully
@ -27,28 +29,31 @@ inode store padding bytes (after the two inodes) written sucessfully
root directory datablocks (name+inode_no pair for welcomefile) written succesfully
padding after the rootdirectory children written succesfully
welcomefilebody has been written succesfully
~/src/simplefs>
psankar@linux-9dni:~/src/simplefs>
linux-okb0:/home/psankar/src/simplefs # insmod simplefs.ko;mount -o loop -t simplefs image /home/psankar/src/simplefs/mount/;dmesg
[ 8717.049630] Sucessfully registered simplefs
[ 8717.056140] The magic number obtained in disk is: [268640275]
[ 8717.056147] simplefs filesystem of version [1] formatted with a block size of [4096] detected in the device.
[ 8717.056183] simplefs is succesfully mounted on [/dev/loop4]
linux-okb0:/home/psankar/src/simplefs # cd mount
linux-okb0:/home/psankar/src/simplefs/mount # ls
vanakkam
linux-okb0:/home/psankar/src/simplefs/mount # ls -lh
total 0
---------- 1 root root 0 Apr 23 14:25 vanakkam
linux-okb0:/home/psankar/src/simplefs/mount # cd ..
linux-okb0:/home/psankar/src/simplefs # umount mount
linux-okb0:/home/psankar/src/simplefs # rmmod simplefs.ko
linux-okb0:/home/psankar/src/simplefs # dmesg -c
[ 8717.049630] Sucessfully registered simplefs
[ 8717.056140] The magic number obtained in disk is: [268640275]
[ 8717.056147] simplefs filesystem of version [1] formatted with a block size of [4096] detected in the device.
[ 8717.056183] simplefs is succesfully mounted on [/dev/loop4]
[ 8735.146533] simplefs superblock is destroyed. Unmount succesful.
[ 8740.101526] Sucessfully unregistered simplefs
linux-okb0:/home/psankar/src/simplefs #
Now as root:
linux-9dni:/home/psankar/src/simplefs # insmod simplefs.ko ; mount -o loop -t simplefs image /home/psankar/src/simplefs/mount/ ; dmesg
[51422.091945] Sucessfully registered simplefs
[51422.094713] The magic number obtained in disk is: [268640275]
[51422.094719] simplefs filesystem of version [1] formatted with a block size of [4096] detected in the device.
[51422.094744] simplefs is succesfully mounted on [/dev/loop5]
linux-9dni:/home/psankar/src/simplefs # cat mount/vanakkam
Love is God. God is Love. Anbe Murugan.
linux-9dni:/home/psankar/src/simplefs # cp mount/vanakkam .
linux-9dni:/home/psankar/src/simplefs # cat vanakkam
Love is God. God is Love. Anbe Murugan.
linux-9dni:/home/psankar/src/simplefs # umount mount; rmmod simplefs.ko ; dmesg
[51422.091945] Sucessfully registered simplefs
[51422.094713] The magic number obtained in disk is: [268640275]
[51422.094719] simplefs filesystem of version [1] formatted with a block size of [4096] detected in the device.
[51422.094744] simplefs is succesfully mounted on [/dev/loop5]
[51469.971919] simplefs superblock is destroyed. Unmount succesful.
[51469.977426] Sucessfully unregistered simplefs
linux-9dni:/home/psankar/src/simplefs #

2
mkfs-simplefs.c
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@ -18,7 +18,7 @@ int main(int argc, char *argv[])
struct simplefs_inode welcomefile_inode;
char welcomefile_name[] = "vanakkam";
char welcomefile_body[] = "Love is God. God is Love. Anbe Murugan.";
char welcomefile_body[] = "Love is God. God is Love. Anbe Murugan.\n";
const uint64_t WELCOMEFILE_INODE_NUMBER = 2;
const uint64_t WELCOMEFILE_DATABLOCK_NUMBER = 3;

55
simple.c
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@ -81,6 +81,52 @@ struct simplefs_inode *simplefs_get_inode(struct super_block *sb,
return NULL;
}
ssize_t simplefs_read(struct file * filp, char __user * buf, size_t len,
loff_t * ppos)
{
/* Hack to make sure that we answer the read call only once and not loop infinitely.
* We need to implement support for filesize in inode to remove this hack */
static int done = 0;
/* After the commit dd37978c5 in the upstream linux kernel,
* we can use just filp->f_inode instead of the
* f->f_path.dentry->d_inode redirection */
struct simplefs_inode *inode =
SIMPLEFS_INODE(filp->f_path.dentry->d_inode);
struct buffer_head *bh;
char *buffer;
int nbytes;
if (done) {
done = 0;
return 0;
}
bh = (struct buffer_head *)sb_bread(filp->f_path.dentry->d_inode->i_sb,
inode->data_block_number);
buffer = (char *)bh->b_data;
nbytes = min(strlen(buffer), len);
if (copy_to_user(buf, buffer, nbytes)) {
brelse(bh);
printk(KERN_ERR
"Error copying file contents to the userspace buffer\n");
return -EFAULT;
}
brelse(bh);
*ppos += nbytes;
done = 1;
return nbytes;
}
const struct file_operations simplefs_file_operations = {
.read = simplefs_read
};
const struct file_operations simplefs_dir_operations = {
.owner = THIS_MODULE,
.readdir = simplefs_readdir,
@ -119,7 +165,14 @@ struct dentry *simplefs_lookup(struct inode *parent_inode,
inode_init_owner(inode, parent_inode, sfs_inode->mode);
inode->i_sb = sb;
inode->i_op = &simplefs_inode_ops;
inode->i_fop = &simplefs_dir_operations;
if (S_ISDIR(inode->i_mode))
inode->i_fop = &simplefs_dir_operations;
else if (S_ISREG(inode->i_mode))
inode->i_fop = &simplefs_file_operations;
else
printk(KERN_ERR
"Unknown inode type. Neither a directory nor a file");
/* FIXME: We should store these times to disk and retrieve them */
inode->i_atime = inode->i_mtime = inode->i_ctime =