A simple filesystem to understand things.

This is a Work In Progress. Do not use this yet.

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 test:
---------


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, 0.00106827 s, 383 MB/s
psankar@linux-9dni:~/src/simplefs> ./mkfs-simplefs image 
Super block written succesfully
root directory inode written succesfully
welcomefile inode written succesfully
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

psankar@linux-9dni:~/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
[ 7064.752268] Sucessfully registered simplefs
[ 7064.756404] The magic number obtained in disk is: [268640275]
[ 7064.756410] simplefs filesystem of version [1] formatted with a block size of [4096] detected in the device.
[ 7064.756457] simplefs is succesfully mounted on [/dev/loop10]
linux-9dni:/home/psankar/src/simplefs # cd mount/
linux-9dni:/home/psankar/src/simplefs/mount # cat vanakkam
Love is God. God is Love. Anbe Murugan.
linux-9dni:/home/psankar/src/simplefs/mount # cp vanakkam hello
linux-9dni:/home/psankar/src/simplefs/mount # cat hello
Love is God. God is Love. Anbe Murugan.
linux-9dni:/home/psankar/src/simplefs/mount # echo "Let there be files :-)" > hello
linux-9dni:/home/psankar/src/simplefs/mount # cat hello
Let there be files :-)
linux-9dni:/home/psankar/src/simplefs/mount # touch world
linux-9dni:/home/psankar/src/simplefs/mount # cat world
linux-9dni:/home/psankar/src/simplefs/mount # echo "Hello World" > world
linux-9dni:/home/psankar/src/simplefs/mount # cat world
Hello World
linux-9dni:/home/psankar/src/simplefs/mount # ..
linux-9dni:/home/psankar/src/simplefs # umount mount ; rmmod simplefs.ko
linux-9dni:/home/psankar/src/simplefs # insmod simplefs.ko ; mount -o loop -t simplefs image /home/psankar/src/simplefs/mount/
linux-9dni:/home/psankar/src/simplefs # cd mount/
linux-9dni:/home/psankar/src/simplefs/mount # cat world
Hello World
linux-9dni:/home/psankar/src/simplefs/mount # cat hello
Let there be files :-)
linux-9dni:/home/psankar/src/simplefs/mount # ..
linux-9dni:/home/psankar/src/simplefs # umount mount ; rmmod simplefs.ko ; dmesg -c
[ 7064.752268] Sucessfully registered simplefs
[ 7064.756404] The magic number obtained in disk is: [268640275]
[ 7064.756410] simplefs filesystem of version [1] formatted with a block size of [4096] detected in the device.
[ 7064.756457] simplefs is succesfully mounted on [/dev/loop10]
[ 7070.816973] Read request for file of size: [41]
[ 7081.274818] No inode found for the filename [hello]
[ 7081.274835] No inode found for the filename [hello]
[ 7081.274853] No inode found for the filename [hello]
[ 7081.274874] simplefs create fs object is called
[ 7081.274888] Got new unique inode number [10]
[ 7081.274890] New file creation request
[ 7081.275037] Returning success after creating the file/directory
[ 7081.275050] Read request for file of size: [41]
[ 7081.275054] file size write begins
[ 7081.275067] The new filesize that is written is: [41] and len was: [41]
[ 7083.645271] Read request for file of size: [41]
[ 7118.672573] file size write begins
[ 7118.672655] The new filesize that is written is: [23] and len was: [23]
[ 7120.387921] Read request for file of size: [23]
[ 7129.434414] No inode found for the filename [world]
[ 7129.434424] simplefs create fs object is called
[ 7129.434429] Got new unique inode number [11]
[ 7129.434430] New file creation request
[ 7129.434568] Returning success after creating the file/directory
[ 7131.279727] Read request for file of size: [0]
[ 7140.382962] file size write begins
[ 7140.383083] The new filesize that is written is: [12] and len was: [12]
[ 7142.150113] Read request for file of size: [12]
[ 7153.773088] simplefs superblock is destroyed. Unmount succesful.
[ 7153.778315] Sucessfully unregistered simplefs
[ 7163.614771] Sucessfully registered simplefs
[ 7163.618539] The magic number obtained in disk is: [268640275]
[ 7163.618546] simplefs filesystem of version [1] formatted with a block size of [4096] detected in the device.
[ 7163.618587] simplefs is succesfully mounted on [/dev/loop11]
[ 7173.341241] Read request for file of size: [12]
[ 7181.062284] Read request for file of size: [23]
[ 7195.867825] simplefs superblock is destroyed. Unmount succesful.
[ 7195.872485] Sucessfully unregistered simplefs
linux-9dni:/home/psankar/src/simplefs #