Trigger Scripts For Trigger Scripts For Extensible File Extensible File Systems Systems Cameron Macdonell Macdonell Cameron Overview Overview � The The Scruf Scruf Framework Framework � � Examples of Extended File Systems Examples of Extended File Systems � � Experiments Experiments � � Concluding Remarks Concluding Remarks � Cameron Macdonell
Scruf - - SCR SCRiptable iptable U User-level ser-level F File system ile system Scruf � Scruf Scruf executes a user script as a user-level executes a user script as a user-level � process whenever a file operation occurs in the process whenever a file operation occurs in the directory (CWD) containing the script directory (CWD) containing the script � Scruf Scruf passes the name of the file being accessed as passes the name of the file being accessed as � a parameter ( $1 a parameter ( $1 ) to the script ) to the script � Locates a script based on its name - Locates a script based on its name - .on.open for .on.open for � example example � Allows extension without changing the Allows extension without changing the � applications applications Cameron Macdonell The Scruf Scruf Framework: A Diagram Framework: A Diagram The .on.open .on.read .on.write … User-level Trigger files Unmodifed Application User-Level open() read() write() … Daemon /proc/scruf VFS Scruf-VFS /usr/ntfs /usr/scovil2 Kernel Cameron Macdonell
Example Extended File Example Extended File Systems Systems � We have built five sample extended file systems: We have built five sample extended file systems: � � Scruf Scruf-CVS -CVS � � Backs up files with open-close semantics Backs up files with open-close semantics � � Scruf Scruf-Trace -Trace � � Logs all file operations Logs all file operations � � Scruf Scruf-Crypt -Crypt � � Transparent access to encrypted files Transparent access to encrypted files � � Scruf Scruf-Compress -Compress � � Transparent access to compressed files Transparent access to compressed files � � Scruf Scruf-Trellis -Trellis � � Remote Data Access Remote Data Access � � Average 40 lines of code Average 40 lines of code � Cameron Macdonell Andrew100 Andrew100 400 400 6.2% 350 350 300 300 250 250 ext2 ext2 Time (s) Time (s) 200 200 Scruf-Trace Scruf-Trace 150 150 100 100 0% 13% 50 50 21.7% 0% 0 1 2 3 4 5 Phase Numbers Phase Numbers Cameron Macdonell
Build of the Linux Kernel Build of the Linux Kernel 3.2% 450 450 400 400 350 350 300 300 ext2 ext2 250 250 Time (s) Time (s) 200 200 Scruf-Trace Scruf-Trace 150 150 21.5% 100 100 50 50 0 make dep make dep make make bzImage bzImage Build Build Stage Stage Cameron Macdonell Running Scruf Scruf with No with No Running Scripts Scripts � Measures the overhead of the framework Measures the overhead of the framework � � Applications should not be hindered if no extensions Applications should not be hindered if no extensions � are used are used � Framework is in place,the daemon is running, Framework is in place,the daemon is running, � there are no there are no scripts in the hierarchy scripts in the hierarchy � What operations are involved? What operations are involved? � � IPC to user-level IPC to user-level � � Search for, and attempted inheritance of, Scripts Search for, and attempted inheritance of, Scripts � � Filters are setup in kernel Filters are setup in kernel � � The highest overhead noted is The highest overhead noted is 0.91% 0.91% � � Overheads are a function of the scripts Overheads are a function of the scripts � Cameron Macdonell
Concluding Remarks Concluding Remarks � Scruf Scruf is simple, effective and flexible is simple, effective and flexible � � Useful extensions can be implemented Useful extensions can be implemented � quickly quickly � Trigger scripts average 40 lines of code Trigger scripts average 40 lines of code � � Applications do not need to be modified Applications do not need to be modified � � Performance Performance � � Negligible overhead from the framework Negligible overhead from the framework � � Asynchronous and Persistent Scripts can Asynchronous and Persistent Scripts can � improve performance when they can be used improve performance when they can be used Cameron Macdonell Cameron Macdonell
Making Life Easier Making Life Easier � Inheritance Inheritance � � Simplifies installation and removal of scripts Simplifies installation and removal of scripts � � With inheritance, trigger scripts are inherited With inheritance, trigger scripts are inherited � into lower directories into lower directories /usr alberta bin .on.read .on.write Inherits cam paullu .on.open thesis Cameron Macdonell Making Life Easier Making Life Easier � Filtering Filtering � � Keeps track of which directory contain which Keeps track of which directory contain which � scripts scripts � Eliminates unnecessary IPC Eliminates unnecessary IPC � User-Level / CWD .on.read .on.open Filtered, no IPC read write open Kernel / Scruf-VFS Cameron Macdonell
Making Life Easier Making Life Easier � Inheritance Inheritance � � Simplifies installation and removal of scripts Simplifies installation and removal of scripts � � With inheritance, trigger scripts are inherited With inheritance, trigger scripts are inherited � into lower directories into lower directories /usr .on.read .on.write /usr/home .on.open inherits /usr/home/cam Cameron Macdonell Sync v. Async Async Scripts Scripts Sync v. Time Daemon Script fork() exec() Synchronous Script SCRUF_API_ARGS … waits computes SCRUF_API_NOOP return to kernel Script Time Daemon fork() exec() Asynchronous Script SCRUF_API_ARGS … return to kernel computes Cameron Macdonell
Scruf-Trellis -Trellis Scruf 200 200 0.26% 180 180 � With development With development � 160 160 Scruf-Trellis should -Trellis should Scruf 140 140 120 120 beat its equivalent beat its equivalent Trellis Trellis 0.08% 100 100 scp; bzip2 scp; bzip2 � Overlapped copying Overlapped copying � 80 80 60 60 and compression and compression 40 40 20 20 0 50 MB 50 MB 100 100 MB MB Size of Size of File File Cameron Macdonell Making Life Easier Making Life Easier � Symbolic Links Symbolic Links � [cam@sunset ~/test]$ ls -al [cam@sunset ~/test]$ ls -al total 16 total 16 drwx drwx--S--- 2 cam grad 4096 Aug 15 14:48 . --S--- 2 cam grad 4096 Aug 15 14:48 . drwxr-sr-x 69 cam grad 4096 Aug 15 14:48 .. drwxr -sr-x 69 cam grad 4096 Aug 15 14:48 .. lrwxrwxrwx 1 cam grad 8 Aug 15 14:47 .on. 1 cam grad 8 Aug 15 14:47 .on.lseek lseek -> .on.open -> .on.open lrwxrwxrwx - -rwx rwx------ 1 cam grad 43 Aug 15 14:46 .on.open ------ 1 cam grad 43 Aug 15 14:46 .on.open lrwxrwxrwx 1 cam grad 8 Aug 15 14:47 .on.read -> .on.open 1 cam grad 8 Aug 15 14:47 .on.read -> .on.open lrwxrwxrwx lrwxrwxrwx lrwxrwxrwx 1 cam grad 8 Aug 15 14:47 .on.release -> .on.open 1 cam grad 8 Aug 15 14:47 .on.release -> .on.open lrwxrwxrwx lrwxrwxrwx 1 cam grad 8 Aug 15 14:47 .on.write -> .on.open 1 cam grad 8 Aug 15 14:47 .on.write -> .on.open - -rw rw------- 1 cam grad 951 Aug 15 14:48 ------- 1 cam grad 951 Aug 15 14:48 anyfile anyfile [cam@sunset ~/test]$ cat .on.open [cam@sunset ~/test]$ cat .on.open #!/bin/sh sh #!/bin/ echo $2 >> /usr usr/scovil3/ /scovil3/logfile logfile echo $2 >> / [cam@sunset ~/test]$ [cam@sunset ~/test]$ Cameron Macdonell
The Scruf Scruf Framework: At User-Level Framework: At User-Level The Run when their corresponding file Run when their corresponding file � � operation occurs operation occurs Can perform two actions Can perform two actions � � 1) 1) Interposed Interposed Action Action File operation continues as normal File operation continues as normal � � 2) Redirection Redirection Action Action 2) Redirect Scruf Scruf-VFS to a different file -VFS to a different file Redirect � � Currently, can only come from .on.open Currently, can only come from .on.open � � Cameron Macdonell Back to Our Example Back to Our Example � For our purpose instead of storing editor For our purpose instead of storing editor � preferences, we want to store an executable preferences, we want to store an executable command command � cvs commit cvs commit filename filename � � Important: Important: we don we don’ ’t want to have to re-write t want to have to re-write � every application to run the script every application to run the script � Solution: Solution: Have the file system look for and Have the file system look for and � execute the scripts when certain file operations execute the scripts when certain file operations (i.e., open) occur (i.e., open) occur Cameron Macdonell
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