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diff --git a/Documentation/filesystems/dlmfs.txt b/Documentation/filesystems/dlmfs.txt deleted file mode 100644 index fcf4d509d118..000000000000 --- a/Documentation/filesystems/dlmfs.txt +++ /dev/null @@ -1,130 +0,0 @@ -dlmfs -================== -A minimal DLM userspace interface implemented via a virtual file -system. - -dlmfs is built with OCFS2 as it requires most of its infrastructure. - -Project web page: http://ocfs2.wiki.kernel.org -Tools web page: https://github.com/markfasheh/ocfs2-tools -OCFS2 mailing lists: http://oss.oracle.com/projects/ocfs2/mailman/ - -All code copyright 2005 Oracle except when otherwise noted. - -CREDITS -======= - -Some code taken from ramfs which is Copyright (C) 2000 Linus Torvalds -and Transmeta Corp. - -Mark Fasheh <mark.fasheh@oracle.com> - -Caveats -======= -- Right now it only works with the OCFS2 DLM, though support for other - DLM implementations should not be a major issue. - -Mount options -============= -None - -Usage -===== - -If you're just interested in OCFS2, then please see ocfs2.txt. The -rest of this document will be geared towards those who want to use -dlmfs for easy to setup and easy to use clustered locking in -userspace. - -Setup -===== - -dlmfs requires that the OCFS2 cluster infrastructure be in -place. Please download ocfs2-tools from the above url and configure a -cluster. - -You'll want to start heartbeating on a volume which all the nodes in -your lockspace can access. The easiest way to do this is via -ocfs2_hb_ctl (distributed with ocfs2-tools). Right now it requires -that an OCFS2 file system be in place so that it can automatically -find its heartbeat area, though it will eventually support heartbeat -against raw disks. - -Please see the ocfs2_hb_ctl and mkfs.ocfs2 manual pages distributed -with ocfs2-tools. - -Once you're heartbeating, DLM lock 'domains' can be easily created / -destroyed and locks within them accessed. - -Locking -======= - -Users may access dlmfs via standard file system calls, or they can use -'libo2dlm' (distributed with ocfs2-tools) which abstracts the file -system calls and presents a more traditional locking api. - -dlmfs handles lock caching automatically for the user, so a lock -request for an already acquired lock will not generate another DLM -call. Userspace programs are assumed to handle their own local -locking. - -Two levels of locks are supported - Shared Read, and Exclusive. -Also supported is a Trylock operation. - -For information on the libo2dlm interface, please see o2dlm.h, -distributed with ocfs2-tools. - -Lock value blocks can be read and written to a resource via read(2) -and write(2) against the fd obtained via your open(2) call. The -maximum currently supported LVB length is 64 bytes (though that is an -OCFS2 DLM limitation). Through this mechanism, users of dlmfs can share -small amounts of data amongst their nodes. - -mkdir(2) signals dlmfs to join a domain (which will have the same name -as the resulting directory) - -rmdir(2) signals dlmfs to leave the domain - -Locks for a given domain are represented by regular inodes inside the -domain directory. Locking against them is done via the open(2) system -call. - -The open(2) call will not return until your lock has been granted or -an error has occurred, unless it has been instructed to do a trylock -operation. If the lock succeeds, you'll get an fd. - -open(2) with O_CREAT to ensure the resource inode is created - dlmfs does -not automatically create inodes for existing lock resources. - -Open Flag Lock Request Type ---------- ----------------- -O_RDONLY Shared Read -O_RDWR Exclusive - -Open Flag Resulting Locking Behavior ---------- -------------------------- -O_NONBLOCK Trylock operation - -You must provide exactly one of O_RDONLY or O_RDWR. - -If O_NONBLOCK is also provided and the trylock operation was valid but -could not lock the resource then open(2) will return ETXTBUSY. - -close(2) drops the lock associated with your fd. - -Modes passed to mkdir(2) or open(2) are adhered to locally. Chown is -supported locally as well. This means you can use them to restrict -access to the resources via dlmfs on your local node only. - -The resource LVB may be read from the fd in either Shared Read or -Exclusive modes via the read(2) system call. It can be written via -write(2) only when open in Exclusive mode. - -Once written, an LVB will be visible to other nodes who obtain Read -Only or higher level locks on the resource. - -See Also -======== -http://opendlm.sourceforge.net/cvsmirror/opendlm/docs/dlmbook_final.pdf - -For more information on the VMS distributed locking API. |