Re: (reiserfs) Re: LVM / Filesystems / High availability

Amos Shapira (amos@butch.gezernet.co.il)
Wed, 24 Jun 1998 03:48:16 +0400

On Tue, June 23 1998, "Theodore Y. Ts'o" <tytso@MIT.EDU> wrote:
|The plan is to eventually add kernel support for moving the location of
|data blocks of a file, and given an inode number and all of the
|directories in which that inode appears, move an inode to another
|location on disk. This would allow a user-mode program to be able to do
|on-line resizing at some point in the future.
|
|This will be a ways off, but theoretically it really isn't all that hard
|to do. (As always, the devil is in the details. :-)

SGI already had exactly such a thing in early IRIX 5's. It was used
by the "live filesystem" defragmentor. As far as I remember, I
learned about it from finding about an syssgi(?) system call parameter
which allowed a process to lock an inode. I didn't dive into this
(not having the kernel sources :-) but it sounded like being able to
lock the inode (and maybe allocate a block from user space? Will try
to check it next time) was enough to let a user program shuffle blocks
around safely.

Cheers,

--Amos

--Amos Shapira | "Of course Australia was marked for
133 Shlomo Ben-Yosef st. | glory, for its people had been chosen
Jerusalem 93 805 | by the finest judges in England."
ISRAEL amos@gezernet.co.il | -- Anonymous

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