Messages in this thread | | | Date | Thu, 31 Oct 2002 22:22:00 -0500 | From | "Theodore Ts'o" <> | Subject | Re: [PATCH] 2/11 Ext2/3 Updates: Extended attributes, ACL, etc. |
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On Tue, Oct 29, 2002 at 12:22:46PM -0500, Jeff Garzik wrote: > tytso@mit.edu wrote: > > >Ext2/3 forward compatibility: on-line resizing > > > > > Is the interface for this going to be ext2meta? Al and sct seemed > to agree that that was the best way act upon the filesystem metadata > while it's online... I'll probably be updating that for 2.5.x VFS > changes in a few weeks, that will provide safe online defrag and a > good interface for other metadata interaction.
I'm not sure ext2meta will be sufficient. It's not just a matter of modifying the on-disk metadata, as would be needed for defrag, but I would also need to modify some of the in-core data structions in the ext2/3 filesystem data structures. For example, when you resize the filesystem, you need to increase the number of group descriptors, which means you need to kmalloc, copy, and then kfree sbi->group_desc out from under the mounted filesystem.
No doubt ext2meta could be modified so it could "reach out and touch" internal ext2/3 fileststem data structures in core. But the locking issues involved get really messy.
My original plan was to adapt Andreas Dilger's on-line resizing patch to use the new block group layout, which would obviate the need to take the filesystem off-line and run ext2prepare first. I'm not opposed to trying to do it via ext2meta, but it seems like it might get complicated and hairy quite quickly.
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