Andreas Dilger wrote:
On Aug 01, 2007 11:46 +0530, Aneesh Kumar K.V wrote:
Andreas Dilger wrote:
On Aug 01, 2007 07:34 +0530, Aneesh Kumar K.V wrote:
undoe2fs can be used to replay the transaction saved
in the transaction file using undo I/O Manager
This should save the mtime of the superblock, and only do the undo
step if the filesystem hasn't changed. Otherwise it could seriously
corrupt the filesystem.
I am not sure i understand this. The Undo I/O manager tracks all the write
happening to the file system and copy the original content of the blocks to
the tdb file. Undoe2fs simply copies these blocks back to the file system.
That way if you look at undoe2fs it doesn't have any knowledge of the file
system at all.
Can you let me know a use case where this will fail.
- modify filesystem with undo manager (e.g. inode resize)
- mount filesystem, make changes, unmount
- run undoe2fs to overwrite filesystem, corrupting it
But that won't corrupt it. It will bring the file system back to
the state before inode resize. I understand that we may want to have
a) Don't replay if file system is mounted
b) Don't replay if UUID doesn't match
But i guess we should allow a replay if file system got changed afterwards.
Ofcourse the changes will no longer be available after the replay.
-aneesh
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