Hi all, I spent last week analyzing a client's corrupted ext3 image to see if I could determine what had gone wrong and caused the filesystem to blow apart. As best as I could tell, a data block got miswritten into a different sector ... which happened to be an indirect block. Some time later the indirect block, which now pointed at one of the inode tables (among other things that shouldn't ever become file data) was loaded as part of a file write, which caused that inode table to be blown to smithereens. Just for fun I tried reading from one of these busted-inode files and ... failed to encounter any errors. Somehow, they didn't find it funny that ext3 would read block numbers from a table with the contents "ibm.com" with a straight face. Fortunately there were backups. :) The client at this point asked if ext4 would do a better job of sanity checking, which got me to wonder why ext4 checksums block groups but not inodes. It's on Ted's todo list, but apparently nobody wrote any patch, so I did. The following two patches are a first draft of adding inode checksum support to both the kernel driver and to the various e2fsprogs. If you have an existing ext* fs with 256-byte inodes, you ought to be able to "tune2fs -O inode_csum /dev/XXX", fsck /dev/XXX, and mount the filesystem with checksumming enabled. It seems to work for me (i386/x86-64), but I'm looking for comments for improvement and perhaps some more testing (ppc64 is still building). This inode checksum feature is not enabled by default. --D -- To unsubscribe from this list: send the line "unsubscribe linux-ext4" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
