Just some quick notes on possible ways to fix the ext2 fsync bug that eXplode found. Whether or not anyone will bother to implement it is another matter. Background: The eXplode file system checker found a bug in ext2 fsync behavior. Do the following: truncate file A, create file B which reallocates one of A's old indirect blocks, fsync file B. If you then crash before file A's metadata is all written out, fsck will complete the truncate for file A... thereby deleting file B's data. So fsync file B doesn't guarantee data is on disk after a crash. Details: http://www.stanford.edu/~engler/explode-osdi06.pdf Two possible solutions I can think of: * Rearrange order of duplicate block checking and fixing file size in fsck. Not sure how hard this is. (Ted?) * Keep a set of "still allocated on disk" block bitmaps that gets flushed whenever a sync happens. Don't allocate these blocks. Journaling file systems already have to do this. -VAL - To unsubscribe from this list: send the line "unsubscribe linux-fsdevel" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
