Hi all, I'm sending you a patch (see the 1/1 patch) which should make undelete process for deleted files on ext4 easier. I do this patch as a part of my Barchelor's thesis with support of Red Hat company. The main changes in patch are following: a) commented out zeroing ex->ee_len, ee->start_hi and ee->start_lo, because these entries are essential for undelete process b) only in inode structure, storing original value of eh->depth and eh->entries. These values are stored to unused entry eh_generation in struct ext4_extent_header after all extents have been definitely removed. eh->entries is 16 bits value and is stored in first half of 32 bits of eh->generation. eh->depth is also 16 bits value and is stored in second half of eh->generation. For storing these valued, I wrote macros to ext4_extents.h. It's should NOT cause problems to store values in eh->generation, because eh->generation is used only, when file is NOT deleted. After delete process, eh->generation can have any value. c) if deletion process removes extents from block, which is not inode (eh->depth > 0), then I'm storing only eh->entries original value to eh->generation, because eh->depth will stay untouched. d) if delete process removes all extent_idx structures from block, which is not in inode (eh->depth > 0), then I'm storing also only eh->entries original value. But in this case, I need to store original eh->entries value for each level separately, because delete process is changing eh->entries value during walking through extent tree. This problem is solved by allocating array, where I will store original values This patch shouldn't break ext4, I tested it with xfs_tests and tests were successfull. I also successfully created undelete application, based on e2fslibs, which demonstrates undelete process. (link: https://github.com/uhliarik/ext4-undelete ) Thanks! Lubos Uhliarik -- 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
