e2find: new ext2/3/4 tool for fast directory entry iterations

[Vincent Caron]

Hello ext users,

  in a recurrent need to be able to traverse large filesystems (10-350M
inodes) backed by spindle-based RAID arrays, I tried several solutions
(like intercepting readdir and sorting by inode, playing with cache
hints, and such), to no avail.

  Since I'm mostly facing ext3 and ext4 filesystems, I wrote a tool
based on libe2fs which replaces the 'find /' part by directly going to
the ext data structures. It has been working great for me for several
months, and I've published it at https://github.com/bearstech/e2find

  There's a data safety issue I'm not quite sure. I'm using libe2fs to
open read-only blockdevices which are mounted and actively written to.
It's obviously unsafe (not from the data-loss p.o.v., but from the
coherent-retrieved-data p.o.v.), but I've never encountered a situation
where e2find would spit incoherent information : all retrieved filenames
exist as seen from the VFS, except those deleted between the enumeration
and resolution phases of e2sync. Since I'm in userland and not locking
any on-disk data structure I'm reading, I wonder what kind of suprises I
should expect in the retrieved data.