Btrfs-progs: setup framework to corrupt specific fields of an inode

A user reported a problem with his fs where he had a bogus isize on his
directory.  In order to make sure my patch for fsck fixes this properly I needed
to be able to corrupt an inode like this, which is what this patch is for.
Eventually I want to extend this to corrupt everything so we can integrate tests
into btrfs-progs to run btrfsck against to make sure we don't regress on fixing
things with btrfsck.  Thanks,

Signed-off-by: Josef Bacik <jbacik@fusionio.com>
Btrfs-progs: allow fsck to fix directory isize errors

A user reported a problem where he was unable to rmdir an empty directory.  This
is because his isize was wrong.  This patch will fix this sort of corruption and
allow him to rmdir his directory.  Thanks

Signed-off-by: Josef Bacik <jbacik@fusionio.com>
Btrfs-progs: make btrfsck fix backrefs that are broken

If you set an file extent item's disk_bytenr to something completely wrong we
won't be able to fix this if it is the only one who has a ref on the original
disk bytenr.  Our extent records know exactly who is supposed to point at them,
so if we have an extent record that has no backrefs we can go and try to lookup
the backrefs ourselves.  If these backrefs do not point to an extent record that
was actually found then we can be pretty sure this extent record is valid and
the backref is bogus.  Then the verify_backref code can do its thing and reset
the backref to point to the right extent record and we can all carry on.  This
fixes a user reported corruption.  Thanks,

Signed-off-by: Josef Bacik <jbacik@fusionio.com>
Btrfs-progs: add ability to corrupt file extent disk bytenr

A user had a corrupt fs where one of his file extents pointed to a completely
bogus disk bytenr.  This patch allows us to corrupt a file system in a similar
way in order to test btrfsck.  Thanks,

Signed-off-by: Josef Bacik <jbacik@fusionio.com>
Btrfs-progs: add make test framework

We need to start adding some sanity tests to btrfs-progs to make sure we aren't
breaking things with our patches.  The most important of these tools is btrfsck.
This patch gets things started by adding a basic btrfsck test that makes sure we
can fix a corruption problem we know we can fix.  Thanks,

Signed-off-by: Josef Bacik <jbacik@fusionio.com>
Btrfs-progs: add a bunch of new statistics to btrfs-calc-size

I've been wanting to get back to the allocator and make some changes to try and
fix our fragmenation woes with lots of metadata.  But in order to make these
changes I need to have something to tell me if my changes are making a real
measurable difference.  So this patch adds a bunch of new statistics to
btrfs-calc-size.  It will tell me how long it took to read in the trees, how
many seeks it had (both forward and backward).  It will tell me how far spread
out the tree is and spit out a nice histogram of the seeks.  Here is some sample
output

Calculating size of extent tree
        Total size: 60.74MB
                Inline data: 0.00
        Total seeks: 5020
                Forward seeks: 3691
                Backward seeks: 1329
                Avg seek len: 929.53MB
        Seek histogram
                      4096 -       4096:       1043 ####
                      8192 -      73728:        760 ###
                     81920 -   52527104:        753 ###
                  53518336 -  168009728:        753 ###
                 168591360 -  696045568:        753 ###
                 696238080 - 7560364032:        753 ###
                7560437760 - 8409739264:        178 |
        Total clusters: 1874
                Avg cluster size: 25.17KB
                Min cluster size: 8.00KB
                Max cluster size: 472.00KB
        Total disk spread: 7.90GB
        Total read time: 0 s 341670 us
        Levels: 4

This way we can have good numbers to back up any changes we make to the
allocator.  Thanks,

Signed-off-by: Josef Bacik <jbacik@fusionio.com>
Btrfs-progs: fix the min ticks check in print_seek_histogram

Before I had been dividing by 5 but that gave me too much output so I changed it
to 20 without changing the min seeks test.  Fix this to avoid a divide by 0
problem.  Thanks,

Signed-off-by: Josef Bacik <jbacik@fusionio.com>