Quoting Theodore Ts'o (tytso@mit.edu):

Are you folks still seeing ext4_mb_generate_buddy or
ext4_mb_release_inode_pa EXT4-fs errors?

I think I may have found a fix for this problem.  Or at least, I've
found one of the causes.  If we get a memory allocation failure from
ext4_mb_new_inode_pa(), it can cause these errors.

Good to hear a probable cause was found. Unfortunately for this bug's
progress, i've switched to a newer kernel altogether since the 3.13
tree in Ubuntu has had a lot of other problems besides this
EXT4 ext_mb_generate_buddy issue.

With 3.15.0 i have not experienced any ext4 issues at all.

If you want me to, i would be willing to boot that VM in 3.13 with this
patch, but as said, it can take ages before the bug was triggered...

Thanks for your hard work.

-Sndr.
-- 
| > Because we read from top to bottom.
| > > Why should i start my email reply *below* the quoted text?
| 4096R/20CC6CD2 - 6D40 1A20 B9AA 87D4 84C7  FBD6 F3A9 9442 20CC 6CD2