[PATCH 0/6] RFC quota: Redesign IO error handling interface

[Dmitry Monakhov <dmonakhov@openvz.org>]

This patchset is tended to provide interface for handling IO errors
from internal quota code.
Any error must being returned to fs-caller to signal about possible
quota inconsistency. I've done it in following way:

1) Handle low-level io errors from dqget() and it's callers
2) Handle errors from dquot_initialize
   This path catch most of IO error, but no all.
3) Check what i_dquot was initialized in each low-level function.
   There are two types of such functions
   3A) Charging functions (alloc_{space,inode}): Caller of such
       function may easy handle an error and abort an operation.
   3B) nofail functions (claim_space,free_{space,inode})
       In most cases caller can not abort an operation even if
       inode's quotas was semi-initialized, so I just skip this
       functions for now.
I would like to know you ideas suggestions about this.
Note: Only ext4's part was basically tested for now, others was just
compile tested.