From: Oliver Xymoron <oxymoron@waste.org>

These patches add the infrastructure for reporting asynchronous write errors
to block devices to userspace.  Error which are detected due to pdflush or VM
writeout are reported at the next fsync, fdatasync, or msync on the given
file, and on close if the error occurs in time.

We do this by propagating any errors into page->mapping->error when they are
detected.  In fsync(), msync(), fdatasync() and close() we return that error
and zero it out.


The Open Group say close() _may_ fail if an I/O error occurred while reading
from or writing to the file system.  Well, in this implementation close() can
return -EIO or -ENOSPC.  And in that case it will succeed, not fail - perhaps
that is what they meant.


There are three patches in this series and testing has only been performed
with all three applied.