Why does xfsdump encounter "WARNING: could not get list of non-root attributes for nondir ino nnnn: Cannot allocate memory (12)"?

[Christoph Hellwig]

On Tue, Jan 03, 2012 at 08:37:06AM +1100, Dave Chinner wrote:
> xfs: handle kmalloc failure when reading attrs
> 
> From: Dave Chinner <dchinner at redhat.com>
> 
> xfsdump uses for a large buffer for extended attributes, which has a
> kmalloc'd shadow buffer in the kernel. This can fail after the
> system has been running for some time as it is a high order
> allocation. Convert this to a vmalloc so that it doesn't require
> contiguous memory and so won't randomly fail while xfsdump is
> running.

I think this should use kmalloc for allocation smaller than a page to
avoid the vmalloc overhead for the usual case of small attributes.

Also the fs/xattr.c code for the normal xattr system calls needs the
same treatment.