[XFS] fix writeback control handling  fix a reversed condition on where to trylock and deal with block layer congestion properly.	Patch from David Chinner and Christoph Hellwig.
[XFS] fix writeback control handling  fix a reversed condition on where to
trylock and deal with block layer congestion properly.	Patch from David
Chinner and Christoph Hellwig.

SGI-PV: 947118
SGI-Modid: xfs-linux-melb:xfs-kern:203830a

Signed-off-by: Christoph Hellwig <923f7720577207a44b32e59bbfbea59d27f1ae8e@sgi.com>
Signed-off-by: Nathan Scott <e2e3f1f24cbc439f8c1ba9b08f9954237d64be64@sgi.com>

TeamVee-Kanas/android_kernel_samsung_kanas,TeamVee-Kanas/android_kernel_samsung_kanas,KristFoundation/Programs,KristFoundation/Programs,TeamVee-Kanas/android_kernel_samsung_kanas,KristFoundation/Programs,TeamVee-Kanas/android_kernel_samsung_kanas,KristFoundation/Programs,KristFoundation/Programs,KristFoundation/Programs,TeamVee-Kanas/android_kernel_samsung_kanas