aoe: improve handling of misbehaving network paths
authorEd Cashin <ecashin@coraid.com>
Tue, 18 Dec 2012 00:04:08 +0000 (16:04 -0800)
committerLinus Torvalds <torvalds@linux-foundation.org>
Tue, 18 Dec 2012 01:15:25 +0000 (17:15 -0800)
commitbbb44e30d07fdc111e34a5ec935b57521cea9499
tree11dda6628c4d7719607891f287c12aa87f06855b
parentb91316f2b7bc0b1d128a9890a2a4895f7e1c74fc
aoe: improve handling of misbehaving network paths

An AoE target can have multiple network ports used for AoE, and in the
aoe driver, those are tracked by the aoetgt struct.  These changes allow
the aoe driver to handle network paths, or aoetgts, that are not working
well, compared to the others.

Paths that do not get responses despite the retransmission of AoE
commands are marked as "tainted", and non-tainted paths are preferred.

Meanwhile, the aoe driver attempts to "probe" the tainted path in the
background by issuing reads of LBA 0 that are padded out to full
(possibly jumbo-frame) size.  If the probes get responses, then the path
is "redeemed", and its taint is removed.

This mechanism has been shown to be helpful in transparently handling
and recovering from real-world network "brown outs" in ways that the
earlier "shoot the help-needing target in the head" mechanism could not.

Signed-off-by: Ed Cashin <ecashin@coraid.com>
Cc: Jens Axboe <axboe@kernel.dk>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
drivers/block/aoe/aoe.h
drivers/block/aoe/aoecmd.c
drivers/block/aoe/aoedev.c