From: Chris Mason <chris.mason@oracle.com>
Date: Sun, 6 May 2012 11:23:47 +0000 (-0400)
Subject: Btrfs: avoid sleeping in verify_parent_transid while atomic
X-Git-Tag: v3.4-rc6~2^2
X-Git-Url: http://git.openpandora.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=b9fab919b748c7b39c19ff236ed6c5682c266dde;p=pandora-kernel.git

Btrfs: avoid sleeping in verify_parent_transid while atomic

verify_parent_transid needs to lock the extent range to make
sure no IO is underway, and so it can safely clear the
uptodate bits if our checks fail.

But, a few callers are using it with spinlocks held.  Most
of the time, the generation numbers are going to match, and
we don't want to switch to a blocking lock just for the error
case.  This adds an atomic flag to verify_parent_transid,
and changes it to return EAGAIN if it needs to block to
properly verifiy things.

Signed-off-by: Chris Mason <chris.mason@oracle.com>
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