From: Sage Weil <sage@redhat.com>
Date: Fri, 26 Sep 2014 15:30:06 +0000 (-0700)
Subject: Btrfs: fix race in WAIT_SYNC ioctl
X-Git-Tag: omap-for-v3.19/prcm-cleanup~117^2~8
X-Git-Url: http://git.openpandora.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=42383020beb1cfb05f5d330cc311931bc4917a97;p=pandora-kernel.git

Btrfs: fix race in WAIT_SYNC ioctl

We check whether transid is already committed via last_trans_committed and
then search through trans_list for pending transactions.  If
last_trans_committed is updated by btrfs_commit_transaction after we check
it (there is no locking), we will fail to find the committed transaction
and return EINVAL to the caller.  This has been observed occasionally by
ceph-osd (which uses this ioctl heavily).

Fix by rechecking whether the provided transid <= last_trans_committed
after the search fails, and if so return 0.

Signed-off-by: Sage Weil <sage@redhat.com>
Signed-off-by: Chris Mason <clm@fb.com>
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