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authorJan Kara <jack@suse.cz>2014-02-20 17:02:27 +0100
committerJan Kara <jack@suse.cz>2014-02-20 21:57:04 +0100
commit1362f4ea20fa63688ba6026e586d9746ff13a846 (patch)
tree6c80329bee77974426663a1af8e5d70ef62759f9 /include/trace/events/writeback.h
parentudf: Fix data corruption on file type conversion (diff)
downloadlinux-1362f4ea20fa63688ba6026e586d9746ff13a846.tar.xz
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quota: Fix race between dqput() and dquot_scan_active()
Currently last dqput() can race with dquot_scan_active() causing it to call callback for an already deactivated dquot. The race is as follows: CPU1 CPU2 dqput() spin_lock(&dq_list_lock); if (atomic_read(&dquot->dq_count) > 1) { - not taken if (test_bit(DQ_ACTIVE_B, &dquot->dq_flags)) { spin_unlock(&dq_list_lock); ->release_dquot(dquot); if (atomic_read(&dquot->dq_count) > 1) - not taken dquot_scan_active() spin_lock(&dq_list_lock); if (!test_bit(DQ_ACTIVE_B, &dquot->dq_flags)) - not taken atomic_inc(&dquot->dq_count); spin_unlock(&dq_list_lock); - proceeds to release dquot ret = fn(dquot, priv); - called for inactive dquot Fix the problem by making sure possible ->release_dquot() is finished by the time we call the callback and new calls to it will notice reference dquot_scan_active() has taken and bail out. CC: stable@vger.kernel.org # >= 2.6.29 Signed-off-by: Jan Kara <jack@suse.cz>
Diffstat (limited to 'include/trace/events/writeback.h')
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