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authorJan Kara <jack@suse.cz>2014-02-20 16:02:27 (GMT)
committerJiri Slaby <jslaby@suse.cz>2014-03-05 16:13:53 (GMT)
commitd1ea22966e9187b0b92f878a02686cbad4ab0d50 (patch)
treeae33b17002fbc010259bc94d15884f5ef5d231c6 /Documentation/SubmittingPatches
parentfea84e6b1cbfec4e124e06633a0d6febe7fad69a (diff)
downloadlinux-fsl-qoriq-d1ea22966e9187b0b92f878a02686cbad4ab0d50.tar.xz
quota: Fix race between dqput() and dquot_scan_active()
commit 1362f4ea20fa63688ba6026e586d9746ff13a846 upstream. 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. Signed-off-by: Jan Kara <jack@suse.cz> Signed-off-by: Jiri Slaby <jslaby@suse.cz>
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