ocfs2: Fix quota locking
OCFS2 had three issues with quota locking: a) When reading dquot from global quota file, we started a transaction while holding dqio_mutex which is prone to deadlocks because other paths do it the other way around b) During ocfs2_sync_dquot we were not protected against concurrent writers on the same node. Because we first copy data to local buffer, a race could happen resulting in old data being written to global quota file and thus causing quota inconsistency after a crash. c) ip_alloc_sem of quota files was acquired while a transaction is started in ocfs2_quota_write which can deadlock because we first get ip_alloc_sem and then start a transaction when extending quota files. We fix the problem a) by pulling all necessary code to ocfs2_acquire_dquot and ocfs2_release_dquot. Thus we no longer depend on generic dquot_acquire to do the locking and can force proper lock ordering. Problems b) and c) are fixed by locking i_mutex and ip_alloc_sem of global quota file in ocfs2_lock_global_qf and removing ip_alloc_sem from ocfs2_quota_read and ocfs2_quota_write. Acked-by: NJoel Becker <Joel.Becker@oracle.com> Signed-off-by: NJan Kara <jack@suse.cz>
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