Date: Mon, 8 Dec 2008 11:04:17 +0000 (UTC) From: Konstantin Belousov <kib@FreeBSD.org> To: src-committers@freebsd.org, svn-src-all@freebsd.org, svn-src-head@freebsd.org Subject: svn commit: r185761 - head/sys/ufs/ufs Message-ID: <200812081104.mB8B4HwA058122@svn.freebsd.org>
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Author: kib Date: Mon Dec 8 11:04:17 2008 New Revision: 185761 URL: http://svn.freebsd.org/changeset/base/185761 Log: The dqrele() function syncs the dq, then acquires the dqh lock, and then does final drop of the the dq reference to put it onto the free list. There is a possibility that the dq would be found by another thread after sync and before the dqh lock is acquired. If that other thread drops the dq before we have taken the dqh lock, the dirty dq is put on the free list. Recheck the DQ_MOD after the dqh lock is relocked. Repeat dqsync() if the dq is dirty. This ensures that up to date dq is written in the quota file and fixes assertion in dqget(). Reported and tested by: Frode Nordahl <frode nordahl net> MFC after: 3 days Modified: head/sys/ufs/ufs/ufs_quota.c Modified: head/sys/ufs/ufs/ufs_quota.c ============================================================================== --- head/sys/ufs/ufs/ufs_quota.c Mon Dec 8 06:54:24 2008 (r185760) +++ head/sys/ufs/ufs/ufs_quota.c Mon Dec 8 11:04:17 2008 (r185761) @@ -1262,7 +1262,7 @@ dqrele(struct vnode *vp, struct dquot *d return; } DQH_UNLOCK(); - +sync: (void) dqsync(vp, dq); DQH_LOCK(); @@ -1271,6 +1271,18 @@ dqrele(struct vnode *vp, struct dquot *d DQH_UNLOCK(); return; } + + /* + * The dq may become dirty after it is synced but before it is + * put to the free list. Checking the DQ_MOD there without + * locking dq should be safe since no other references to the + * dq exist. + */ + if ((dq->dq_flags & DQ_MOD) != 0) { + dq->dq_cnt++; + DQH_UNLOCK(); + goto sync; + } TAILQ_INSERT_TAIL(&dqfreelist, dq, dq_freelist); DQH_UNLOCK(); }
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