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Direct access to the quota files, in particular, lookup, causes lock

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conflict with the quota metadata access.  Mark quota vnode lock as
recursive and always exclusive to avoid the problem.

Reported by:	hrs
Tested by:	hrs, pho
Sponsored by:	The FreeBSD Foundation
MFC after:	1 week
This commit is contained in:
Konstantin Belousov 2014-08-29 09:04:24 +00:00
parent 575e02d94f
commit c6fef2d49a
1 changed files with 13 additions and 0 deletions
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13
sys/ufs/ufs/ufs_quota.c
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@ -557,8 +557,21 @@ quotaon(struct thread *td, struct mount *mp, int type, void *fname)
if (*vpp != vp)
quotaoff1(td, mp, type);
/*
* When the directory vnode containing the quota file is
* inactivated, due to the shared lookup of the quota file
* vput()ing the dvp, the qsyncvp() call for the containing
* directory would try to acquire the quota lock exclusive.
* At the same time, lookup already locked the quota vnode
* shared. Mark the quota vnode lock as allowing recursion
* and automatically converting shared locks to exclusive.
*
* Also mark quota vnode as system.
*/
vn_lock(vp, LK_EXCLUSIVE | LK_RETRY);
vp->v_vflag |= VV_SYSTEM;
VN_LOCK_AREC(vp);
VN_LOCK_DSHARE(vp);
VOP_UNLOCK(vp, 0);
*vpp = vp;
/*