xfs: avoid nesting transactions in xfs_qm_scall_setqlim()
Lockdep reports: ============================================= [ INFO: possible recursive locking detected ] 3.9.0+ #3 Not tainted --------------------------------------------- setquota/28368 is trying to acquire lock: (sb_internal){++++.?}, at: [<c11e8846>] xfs_trans_alloc+0x26/0x50 but task is already holding lock: (sb_internal){++++.?}, at: [<c11e8846>] xfs_trans_alloc+0x26/0x50 from xfs_qm_scall_setqlim()->xfs_dqread() when a dquot needs to be allocated. xfs_qm_scall_setqlim() is starting a transaction and then not passing it into xfs_qm_dqet() and so it starts it's own transaction when allocating the dquot. Splat! Fix this by not allocating the dquot in xfs_qm_scall_setqlim() inside the setqlim transaction. This requires getting the dquot first (and allocating it if necessary) then dropping and relocking the dquot before joining it to the setqlim transaction. Reported-by: Michael L. Semon <mlsemon35@gmail.com> Signed-off-by: Dave Chinner <dchinner@redhat.com> Reviewed-by: Ben Myers <bpm@sgi.com> Signed-off-by: Ben Myers <bpm@sgi.com> (cherry picked from commit f648167f3ac79018c210112508c732ea9bf67c7b)
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@ -489,31 +489,36 @@ xfs_qm_scall_setqlim(
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if ((newlim->d_fieldmask & XFS_DQ_MASK) == 0)
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if ((newlim->d_fieldmask & XFS_DQ_MASK) == 0)
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return 0;
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return 0;
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/*
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* We don't want to race with a quotaoff so take the quotaoff lock.
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* We don't hold an inode lock, so there's nothing else to stop
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* a quotaoff from happening.
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*/
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mutex_lock(&q->qi_quotaofflock);
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/*
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* Get the dquot (locked) before we start, as we need to do a
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* transaction to allocate it if it doesn't exist. Once we have the
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* dquot, unlock it so we can start the next transaction safely. We hold
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* a reference to the dquot, so it's safe to do this unlock/lock without
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* it being reclaimed in the mean time.
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*/
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error = xfs_qm_dqget(mp, NULL, id, type, XFS_QMOPT_DQALLOC, &dqp);
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if (error) {
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ASSERT(error != ENOENT);
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goto out_unlock;
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}
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xfs_dqunlock(dqp);
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tp = xfs_trans_alloc(mp, XFS_TRANS_QM_SETQLIM);
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tp = xfs_trans_alloc(mp, XFS_TRANS_QM_SETQLIM);
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error = xfs_trans_reserve(tp, 0, XFS_QM_SETQLIM_LOG_RES(mp),
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error = xfs_trans_reserve(tp, 0, XFS_QM_SETQLIM_LOG_RES(mp),
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0, 0, XFS_DEFAULT_LOG_COUNT);
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0, 0, XFS_DEFAULT_LOG_COUNT);
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if (error) {
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if (error) {
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xfs_trans_cancel(tp, 0);
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xfs_trans_cancel(tp, 0);
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return (error);
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goto out_rele;
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}
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}
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/*
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xfs_dqlock(dqp);
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* We don't want to race with a quotaoff so take the quotaoff lock.
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* (We don't hold an inode lock, so there's nothing else to stop
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* a quotaoff from happening). (XXXThis doesn't currently happen
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* because we take the vfslock before calling xfs_qm_sysent).
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*/
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mutex_lock(&q->qi_quotaofflock);
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/*
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* Get the dquot (locked), and join it to the transaction.
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* Allocate the dquot if this doesn't exist.
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*/
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if ((error = xfs_qm_dqget(mp, NULL, id, type, XFS_QMOPT_DQALLOC, &dqp))) {
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xfs_trans_cancel(tp, XFS_TRANS_ABORT);
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ASSERT(error != ENOENT);
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goto out_unlock;
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}
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xfs_trans_dqjoin(tp, dqp);
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xfs_trans_dqjoin(tp, dqp);
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ddq = &dqp->q_core;
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ddq = &dqp->q_core;
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@ -621,9 +626,10 @@ xfs_qm_scall_setqlim(
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xfs_trans_log_dquot(tp, dqp);
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xfs_trans_log_dquot(tp, dqp);
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error = xfs_trans_commit(tp, 0);
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error = xfs_trans_commit(tp, 0);
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xfs_qm_dqrele(dqp);
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out_unlock:
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out_rele:
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xfs_qm_dqrele(dqp);
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out_unlock:
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mutex_unlock(&q->qi_quotaofflock);
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mutex_unlock(&q->qi_quotaofflock);
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return error;
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return error;
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}
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}
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