From 08fb39051f5581df45ae2a20c6cf2d0c4cddf7c2 Mon Sep 17 00:00:00 2001 From: Dave Chinner Date: Tue, 21 May 2013 18:02:00 +1000 Subject: [PATCH] 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: [] xfs_trans_alloc+0x26/0x50 but task is already holding lock: (sb_internal){++++.?}, at: [] 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 Signed-off-by: Dave Chinner Reviewed-by: Ben Myers Signed-off-by: Ben Myers (cherry picked from commit f648167f3ac79018c210112508c732ea9bf67c7b) --- fs/xfs/xfs_qm_syscalls.c | 40 +++++++++++++++++++++++----------------- 1 file changed, 23 insertions(+), 17 deletions(-) diff --git a/fs/xfs/xfs_qm_syscalls.c b/fs/xfs/xfs_qm_syscalls.c index c41190cad6e9..6cdf6ffc36a1 100644 --- a/fs/xfs/xfs_qm_syscalls.c +++ b/fs/xfs/xfs_qm_syscalls.c @@ -489,31 +489,36 @@ xfs_qm_scall_setqlim( if ((newlim->d_fieldmask & XFS_DQ_MASK) == 0) return 0; - tp = xfs_trans_alloc(mp, XFS_TRANS_QM_SETQLIM); - error = xfs_trans_reserve(tp, 0, XFS_QM_SETQLIM_LOG_RES(mp), - 0, 0, XFS_DEFAULT_LOG_COUNT); - if (error) { - xfs_trans_cancel(tp, 0); - return (error); - } - /* * We don't want to race with a quotaoff so take the quotaoff lock. - * (We don't hold an inode lock, so there's nothing else to stop - * a quotaoff from happening). (XXXThis doesn't currently happen - * because we take the vfslock before calling xfs_qm_sysent). + * We don't hold an inode lock, so there's nothing else to stop + * a quotaoff from happening. */ mutex_lock(&q->qi_quotaofflock); /* - * Get the dquot (locked), and join it to the transaction. - * Allocate the dquot if this doesn't exist. + * Get the dquot (locked) before we start, as we need to do a + * transaction to allocate it if it doesn't exist. Once we have the + * dquot, unlock it so we can start the next transaction safely. We hold + * a reference to the dquot, so it's safe to do this unlock/lock without + * it being reclaimed in the mean time. */ - if ((error = xfs_qm_dqget(mp, NULL, id, type, XFS_QMOPT_DQALLOC, &dqp))) { - xfs_trans_cancel(tp, XFS_TRANS_ABORT); + error = xfs_qm_dqget(mp, NULL, id, type, XFS_QMOPT_DQALLOC, &dqp); + if (error) { ASSERT(error != ENOENT); goto out_unlock; } + xfs_dqunlock(dqp); + + tp = xfs_trans_alloc(mp, XFS_TRANS_QM_SETQLIM); + error = xfs_trans_reserve(tp, 0, XFS_QM_SETQLIM_LOG_RES(mp), + 0, 0, XFS_DEFAULT_LOG_COUNT); + if (error) { + xfs_trans_cancel(tp, 0); + goto out_rele; + } + + xfs_dqlock(dqp); xfs_trans_dqjoin(tp, dqp); ddq = &dqp->q_core; @@ -621,9 +626,10 @@ xfs_qm_scall_setqlim( xfs_trans_log_dquot(tp, dqp); error = xfs_trans_commit(tp, 0); - xfs_qm_dqrele(dqp); - out_unlock: +out_rele: + xfs_qm_dqrele(dqp); +out_unlock: mutex_unlock(&q->qi_quotaofflock); return error; } -- 2.34.1