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authorDave Chinner <dchinner@redhat.com>2013-05-21 18:02:00 +1000
committerBen Myers <bpm@sgi.com>2013-05-21 13:57:05 -0500
commitf648167f3ac79018c210112508c732ea9bf67c7b (patch)
tree29ceb96b625f9841dfad5633cff25dded3ef2ad6 /fs/xfs/xfs_qm_syscalls.c
parente461fcb194172b3f709e0b478d2ac1bdac7ab9a3 (diff)
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>
Diffstat (limited to 'fs/xfs/xfs_qm_syscalls.c')
-rw-r--r--fs/xfs/xfs_qm_syscalls.c40
1 files 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;
}