1 // SPDX-License-Identifier: GPL-2.0-or-later
2 /*
3 * Copyright (C) 2019 Oracle. All Rights Reserved.
4 * Author: Darrick J. Wong <darrick.wong@oracle.com>
5 */
6 #include "xfs.h"
7 #include "xfs_fs.h"
8 #include "xfs_shared.h"
9 #include "xfs_format.h"
10 #include "xfs_log_format.h"
11 #include "xfs_trans_resv.h"
12 #include "xfs_mount.h"
13 #include "xfs_trace.h"
14 #include "xfs_sysctl.h"
15 #include "xfs_pwork.h"
16 #include <linux/nmi.h>
17
18 /*
19 * Parallel Work Queue
20 * ===================
21 *
22 * Abstract away the details of running a large and "obviously" parallelizable
23 * task across multiple CPUs. Callers initialize the pwork control object with
24 * a desired level of parallelization and a work function. Next, they embed
25 * struct xfs_pwork in whatever structure they use to pass work context to a
26 * worker thread and queue that pwork. The work function will be passed the
27 * pwork item when it is run (from process context) and any returned error will
28 * be recorded in xfs_pwork_ctl.error. Work functions should check for errors
29 * and abort if necessary; the non-zeroness of xfs_pwork_ctl.error does not
30 * stop workqueue item processing.
31 *
32 * This is the rough equivalent of the xfsprogs workqueue code, though we can't
33 * reuse that name here.
34 */
35
36 /* Invoke our caller's function. */
37 static void
38 xfs_pwork_work(
39 struct work_struct *work)
40 {
41 struct xfs_pwork *pwork;
42 struct xfs_pwork_ctl *pctl;
43 int error;
44
45 pwork = container_of(work, struct xfs_pwork, work);
46 pctl = pwork->pctl;
47 error = pctl->work_fn(pctl->mp, pwork);
48 if (error && !pctl->error)
49 pctl->error = error;
50 if (atomic_dec_and_test(&pctl->nr_work))
51 wake_up(&pctl->poll_wait);
52 }
53
54 /*
55 * Set up control data for parallel work. @work_fn is the function that will
56 * be called. @tag will be written into the kernel threads. @nr_threads is
57 * the level of parallelism desired, or 0 for no limit.
58 */
59 int
60 xfs_pwork_init(
61 struct xfs_mount *mp,
62 struct xfs_pwork_ctl *pctl,
63 xfs_pwork_work_fn work_fn,
64 const char *tag)
65 {
66 unsigned int nr_threads = 0;
67
68 #ifdef DEBUG
69 if (xfs_globals.pwork_threads >= 0)
70 nr_threads = xfs_globals.pwork_threads;
71 #endif
72 trace_xfs_pwork_init(mp, nr_threads, current->pid);
73
74 pctl->wq = alloc_workqueue("%s-%d",
75 WQ_UNBOUND | WQ_SYSFS | WQ_FREEZABLE, nr_threads, tag,
76 current->pid);
77 if (!pctl->wq)
78 return -ENOMEM;
79 pctl->work_fn = work_fn;
80 pctl->error = 0;
81 pctl->mp = mp;
82 atomic_set(&pctl->nr_work, 0);
83 init_waitqueue_head(&pctl->poll_wait);
84
85 return 0;
86 }
87
88 /* Queue some parallel work. */
89 void
90 xfs_pwork_queue(
91 struct xfs_pwork_ctl *pctl,
92 struct xfs_pwork *pwork)
93 {
94 INIT_WORK(&pwork->work, xfs_pwork_work);
95 pwork->pctl = pctl;
96 atomic_inc(&pctl->nr_work);
97 queue_work(pctl->wq, &pwork->work);
98 }
99
100 /* Wait for the work to finish and tear down the control structure. */
101 int
102 xfs_pwork_destroy(
103 struct xfs_pwork_ctl *pctl)
104 {
105 destroy_workqueue(pctl->wq);
106 pctl->wq = NULL;
107 return pctl->error;
108 }
109
110 /*
111 * Wait for the work to finish by polling completion status and touch the soft
112 * lockup watchdog. This is for callers such as mount which hold locks.
113 */
114 void
115 xfs_pwork_poll(
116 struct xfs_pwork_ctl *pctl)
117 {
118 while (wait_event_timeout(pctl->poll_wait,
119 atomic_read(&pctl->nr_work) == 0, HZ) == 0)
120 touch_softlockup_watchdog();
121 }
122
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