1 // SPDX-License-Identifier: GPL-2.0
2 /*
3  * Copyright (c) 2000-2002,2005 Silicon Graphics, Inc.
4  * Copyright (c) 2008 Dave Chinner
5  * All Rights Reserved.
6  */
7 #include "xfs.h"
8 #include "xfs_fs.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_trans.h"
14 #include "xfs_trans_priv.h"
15 #include "xfs_trace.h"
16 #include "xfs_errortag.h"
17 #include "xfs_error.h"
18 #include "xfs_log.h"
19 
20 #ifdef DEBUG
21 /*
22  * Check that the list is sorted as it should be.
23  *
24  * Called with the ail lock held, but we don't want to assert fail with it
25  * held otherwise we'll lock everything up and won't be able to debug the
26  * cause. Hence we sample and check the state under the AIL lock and return if
27  * everything is fine, otherwise we drop the lock and run the ASSERT checks.
28  * Asserts may not be fatal, so pick the lock back up and continue onwards.
29  */
30 STATIC void
xfs_ail_check(struct xfs_ail * ailp,struct xfs_log_item * lip)31 xfs_ail_check(
32 	struct xfs_ail		*ailp,
33 	struct xfs_log_item	*lip)
34 {
35 	struct xfs_log_item	*prev_lip;
36 	struct xfs_log_item	*next_lip;
37 	xfs_lsn_t		prev_lsn = NULLCOMMITLSN;
38 	xfs_lsn_t		next_lsn = NULLCOMMITLSN;
39 	xfs_lsn_t		lsn;
40 	bool			in_ail;
41 
42 
43 	if (list_empty(&ailp->ail_head))
44 		return;
45 
46 	/*
47 	 * Sample then check the next and previous entries are valid.
48 	 */
49 	in_ail = test_bit(XFS_LI_IN_AIL, &lip->li_flags);
50 	prev_lip = list_entry(lip->li_ail.prev, struct xfs_log_item, li_ail);
51 	if (&prev_lip->li_ail != &ailp->ail_head)
52 		prev_lsn = prev_lip->li_lsn;
53 	next_lip = list_entry(lip->li_ail.next, struct xfs_log_item, li_ail);
54 	if (&next_lip->li_ail != &ailp->ail_head)
55 		next_lsn = next_lip->li_lsn;
56 	lsn = lip->li_lsn;
57 
58 	if (in_ail &&
59 	    (prev_lsn == NULLCOMMITLSN || XFS_LSN_CMP(prev_lsn, lsn) <= 0) &&
60 	    (next_lsn == NULLCOMMITLSN || XFS_LSN_CMP(next_lsn, lsn) >= 0))
61 		return;
62 
63 	spin_unlock(&ailp->ail_lock);
64 	ASSERT(in_ail);
65 	ASSERT(prev_lsn == NULLCOMMITLSN || XFS_LSN_CMP(prev_lsn, lsn) <= 0);
66 	ASSERT(next_lsn == NULLCOMMITLSN || XFS_LSN_CMP(next_lsn, lsn) >= 0);
67 	spin_lock(&ailp->ail_lock);
68 }
69 #else /* !DEBUG */
70 #define	xfs_ail_check(a,l)
71 #endif /* DEBUG */
72 
73 /*
74  * Return a pointer to the last item in the AIL.  If the AIL is empty, then
75  * return NULL.
76  */
77 static xfs_log_item_t *
xfs_ail_max(struct xfs_ail * ailp)78 xfs_ail_max(
79 	struct xfs_ail  *ailp)
80 {
81 	if (list_empty(&ailp->ail_head))
82 		return NULL;
83 
84 	return list_entry(ailp->ail_head.prev, xfs_log_item_t, li_ail);
85 }
86 
87 /*
88  * Return a pointer to the item which follows the given item in the AIL.  If
89  * the given item is the last item in the list, then return NULL.
90  */
91 static xfs_log_item_t *
xfs_ail_next(struct xfs_ail * ailp,xfs_log_item_t * lip)92 xfs_ail_next(
93 	struct xfs_ail  *ailp,
94 	xfs_log_item_t  *lip)
95 {
96 	if (lip->li_ail.next == &ailp->ail_head)
97 		return NULL;
98 
99 	return list_first_entry(&lip->li_ail, xfs_log_item_t, li_ail);
100 }
101 
102 /*
103  * This is called by the log manager code to determine the LSN of the tail of
104  * the log.  This is exactly the LSN of the first item in the AIL.  If the AIL
105  * is empty, then this function returns 0.
106  *
107  * We need the AIL lock in order to get a coherent read of the lsn of the last
108  * item in the AIL.
109  */
110 xfs_lsn_t
xfs_ail_min_lsn(struct xfs_ail * ailp)111 xfs_ail_min_lsn(
112 	struct xfs_ail	*ailp)
113 {
114 	xfs_lsn_t	lsn = 0;
115 	xfs_log_item_t	*lip;
116 
117 	spin_lock(&ailp->ail_lock);
118 	lip = xfs_ail_min(ailp);
119 	if (lip)
120 		lsn = lip->li_lsn;
121 	spin_unlock(&ailp->ail_lock);
122 
123 	return lsn;
124 }
125 
126 /*
127  * Return the maximum lsn held in the AIL, or zero if the AIL is empty.
128  */
129 static xfs_lsn_t
xfs_ail_max_lsn(struct xfs_ail * ailp)130 xfs_ail_max_lsn(
131 	struct xfs_ail  *ailp)
132 {
133 	xfs_lsn_t       lsn = 0;
134 	xfs_log_item_t  *lip;
135 
136 	spin_lock(&ailp->ail_lock);
137 	lip = xfs_ail_max(ailp);
138 	if (lip)
139 		lsn = lip->li_lsn;
140 	spin_unlock(&ailp->ail_lock);
141 
142 	return lsn;
143 }
144 
145 /*
146  * The cursor keeps track of where our current traversal is up to by tracking
147  * the next item in the list for us. However, for this to be safe, removing an
148  * object from the AIL needs to invalidate any cursor that points to it. hence
149  * the traversal cursor needs to be linked to the struct xfs_ail so that
150  * deletion can search all the active cursors for invalidation.
151  */
152 STATIC void
xfs_trans_ail_cursor_init(struct xfs_ail * ailp,struct xfs_ail_cursor * cur)153 xfs_trans_ail_cursor_init(
154 	struct xfs_ail		*ailp,
155 	struct xfs_ail_cursor	*cur)
156 {
157 	cur->item = NULL;
158 	list_add_tail(&cur->list, &ailp->ail_cursors);
159 }
160 
161 /*
162  * Get the next item in the traversal and advance the cursor.  If the cursor
163  * was invalidated (indicated by a lip of 1), restart the traversal.
164  */
165 struct xfs_log_item *
xfs_trans_ail_cursor_next(struct xfs_ail * ailp,struct xfs_ail_cursor * cur)166 xfs_trans_ail_cursor_next(
167 	struct xfs_ail		*ailp,
168 	struct xfs_ail_cursor	*cur)
169 {
170 	struct xfs_log_item	*lip = cur->item;
171 
172 	if ((uintptr_t)lip & 1)
173 		lip = xfs_ail_min(ailp);
174 	if (lip)
175 		cur->item = xfs_ail_next(ailp, lip);
176 	return lip;
177 }
178 
179 /*
180  * When the traversal is complete, we need to remove the cursor from the list
181  * of traversing cursors.
182  */
183 void
xfs_trans_ail_cursor_done(struct xfs_ail_cursor * cur)184 xfs_trans_ail_cursor_done(
185 	struct xfs_ail_cursor	*cur)
186 {
187 	cur->item = NULL;
188 	list_del_init(&cur->list);
189 }
190 
191 /*
192  * Invalidate any cursor that is pointing to this item. This is called when an
193  * item is removed from the AIL. Any cursor pointing to this object is now
194  * invalid and the traversal needs to be terminated so it doesn't reference a
195  * freed object. We set the low bit of the cursor item pointer so we can
196  * distinguish between an invalidation and the end of the list when getting the
197  * next item from the cursor.
198  */
199 STATIC void
xfs_trans_ail_cursor_clear(struct xfs_ail * ailp,struct xfs_log_item * lip)200 xfs_trans_ail_cursor_clear(
201 	struct xfs_ail		*ailp,
202 	struct xfs_log_item	*lip)
203 {
204 	struct xfs_ail_cursor	*cur;
205 
206 	list_for_each_entry(cur, &ailp->ail_cursors, list) {
207 		if (cur->item == lip)
208 			cur->item = (struct xfs_log_item *)
209 					((uintptr_t)cur->item | 1);
210 	}
211 }
212 
213 /*
214  * Find the first item in the AIL with the given @lsn by searching in ascending
215  * LSN order and initialise the cursor to point to the next item for a
216  * ascending traversal.  Pass a @lsn of zero to initialise the cursor to the
217  * first item in the AIL. Returns NULL if the list is empty.
218  */
219 xfs_log_item_t *
xfs_trans_ail_cursor_first(struct xfs_ail * ailp,struct xfs_ail_cursor * cur,xfs_lsn_t lsn)220 xfs_trans_ail_cursor_first(
221 	struct xfs_ail		*ailp,
222 	struct xfs_ail_cursor	*cur,
223 	xfs_lsn_t		lsn)
224 {
225 	xfs_log_item_t		*lip;
226 
227 	xfs_trans_ail_cursor_init(ailp, cur);
228 
229 	if (lsn == 0) {
230 		lip = xfs_ail_min(ailp);
231 		goto out;
232 	}
233 
234 	list_for_each_entry(lip, &ailp->ail_head, li_ail) {
235 		if (XFS_LSN_CMP(lip->li_lsn, lsn) >= 0)
236 			goto out;
237 	}
238 	return NULL;
239 
240 out:
241 	if (lip)
242 		cur->item = xfs_ail_next(ailp, lip);
243 	return lip;
244 }
245 
246 static struct xfs_log_item *
__xfs_trans_ail_cursor_last(struct xfs_ail * ailp,xfs_lsn_t lsn)247 __xfs_trans_ail_cursor_last(
248 	struct xfs_ail		*ailp,
249 	xfs_lsn_t		lsn)
250 {
251 	xfs_log_item_t		*lip;
252 
253 	list_for_each_entry_reverse(lip, &ailp->ail_head, li_ail) {
254 		if (XFS_LSN_CMP(lip->li_lsn, lsn) <= 0)
255 			return lip;
256 	}
257 	return NULL;
258 }
259 
260 /*
261  * Find the last item in the AIL with the given @lsn by searching in descending
262  * LSN order and initialise the cursor to point to that item.  If there is no
263  * item with the value of @lsn, then it sets the cursor to the last item with an
264  * LSN lower than @lsn.  Returns NULL if the list is empty.
265  */
266 struct xfs_log_item *
xfs_trans_ail_cursor_last(struct xfs_ail * ailp,struct xfs_ail_cursor * cur,xfs_lsn_t lsn)267 xfs_trans_ail_cursor_last(
268 	struct xfs_ail		*ailp,
269 	struct xfs_ail_cursor	*cur,
270 	xfs_lsn_t		lsn)
271 {
272 	xfs_trans_ail_cursor_init(ailp, cur);
273 	cur->item = __xfs_trans_ail_cursor_last(ailp, lsn);
274 	return cur->item;
275 }
276 
277 /*
278  * Splice the log item list into the AIL at the given LSN. We splice to the
279  * tail of the given LSN to maintain insert order for push traversals. The
280  * cursor is optional, allowing repeated updates to the same LSN to avoid
281  * repeated traversals.  This should not be called with an empty list.
282  */
283 static void
xfs_ail_splice(struct xfs_ail * ailp,struct xfs_ail_cursor * cur,struct list_head * list,xfs_lsn_t lsn)284 xfs_ail_splice(
285 	struct xfs_ail		*ailp,
286 	struct xfs_ail_cursor	*cur,
287 	struct list_head	*list,
288 	xfs_lsn_t		lsn)
289 {
290 	struct xfs_log_item	*lip;
291 
292 	ASSERT(!list_empty(list));
293 
294 	/*
295 	 * Use the cursor to determine the insertion point if one is
296 	 * provided.  If not, or if the one we got is not valid,
297 	 * find the place in the AIL where the items belong.
298 	 */
299 	lip = cur ? cur->item : NULL;
300 	if (!lip || (uintptr_t)lip & 1)
301 		lip = __xfs_trans_ail_cursor_last(ailp, lsn);
302 
303 	/*
304 	 * If a cursor is provided, we know we're processing the AIL
305 	 * in lsn order, and future items to be spliced in will
306 	 * follow the last one being inserted now.  Update the
307 	 * cursor to point to that last item, now while we have a
308 	 * reliable pointer to it.
309 	 */
310 	if (cur)
311 		cur->item = list_entry(list->prev, struct xfs_log_item, li_ail);
312 
313 	/*
314 	 * Finally perform the splice.  Unless the AIL was empty,
315 	 * lip points to the item in the AIL _after_ which the new
316 	 * items should go.  If lip is null the AIL was empty, so
317 	 * the new items go at the head of the AIL.
318 	 */
319 	if (lip)
320 		list_splice(list, &lip->li_ail);
321 	else
322 		list_splice(list, &ailp->ail_head);
323 }
324 
325 /*
326  * Delete the given item from the AIL.  Return a pointer to the item.
327  */
328 static void
xfs_ail_delete(struct xfs_ail * ailp,xfs_log_item_t * lip)329 xfs_ail_delete(
330 	struct xfs_ail  *ailp,
331 	xfs_log_item_t  *lip)
332 {
333 	xfs_ail_check(ailp, lip);
334 	list_del(&lip->li_ail);
335 	xfs_trans_ail_cursor_clear(ailp, lip);
336 }
337 
338 static inline uint
xfsaild_push_item(struct xfs_ail * ailp,struct xfs_log_item * lip)339 xfsaild_push_item(
340 	struct xfs_ail		*ailp,
341 	struct xfs_log_item	*lip)
342 {
343 	/*
344 	 * If log item pinning is enabled, skip the push and track the item as
345 	 * pinned. This can help induce head-behind-tail conditions.
346 	 */
347 	if (XFS_TEST_ERROR(false, ailp->ail_mount, XFS_ERRTAG_LOG_ITEM_PIN))
348 		return XFS_ITEM_PINNED;
349 
350 	return lip->li_ops->iop_push(lip, &ailp->ail_buf_list);
351 }
352 
353 static long
xfsaild_push(struct xfs_ail * ailp)354 xfsaild_push(
355 	struct xfs_ail		*ailp)
356 {
357 	xfs_mount_t		*mp = ailp->ail_mount;
358 	struct xfs_ail_cursor	cur;
359 	xfs_log_item_t		*lip;
360 	xfs_lsn_t		lsn;
361 	xfs_lsn_t		target;
362 	long			tout;
363 	int			stuck = 0;
364 	int			flushing = 0;
365 	int			count = 0;
366 
367 	/*
368 	 * If we encountered pinned items or did not finish writing out all
369 	 * buffers the last time we ran, force the log first and wait for it
370 	 * before pushing again.
371 	 */
372 	if (ailp->ail_log_flush && ailp->ail_last_pushed_lsn == 0 &&
373 	    (!list_empty_careful(&ailp->ail_buf_list) ||
374 	     xfs_ail_min_lsn(ailp))) {
375 		ailp->ail_log_flush = 0;
376 
377 		XFS_STATS_INC(mp, xs_push_ail_flush);
378 		xfs_log_force(mp, XFS_LOG_SYNC);
379 	}
380 
381 	spin_lock(&ailp->ail_lock);
382 
383 	/* barrier matches the ail_target update in xfs_ail_push() */
384 	smp_rmb();
385 	target = ailp->ail_target;
386 	ailp->ail_target_prev = target;
387 
388 	lip = xfs_trans_ail_cursor_first(ailp, &cur, ailp->ail_last_pushed_lsn);
389 	if (!lip) {
390 		/*
391 		 * If the AIL is empty or our push has reached the end we are
392 		 * done now.
393 		 */
394 		xfs_trans_ail_cursor_done(&cur);
395 		spin_unlock(&ailp->ail_lock);
396 		goto out_done;
397 	}
398 
399 	XFS_STATS_INC(mp, xs_push_ail);
400 
401 	lsn = lip->li_lsn;
402 	while ((XFS_LSN_CMP(lip->li_lsn, target) <= 0)) {
403 		int	lock_result;
404 
405 		/*
406 		 * Note that iop_push may unlock and reacquire the AIL lock.  We
407 		 * rely on the AIL cursor implementation to be able to deal with
408 		 * the dropped lock.
409 		 */
410 		lock_result = xfsaild_push_item(ailp, lip);
411 		switch (lock_result) {
412 		case XFS_ITEM_SUCCESS:
413 			XFS_STATS_INC(mp, xs_push_ail_success);
414 			trace_xfs_ail_push(lip);
415 
416 			ailp->ail_last_pushed_lsn = lsn;
417 			break;
418 
419 		case XFS_ITEM_FLUSHING:
420 			/*
421 			 * The item or its backing buffer is already beeing
422 			 * flushed.  The typical reason for that is that an
423 			 * inode buffer is locked because we already pushed the
424 			 * updates to it as part of inode clustering.
425 			 *
426 			 * We do not want to to stop flushing just because lots
427 			 * of items are already beeing flushed, but we need to
428 			 * re-try the flushing relatively soon if most of the
429 			 * AIL is beeing flushed.
430 			 */
431 			XFS_STATS_INC(mp, xs_push_ail_flushing);
432 			trace_xfs_ail_flushing(lip);
433 
434 			flushing++;
435 			ailp->ail_last_pushed_lsn = lsn;
436 			break;
437 
438 		case XFS_ITEM_PINNED:
439 			XFS_STATS_INC(mp, xs_push_ail_pinned);
440 			trace_xfs_ail_pinned(lip);
441 
442 			stuck++;
443 			ailp->ail_log_flush++;
444 			break;
445 		case XFS_ITEM_LOCKED:
446 			XFS_STATS_INC(mp, xs_push_ail_locked);
447 			trace_xfs_ail_locked(lip);
448 
449 			stuck++;
450 			break;
451 		default:
452 			ASSERT(0);
453 			break;
454 		}
455 
456 		count++;
457 
458 		/*
459 		 * Are there too many items we can't do anything with?
460 		 *
461 		 * If we we are skipping too many items because we can't flush
462 		 * them or they are already being flushed, we back off and
463 		 * given them time to complete whatever operation is being
464 		 * done. i.e. remove pressure from the AIL while we can't make
465 		 * progress so traversals don't slow down further inserts and
466 		 * removals to/from the AIL.
467 		 *
468 		 * The value of 100 is an arbitrary magic number based on
469 		 * observation.
470 		 */
471 		if (stuck > 100)
472 			break;
473 
474 		lip = xfs_trans_ail_cursor_next(ailp, &cur);
475 		if (lip == NULL)
476 			break;
477 		lsn = lip->li_lsn;
478 	}
479 	xfs_trans_ail_cursor_done(&cur);
480 	spin_unlock(&ailp->ail_lock);
481 
482 	if (xfs_buf_delwri_submit_nowait(&ailp->ail_buf_list))
483 		ailp->ail_log_flush++;
484 
485 	if (!count || XFS_LSN_CMP(lsn, target) >= 0) {
486 out_done:
487 		/*
488 		 * We reached the target or the AIL is empty, so wait a bit
489 		 * longer for I/O to complete and remove pushed items from the
490 		 * AIL before we start the next scan from the start of the AIL.
491 		 */
492 		tout = 50;
493 		ailp->ail_last_pushed_lsn = 0;
494 	} else if (((stuck + flushing) * 100) / count > 90) {
495 		/*
496 		 * Either there is a lot of contention on the AIL or we are
497 		 * stuck due to operations in progress. "Stuck" in this case
498 		 * is defined as >90% of the items we tried to push were stuck.
499 		 *
500 		 * Backoff a bit more to allow some I/O to complete before
501 		 * restarting from the start of the AIL. This prevents us from
502 		 * spinning on the same items, and if they are pinned will all
503 		 * the restart to issue a log force to unpin the stuck items.
504 		 */
505 		tout = 20;
506 		ailp->ail_last_pushed_lsn = 0;
507 	} else {
508 		/*
509 		 * Assume we have more work to do in a short while.
510 		 */
511 		tout = 10;
512 	}
513 
514 	return tout;
515 }
516 
517 static int
xfsaild(void * data)518 xfsaild(
519 	void		*data)
520 {
521 	struct xfs_ail	*ailp = data;
522 	long		tout = 0;	/* milliseconds */
523 	unsigned int	noreclaim_flag;
524 
525 	noreclaim_flag = memalloc_noreclaim_save();
526 	set_freezable();
527 
528 	while (1) {
529 		if (tout && tout <= 20)
530 			set_current_state(TASK_KILLABLE);
531 		else
532 			set_current_state(TASK_INTERRUPTIBLE);
533 
534 		/*
535 		 * Check kthread_should_stop() after we set the task state to
536 		 * guarantee that we either see the stop bit and exit or the
537 		 * task state is reset to runnable such that it's not scheduled
538 		 * out indefinitely and detects the stop bit at next iteration.
539 		 * A memory barrier is included in above task state set to
540 		 * serialize again kthread_stop().
541 		 */
542 		if (kthread_should_stop()) {
543 			__set_current_state(TASK_RUNNING);
544 
545 			/*
546 			 * The caller forces out the AIL before stopping the
547 			 * thread in the common case, which means the delwri
548 			 * queue is drained. In the shutdown case, the queue may
549 			 * still hold relogged buffers that haven't been
550 			 * submitted because they were pinned since added to the
551 			 * queue.
552 			 *
553 			 * Log I/O error processing stales the underlying buffer
554 			 * and clears the delwri state, expecting the buf to be
555 			 * removed on the next submission attempt. That won't
556 			 * happen if we're shutting down, so this is the last
557 			 * opportunity to release such buffers from the queue.
558 			 */
559 			ASSERT(list_empty(&ailp->ail_buf_list) ||
560 			       XFS_FORCED_SHUTDOWN(ailp->ail_mount));
561 			xfs_buf_delwri_cancel(&ailp->ail_buf_list);
562 			break;
563 		}
564 
565 		spin_lock(&ailp->ail_lock);
566 
567 		/*
568 		 * Idle if the AIL is empty and we are not racing with a target
569 		 * update. We check the AIL after we set the task to a sleep
570 		 * state to guarantee that we either catch an ail_target update
571 		 * or that a wake_up resets the state to TASK_RUNNING.
572 		 * Otherwise, we run the risk of sleeping indefinitely.
573 		 *
574 		 * The barrier matches the ail_target update in xfs_ail_push().
575 		 */
576 		smp_rmb();
577 		if (!xfs_ail_min(ailp) &&
578 		    ailp->ail_target == ailp->ail_target_prev) {
579 			spin_unlock(&ailp->ail_lock);
580 			freezable_schedule();
581 			tout = 0;
582 			continue;
583 		}
584 		spin_unlock(&ailp->ail_lock);
585 
586 		if (tout)
587 			freezable_schedule_timeout(msecs_to_jiffies(tout));
588 
589 		__set_current_state(TASK_RUNNING);
590 
591 		try_to_freeze();
592 
593 		tout = xfsaild_push(ailp);
594 	}
595 
596 	memalloc_noreclaim_restore(noreclaim_flag);
597 	return 0;
598 }
599 
600 /*
601  * This routine is called to move the tail of the AIL forward.  It does this by
602  * trying to flush items in the AIL whose lsns are below the given
603  * threshold_lsn.
604  *
605  * The push is run asynchronously in a workqueue, which means the caller needs
606  * to handle waiting on the async flush for space to become available.
607  * We don't want to interrupt any push that is in progress, hence we only queue
608  * work if we set the pushing bit approriately.
609  *
610  * We do this unlocked - we only need to know whether there is anything in the
611  * AIL at the time we are called. We don't need to access the contents of
612  * any of the objects, so the lock is not needed.
613  */
614 void
xfs_ail_push(struct xfs_ail * ailp,xfs_lsn_t threshold_lsn)615 xfs_ail_push(
616 	struct xfs_ail	*ailp,
617 	xfs_lsn_t	threshold_lsn)
618 {
619 	xfs_log_item_t	*lip;
620 
621 	lip = xfs_ail_min(ailp);
622 	if (!lip || XFS_FORCED_SHUTDOWN(ailp->ail_mount) ||
623 	    XFS_LSN_CMP(threshold_lsn, ailp->ail_target) <= 0)
624 		return;
625 
626 	/*
627 	 * Ensure that the new target is noticed in push code before it clears
628 	 * the XFS_AIL_PUSHING_BIT.
629 	 */
630 	smp_wmb();
631 	xfs_trans_ail_copy_lsn(ailp, &ailp->ail_target, &threshold_lsn);
632 	smp_wmb();
633 
634 	wake_up_process(ailp->ail_task);
635 }
636 
637 /*
638  * Push out all items in the AIL immediately
639  */
640 void
xfs_ail_push_all(struct xfs_ail * ailp)641 xfs_ail_push_all(
642 	struct xfs_ail  *ailp)
643 {
644 	xfs_lsn_t       threshold_lsn = xfs_ail_max_lsn(ailp);
645 
646 	if (threshold_lsn)
647 		xfs_ail_push(ailp, threshold_lsn);
648 }
649 
650 /*
651  * Push out all items in the AIL immediately and wait until the AIL is empty.
652  */
653 void
xfs_ail_push_all_sync(struct xfs_ail * ailp)654 xfs_ail_push_all_sync(
655 	struct xfs_ail  *ailp)
656 {
657 	struct xfs_log_item	*lip;
658 	DEFINE_WAIT(wait);
659 
660 	spin_lock(&ailp->ail_lock);
661 	while ((lip = xfs_ail_max(ailp)) != NULL) {
662 		prepare_to_wait(&ailp->ail_empty, &wait, TASK_UNINTERRUPTIBLE);
663 		ailp->ail_target = lip->li_lsn;
664 		wake_up_process(ailp->ail_task);
665 		spin_unlock(&ailp->ail_lock);
666 		schedule();
667 		spin_lock(&ailp->ail_lock);
668 	}
669 	spin_unlock(&ailp->ail_lock);
670 
671 	finish_wait(&ailp->ail_empty, &wait);
672 }
673 
674 /*
675  * xfs_trans_ail_update - bulk AIL insertion operation.
676  *
677  * @xfs_trans_ail_update takes an array of log items that all need to be
678  * positioned at the same LSN in the AIL. If an item is not in the AIL, it will
679  * be added.  Otherwise, it will be repositioned  by removing it and re-adding
680  * it to the AIL. If we move the first item in the AIL, update the log tail to
681  * match the new minimum LSN in the AIL.
682  *
683  * This function takes the AIL lock once to execute the update operations on
684  * all the items in the array, and as such should not be called with the AIL
685  * lock held. As a result, once we have the AIL lock, we need to check each log
686  * item LSN to confirm it needs to be moved forward in the AIL.
687  *
688  * To optimise the insert operation, we delete all the items from the AIL in
689  * the first pass, moving them into a temporary list, then splice the temporary
690  * list into the correct position in the AIL. This avoids needing to do an
691  * insert operation on every item.
692  *
693  * This function must be called with the AIL lock held.  The lock is dropped
694  * before returning.
695  */
696 void
xfs_trans_ail_update_bulk(struct xfs_ail * ailp,struct xfs_ail_cursor * cur,struct xfs_log_item ** log_items,int nr_items,xfs_lsn_t lsn)697 xfs_trans_ail_update_bulk(
698 	struct xfs_ail		*ailp,
699 	struct xfs_ail_cursor	*cur,
700 	struct xfs_log_item	**log_items,
701 	int			nr_items,
702 	xfs_lsn_t		lsn) __releases(ailp->ail_lock)
703 {
704 	xfs_log_item_t		*mlip;
705 	int			mlip_changed = 0;
706 	int			i;
707 	LIST_HEAD(tmp);
708 
709 	ASSERT(nr_items > 0);		/* Not required, but true. */
710 	mlip = xfs_ail_min(ailp);
711 
712 	for (i = 0; i < nr_items; i++) {
713 		struct xfs_log_item *lip = log_items[i];
714 		if (test_and_set_bit(XFS_LI_IN_AIL, &lip->li_flags)) {
715 			/* check if we really need to move the item */
716 			if (XFS_LSN_CMP(lsn, lip->li_lsn) <= 0)
717 				continue;
718 
719 			trace_xfs_ail_move(lip, lip->li_lsn, lsn);
720 			xfs_ail_delete(ailp, lip);
721 			if (mlip == lip)
722 				mlip_changed = 1;
723 		} else {
724 			trace_xfs_ail_insert(lip, 0, lsn);
725 		}
726 		lip->li_lsn = lsn;
727 		list_add(&lip->li_ail, &tmp);
728 	}
729 
730 	if (!list_empty(&tmp))
731 		xfs_ail_splice(ailp, cur, &tmp, lsn);
732 
733 	if (mlip_changed) {
734 		if (!XFS_FORCED_SHUTDOWN(ailp->ail_mount))
735 			xlog_assign_tail_lsn_locked(ailp->ail_mount);
736 		spin_unlock(&ailp->ail_lock);
737 
738 		xfs_log_space_wake(ailp->ail_mount);
739 	} else {
740 		spin_unlock(&ailp->ail_lock);
741 	}
742 }
743 
744 bool
xfs_ail_delete_one(struct xfs_ail * ailp,struct xfs_log_item * lip)745 xfs_ail_delete_one(
746 	struct xfs_ail		*ailp,
747 	struct xfs_log_item	*lip)
748 {
749 	struct xfs_log_item	*mlip = xfs_ail_min(ailp);
750 
751 	trace_xfs_ail_delete(lip, mlip->li_lsn, lip->li_lsn);
752 	xfs_ail_delete(ailp, lip);
753 	xfs_clear_li_failed(lip);
754 	clear_bit(XFS_LI_IN_AIL, &lip->li_flags);
755 	lip->li_lsn = 0;
756 
757 	return mlip == lip;
758 }
759 
760 /**
761  * Remove a log items from the AIL
762  *
763  * @xfs_trans_ail_delete_bulk takes an array of log items that all need to
764  * removed from the AIL. The caller is already holding the AIL lock, and done
765  * all the checks necessary to ensure the items passed in via @log_items are
766  * ready for deletion. This includes checking that the items are in the AIL.
767  *
768  * For each log item to be removed, unlink it  from the AIL, clear the IN_AIL
769  * flag from the item and reset the item's lsn to 0. If we remove the first
770  * item in the AIL, update the log tail to match the new minimum LSN in the
771  * AIL.
772  *
773  * This function will not drop the AIL lock until all items are removed from
774  * the AIL to minimise the amount of lock traffic on the AIL. This does not
775  * greatly increase the AIL hold time, but does significantly reduce the amount
776  * of traffic on the lock, especially during IO completion.
777  *
778  * This function must be called with the AIL lock held.  The lock is dropped
779  * before returning.
780  */
781 void
xfs_trans_ail_delete(struct xfs_ail * ailp,struct xfs_log_item * lip,int shutdown_type)782 xfs_trans_ail_delete(
783 	struct xfs_ail		*ailp,
784 	struct xfs_log_item	*lip,
785 	int			shutdown_type) __releases(ailp->ail_lock)
786 {
787 	struct xfs_mount	*mp = ailp->ail_mount;
788 	bool			mlip_changed;
789 
790 	if (!test_bit(XFS_LI_IN_AIL, &lip->li_flags)) {
791 		spin_unlock(&ailp->ail_lock);
792 		if (!XFS_FORCED_SHUTDOWN(mp)) {
793 			xfs_alert_tag(mp, XFS_PTAG_AILDELETE,
794 	"%s: attempting to delete a log item that is not in the AIL",
795 					__func__);
796 			xfs_force_shutdown(mp, shutdown_type);
797 		}
798 		return;
799 	}
800 
801 	mlip_changed = xfs_ail_delete_one(ailp, lip);
802 	if (mlip_changed) {
803 		if (!XFS_FORCED_SHUTDOWN(mp))
804 			xlog_assign_tail_lsn_locked(mp);
805 		if (list_empty(&ailp->ail_head))
806 			wake_up_all(&ailp->ail_empty);
807 	}
808 
809 	spin_unlock(&ailp->ail_lock);
810 	if (mlip_changed)
811 		xfs_log_space_wake(ailp->ail_mount);
812 }
813 
814 int
xfs_trans_ail_init(xfs_mount_t * mp)815 xfs_trans_ail_init(
816 	xfs_mount_t	*mp)
817 {
818 	struct xfs_ail	*ailp;
819 
820 	ailp = kmem_zalloc(sizeof(struct xfs_ail), KM_MAYFAIL);
821 	if (!ailp)
822 		return -ENOMEM;
823 
824 	ailp->ail_mount = mp;
825 	INIT_LIST_HEAD(&ailp->ail_head);
826 	INIT_LIST_HEAD(&ailp->ail_cursors);
827 	spin_lock_init(&ailp->ail_lock);
828 	INIT_LIST_HEAD(&ailp->ail_buf_list);
829 	init_waitqueue_head(&ailp->ail_empty);
830 
831 	ailp->ail_task = kthread_run(xfsaild, ailp, "xfsaild/%s",
832 			ailp->ail_mount->m_fsname);
833 	if (IS_ERR(ailp->ail_task))
834 		goto out_free_ailp;
835 
836 	mp->m_ail = ailp;
837 	return 0;
838 
839 out_free_ailp:
840 	kmem_free(ailp);
841 	return -ENOMEM;
842 }
843 
844 void
xfs_trans_ail_destroy(xfs_mount_t * mp)845 xfs_trans_ail_destroy(
846 	xfs_mount_t	*mp)
847 {
848 	struct xfs_ail	*ailp = mp->m_ail;
849 
850 	kthread_stop(ailp->ail_task);
851 	kmem_free(ailp);
852 }
853