1 /*
2 * CDDL HEADER START
3 *
4 * The contents of this file are subject to the terms of the
5 * Common Development and Distribution License (the "License").
6 * You may not use this file except in compliance with the License.
7 *
8 * You can obtain a copy of the license at usr/src/OPENSOLARIS.LICENSE
9 * or http://www.opensolaris.org/os/licensing.
10 * See the License for the specific language governing permissions
11 * and limitations under the License.
12 *
13 * When distributing Covered Code, include this CDDL HEADER in each
14 * file and include the License file at usr/src/OPENSOLARIS.LICENSE.
15 * If applicable, add the following below this CDDL HEADER, with the
16 * fields enclosed by brackets "[]" replaced with your own identifying
17 * information: Portions Copyright [yyyy] [name of copyright owner]
18 *
19 * CDDL HEADER END
20 */
21 /*
22 * Copyright 2009 Sun Microsystems, Inc. All rights reserved.
23 * Use is subject to license terms.
24 */
25
26 #include <sys/scsi/scsi.h>
27 #include <sys/ddi.h>
28 #include <sys/sunddi.h>
29 #include <sys/thread.h>
30 #include <sys/var.h>
31
32 #include "sd_xbuf.h"
33
34 /*
35 * xbuf.c: buf(9s) extension facility.
36 *
37 * The buf(9S) extension facility is intended to allow block drivers to
38 * allocate additional memory that is associated with a particular buf(9S)
39 * struct. It is further intended to help in addressing the usual set of
40 * problems associated with such allocations, in particular those involving
41 * recovery from allocation failures, especially in code paths that the
42 * system relies on to free memory.
43 *
44 * CAVEAT: Currently this code is completely private to the sd driver and in
45 * NO WAY constitutes a public or supported interface of any kind. It is
46 * envisioned that this may one day migrate into the Solaris DDI, but until
47 * that time this ought to be considered completely unstable and is subject
48 * to change without notice. This code may NOT in any way be utilized by
49 * ANY code outside the sd driver.
50 */
51
52
53 static int xbuf_iostart(ddi_xbuf_attr_t xap);
54 static void xbuf_dispatch(ddi_xbuf_attr_t xap);
55 static void xbuf_restart_callback(void *arg);
56 static void xbuf_enqueue(struct buf *bp, ddi_xbuf_attr_t xap);
57 static int xbuf_brk_done(struct buf *bp);
58
59
60 /*
61 * Note: Should this be exposed to the caller.... do we want to give the
62 * caller the fexibility of specifying the parameters for the thread pool?
63 * Note: these values are just estimates at this time, based upon what
64 * seems reasonable for the sd driver. It may be preferable to make these
65 * parameters self-scaling in a real (future) implementation.
66 */
67 #define XBUF_TQ_MINALLOC 64
68 #define XBUF_TQ_MAXALLOC 512
69 #define XBUF_DISPATCH_DELAY (drv_usectohz(50000)) /* 50 msec */
70
71 static taskq_t *xbuf_tq = NULL;
72 static int xbuf_attr_tq_minalloc = XBUF_TQ_MINALLOC;
73 static int xbuf_attr_tq_maxalloc = XBUF_TQ_MAXALLOC;
74
75 static kmutex_t xbuf_mutex = { 0 };
76 static uint32_t xbuf_refcount = 0;
77
78 /*
79 * Private wrapper for buf cloned via ddi_xbuf_qstrategy()
80 */
81 struct xbuf_brk {
82 kmutex_t mutex;
83 struct buf *bp0;
84 uint8_t nbufs; /* number of buf allocated */
85 uint8_t active; /* number of active xfer */
86
87 size_t brksize; /* break size used for this buf */
88 int brkblk;
89
90 /* xfer position */
91 off_t off;
92 off_t noff;
93 daddr_t blkno;
94 };
95
96 _NOTE(DATA_READABLE_WITHOUT_LOCK(xbuf_brk::off))
97
98 /*
99 * Hack needed in the prototype so buf breakup will work.
100 * Here we can rely on the sd code not changing the value in
101 * b_forw.
102 */
103 #define b_clone_private b_forw
104
105
106 /* ARGSUSED */
107 DDII ddi_xbuf_attr_t
108 ddi_xbuf_attr_create(size_t xsize,
109 void (*xa_strategy)(struct buf *bp, ddi_xbuf_t xp, void *attr_arg),
110 void *attr_arg, uint32_t active_limit, uint32_t reserve_limit,
111 major_t major, int flags)
112 {
113 ddi_xbuf_attr_t xap;
114
115 xap = kmem_zalloc(sizeof (struct __ddi_xbuf_attr), KM_SLEEP);
116
117 mutex_init(&xap->xa_mutex, NULL, MUTEX_DRIVER, NULL);
118 mutex_init(&xap->xa_reserve_mutex, NULL, MUTEX_DRIVER, NULL);
119
120 /* Future: Allow the caller to specify alignment requirements? */
121 xap->xa_allocsize = max(xsize, sizeof (void *));
122 xap->xa_active_limit = active_limit;
123 xap->xa_active_lowater = xap->xa_active_limit / 2;
124 xap->xa_reserve_limit = reserve_limit;
125 xap->xa_strategy = xa_strategy;
126 xap->xa_attr_arg = attr_arg;
127
128 mutex_enter(&xbuf_mutex);
129 if (xbuf_refcount == 0) {
130 ASSERT(xbuf_tq == NULL);
131 /*
132 * Note: Would be nice if: (1) #threads in the taskq pool (set
133 * to the value of 'ncpus' at the time the taskq is created)
134 * could adjust automatically with DR; (2) the taskq
135 * minalloc/maxalloc counts could be grown/shrunk on the fly.
136 */
137 xbuf_tq = taskq_create("xbuf_taskq", ncpus,
138 (v.v_maxsyspri - 2), xbuf_attr_tq_minalloc,
139 xbuf_attr_tq_maxalloc, TASKQ_PREPOPULATE);
140 }
141 xbuf_refcount++;
142 mutex_exit(&xbuf_mutex);
143
144 /* In this prototype we just always use the global system pool. */
145 xap->xa_tq = xbuf_tq;
146
147 return (xap);
148 }
149
150
151 DDII void
152 ddi_xbuf_attr_destroy(ddi_xbuf_attr_t xap)
153 {
154 ddi_xbuf_t xp;
155
156 mutex_destroy(&xap->xa_mutex);
157 mutex_destroy(&xap->xa_reserve_mutex);
158
159 /* Free any xbufs on the reserve list */
160 while (xap->xa_reserve_count != 0) {
161 xp = xap->xa_reserve_headp;
162 xap->xa_reserve_headp = *((void **)xp);
163 xap->xa_reserve_count--;
164 kmem_free(xp, xap->xa_allocsize);
165 }
166 ASSERT(xap->xa_reserve_headp == NULL);
167
168 mutex_enter(&xbuf_mutex);
169 ASSERT((xbuf_refcount != 0) && (xbuf_tq != NULL));
170 xbuf_refcount--;
171 if (xbuf_refcount == 0) {
172 taskq_destroy(xbuf_tq);
173 xbuf_tq = NULL;
174 }
175 mutex_exit(&xbuf_mutex);
176
177 kmem_free(xap, sizeof (struct __ddi_xbuf_attr));
178 }
179
180
181 /* ARGSUSED */
182 DDII void
183 ddi_xbuf_attr_register_devinfo(ddi_xbuf_attr_t xbuf_attr, dev_info_t *dip)
184 {
185 /* Currently a no-op in this prototype */
186 }
187
188
189 /* ARGSUSED */
190 DDII void
191 ddi_xbuf_attr_unregister_devinfo(ddi_xbuf_attr_t xbuf_attr, dev_info_t *dip)
192 {
193 /* Currently a no-op in this prototype */
194 }
195
196 DDII int
197 ddi_xbuf_attr_setup_brk(ddi_xbuf_attr_t xap, size_t size)
198 {
199 if (size < DEV_BSIZE)
200 return (0);
201
202 mutex_enter(&xap->xa_mutex);
203 xap->xa_brksize = size & ~(DEV_BSIZE - 1);
204 mutex_exit(&xap->xa_mutex);
205 return (1);
206 }
207
208
209
210 /*
211 * Enqueue the given buf and attempt to initiate IO.
212 * Called from the driver strategy(9E) routine.
213 */
214
215 DDII int
216 ddi_xbuf_qstrategy(struct buf *bp, ddi_xbuf_attr_t xap)
217 {
218 ASSERT(xap != NULL);
219 ASSERT(!mutex_owned(&xap->xa_mutex));
220 ASSERT(!mutex_owned(&xap->xa_reserve_mutex));
221
222 mutex_enter(&xap->xa_mutex);
223
224 ASSERT((bp->b_bcount & (DEV_BSIZE - 1)) == 0);
225
226 /*
227 * Breakup buf if necessary. bp->b_private is temporarily
228 * used to save xbuf_brk
229 */
230 if (xap->xa_brksize && bp->b_bcount > xap->xa_brksize) {
231 struct xbuf_brk *brkp;
232
233 brkp = kmem_zalloc(sizeof (struct xbuf_brk), KM_SLEEP);
234 _NOTE(NOW_INVISIBLE_TO_OTHER_THREADS(*brkp))
235 mutex_init(&brkp->mutex, NULL, MUTEX_DRIVER, NULL);
236 brkp->bp0 = bp;
237 brkp->brksize = xap->xa_brksize;
238 brkp->brkblk = btodt(xap->xa_brksize);
239 brkp->noff = xap->xa_brksize;
240 brkp->blkno = bp->b_blkno;
241 _NOTE(NOW_VISIBLE_TO_OTHER_THREADS(*brkp))
242 bp->b_private = brkp;
243 } else {
244 bp->b_private = NULL;
245 }
246
247 /* Enqueue buf */
248 if (xap->xa_headp == NULL) {
249 xap->xa_headp = xap->xa_tailp = bp;
250 } else {
251 xap->xa_tailp->av_forw = bp;
252 xap->xa_tailp = bp;
253 }
254 bp->av_forw = NULL;
255
256 xap->xa_pending++;
257 mutex_exit(&xap->xa_mutex);
258 return (xbuf_iostart(xap));
259 }
260
261
262 /*
263 * Drivers call this immediately before calling biodone(9F), to notify the
264 * framework that the indicated xbuf is no longer being used by the driver.
265 * May be called under interrupt context.
266 */
267
268 DDII int
269 ddi_xbuf_done(struct buf *bp, ddi_xbuf_attr_t xap)
270 {
271 ddi_xbuf_t xp;
272 int done;
273
274 ASSERT(bp != NULL);
275 ASSERT(xap != NULL);
276 ASSERT(!mutex_owned(&xap->xa_mutex));
277 ASSERT(!mutex_owned(&xap->xa_reserve_mutex));
278
279 xp = ddi_xbuf_get(bp, xap);
280
281 mutex_enter(&xap->xa_mutex);
282
283 #ifdef SDDEBUG
284 if (xap->xa_active_limit != 0) {
285 ASSERT(xap->xa_active_count > 0);
286 }
287 #endif
288 xap->xa_active_count--;
289
290 if (xap->xa_reserve_limit != 0) {
291 mutex_enter(&xap->xa_reserve_mutex);
292 if (xap->xa_reserve_count < xap->xa_reserve_limit) {
293 /* Put this xbuf onto the reserve list & exit */
294 *((void **)xp) = xap->xa_reserve_headp;
295 xap->xa_reserve_headp = xp;
296 xap->xa_reserve_count++;
297 mutex_exit(&xap->xa_reserve_mutex);
298 goto done;
299 }
300 mutex_exit(&xap->xa_reserve_mutex);
301 }
302
303 kmem_free(xp, xap->xa_allocsize); /* return it to the system */
304
305 done:
306 if (bp->b_iodone == xbuf_brk_done) {
307 struct xbuf_brk *brkp = (struct xbuf_brk *)bp->b_clone_private;
308
309 brkp->active--;
310 if (brkp->active || xap->xa_headp == brkp->bp0) {
311 done = 0;
312 } else {
313 brkp->off = -1; /* mark bp0 as completed */
314 done = 1;
315 }
316 } else {
317 done = 1;
318 }
319
320 if ((xap->xa_active_limit == 0) ||
321 (xap->xa_active_count <= xap->xa_active_lowater)) {
322 xbuf_dispatch(xap);
323 }
324
325 mutex_exit(&xap->xa_mutex);
326 return (done);
327 }
328
329 static int
330 xbuf_brk_done(struct buf *bp)
331 {
332 struct xbuf_brk *brkp = (struct xbuf_brk *)bp->b_clone_private;
333 struct buf *bp0 = brkp->bp0;
334 int done;
335
336 mutex_enter(&brkp->mutex);
337 if (bp->b_flags & B_ERROR && !(bp0->b_flags & B_ERROR)) {
338 bp0->b_flags |= B_ERROR;
339 bp0->b_error = bp->b_error;
340 }
341 if (bp->b_resid)
342 bp0->b_resid = bp0->b_bcount;
343
344 freerbuf(bp);
345 brkp->nbufs--;
346
347 done = (brkp->off == -1 && brkp->nbufs == 0);
348 mutex_exit(&brkp->mutex);
349
350 /* All buf segments done */
351 if (done) {
352 mutex_destroy(&brkp->mutex);
353 kmem_free(brkp, sizeof (struct xbuf_brk));
354 biodone(bp0);
355 }
356 return (0);
357 }
358
359 DDII void
360 ddi_xbuf_dispatch(ddi_xbuf_attr_t xap)
361 {
362 mutex_enter(&xap->xa_mutex);
363 if ((xap->xa_active_limit == 0) ||
364 (xap->xa_active_count <= xap->xa_active_lowater)) {
365 xbuf_dispatch(xap);
366 }
367 mutex_exit(&xap->xa_mutex);
368 }
369
370
371 /*
372 * ISSUE: in this prototype we cannot really implement ddi_xbuf_get()
373 * unless we explicitly hide the xbuf pointer somewhere in the buf
374 * during allocation, and then rely on the driver never changing it.
375 * We can probably get away with using b_private for this for now,
376 * tho it really is kinda gnarly.....
377 */
378
379 /* ARGSUSED */
380 DDII ddi_xbuf_t
381 ddi_xbuf_get(struct buf *bp, ddi_xbuf_attr_t xap)
382 {
383 return (bp->b_private);
384 }
385
386
387 /*
388 * Initiate IOs for bufs on the queue. Called from kernel thread or taskq
389 * thread context. May execute concurrently for the same ddi_xbuf_attr_t.
390 */
391
392 static int
393 xbuf_iostart(ddi_xbuf_attr_t xap)
394 {
395 struct buf *bp;
396 ddi_xbuf_t xp;
397
398 ASSERT(xap != NULL);
399 ASSERT(!mutex_owned(&xap->xa_mutex));
400 ASSERT(!mutex_owned(&xap->xa_reserve_mutex));
401
402 /*
403 * For each request on the queue, attempt to allocate the specified
404 * xbuf extension area, and call the driver's iostart() routine.
405 * We process as many requests on the queue as we can, until either
406 * (1) we run out of requests; or
407 * (2) we run out of resources; or
408 * (3) we reach the maximum limit for the given ddi_xbuf_attr_t.
409 */
410 for (;;) {
411 mutex_enter(&xap->xa_mutex);
412
413 if ((bp = xap->xa_headp) == NULL) {
414 break; /* queue empty */
415 }
416
417 if ((xap->xa_active_limit != 0) &&
418 (xap->xa_active_count >= xap->xa_active_limit)) {
419 break; /* allocation limit reached */
420 }
421
422 /*
423 * If the reserve_limit is non-zero then work with the
424 * reserve else always allocate a new struct.
425 */
426 if (xap->xa_reserve_limit != 0) {
427 /*
428 * Don't penalize EVERY I/O by always allocating a new
429 * struct. for the sake of maintaining and not touching
430 * a reserve for a pathalogical condition that may never
431 * happen. Use the reserve entries first, this uses it
432 * like a local pool rather than a reserve that goes
433 * untouched. Make sure it's re-populated whenever it
434 * gets fully depleted just in case it really is needed.
435 * This is safe because under the pathalogical
436 * condition, when the system runs out of memory such
437 * that the below allocs fail, the reserve will still
438 * be available whether the entries are saved away on
439 * the queue unused or in-transport somewhere. Thus
440 * progress can still continue, however slowly.
441 */
442 mutex_enter(&xap->xa_reserve_mutex);
443 if (xap->xa_reserve_count != 0) {
444 ASSERT(xap->xa_reserve_headp != NULL);
445 /* Grab an xbuf from the reserve */
446 xp = xap->xa_reserve_headp;
447 xap->xa_reserve_headp = *((void **)xp);
448 ASSERT(xap->xa_reserve_count > 0);
449 xap->xa_reserve_count--;
450 } else {
451 /*
452 * Either this is the first time through,
453 * or the reserve has been totally depleted.
454 * Re-populate the reserve (pool). Excess
455 * structs. get released in the done path.
456 */
457 while (xap->xa_reserve_count <
458 xap->xa_reserve_limit) {
459 xp = kmem_alloc(xap->xa_allocsize,
460 KM_NOSLEEP);
461 if (xp == NULL) {
462 break;
463 }
464 *((void **)xp) = xap->xa_reserve_headp;
465 xap->xa_reserve_headp = xp;
466 xap->xa_reserve_count++;
467 }
468 /* And one more to use right now. */
469 xp = kmem_alloc(xap->xa_allocsize, KM_NOSLEEP);
470 }
471 mutex_exit(&xap->xa_reserve_mutex);
472 } else {
473 /*
474 * Try to alloc a new xbuf struct. If this fails just
475 * exit for now. We'll get back here again either upon
476 * cmd completion or via the timer handler.
477 * Question: what if the allocation attempt for the very
478 * first cmd. fails? There are no outstanding cmds so
479 * how do we get back here?
480 * Should look at un_ncmds_in_transport, if it's zero
481 * then schedule xbuf_restart_callback via the timer.
482 * Athough that breaks the architecture by bringing
483 * softstate data into this code.
484 */
485 xp = kmem_alloc(xap->xa_allocsize, KM_NOSLEEP);
486 }
487 if (xp == NULL) {
488 break; /* Can't process a cmd. right now. */
489 }
490
491 /*
492 * Always run the counter. It's used/needed when xa_active_limit
493 * is non-zero which is the typical (and right now only) case.
494 */
495 xap->xa_active_count++;
496
497 if (bp->b_private) {
498 struct xbuf_brk *brkp = bp->b_private;
499 struct buf *bp0 = bp;
500
501 brkp->active++;
502
503 mutex_enter(&brkp->mutex);
504 brkp->nbufs++;
505 mutex_exit(&brkp->mutex);
506
507 if (brkp->noff < bp0->b_bcount) {
508 bp = bioclone(bp0, brkp->off, brkp->brksize,
509 bp0->b_edev, brkp->blkno, xbuf_brk_done,
510 NULL, KM_SLEEP);
511
512 /* update xfer position */
513 brkp->off = brkp->noff;
514 brkp->noff += brkp->brksize;
515 brkp->blkno += brkp->brkblk;
516 } else {
517 bp = bioclone(bp0, brkp->off,
518 bp0->b_bcount - brkp->off, bp0->b_edev,
519 brkp->blkno, xbuf_brk_done, NULL, KM_SLEEP);
520
521 /* unlink the buf from the list */
522 xap->xa_headp = bp0->av_forw;
523 bp0->av_forw = NULL;
524 }
525 bp->b_clone_private = (struct buf *)brkp;
526 } else {
527 /* unlink the buf from the list */
528 xap->xa_headp = bp->av_forw;
529 bp->av_forw = NULL;
530 }
531
532 /*
533 * Hack needed in the prototype so ddi_xbuf_get() will work.
534 * Here we can rely on the sd code not changing the value in
535 * b_private (in fact it wants it there). See ddi_get_xbuf()
536 */
537 bp->b_private = xp;
538
539 /* call the driver's iostart routine */
540 mutex_exit(&xap->xa_mutex);
541 (*(xap->xa_strategy))(bp, xp, xap->xa_attr_arg);
542 }
543
544 ASSERT(xap->xa_pending > 0);
545 xap->xa_pending--;
546 mutex_exit(&xap->xa_mutex);
547 return (0);
548 }
549
550
551 /*
552 * Re-start IO processing if there is anything on the queue, AND if the
553 * restart function is not already running/pending for this ddi_xbuf_attr_t
554 */
555 static void
556 xbuf_dispatch(ddi_xbuf_attr_t xap)
557 {
558 ASSERT(xap != NULL);
559 ASSERT(xap->xa_tq != NULL);
560 ASSERT(mutex_owned(&xap->xa_mutex));
561
562 if ((xap->xa_headp != NULL) && (xap->xa_timeid == NULL) &&
563 (xap->xa_pending == 0)) {
564 /*
565 * First try to see if we can dispatch the restart function
566 * immediately, in a taskq thread. If this fails, then
567 * schedule a timeout(9F) callback to try again later.
568 */
569 if (taskq_dispatch(xap->xa_tq,
570 (void (*)(void *)) xbuf_iostart, xap, KM_NOSLEEP) == 0) {
571 /*
572 * Unable to enqueue the request for the taskq thread,
573 * try again later. Note that this will keep re-trying
574 * until taskq_dispatch() succeeds.
575 */
576 xap->xa_timeid = timeout(xbuf_restart_callback, xap,
577 XBUF_DISPATCH_DELAY);
578 } else {
579 /*
580 * This indicates that xbuf_iostart() will soon be
581 * run for this ddi_xbuf_attr_t, and we do not need to
582 * schedule another invocation via timeout/taskq
583 */
584 xap->xa_pending++;
585 }
586 }
587 }
588
589 /* timeout(9F) callback routine for xbuf restart mechanism. */
590 static void
591 xbuf_restart_callback(void *arg)
592 {
593 ddi_xbuf_attr_t xap = arg;
594
595 ASSERT(xap != NULL);
596 ASSERT(xap->xa_tq != NULL);
597 ASSERT(!mutex_owned(&xap->xa_mutex));
598
599 mutex_enter(&xap->xa_mutex);
600 xap->xa_timeid = NULL;
601 xbuf_dispatch(xap);
602 mutex_exit(&xap->xa_mutex);
603 }
604
605
606 DDII void
607 ddi_xbuf_flushq(ddi_xbuf_attr_t xap, int (*funcp)(struct buf *))
608 {
609 struct buf *bp;
610 struct buf *next_bp;
611 struct buf *prev_bp = NULL;
612
613 ASSERT(xap != NULL);
614 ASSERT(xap->xa_tq != NULL);
615 ASSERT(!mutex_owned(&xap->xa_mutex));
616
617 mutex_enter(&xap->xa_mutex);
618
619 for (bp = xap->xa_headp; bp != NULL; bp = next_bp) {
620
621 next_bp = bp->av_forw; /* Save for next iteration */
622
623 /*
624 * If the user-supplied function is non-NULL and returns
625 * FALSE, then just leave the current bp on the queue.
626 */
627 if ((funcp != NULL) && (!(*funcp)(bp))) {
628 prev_bp = bp;
629 continue;
630 }
631
632 /* de-queue the bp */
633 if (bp == xap->xa_headp) {
634 xap->xa_headp = next_bp;
635 if (xap->xa_headp == NULL) {
636 xap->xa_tailp = NULL;
637 }
638 } else {
639 ASSERT(xap->xa_headp != NULL);
640 ASSERT(prev_bp != NULL);
641 if (bp == xap->xa_tailp) {
642 ASSERT(next_bp == NULL);
643 xap->xa_tailp = prev_bp;
644 }
645 prev_bp->av_forw = next_bp;
646 }
647 bp->av_forw = NULL;
648
649 /* Add the bp to the flush queue */
650 if (xap->xa_flush_headp == NULL) {
651 ASSERT(xap->xa_flush_tailp == NULL);
652 xap->xa_flush_headp = xap->xa_flush_tailp = bp;
653 } else {
654 ASSERT(xap->xa_flush_tailp != NULL);
655 xap->xa_flush_tailp->av_forw = bp;
656 xap->xa_flush_tailp = bp;
657 }
658 }
659
660 while ((bp = xap->xa_flush_headp) != NULL) {
661 xap->xa_flush_headp = bp->av_forw;
662 if (xap->xa_flush_headp == NULL) {
663 xap->xa_flush_tailp = NULL;
664 }
665 mutex_exit(&xap->xa_mutex);
666 bioerror(bp, EIO);
667 bp->b_resid = bp->b_bcount;
668 biodone(bp);
669 mutex_enter(&xap->xa_mutex);
670 }
671
672 mutex_exit(&xap->xa_mutex);
673 }