2 * Copyright (c) 2007 The DragonFly Project. All rights reserved.
4 * This code is derived from software contributed to The DragonFly Project
5 * by Matthew Dillon <dillon@backplane.com>
7 * Redistribution and use in source and binary forms, with or without
8 * modification, are permitted provided that the following conditions
11 * 1. Redistributions of source code must retain the above copyright
12 * notice, this list of conditions and the following disclaimer.
13 * 2. Redistributions in binary form must reproduce the above copyright
14 * notice, this list of conditions and the following disclaimer in
15 * the documentation and/or other materials provided with the
17 * 3. Neither the name of The DragonFly Project nor the names of its
18 * contributors may be used to endorse or promote products derived
19 * from this software without specific, prior written permission.
21 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
22 * ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
23 * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
24 * FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
25 * COPYRIGHT HOLDERS OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
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27 * BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
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29 * AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
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31 * OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
34 * $DragonFly: src/sys/vfs/hammer/hammer_io.c,v 1.21 2008/02/10 18:58:22 dillon Exp $
37 * IO Primitives and buffer cache management
39 * All major data-tracking structures in HAMMER contain a struct hammer_io
40 * which is used to manage their backing store. We use filesystem buffers
41 * for backing store and we leave them passively associated with their
44 * If the kernel tries to release a passively associated buf which we cannot
45 * yet let go we set B_LOCKED in the buffer and then actively released it
50 #include <sys/fcntl.h>
51 #include <sys/nlookup.h>
55 static void hammer_io_deallocate(struct buf
*bp
);
56 static int hammer_io_checkwrite(struct buf
*bp
);
59 * Initialize an already-zero'd hammer_io structure
62 hammer_io_init(hammer_io_t io
, enum hammer_io_type type
)
65 TAILQ_INIT(&io
->deplist
);
69 * Helper routine to disassociate a buffer cache buffer from an I/O
70 * structure. Called with the io structure exclusively locked.
72 * The io may have 0 or 1 references depending on who called us. The
73 * caller is responsible for dealing with the refs.
75 * This call can only be made when no action is required on the buffer.
76 * HAMMER must own the buffer (released == 0) since we mess around with it.
79 hammer_io_disassociate(hammer_io_structure_t iou
, int elseit
)
81 struct buf
*bp
= iou
->io
.bp
;
83 KKASSERT(TAILQ_EMPTY(&iou
->io
.deplist
) && iou
->io
.modified
== 0);
86 bp
->b_flags
&= ~B_LOCKED
;
88 KKASSERT(iou
->io
.released
== 0);
92 KKASSERT(iou
->io
.released
);
95 switch(iou
->io
.type
) {
96 case HAMMER_STRUCTURE_VOLUME
:
97 iou
->volume
.ondisk
= NULL
;
99 case HAMMER_STRUCTURE_BUFFER
:
100 iou
->buffer
.ondisk
= NULL
;
106 * Wait for any physical IO to complete
109 hammer_io_wait(hammer_io_t io
)
113 tsleep_interlock(io
);
116 tsleep(io
, 0, "hmrflw", 0);
117 if (io
->running
== 0)
119 tsleep_interlock(io
);
121 if (io
->running
== 0)
129 hammer_io_waitdep(hammer_io_t io
)
131 while (TAILQ_FIRST(&io
->deplist
)) {
132 kprintf("waitdep %p\n", io
);
133 tsleep(io
, 0, "hmrdep", hz
);
138 * Load bp for a HAMMER structure. The io is exclusively locked by the
142 hammer_io_read(struct vnode
*devvp
, struct hammer_io
*io
)
147 if ((bp
= io
->bp
) == NULL
) {
148 error
= bread(devvp
, io
->offset
, HAMMER_BUFSIZE
, &io
->bp
);
151 bp
->b_ops
= &hammer_bioops
;
152 LIST_INSERT_HEAD(&bp
->b_dep
, &io
->worklist
, node
);
155 io
->modified
= 0; /* no new modifications yet */
156 io
->released
= 0; /* we hold an active lock on bp */
166 * Similar to hammer_io_read() but returns a zero'd out buffer instead.
167 * vfs_bio_clrbuf() is kinda nasty, enforce serialization against background
168 * I/O so we can call it.
170 * The caller is responsible for calling hammer_modify_*() on the appropriate
174 hammer_io_new(struct vnode
*devvp
, struct hammer_io
*io
)
178 if ((bp
= io
->bp
) == NULL
) {
179 io
->bp
= getblk(devvp
, io
->offset
, HAMMER_BUFSIZE
, 0, 0);
181 bp
->b_ops
= &hammer_bioops
;
182 LIST_INSERT_HEAD(&bp
->b_dep
, &io
->worklist
, node
);
200 * This routine is called on the last reference to a hammer structure.
201 * The io is usually locked exclusively (but may not be during unmount).
203 * If flush is 1, or B_LOCKED was set indicating that the kernel
204 * wanted to recycle the buffer, and there are no dependancies, this
205 * function will issue an asynchronous write.
207 * If flush is 2 this function waits until all I/O has completed and
208 * disassociates the bp from the IO before returning, unless there
209 * are still other references.
212 hammer_io_release(struct hammer_io
*io
, int flush
)
216 if ((bp
= io
->bp
) == NULL
)
221 * If flush is 2 wait for dependancies
223 while (flush
== 2 && TAILQ_FIRST(&io
->deplist
)) {
224 hammer_io_wait(TAILQ_FIRST(&io
->deplist
));
229 * Try to flush a dirty IO to disk if asked to by the caller
230 * or if the kernel tried to flush the buffer in the past.
232 * The flush will fail if any dependancies are present.
234 if (io
->modified
&& (flush
|| bp
->b_flags
& B_LOCKED
))
238 * If flush is 2 we wait for the IO to complete.
240 if (flush
== 2 && io
->running
) {
245 * Actively or passively release the buffer. Modified IOs with
246 * dependancies cannot be released.
248 if (flush
&& io
->modified
== 0 && io
->running
== 0) {
249 KKASSERT(TAILQ_EMPTY(&io
->deplist
));
255 hammer_io_disassociate((hammer_io_structure_t
)io
, 1);
256 } else if (io
->modified
) {
257 if (io
->released
== 0 && TAILQ_EMPTY(&io
->deplist
)) {
261 } else if (io
->released
== 0) {
268 * This routine is called with a locked IO when a flush is desired and
269 * no other references to the structure exists other then ours. This
270 * routine is ONLY called when HAMMER believes it is safe to flush a
271 * potentially modified buffer out.
274 hammer_io_flush(struct hammer_io
*io
)
279 * Can't flush if the IO isn't modified or if it has dependancies.
281 if (io
->modified
== 0)
283 if (TAILQ_FIRST(&io
->deplist
))
289 * XXX - umount syncs buffers without referencing them, check for 0
292 KKASSERT(io
->lock
.refs
== 0 || io
->lock
.refs
== 1);
295 * Reset modified to 0 here and re-check it after the IO completes.
296 * This is only legal when lock.refs == 1 (otherwise we might clear
297 * the modified bit while there are still users of the cluster
298 * modifying the data).
300 * NOTE: We have no dependancies so we don't have to worry about
301 * cluster-open's here.
303 * Do this before potentially blocking so any attempt to modify the
304 * ondisk while we are blocked blocks waiting for us.
306 io
->modified
= 0; /* force interlock */
311 /* BUF_KERNPROC(io->bp); */
319 /************************************************************************
321 ************************************************************************
323 * These routines deal with dependancies created when IO buffers get
324 * modified. The caller must call hammer_modify_*() on a referenced
325 * HAMMER structure prior to modifying its on-disk data.
327 * Any intent to modify an IO buffer acquires the related bp and imposes
328 * various write ordering dependancies.
332 * Mark a HAMMER structure as undergoing modification. Return 1 when applying
333 * a non-NULL ordering dependancy for the first time, 0 otherwise.
335 * list can be NULL, indicating that a structural modification is being made
336 * without creating an ordering dependancy.
340 hammer_io_modify(hammer_io_t io
, struct hammer_io_list
*list
)
345 * Shortcut if nothing to do.
347 KKASSERT(io
->lock
.refs
!= 0 && io
->bp
!= NULL
);
348 if (io
->modified
&& io
->released
== 0 &&
349 (io
->entry_list
|| list
== NULL
)) {
353 hammer_lock_ex(&io
->lock
);
357 BUF_KERNPROC(io
->bp
);
359 KKASSERT(io
->modified
!= 0);
361 if (io
->entry_list
== NULL
) {
362 io
->entry_list
= list
;
364 TAILQ_INSERT_TAIL(list
, io
, entry
);
370 /* only one dependancy is allowed */
371 KKASSERT(list
== NULL
|| io
->entry_list
== list
);
374 hammer_unlock(&io
->lock
);
379 hammer_modify_volume(hammer_volume_t volume
, void *base
, int len
)
381 hammer_io_modify(&volume
->io
, NULL
);
384 intptr_t rel_offset
= (intptr_t)base
- (intptr_t)volume
->ondisk
;
385 KKASSERT((rel_offset
& ~(intptr_t)HAMMER_BUFMASK
) == 0);
386 hammer_generate_undo(volume
->hmp
,
387 HAMMER_ENCODE_RAW_VOLUME(volume
->vol_no
, rel_offset
),
393 * Caller intends to modify a buffer's ondisk structure. The related
394 * cluster must be marked open prior to being able to flush the modified
395 * buffer so get that I/O going now.
398 hammer_modify_buffer(hammer_buffer_t buffer
, void *base
, int len
)
400 hammer_io_modify(&buffer
->io
, NULL
);
402 intptr_t rel_offset
= (intptr_t)base
- (intptr_t)buffer
->ondisk
;
403 KKASSERT((rel_offset
& ~(intptr_t)HAMMER_BUFMASK
) == 0);
404 hammer_generate_undo(buffer
->volume
->hmp
,
405 buffer
->zone2_offset
+ rel_offset
,
411 * Mark an entity as not being dirty any more -- this usually occurs when
412 * the governing a-list has freed the entire entity.
417 hammer_io_clear_modify(struct hammer_io
*io
)
423 if ((bp
= io
->bp
) != NULL
) {
426 /* BUF_KERNPROC(io->bp); */
430 if (io
->modified
== 0) {
431 kprintf("hammer_io_clear_modify: cleared %p\n", io
);
441 /************************************************************************
443 ************************************************************************
448 * Pre-IO initiation kernel callback - cluster build only
451 hammer_io_start(struct buf
*bp
)
456 * Post-IO completion kernel callback
458 * NOTE: HAMMER may modify a buffer after initiating I/O. The modified bit
459 * may also be set if we were marking a cluster header open. Only remove
460 * our dependancy if the modified bit is clear.
463 hammer_io_complete(struct buf
*bp
)
465 union hammer_io_structure
*iou
= (void *)LIST_FIRST(&bp
->b_dep
);
467 KKASSERT(iou
->io
.released
== 1);
470 * If this was a write and the modified bit is still clear we can
471 * remove ourselves from the dependancy list.
473 * If no lock references remain and we can acquire the IO lock and
474 * someone at some point wanted us to flush (B_LOCKED test), then
475 * try to dispose of the IO.
477 if (iou
->io
.modified
== 0 && iou
->io
.entry_list
) {
478 TAILQ_REMOVE(iou
->io
.entry_list
, &iou
->io
, entry
);
479 iou
->io
.entry_list
= NULL
;
482 if (iou
->io
.waiting
) {
488 * Someone wanted us to flush, try to clean out the buffer.
490 if ((bp
->b_flags
& B_LOCKED
) && iou
->io
.lock
.refs
== 0) {
491 KKASSERT(iou
->io
.modified
== 0);
492 bp
->b_flags
&= ~B_LOCKED
;
493 hammer_io_deallocate(bp
);
494 /* structure may be dead now */
499 * Callback from kernel when it wishes to deallocate a passively
500 * associated structure. This case can only occur with read-only
503 * If we cannot disassociate we set B_LOCKED to prevent the buffer
504 * from getting reused.
506 * WARNING: Because this can be called directly by getnewbuf we cannot
507 * recurse into the tree. If a bp cannot be immediately disassociated
508 * our only recourse is to set B_LOCKED.
510 * WARNING: If the HAMMER structure is passively cached we have to
514 hammer_io_deallocate(struct buf
*bp
)
516 hammer_io_structure_t iou
= (void *)LIST_FIRST(&bp
->b_dep
);
518 KKASSERT((bp
->b_flags
& B_LOCKED
) == 0 && iou
->io
.running
== 0);
519 if (iou
->io
.lock
.refs
> 0 || iou
->io
.modified
) {
520 bp
->b_flags
|= B_LOCKED
;
522 /* XXX interlock against ref or another disassociate */
523 /* XXX this can leave HAMMER structures lying around */
524 hammer_io_disassociate(iou
, 0);
526 switch(iou
->io
.type
) {
527 case HAMMER_STRUCTURE_VOLUME
:
528 hammer_rel_volume(&iou
->volume
, 1);
530 case HAMMER_STRUCTURE_BUFFER
:
531 hammer_rel_buffer(&iou
->buffer
, 1);
539 hammer_io_fsync(struct vnode
*vp
)
545 * NOTE: will not be called unless we tell the kernel about the
546 * bioops. Unused... we use the mount's VFS_SYNC instead.
549 hammer_io_sync(struct mount
*mp
)
555 hammer_io_movedeps(struct buf
*bp1
, struct buf
*bp2
)
560 * I/O pre-check for reading and writing. HAMMER only uses this for
561 * B_CACHE buffers so checkread just shouldn't happen, but if it does
564 * Writing is a different case. We don't want the kernel to try to write
565 * out a buffer that HAMMER may be modifying passively or which has a
568 * This code enforces the following write ordering: buffers, then cluster
569 * headers, then volume headers.
572 hammer_io_checkread(struct buf
*bp
)
578 hammer_io_checkwrite(struct buf
*bp
)
580 union hammer_io_structure
*iou
= (void *)LIST_FIRST(&bp
->b_dep
);
582 KKASSERT(TAILQ_EMPTY(&iou
->io
.deplist
));
585 * We are called from the kernel on delayed-write buffers, and
586 * called from hammer_io_flush() on flush requests. There should
587 * be no dependancies in either case.
589 * In the case of delayed-writes, the introduction of a dependancy
590 * will block until the bp can be reacquired, and the bp is then
591 * simply not released until the dependancy can be satisfied.
593 * We can only clear the modified bit when entered from the kernel
594 * if io.lock.refs == 0.
596 if (iou
->io
.lock
.refs
== 0) {
597 iou
->io
.modified
= 0;
603 * Return non-zero if the caller should flush the structure associated
604 * with this io sub-structure.
607 hammer_io_checkflush(struct hammer_io
*io
)
609 if (io
->bp
== NULL
|| (io
->bp
->b_flags
& B_LOCKED
)) {
616 * Return non-zero if we wish to delay the kernel's attempt to flush
617 * this buffer to disk.
620 hammer_io_countdeps(struct buf
*bp
, int n
)
625 struct bio_ops hammer_bioops
= {
626 .io_start
= hammer_io_start
,
627 .io_complete
= hammer_io_complete
,
628 .io_deallocate
= hammer_io_deallocate
,
629 .io_fsync
= hammer_io_fsync
,
630 .io_sync
= hammer_io_sync
,
631 .io_movedeps
= hammer_io_movedeps
,
632 .io_countdeps
= hammer_io_countdeps
,
633 .io_checkread
= hammer_io_checkread
,
634 .io_checkwrite
= hammer_io_checkwrite
,