224d5539a9
Add a mutex and protect the allocation and traversal of the list with it. When we allocate a page for devstat use we drop the mutex and use M_WAITOK this is not nice, but under the given circumstances the best we can do. In the sysctl handler for returning the devstat entries we do not want to hold the mutex across copyout(9) calls, so we keep a very careful eye on the devstat_generation count, and abandon with EBUSY if it changes under our feet. Specifically test for BIO_WRITE, rather than default non-read,non-deletes as write. Make the default be DEVSTAT_NO_DATA. Add atomic increments of the sequence[01] fields so applications using the mmap'ed view stand a chance of detecting updates in progress. Reviewed by: ken
533 lines
14 KiB
C
533 lines
14 KiB
C
/*
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* Copyright (c) 1997, 1998, 1999 Kenneth D. Merry.
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* All rights reserved.
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*
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* Redistribution and use in source and binary forms, with or without
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* modification, are permitted provided that the following conditions
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* are met:
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* 1. Redistributions of source code must retain the above copyright
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* notice, this list of conditions and the following disclaimer.
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* 2. Redistributions in binary form must reproduce the above copyright
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* notice, this list of conditions and the following disclaimer in the
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* documentation and/or other materials provided with the distribution.
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* 3. The name of the author may not be used to endorse or promote products
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* derived from this software without specific prior written permission.
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*
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* THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
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* ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
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* IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
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* ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
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* FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
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* DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
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* OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
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* HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
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* LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
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* OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
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* SUCH DAMAGE.
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*
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* $FreeBSD$
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*/
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#include <sys/param.h>
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#include <sys/kernel.h>
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#include <sys/systm.h>
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#include <sys/bio.h>
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#include <sys/devicestat.h>
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#include <sys/sysctl.h>
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#include <sys/malloc.h>
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#include <sys/lock.h>
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#include <sys/mutex.h>
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#include <sys/conf.h>
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#include <vm/vm.h>
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#include <vm/pmap.h>
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#include <machine/atomic.h>
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static int devstat_num_devs;
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static u_int devstat_generation;
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static int devstat_version = DEVSTAT_VERSION;
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static int devstat_current_devnumber;
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static struct mtx devstat_mutex;
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static struct devstatlist device_statq;
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static struct devstat *devstat_alloc(void);
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static void devstat_free(struct devstat *);
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static void devstat_add_entry(struct devstat *ds, const void *dev_name,
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int unit_number, u_int32_t block_size,
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devstat_support_flags flags,
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devstat_type_flags device_type,
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devstat_priority priority);
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/*
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* Allocate a devstat and initialize it
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*/
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struct devstat *
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devstat_new_entry(const void *dev_name,
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int unit_number, u_int32_t block_size,
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devstat_support_flags flags,
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devstat_type_flags device_type,
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devstat_priority priority)
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{
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struct devstat *ds;
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static int once;
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if (!once) {
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STAILQ_INIT(&device_statq);
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mtx_init(&devstat_mutex, "devstat", NULL, MTX_DEF);
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once = 1;
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}
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mtx_assert(&devstat_mutex, MA_NOTOWNED);
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ds = devstat_alloc();
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mtx_lock(&devstat_mutex);
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devstat_add_entry(ds, dev_name, unit_number, block_size,
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flags, device_type, priority);
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mtx_unlock(&devstat_mutex);
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return (ds);
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}
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/*
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* Take a malloced and zeroed devstat structure given to us, fill it in
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* and add it to the queue of devices.
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*/
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static void
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devstat_add_entry(struct devstat *ds, const void *dev_name,
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int unit_number, u_int32_t block_size,
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devstat_support_flags flags,
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devstat_type_flags device_type,
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devstat_priority priority)
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{
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struct devstatlist *devstat_head;
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struct devstat *ds_tmp;
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mtx_assert(&devstat_mutex, MA_OWNED);
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devstat_num_devs++;
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devstat_head = &device_statq;
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/*
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* Priority sort. Each driver passes in its priority when it adds
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* its devstat entry. Drivers are sorted first by priority, and
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* then by probe order.
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*
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* For the first device, we just insert it, since the priority
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* doesn't really matter yet. Subsequent devices are inserted into
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* the list using the order outlined above.
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*/
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if (devstat_num_devs == 1)
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STAILQ_INSERT_TAIL(devstat_head, ds, dev_links);
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else {
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STAILQ_FOREACH(ds_tmp, devstat_head, dev_links) {
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struct devstat *ds_next;
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ds_next = STAILQ_NEXT(ds_tmp, dev_links);
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/*
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* If we find a break between higher and lower
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* priority items, and if this item fits in the
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* break, insert it. This also applies if the
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* "lower priority item" is the end of the list.
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*/
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if ((priority <= ds_tmp->priority)
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&& ((ds_next == NULL)
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|| (priority > ds_next->priority))) {
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STAILQ_INSERT_AFTER(devstat_head, ds_tmp, ds,
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dev_links);
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break;
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} else if (priority > ds_tmp->priority) {
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/*
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* If this is the case, we should be able
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* to insert ourselves at the head of the
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* list. If we can't, something is wrong.
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*/
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if (ds_tmp == STAILQ_FIRST(devstat_head)) {
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STAILQ_INSERT_HEAD(devstat_head,
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ds, dev_links);
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break;
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} else {
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STAILQ_INSERT_TAIL(devstat_head,
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ds, dev_links);
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printf("devstat_add_entry: HELP! "
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"sorting problem detected "
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"for name %p unit %d\n",
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dev_name, unit_number);
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break;
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}
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}
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}
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}
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ds->device_number = devstat_current_devnumber++;
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ds->unit_number = unit_number;
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strlcpy(ds->device_name, dev_name, DEVSTAT_NAME_LEN);
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ds->block_size = block_size;
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ds->flags = flags;
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ds->device_type = device_type;
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ds->priority = priority;
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binuptime(&ds->creation_time);
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devstat_generation++;
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}
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/*
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* Remove a devstat structure from the list of devices.
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*/
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void
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devstat_remove_entry(struct devstat *ds)
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{
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struct devstatlist *devstat_head;
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mtx_assert(&devstat_mutex, MA_NOTOWNED);
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if (ds == NULL)
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return;
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mtx_lock(&devstat_mutex);
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devstat_head = &device_statq;
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/* Remove this entry from the devstat queue */
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atomic_add_acq_int(&ds->sequence1, 1);
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devstat_num_devs--;
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STAILQ_REMOVE(devstat_head, ds, devstat, dev_links);
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devstat_free(ds);
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devstat_generation++;
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mtx_unlock(&devstat_mutex);
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}
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/*
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* Record a transaction start.
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*
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* See comments for devstat_end_transaction(). Ordering is very important
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* here.
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*/
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void
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devstat_start_transaction(struct devstat *ds, struct bintime *now)
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{
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mtx_assert(&devstat_mutex, MA_NOTOWNED);
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/* sanity check */
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if (ds == NULL)
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return;
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atomic_add_acq_int(&ds->sequence1, 1);
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/*
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* We only want to set the start time when we are going from idle
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* to busy. The start time is really the start of the latest busy
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* period.
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*/
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if (ds->start_count == ds->end_count) {
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if (now != NULL)
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ds->busy_from = *now;
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else
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binuptime(&ds->busy_from);
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}
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ds->start_count++;
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atomic_add_rel_int(&ds->sequence0, 1);
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}
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void
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devstat_start_transaction_bio(struct devstat *ds, struct bio *bp)
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{
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mtx_assert(&devstat_mutex, MA_NOTOWNED);
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/* sanity check */
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if (ds == NULL)
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return;
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binuptime(&bp->bio_t0);
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devstat_start_transaction(ds, &bp->bio_t0);
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}
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/*
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* Record the ending of a transaction, and incrment the various counters.
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*
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* Ordering in this function, and in devstat_start_transaction() is VERY
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* important. The idea here is to run without locks, so we are very
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* careful to only modify some fields on the way "down" (i.e. at
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* transaction start) and some fields on the way "up" (i.e. at transaction
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* completion). One exception is busy_from, which we only modify in
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* devstat_start_transaction() when there are no outstanding transactions,
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* and thus it can't be modified in devstat_end_transaction()
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* simultaneously.
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*
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* The sequence0 and sequence1 fields are provided to enable an application
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* spying on the structures with mmap(2) to tell when a structure is in a
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* consistent state or not.
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*
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* For this to work 100% reliably, it is important that the two fields
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* are at opposite ends of the structure and that they are incremented
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* in the opposite order of how a memcpy(3) in userland would copy them.
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* We assume that the copying happens front to back, but there is actually
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* no way short of writing your own memcpy(3) replacement to guarantee
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* this will be the case.
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*
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* In addition to this, being a kind of locks, they must be updated with
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* atomic instructions using appropriate memory barriers.
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*/
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void
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devstat_end_transaction(struct devstat *ds, u_int32_t bytes,
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devstat_tag_type tag_type, devstat_trans_flags flags,
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struct bintime *now, struct bintime *then)
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{
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struct bintime dt, lnow;
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mtx_assert(&devstat_mutex, MA_NOTOWNED);
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/* sanity check */
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if (ds == NULL)
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return;
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if (now == NULL) {
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now = &lnow;
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binuptime(now);
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}
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atomic_add_acq_int(&ds->sequence1, 1);
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/* Update byte and operations counts */
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ds->bytes[flags] += bytes;
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ds->operations[flags]++;
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/*
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* Keep a count of the various tag types sent.
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*/
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if ((ds->flags & DEVSTAT_NO_ORDERED_TAGS) == 0 &&
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tag_type != DEVSTAT_TAG_NONE)
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ds->tag_types[tag_type]++;
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if (then != NULL) {
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/* Update duration of operations */
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dt = *now;
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bintime_sub(&dt, then);
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bintime_add(&ds->duration[flags], &dt);
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}
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/* Accumulate busy time */
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dt = *now;
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bintime_sub(&dt, &ds->busy_from);
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bintime_add(&ds->busy_time, &dt);
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ds->busy_from = *now;
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ds->end_count++;
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atomic_add_rel_int(&ds->sequence0, 1);
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}
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void
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devstat_end_transaction_bio(struct devstat *ds, struct bio *bp)
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{
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devstat_trans_flags flg;
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mtx_assert(&devstat_mutex, MA_NOTOWNED);
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/* sanity check */
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if (ds == NULL)
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return;
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if (bp->bio_cmd == BIO_DELETE)
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flg = DEVSTAT_FREE;
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else if (bp->bio_cmd == BIO_READ)
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flg = DEVSTAT_READ;
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else if (bp->bio_cmd == BIO_WRITE)
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flg = DEVSTAT_WRITE;
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else
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flg = DEVSTAT_NO_DATA;
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devstat_end_transaction(ds, bp->bio_bcount - bp->bio_resid,
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DEVSTAT_TAG_SIMPLE, flg, NULL, &bp->bio_t0);
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}
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/*
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* This is the sysctl handler for the devstat package. The data pushed out
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* on the kern.devstat.all sysctl variable consists of the current devstat
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* generation number, and then an array of devstat structures, one for each
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* device in the system.
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*
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* This is more cryptic that obvious, but basically we neither can nor
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* want to hold the devstat_mutex for any amount of time, so we grab it
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* only when we need to and keep an eye on devstat_generation all the time.
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*/
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static int
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sysctl_devstat(SYSCTL_HANDLER_ARGS)
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{
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int error;
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u_int mygen;
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struct devstat *nds;
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mtx_assert(&devstat_mutex, MA_NOTOWNED);
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if (devstat_num_devs == 0)
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return(EINVAL);
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/*
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* XXX devstat_generation should really be "volatile" but that
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* XXX freaks out the sysctl macro below. The places where we
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* XXX change it and inspect it are bracketed in the mutex which
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* XXX guarantees us proper write barriers. I don't belive the
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* XXX compiler is allowed to optimize mygen away across calls
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* XXX to other functions, so the following is belived to be safe.
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*/
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mygen = devstat_generation;
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error = SYSCTL_OUT(req, &mygen, sizeof(mygen));
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if (error != 0)
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return (error);
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mtx_lock(&devstat_mutex);
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nds = STAILQ_FIRST(&device_statq);
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if (mygen != devstat_generation)
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error = EBUSY;
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mtx_unlock(&devstat_mutex);
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if (error != 0)
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return (error);
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for (;nds != NULL;) {
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error = SYSCTL_OUT(req, nds, sizeof(struct devstat));
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if (error != 0)
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return (error);
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mtx_lock(&devstat_mutex);
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if (mygen != devstat_generation)
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error = EBUSY;
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else
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nds = STAILQ_NEXT(nds, dev_links);
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mtx_unlock(&devstat_mutex);
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if (error != 0)
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return (error);
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}
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return(error);
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}
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/*
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* Sysctl entries for devstat. The first one is a node that all the rest
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* hang off of.
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*/
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SYSCTL_NODE(_kern, OID_AUTO, devstat, CTLFLAG_RD, 0, "Device Statistics");
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SYSCTL_PROC(_kern_devstat, OID_AUTO, all, CTLFLAG_RD|CTLTYPE_OPAQUE,
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0, 0, sysctl_devstat, "S,devstat", "All devices in the devstat list");
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/*
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* Export the number of devices in the system so that userland utilities
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* can determine how much memory to allocate to hold all the devices.
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*/
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SYSCTL_INT(_kern_devstat, OID_AUTO, numdevs, CTLFLAG_RD,
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&devstat_num_devs, 0, "Number of devices in the devstat list");
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SYSCTL_LONG(_kern_devstat, OID_AUTO, generation, CTLFLAG_RD,
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&devstat_generation, 0, "Devstat list generation");
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SYSCTL_INT(_kern_devstat, OID_AUTO, version, CTLFLAG_RD,
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&devstat_version, 0, "Devstat list version number");
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/*
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* Allocator for struct devstat structures. We sub-allocate these from pages
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* which we get from malloc. These pages are exported for mmap(2)'ing through
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* a miniature device driver
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*/
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#define statsperpage (PAGE_SIZE / sizeof(struct devstat))
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static d_mmap_t devstat_mmap;
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static struct cdevsw devstat_cdevsw = {
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.d_open = nullopen,
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.d_close = nullclose,
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.d_mmap = devstat_mmap,
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.d_name = "devstat",
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};
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struct statspage {
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TAILQ_ENTRY(statspage) list;
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struct devstat *stat;
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u_int nfree;
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};
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static TAILQ_HEAD(, statspage) pagelist = TAILQ_HEAD_INITIALIZER(pagelist);
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static MALLOC_DEFINE(M_DEVSTAT, "devstat", "Device statistics");
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static int
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devstat_mmap(dev_t dev, vm_offset_t offset, vm_offset_t *paddr, int nprot)
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{
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struct statspage *spp;
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if (nprot != VM_PROT_READ)
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return (-1);
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TAILQ_FOREACH(spp, &pagelist, list) {
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if (offset == 0) {
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*paddr = vtophys(spp->stat);
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return (0);
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}
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offset -= PAGE_SIZE;
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}
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return (-1);
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}
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static struct devstat *
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devstat_alloc(void)
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{
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struct devstat *dsp;
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struct statspage *spp;
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u_int u;
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static int once;
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mtx_assert(&devstat_mutex, MA_NOTOWNED);
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if (!once) {
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make_dev(&devstat_cdevsw, 0,
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UID_ROOT, GID_WHEEL, 0400, DEVSTAT_DEVICE_NAME);
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once = 1;
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}
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mtx_lock(&devstat_mutex);
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for (;;) {
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TAILQ_FOREACH(spp, &pagelist, list) {
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if (spp->nfree > 0)
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break;
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}
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if (spp != NULL)
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break;
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/*
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* We had no free slot in any of our pages, drop the mutex
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* and get another page. In theory we could have more than
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* one process doing this at the same time and consequently
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* we may allocate more pages than we will need. That is
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* Just Too Bad[tm], we can live with that.
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*/
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mtx_unlock(&devstat_mutex);
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spp = malloc(sizeof *spp, M_DEVSTAT, M_ZERO | M_WAITOK);
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spp->stat = malloc(PAGE_SIZE, M_DEVSTAT, M_ZERO | M_WAITOK);
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spp->nfree = statsperpage;
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mtx_lock(&devstat_mutex);
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/*
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* It would make more sense to add the new page at the head
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* but the order on the list determine the sequence of the
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* mapping so we can't do that.
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*/
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TAILQ_INSERT_TAIL(&pagelist, spp, list);
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}
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dsp = spp->stat;
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for (u = 0; u < statsperpage; u++) {
|
|
if (dsp->allocated == 0)
|
|
break;
|
|
dsp++;
|
|
}
|
|
spp->nfree--;
|
|
dsp->allocated = 1;
|
|
mtx_unlock(&devstat_mutex);
|
|
return (dsp);
|
|
}
|
|
|
|
static void
|
|
devstat_free(struct devstat *dsp)
|
|
{
|
|
struct statspage *spp;
|
|
|
|
mtx_assert(&devstat_mutex, MA_OWNED);
|
|
bzero(dsp, sizeof *dsp);
|
|
TAILQ_FOREACH(spp, &pagelist, list) {
|
|
if (dsp >= spp->stat && dsp < (spp->stat + statsperpage)) {
|
|
spp->nfree++;
|
|
return;
|
|
}
|
|
}
|
|
}
|
|
|
|
SYSCTL_INT(_debug_sizeof, OID_AUTO, devstat, CTLFLAG_RD,
|
|
0, sizeof(struct devstat), "sizeof(struct devstat)");
|