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/* $OpenBSD: nfs_aiod.c,v 1.7 2015/08/28 00:03:54 deraadt Exp $ */
/*
* Copyright (c) 1989, 1993
* The Regents of the University of California. All rights reserved.
*
* This code is derived from software contributed to Berkeley by
* Rick Macklem at The University of Guelph.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions
* are met:
* 1. Redistributions of source code must retain the above copyright
* notice, this list of conditions and the following disclaimer.
* 2. Redistributions in binary form must reproduce the above copyright
* notice, this list of conditions and the following disclaimer in the
* documentation and/or other materials provided with the distribution.
* 3. Neither the name of the University nor the names of its contributors
* may be used to endorse or promote products derived from this software
* without specific prior written permission.
*
* THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
* ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
* IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
* ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
* FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
* DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
* OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
* HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
* LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
* OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
* SUCH DAMAGE.
*/
#include <sys/param.h>
#include <sys/systm.h>
#include <sys/kernel.h>
#include <sys/proc.h>
#include <sys/malloc.h>
#include <sys/mount.h>
#include <sys/vnode.h>
#include <sys/kthread.h>
#include <sys/rwlock.h>
#include <sys/signalvar.h>
#include <sys/queue.h>
#include <sys/mutex.h>
#include <nfs/rpcv2.h>
#include <nfs/nfsproto.h>
#include <nfs/nfs.h>
#include <nfs/nfsnode.h>
#include <nfs/nfs_var.h>
#include <nfs/nfsmount.h>
/* The nfs_aiodl_mtx mutex protects the two lists. */
struct mutex nfs_aiodl_mtx;
struct nfs_aiodhead nfs_aiods_all;
struct nfs_aiodhead nfs_aiods_idle;
/* Current number of "running" aiods. Defaults to NFS_DEFASYNCDAEMON (4). */
int nfs_numaiods = -1;
/* Maximum # of buf to queue on an aiod. */
int nfs_aiodbufqmax;
/*
* Asynchronous I/O threads for client nfs.
* They do read-ahead and write-behind operations on the block I/O cache.
* Never returns unless it fails or gets killed.
*/
void
nfs_aiod(void *arg)
{
struct nfs_aiod *aiod;
struct nfsmount *nmp;
struct buf *bp;
aiod = malloc(sizeof(*aiod), M_TEMP, M_WAITOK|M_ZERO);
mtx_enter(&nfs_aiodl_mtx);
LIST_INSERT_HEAD(&nfs_aiods_all, aiod, nad_all);
LIST_INSERT_HEAD(&nfs_aiods_idle, aiod, nad_idle);
mtx_leave(&nfs_aiodl_mtx);
nfs_numaiods++;
/*
* Enforce an upper limit on how many bufs we'll queue up for
* a given aiod. This is arbitrarily chosen to be a quarter of
* the number of bufs in the system, divided evenly between
* the running aiods.
*
* Since the number of bufs in the system is dynamic, and the
* aiods are usually started up very early (during boot), the
* number of buffers available is pretty low, so the limit we
* enforce is way to low: So, always allow a minimum of 64 bufs.
* XXX: Footshooting.
*/
nfs_aiodbufqmax = max((bcstats.numbufs / 4) / nfs_numaiods, 64);
loop: /* Loop around until SIGKILL */
if (aiod->nad_flags & NFSAIOD_WAKEUP) {
mtx_enter(&nfs_aiodl_mtx);
LIST_INSERT_HEAD(&nfs_aiods_idle, aiod, nad_idle);
mtx_leave(&nfs_aiodl_mtx);
aiod->nad_flags &= ~NFSAIOD_WAKEUP;
}
while (1) {
nmp = aiod->nad_mnt;
if (nmp) {
aiod->nad_mnt = NULL;
break;
}
while (!(aiod->nad_flags & NFSAIOD_WAKEUP))
tsleep(aiod, PWAIT, "aiodidle", 0);
/*
* Wakeup for this aiod happens in one of the following
* situations:
* - The thread is being asked to exit by nfs_set_naiod(), or
* - nfs_asyncio() has found work for this thread on a mount.
*
* In the former case, check to see if nfs_asyncio() has just
* found some work for this thread, and if so, ignore it until
* later.
*/
if (aiod->nad_flags & NFSAIOD_EXIT) {
if (aiod->nad_mnt == NULL)
goto out1;
else
break;
}
}
while ((bp = TAILQ_FIRST(&nmp->nm_bufq)) != NULL) {
/* Take one off the front of the list */
TAILQ_REMOVE(&nmp->nm_bufq, bp, b_freelist);
nmp->nm_bufqlen--;
nfs_doio(bp, NULL);
}
KASSERT(nmp->nm_naiods > 0);
nmp->nm_naiods--;
if (aiod->nad_flags & NFSAIOD_EXIT)
goto out1;
goto loop;
out1:
free(aiod, M_TEMP, sizeof(*aiod));
nfs_numaiods--;
KASSERT(nfs_numaiods >= 0);
/* Rejust the limit of bufs to queue. See comment above. */
if (nfs_numaiods > 0)
nfs_aiodbufqmax = max((bcstats.numbufs / 4) / nfs_numaiods, 64);
else
nfs_aiodbufqmax = 0;
kthread_exit(0);
}
int
nfs_set_naiod(int howmany)
{
struct nfs_aiod *aiod;
int want, error;
KASSERT(howmany >= 0);
error = 0;
if (nfs_numaiods == -1)
nfs_numaiods = 0;
want = howmany - nfs_numaiods;
if (want > 0) {
/* Add more. */
want = min(want, NFS_MAXASYNCDAEMON);
while (want > 0) {
error = kthread_create(nfs_aiod, NULL, NULL, "nfsaio");
if (error)
return (error);
want--;
}
} else if (want < 0) {
/* Get rid of some. */
want = -want;
want = min(want, nfs_numaiods);
/* Favour idle aiod's. */
mtx_enter(&nfs_aiodl_mtx);
while (!LIST_EMPTY(&nfs_aiods_idle) && want > 0) {
aiod = LIST_FIRST(&nfs_aiods_idle);
LIST_REMOVE(aiod, nad_idle);
LIST_REMOVE(aiod, nad_all); /* Yuck. */
aiod->nad_flags |= NFSAIOD_QUIT;
wakeup_one(aiod);
want--;
}
while (!LIST_EMPTY(&nfs_aiods_all) && want > 0) {
aiod = LIST_FIRST(&nfs_aiods_all);
LIST_REMOVE(aiod, nad_all);
aiod->nad_flags |= NFSAIOD_QUIT;
wakeup_one(aiod);
want--;
}
mtx_leave(&nfs_aiodl_mtx);
}
/* ignore the want == nfs_numaiods case, since it means no work */
return (error);
}
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