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NetBSD/sys/kern/vfs_bio.c

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/* $NetBSD: vfs_bio.c,v 1.101 2003/12/30 20:40:39 thorpej Exp $ */
/*-
* Copyright (c) 1982, 1986, 1989, 1993
* The Regents of the University of California. All rights reserved.
* (c) UNIX System Laboratories, Inc.
* All or some portions of this file are derived from material licensed
* to the University of California by American Telephone and Telegraph
* Co. or Unix System Laboratories, Inc. and are reproduced herein with
* the permission of UNIX System Laboratories, Inc.
*
* 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.
*
* @(#)vfs_bio.c 8.6 (Berkeley) 1/11/94
*/
/*-
* Copyright (c) 1994 Christopher G. Demetriou
*
* 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. All advertising materials mentioning features or use of this software
* must display the following acknowledgement:
* This product includes software developed by the University of
* California, Berkeley and its contributors.
* 4. 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.
*
* @(#)vfs_bio.c 8.6 (Berkeley) 1/11/94
*/
/*
* Some references:
* Bach: The Design of the UNIX Operating System (Prentice Hall, 1986)
* Leffler, et al.: The Design and Implementation of the 4.3BSD
* UNIX Operating System (Addison Welley, 1989)
*/
#include "opt_bufcache.h"
#include "opt_softdep.h"
#include <sys/cdefs.h>
__KERNEL_RCSID(0, "$NetBSD: vfs_bio.c,v 1.101 2003/12/30 20:40:39 thorpej Exp $");
#include <sys/param.h>
#include <sys/systm.h>
#include <sys/kernel.h>
#include <sys/proc.h>
#include <sys/buf.h>
#include <sys/vnode.h>
#include <sys/mount.h>
#include <sys/malloc.h>
#include <sys/resourcevar.h>
#include <sys/sysctl.h>
#include <sys/conf.h>
#include <uvm/uvm.h>
#include <miscfs/specfs/specdev.h>
#ifndef BUFPAGES
# define BUFPAGES 0
#endif
#ifdef BUFCACHE
# if (BUFCACHE < 5) || (BUFCACHE > 95)
# error BUFCACHE is not between 5 and 95
# endif
#else
# define BUFCACHE 30
#endif
u_int nbuf; /* XXX - for softdep_lockedbufs */
u_int bufpages = BUFPAGES; /* optional hardwired count */
u_int bufcache = BUFCACHE; /* max % of RAM to use for buffer cache */
/* Macros to clear/set/test flags. */
#define SET(t, f) (t) |= (f)
#define CLR(t, f) (t) &= ~(f)
#define ISSET(t, f) ((t) & (f))
/*
* Definitions for the buffer hash lists.
*/
#define BUFHASH(dvp, lbn) \
(&bufhashtbl[(((long)(dvp) >> 8) + (int)(lbn)) & bufhash])
LIST_HEAD(bufhashhdr, buf) *bufhashtbl, invalhash;
u_long bufhash;
#ifndef SOFTDEP
struct bio_ops bioops; /* I/O operation notification */
#endif
/*
* Insq/Remq for the buffer hash lists.
*/
#define binshash(bp, dp) LIST_INSERT_HEAD(dp, bp, b_hash)
#define bremhash(bp) LIST_REMOVE(bp, b_hash)
/*
* Definitions for the buffer free lists.
*/
#define BQUEUES 3 /* number of free buffer queues */
#define BQ_LOCKED 0 /* super-blocks &c */
#define BQ_LRU 1 /* lru, useful buffers */
#define BQ_AGE 2 /* rubbish */
TAILQ_HEAD(bqueues, buf) bufqueues[BQUEUES];
int needbuffer;
/*
* Buffer queue lock.
* Take this lock first if also taking some buffer's b_interlock.
*/
struct simplelock bqueue_slock = SIMPLELOCK_INITIALIZER;
/*
* Buffer pool for I/O buffers.
*/
struct pool bufpool;
/* XXX - somewhat gross.. */
#if MAXBSIZE == 0x2000
#define NMEMPOOLS 4
#elif MAXBSIZE == 0x4000
#define NMEMPOOLS 5
#elif MAXBSIZE == 0x8000
#define NMEMPOOLS 6
#else
#define NMEMPOOLS 7
#endif
#define MEMPOOL_INDEX_OFFSET 10 /* smallest pool is 1k */
#if (1 << (NMEMPOOLS + MEMPOOL_INDEX_OFFSET - 1)) != MAXBSIZE
#error update vfs_bio buffer memory parameters
#endif
/* Buffer memory pools */
static struct pool bmempools[NMEMPOOLS];
static struct vm_map *buf_map;
/*
* Buffer memory pool allocator.
*/
static void *
bufpool_page_alloc(struct pool *pp, int flags)
{
return (void *)uvm_km_kmemalloc1(buf_map,
uvm.kernel_object, MAXBSIZE, MAXBSIZE,
UVM_UNKNOWN_OFFSET,
(flags & PR_WAITOK) ? 0
: UVM_KMF_NOWAIT);
}
static void
bufpool_page_free(struct pool *pp, void *v)
{
uvm_km_free(kernel_map, (vaddr_t)v, MAXBSIZE);
}
static struct pool_allocator bufmempool_allocator = {
bufpool_page_alloc, bufpool_page_free, MAXBSIZE,
};
/* Buffer memory management variables */
u_long bufmem_valimit;
u_long bufmem_hiwater;
u_long bufmem_lowater;
u_long bufmem;
/*
* MD code can call this to set a hard limit on the amount
* of virtual memory used by the buffer cache.
*/
int
buf_setvalimit(vsize_t sz)
{
/* We need to accommodate at least NMEMPOOLS of MAXBSIZE each */
if (sz < NMEMPOOLS * MAXBSIZE)
return EINVAL;
bufmem_valimit = sz;
return 0;
}
static int buf_trim(void);
/*
* bread()/breadn() helper.
*/
static __inline struct buf *bio_doread(struct vnode *, daddr_t, int,
struct ucred *, int);
int count_lock_queue(void);
/*
* Insq/Remq for the buffer free lists.
* Call with buffer queue locked.
*/
#define binsheadfree(bp, dp) TAILQ_INSERT_HEAD(dp, bp, b_freelist)
#define binstailfree(bp, dp) TAILQ_INSERT_TAIL(dp, bp, b_freelist)
#ifdef DEBUG
int debug_verify_freelist = 0;
static int checkfreelist(struct buf *bp, struct bqueues *dp)
{
struct buf *b;
TAILQ_FOREACH(b, dp, b_freelist) {
if (b == bp)
return 1;
}
return 0;
}
#endif
void
bremfree(struct buf *bp)
{
struct bqueues *dp = NULL;
LOCK_ASSERT(simple_lock_held(&bqueue_slock));
KDASSERT(!debug_verify_freelist ||
checkfreelist(bp, &bufqueues[BQ_AGE]) ||
checkfreelist(bp, &bufqueues[BQ_LRU]) ||
checkfreelist(bp, &bufqueues[BQ_LOCKED]) );
/*
* We only calculate the head of the freelist when removing
* the last element of the list as that is the only time that
* it is needed (e.g. to reset the tail pointer).
*
* NB: This makes an assumption about how tailq's are implemented.
*
* We break the TAILQ abstraction in order to efficiently remove a
* buffer from its freelist without having to know exactly which
* freelist it is on.
*/
if (TAILQ_NEXT(bp, b_freelist) == NULL) {
for (dp = bufqueues; dp < &bufqueues[BQUEUES]; dp++)
if (dp->tqh_last == &bp->b_freelist.tqe_next)
break;
if (dp == &bufqueues[BQUEUES])
panic("bremfree: lost tail");
}
TAILQ_REMOVE(dp, bp, b_freelist);
}
u_long
buf_memcalc(void)
{
u_long n;
/*
* Determine the upper bound of memory to use for buffers.
*
* - If bufpages is specified, use that as the number
* pages.
*
* - Otherwise, use bufcache as the percentage of
* physical memory.
*/
if (bufpages != 0) {
n = bufpages;
} else {
if (bufcache < 5) {
printf("forcing bufcache %d -> 5", bufcache);
bufcache = 5;
}
if (bufcache > 95) {
printf("forcing bufcache %d -> 95", bufcache);
bufcache = 95;
}
n = physmem / 100 * bufcache;
}
n <<= PAGE_SHIFT;
if (bufmem_valimit != 0 && n > bufmem_valimit)
n = bufmem_valimit;
return (n);
}
/*
* Initialize buffers and hash links for buffers.
*/
void
bufinit(void)
{
struct bqueues *dp;
int smallmem;
u_int i;
/*
* Initialize buffer cache memory parameters.
*/
bufmem = 0;
bufmem_hiwater = buf_memcalc();
/* lowater is approx. 2% of memory (with bufcache=30) */
bufmem_lowater = (bufmem_hiwater >> 4);
if (bufmem_lowater < 64 * 1024)
/* Ensure a reasonable minimum value */
bufmem_lowater = 64 * 1024;
if (bufmem_valimit != 0) {
vaddr_t minaddr = 0, maxaddr;
buf_map = uvm_km_suballoc(kernel_map, &minaddr, &maxaddr,
bufmem_valimit, VM_MAP_PAGEABLE,
FALSE, 0);
if (buf_map == NULL)
panic("bufinit: cannot allocate submap");
} else
buf_map = kernel_map;
/*
* Initialize the buffer pools.
*/
pool_init(&bufpool, sizeof(struct buf), 0, 0, 0, "bufpl", NULL);
/* On "small" machines use small pool page sizes where possible */
smallmem = (physmem < atop(16*1024*1024));
for (i = 0; i < NMEMPOOLS; i++) {
struct pool_allocator *pa;
struct pool *pp = &bmempools[i];
u_int size = 1 << (i + MEMPOOL_INDEX_OFFSET);
char *name = malloc(8, M_TEMP, M_WAITOK);
snprintf(name, 8, "buf%dk", 1 << i);
pa = (size <= PAGE_SIZE && smallmem)
? &pool_allocator_nointr
: &bufmempool_allocator;
pool_init(pp, size, 0, 0, 0, name, pa);
pool_setlowat(pp, 1);
}
/* Initialize the buffer queues */
for (dp = bufqueues; dp < &bufqueues[BQUEUES]; dp++)
TAILQ_INIT(dp);
/*
* Estimate hash table size based on the amount of memory we
* intend to use for the buffer cache. The average buffer
* size is dependent on our clients (i.e. filesystems).
*
* For now, use an empirical 3K per buffer.
*/
nbuf = (bufmem_hiwater / 1024) / 3;
bufhashtbl = hashinit(nbuf, HASH_LIST, M_CACHE, M_WAITOK, &bufhash);
}
static int
buf_lotsfree(void)
{
return (bufmem < bufmem_lowater ||
(bufmem < bufmem_hiwater && uvmexp.free > 2*uvmexp.freetarg));
}
/*
* Return estimate of # of buffers we think need to be
* released to help resolve low memory conditions.
*/
static int
buf_canrelease(void)
{
int n;
if (bufmem < bufmem_lowater)
return 0;
n = uvmexp.freetarg - uvmexp.free;
if (n < 0)
n = 0;
return 2*n;
}
/*
* Buffer memory allocation helper functions
*/
static __inline u_long
buf_mempoolidx(u_long size)
{
u_int n = 0;
size -= 1;
size >>= MEMPOOL_INDEX_OFFSET;
while (size) {
size >>= 1;
n += 1;
}
if (n >= NMEMPOOLS)
panic("buf mem pool index %d", n);
return n;
}
static __inline u_long
buf_roundsize(u_long size)
{
/* Round up to nearest power of 2 */
return (1 << (buf_mempoolidx(size) + MEMPOOL_INDEX_OFFSET));
}
static __inline caddr_t
buf_malloc(size_t size)
{
u_int n = buf_mempoolidx(size);
caddr_t addr;
int s;
while (1) {
addr = pool_get(&bmempools[n], PR_NOWAIT);
if (addr != NULL)
break;
/* No memory, see if we can free some. If so, try again */
if (buf_drain(1) > 0)
continue;
/* Wait for buffers to arrive on the LRU queue */
s = splbio();
simple_lock(&bqueue_slock);
needbuffer = 1;
ltsleep(&needbuffer, PNORELOCK | (PRIBIO+1),
"buf_malloc", 0, &bqueue_slock);
splx(s);
}
return addr;
}
static void
buf_mrelease(caddr_t addr, size_t size)
{
pool_put(&bmempools[buf_mempoolidx(size)], addr);
}
static __inline struct buf *
bio_doread(struct vnode *vp, daddr_t blkno, int size, struct ucred *cred,
int async)
{
struct buf *bp;
struct lwp *l = (curlwp != NULL ? curlwp : &lwp0); /* XXX */
struct proc *p = l->l_proc;
bp = getblk(vp, blkno, size, 0, 0);
#ifdef DIAGNOSTIC
if (bp == NULL) {
panic("bio_doread: no such buf");
}
#endif
/*
* If buffer does not have data valid, start a read.
* Note that if buffer is B_INVAL, getblk() won't return it.
* Therefore, it's valid if its I/O has completed or been delayed.
*/
if (!ISSET(bp->b_flags, (B_DONE | B_DELWRI))) {
/* Start I/O for the buffer. */
SET(bp->b_flags, B_READ | async);
VOP_STRATEGY(bp);
/* Pay for the read. */
p->p_stats->p_ru.ru_inblock++;
} else if (async) {
brelse(bp);
}
return (bp);
}
/*
* Read a disk block.
* This algorithm described in Bach (p.54).
*/
int
bread(struct vnode *vp, daddr_t blkno, int size, struct ucred *cred,
struct buf **bpp)
{
struct buf *bp;
/* Get buffer for block. */
bp = *bpp = bio_doread(vp, blkno, size, cred, 0);
/* Wait for the read to complete, and return result. */
return (biowait(bp));
}
/*
* Read-ahead multiple disk blocks. The first is sync, the rest async.
* Trivial modification to the breada algorithm presented in Bach (p.55).
*/
int
breadn(struct vnode *vp, daddr_t blkno, int size, daddr_t *rablks,
int *rasizes, int nrablks, struct ucred *cred, struct buf **bpp)
{
struct buf *bp;
int i;
bp = *bpp = bio_doread(vp, blkno, size, cred, 0);
/*
* For each of the read-ahead blocks, start a read, if necessary.
*/
for (i = 0; i < nrablks; i++) {
/* If it's in the cache, just go on to next one. */
if (incore(vp, rablks[i]))
continue;
/* Get a buffer for the read-ahead block */
(void) bio_doread(vp, rablks[i], rasizes[i], cred, B_ASYNC);
}
/* Otherwise, we had to start a read for it; wait until it's valid. */
return (biowait(bp));
}
/*
* Read with single-block read-ahead. Defined in Bach (p.55), but
* implemented as a call to breadn().
* XXX for compatibility with old file systems.
*/
int
breada(struct vnode *vp, daddr_t blkno, int size, daddr_t rablkno,
int rabsize, struct ucred *cred, struct buf **bpp)
{
return (breadn(vp, blkno, size, &rablkno, &rabsize, 1, cred, bpp));
}
/*
* Block write. Described in Bach (p.56)
*/
int
bwrite(struct buf *bp)
{
int rv, sync, wasdelayed, s;
struct lwp *l = (curlwp != NULL ? curlwp : &lwp0); /* XXX */
struct proc *p = l->l_proc;
struct vnode *vp;
struct mount *mp;
KASSERT(ISSET(bp->b_flags, B_BUSY));
vp = bp->b_vp;
if (vp != NULL) {
if (vp->v_type == VBLK)
mp = vp->v_specmountpoint;
else
mp = vp->v_mount;
} else {
mp = NULL;
}
/*
* Remember buffer type, to switch on it later. If the write was
* synchronous, but the file system was mounted with MNT_ASYNC,
* convert it to a delayed write.
* XXX note that this relies on delayed tape writes being converted
* to async, not sync writes (which is safe, but ugly).
*/
sync = !ISSET(bp->b_flags, B_ASYNC);
if (sync && mp != NULL && ISSET(mp->mnt_flag, MNT_ASYNC)) {
bdwrite(bp);
return (0);
}
/*
* Collect statistics on synchronous and asynchronous writes.
* Writes to block devices are charged to their associated
* filesystem (if any).
*/
if (mp != NULL) {
if (sync)
mp->mnt_stat.f_syncwrites++;
else
mp->mnt_stat.f_asyncwrites++;
}
s = splbio();
simple_lock(&bp->b_interlock);
wasdelayed = ISSET(bp->b_flags, B_DELWRI);
CLR(bp->b_flags, (B_READ | B_DONE | B_ERROR | B_DELWRI));
/*
* Pay for the I/O operation and make sure the buf is on the correct
* vnode queue.
*/
if (wasdelayed)
reassignbuf(bp, bp->b_vp);
else
p->p_stats->p_ru.ru_oublock++;
/* Initiate disk write. Make sure the appropriate party is charged. */
V_INCR_NUMOUTPUT(bp->b_vp);
simple_unlock(&bp->b_interlock);
splx(s);
VOP_STRATEGY(bp);
if (sync) {
/* If I/O was synchronous, wait for it to complete. */
rv = biowait(bp);
/* Release the buffer. */
brelse(bp);
return (rv);
} else {
return (0);
}
}
int
vn_bwrite(void *v)
{
struct vop_bwrite_args *ap = v;
return (bwrite(ap->a_bp));
}
/*
* Delayed write.
*
* The buffer is marked dirty, but is not queued for I/O.
* This routine should be used when the buffer is expected
* to be modified again soon, typically a small write that
* partially fills a buffer.
*
* NB: magnetic tapes cannot be delayed; they must be
* written in the order that the writes are requested.
*
* Described in Leffler, et al. (pp. 208-213).
*/
void
bdwrite(struct buf *bp)
{
struct lwp *l = (curlwp != NULL ? curlwp : &lwp0); /* XXX */
struct proc *p = l->l_proc;
const struct bdevsw *bdev;
int s;
/* If this is a tape block, write the block now. */
bdev = bdevsw_lookup(bp->b_dev);
if (bdev != NULL && bdev->d_type == D_TAPE) {
bawrite(bp);
return;
}
/*
* If the block hasn't been seen before:
* (1) Mark it as having been seen,
* (2) Charge for the write,
* (3) Make sure it's on its vnode's correct block list.
*/
s = splbio();
simple_lock(&bp->b_interlock);
KASSERT(ISSET(bp->b_flags, B_BUSY));
if (!ISSET(bp->b_flags, B_DELWRI)) {
SET(bp->b_flags, B_DELWRI);
p->p_stats->p_ru.ru_oublock++;
reassignbuf(bp, bp->b_vp);
}
/* Otherwise, the "write" is done, so mark and release the buffer. */
CLR(bp->b_flags, B_DONE);
simple_unlock(&bp->b_interlock);
splx(s);
brelse(bp);
}
/*
* Asynchronous block write; just an asynchronous bwrite().
*/
void
bawrite(struct buf *bp)
{
int s;
s = splbio();
simple_lock(&bp->b_interlock);
KASSERT(ISSET(bp->b_flags, B_BUSY));
SET(bp->b_flags, B_ASYNC);
simple_unlock(&bp->b_interlock);
splx(s);
VOP_BWRITE(bp);
}
/*
* Same as first half of bdwrite, mark buffer dirty, but do not release it.
* Call at splbio() and with the buffer interlock locked.
* Note: called only from biodone() through ffs softdep's bioops.io_complete()
*/
void
bdirty(struct buf *bp)
{
struct lwp *l = (curlwp != NULL ? curlwp : &lwp0); /* XXX */
struct proc *p = l->l_proc;
LOCK_ASSERT(simple_lock_held(&bp->b_interlock));
KASSERT(ISSET(bp->b_flags, B_BUSY));
CLR(bp->b_flags, B_AGE);
if (!ISSET(bp->b_flags, B_DELWRI)) {
SET(bp->b_flags, B_DELWRI);
p->p_stats->p_ru.ru_oublock++;
reassignbuf(bp, bp->b_vp);
}
}
/*
* Release a buffer on to the free lists.
* Described in Bach (p. 46).
*/
void
brelse(struct buf *bp)
{
struct bqueues *bufq;
int s;
/* Block disk interrupts. */
s = splbio();
simple_lock(&bqueue_slock);
simple_lock(&bp->b_interlock);
KASSERT(ISSET(bp->b_flags, B_BUSY));
KASSERT(!ISSET(bp->b_flags, B_CALL));
/* Wake up any processes waiting for any buffer to become free. */
if (needbuffer) {
needbuffer = 0;
wakeup(&needbuffer);
}
/* Wake up any proceeses waiting for _this_ buffer to become free. */
if (ISSET(bp->b_flags, B_WANTED)) {
CLR(bp->b_flags, B_WANTED|B_AGE);
wakeup(bp);
}
/*
* Determine which queue the buffer should be on, then put it there.
*/
/* If it's locked, don't report an error; try again later. */
if (ISSET(bp->b_flags, (B_LOCKED|B_ERROR)) == (B_LOCKED|B_ERROR))
CLR(bp->b_flags, B_ERROR);
/* If it's not cacheable, or an error, mark it invalid. */
if (ISSET(bp->b_flags, (B_NOCACHE|B_ERROR)))
SET(bp->b_flags, B_INVAL);
if (ISSET(bp->b_flags, B_VFLUSH)) {
/*
* This is a delayed write buffer that was just flushed to
* disk. It is still on the LRU queue. If it's become
* invalid, then we need to move it to a different queue;
* otherwise leave it in its current position.
*/
CLR(bp->b_flags, B_VFLUSH);
if (!ISSET(bp->b_flags, B_ERROR|B_INVAL|B_LOCKED|B_AGE)) {
KDASSERT(!debug_verify_freelist || checkfreelist(bp, &bufqueues[BQ_LRU]));
goto already_queued;
} else {
bremfree(bp);
}
}
KDASSERT(!debug_verify_freelist || !checkfreelist(bp, &bufqueues[BQ_AGE]));
KDASSERT(!debug_verify_freelist || !checkfreelist(bp, &bufqueues[BQ_LRU]));
KDASSERT(!debug_verify_freelist || !checkfreelist(bp, &bufqueues[BQ_LOCKED]));
if ((bp->b_bufsize <= 0) || ISSET(bp->b_flags, B_INVAL)) {
/*
* If it's invalid or empty, dissociate it from its vnode
* and put on the head of the appropriate queue.
*/
if (LIST_FIRST(&bp->b_dep) != NULL && bioops.io_deallocate)
(*bioops.io_deallocate)(bp);
CLR(bp->b_flags, B_DONE|B_DELWRI);
if (bp->b_vp) {
reassignbuf(bp, bp->b_vp);
brelvp(bp);
}
if (bp->b_bufsize <= 0)
/* no data */
goto already_queued;
else
/* invalid data */
bufq = &bufqueues[BQ_AGE];
binsheadfree(bp, bufq);
} else {
/*
* It has valid data. Put it on the end of the appropriate
* queue, so that it'll stick around for as long as possible.
* If buf is AGE, but has dependencies, must put it on last
* bufqueue to be scanned, ie LRU. This protects against the
* livelock where BQ_AGE only has buffers with dependencies,
* and we thus never get to the dependent buffers in BQ_LRU.
*/
if (ISSET(bp->b_flags, B_LOCKED))
/* locked in core */
bufq = &bufqueues[BQ_LOCKED];
else if (!ISSET(bp->b_flags, B_AGE))
/* valid data */
bufq = &bufqueues[BQ_LRU];
else {
/* stale but valid data */
int has_deps;
if (LIST_FIRST(&bp->b_dep) != NULL &&
bioops.io_countdeps)
has_deps = (*bioops.io_countdeps)(bp, 0);
else
has_deps = 0;
bufq = has_deps ? &bufqueues[BQ_LRU] :
&bufqueues[BQ_AGE];
}
binstailfree(bp, bufq);
}
already_queued:
/* Unlock the buffer. */
CLR(bp->b_flags, B_AGE|B_ASYNC|B_BUSY|B_NOCACHE);
SET(bp->b_flags, B_CACHE);
/* Allow disk interrupts. */
simple_unlock(&bp->b_interlock);
simple_unlock(&bqueue_slock);
if (bp->b_bufsize <= 0) {
#ifdef DEBUG
memset((char *)bp, 0, sizeof(*bp));
#endif
pool_put(&bufpool, bp);
}
splx(s);
}
/*
* Determine if a block is in the cache.
* Just look on what would be its hash chain. If it's there, return
* a pointer to it, unless it's marked invalid. If it's marked invalid,
* we normally don't return the buffer, unless the caller explicitly
* wants us to.
*/
struct buf *
incore(struct vnode *vp, daddr_t blkno)
{
struct buf *bp;
/* Search hash chain */
LIST_FOREACH(bp, BUFHASH(vp, blkno), b_hash) {
if (bp->b_lblkno == blkno && bp->b_vp == vp &&
!ISSET(bp->b_flags, B_INVAL))
return (bp);
}
return (NULL);
}
/*
* Get a block of requested size that is associated with
* a given vnode and block offset. If it is found in the
* block cache, mark it as having been found, make it busy
* and return it. Otherwise, return an empty block of the
* correct size. It is up to the caller to insure that the
* cached blocks be of the correct size.
*/
struct buf *
getblk(struct vnode *vp, daddr_t blkno, int size, int slpflag, int slptimeo)
{
struct buf *bp;
int s, err;
int preserve;
start:
s = splbio();
simple_lock(&bqueue_slock);
bp = incore(vp, blkno);
if (bp != NULL) {
simple_lock(&bp->b_interlock);
if (ISSET(bp->b_flags, B_BUSY)) {
simple_unlock(&bqueue_slock);
if (curproc == uvm.pagedaemon_proc) {
simple_unlock(&bp->b_interlock);
splx(s);
return NULL;
}
SET(bp->b_flags, B_WANTED);
err = ltsleep(bp, slpflag | (PRIBIO + 1) | PNORELOCK,
"getblk", slptimeo, &bp->b_interlock);
splx(s);
if (err)
return (NULL);
goto start;
}
#ifdef DIAGNOSTIC
if (ISSET(bp->b_flags, B_DONE|B_DELWRI) &&
bp->b_bcount < size && vp->v_type != VBLK)
panic("getblk: block size invariant failed");
#endif
SET(bp->b_flags, B_BUSY);
bremfree(bp);
preserve = 1;
} else {
if ((bp = getnewbuf(slpflag, slptimeo, 0)) == NULL) {
simple_unlock(&bqueue_slock);
splx(s);
goto start;
}
binshash(bp, BUFHASH(vp, blkno));
bp->b_blkno = bp->b_lblkno = bp->b_rawblkno = blkno;
bgetvp(vp, bp);
preserve = 0;
}
simple_unlock(&bp->b_interlock);
simple_unlock(&bqueue_slock);
splx(s);
/*
* LFS can't track total size of B_LOCKED buffer (locked_queue_bytes)
* if we re-size buffers here.
*/
if (ISSET(bp->b_flags, B_LOCKED)) {
KASSERT(bp->b_bufsize >= size);
} else {
allocbuf(bp, size, preserve);
}
return (bp);
}
/*
* Get an empty, disassociated buffer of given size.
*/
struct buf *
geteblk(int size)
{
struct buf *bp;
int s;
s = splbio();
simple_lock(&bqueue_slock);
while ((bp = getnewbuf(0, 0, 0)) == 0)
;
SET(bp->b_flags, B_INVAL);
binshash(bp, &invalhash);
simple_unlock(&bqueue_slock);
simple_unlock(&bp->b_interlock);
splx(s);
allocbuf(bp, size, 0);
return (bp);
}
/*
* Expand or contract the actual memory allocated to a buffer.
*
* If the buffer shrinks, data is lost, so it's up to the
* caller to have written it out *first*; this routine will not
* start a write. If the buffer grows, it's the callers
* responsibility to fill out the buffer's additional contents.
*/
void
allocbuf(struct buf *bp, int size, int preserve)
{
vsize_t oldsize, desired_size;
caddr_t addr;
int s, delta;
desired_size = buf_roundsize(size);
if (desired_size > MAXBSIZE)
printf("allocbuf: buffer larger than MAXBSIZE requested");
bp->b_bcount = size;
oldsize = bp->b_bufsize;
if (oldsize == desired_size)
return;
/*
* If we want a buffer of a different size, re-allocate the
* buffer's memory; copy old content only if needed.
*/
addr = buf_malloc(desired_size);
if (preserve)
memcpy(addr, bp->b_data, MIN(oldsize,desired_size));
if (bp->b_data != NULL)
buf_mrelease(bp->b_data, oldsize);
bp->b_data = addr;
bp->b_bufsize = desired_size;
/*
* Update overall buffer memory counter (protected by bqueue_slock)
*/
delta = (long)desired_size - (long)oldsize;
s = splbio();
simple_lock(&bqueue_slock);
if ((bufmem += delta) > bufmem_hiwater) {
/*
* Need to trim overall memory usage.
*/
while (buf_canrelease()) {
if (buf_trim() == 0)
break;
}
}
simple_unlock(&bqueue_slock);
splx(s);
}
/*
* Find a buffer which is available for use.
* Select something from a free list.
* Preference is to AGE list, then LRU list.
*
* Called at splbio and with buffer queues locked.
* Return buffer locked.
*/
struct buf *
getnewbuf(int slpflag, int slptimeo, int from_bufq)
{
struct buf *bp;
start:
LOCK_ASSERT(simple_lock_held(&bqueue_slock));
/*
* Get a new buffer from the pool; but use NOWAIT because
* we have the buffer queues locked.
*/
if (buf_lotsfree() && !from_bufq &&
(bp = pool_get(&bufpool, PR_NOWAIT)) != NULL) {
memset((char *)bp, 0, sizeof(*bp));
BUF_INIT(bp);
bp->b_dev = NODEV;
bp->b_vnbufs.le_next = NOLIST;
bp->b_flags = B_BUSY;
return (bp);
}
if ((bp = TAILQ_FIRST(&bufqueues[BQ_AGE])) != NULL ||
(bp = TAILQ_FIRST(&bufqueues[BQ_LRU])) != NULL) {
simple_lock(&bp->b_interlock);
bremfree(bp);
} else {
/* wait for a free buffer of any kind */
needbuffer = 1;
ltsleep(&needbuffer, slpflag|(PRIBIO+1),
"getnewbuf", slptimeo, &bqueue_slock);
return (NULL);
}
#ifdef DIAGNOSTIC
if (bp->b_bufsize <= 0)
panic("buffer %p: on queue but empty", bp);
#endif
if (ISSET(bp->b_flags, B_VFLUSH)) {
/*
* This is a delayed write buffer being flushed to disk. Make
* sure it gets aged out of the queue when it's finished, and
* leave it off the LRU queue.
*/
CLR(bp->b_flags, B_VFLUSH);
SET(bp->b_flags, B_AGE);
simple_unlock(&bp->b_interlock);
goto start;
}
/* Buffer is no longer on free lists. */
SET(bp->b_flags, B_BUSY);
/*
* If buffer was a delayed write, start it and return NULL
* (since we might sleep while starting the write).
*/
if (ISSET(bp->b_flags, B_DELWRI)) {
/*
* This buffer has gone through the LRU, so make sure it gets
* reused ASAP.
*/
SET(bp->b_flags, B_AGE);
simple_unlock(&bp->b_interlock);
simple_unlock(&bqueue_slock);
bawrite(bp);
simple_lock(&bqueue_slock);
return (NULL);
}
/* disassociate us from our vnode, if we had one... */
if (bp->b_vp)
brelvp(bp);
if (LIST_FIRST(&bp->b_dep) != NULL && bioops.io_deallocate)
(*bioops.io_deallocate)(bp);
/* clear out various other fields */
bp->b_flags = B_BUSY;
bp->b_dev = NODEV;
bp->b_blkno = bp->b_lblkno = bp->b_rawblkno = 0;
bp->b_iodone = 0;
bp->b_error = 0;
bp->b_resid = 0;
bp->b_bcount = 0;
bremhash(bp);
return (bp);
}
/*
* Attempt to free an aged buffer off the queues.
* Called at splbio and with queue lock held.
* Returns the amount of buffer memory freed.
*/
int
buf_trim(void)
{
struct buf *bp;
long size = 0;
int wanted;
/* Instruct getnewbuf() to get buffers off the queues */
if ((bp = getnewbuf(PCATCH, 1, 1)) == NULL)
return 0;
wanted = ISSET(bp->b_flags, B_WANTED);
simple_unlock(&bp->b_interlock);
if (wanted) {
printf("buftrim: got WANTED buffer\n");
SET(bp->b_flags, B_INVAL);
binshash(bp, &invalhash);
simple_unlock(&bqueue_slock);
goto out;
}
size = bp->b_bufsize;
bufmem -= size;
simple_unlock(&bqueue_slock);
if (size > 0) {
buf_mrelease(bp->b_data, size);
bp->b_bcount = bp->b_bufsize = 0;
}
out:
/* brelse() will return the buffer to the global buffer pool */
brelse(bp);
simple_lock(&bqueue_slock);
return size;
}
int
buf_drain(int n)
{
int s, size = 0;
/* If not asked for a specific amount, make our own estimate */
if (n == 0)
n = buf_canrelease();
s = splbio();
simple_lock(&bqueue_slock);
while (n-- > 0 && bufmem > bufmem_lowater)
size += buf_trim();
simple_unlock(&bqueue_slock);
splx(s);
return size;
}
/*
* Wait for operations on the buffer to complete.
* When they do, extract and return the I/O's error value.
*/
int
biowait(struct buf *bp)
{
int s, error;
s = splbio();
simple_lock(&bp->b_interlock);
while (!ISSET(bp->b_flags, B_DONE | B_DELWRI))
ltsleep(bp, PRIBIO + 1, "biowait", 0, &bp->b_interlock);
/* check for interruption of I/O (e.g. via NFS), then errors. */
if (ISSET(bp->b_flags, B_EINTR)) {
CLR(bp->b_flags, B_EINTR);
error = EINTR;
} else if (ISSET(bp->b_flags, B_ERROR))
error = bp->b_error ? bp->b_error : EIO;
else
error = 0;
simple_unlock(&bp->b_interlock);
splx(s);
return (error);
}
/*
* Mark I/O complete on a buffer.
*
* If a callback has been requested, e.g. the pageout
* daemon, do so. Otherwise, awaken waiting processes.
*
* [ Leffler, et al., says on p.247:
* "This routine wakes up the blocked process, frees the buffer
* for an asynchronous write, or, for a request by the pagedaemon
* process, invokes a procedure specified in the buffer structure" ]
*
* In real life, the pagedaemon (or other system processes) wants
* to do async stuff to, and doesn't want the buffer brelse()'d.
* (for swap pager, that puts swap buffers on the free lists (!!!),
* for the vn device, that puts malloc'd buffers on the free lists!)
*/
void
biodone(struct buf *bp)
{
int s = splbio();
simple_lock(&bp->b_interlock);
if (ISSET(bp->b_flags, B_DONE))
panic("biodone already");
SET(bp->b_flags, B_DONE); /* note that it's done */
if (LIST_FIRST(&bp->b_dep) != NULL && bioops.io_complete)
(*bioops.io_complete)(bp);
if (!ISSET(bp->b_flags, B_READ)) /* wake up reader */
vwakeup(bp);
/*
* If necessary, call out. Unlock the buffer before calling
* iodone() as the buffer isn't valid any more when it return.
*/
if (ISSET(bp->b_flags, B_CALL)) {
CLR(bp->b_flags, B_CALL); /* but note callout done */
simple_unlock(&bp->b_interlock);
(*bp->b_iodone)(bp);
} else {
if (ISSET(bp->b_flags, B_ASYNC)) { /* if async, release */
simple_unlock(&bp->b_interlock);
brelse(bp);
} else { /* or just wakeup the buffer */
CLR(bp->b_flags, B_WANTED);
wakeup(bp);
simple_unlock(&bp->b_interlock);
}
}
splx(s);
}
/*
* Return a count of buffers on the "locked" queue.
*/
int
count_lock_queue(void)
{
struct buf *bp;
int n = 0;
simple_lock(&bqueue_slock);
TAILQ_FOREACH(bp, &bufqueues[BQ_LOCKED], b_freelist)
n++;
simple_unlock(&bqueue_slock);
return (n);
}
/*
* Wait for all buffers to complete I/O
* Return the number of "stuck" buffers.
*/
int
buf_syncwait(void)
{
struct buf *bp;
int iter, nbusy, nbusy_prev = 0, dcount, s, ihash;
dcount = 10000;
for (iter = 0; iter < 20;) {
s = splbio();
simple_lock(&bqueue_slock);
nbusy = 0;
for (ihash = 0; ihash < bufhash+1; ihash++) {
LIST_FOREACH(bp, &bufhashtbl[ihash], b_hash) {
if ((bp->b_flags & (B_BUSY|B_INVAL|B_READ)) == B_BUSY)
nbusy++;
/*
* With soft updates, some buffers that are
* written will be remarked as dirty until other
* buffers are written.
*/
if (bp->b_vp && bp->b_vp->v_mount
&& (bp->b_vp->v_mount->mnt_flag & MNT_SOFTDEP)
&& (bp->b_flags & B_DELWRI)) {
simple_lock(&bp->b_interlock);
bremfree(bp);
bp->b_flags |= B_BUSY;
nbusy++;
simple_unlock(&bp->b_interlock);
simple_unlock(&bqueue_slock);
bawrite(bp);
if (dcount-- <= 0) {
printf("softdep ");
goto fail;
}
simple_lock(&bqueue_slock);
}
}
}
simple_unlock(&bqueue_slock);
splx(s);
if (nbusy == 0)
break;
if (nbusy_prev == 0)
nbusy_prev = nbusy;
printf("%d ", nbusy);
tsleep(&nbusy, PRIBIO, "bflush",
(iter == 0) ? 1 : hz / 25 * iter);
if (nbusy >= nbusy_prev) /* we didn't flush anything */
iter++;
else
nbusy_prev = nbusy;
}
if (nbusy) {
fail:;
#if defined(DEBUG) || defined(DEBUG_HALT_BUSY)
printf("giving up\nPrinting vnodes for busy buffers\n");
for (ihash = 0; ihash < bufhash+1; ihash++) {
LIST_FOREACH(bp, &bufhashtbl[ihash], b_hash) {
if ((bp->b_flags & (B_BUSY|B_INVAL|B_READ)) == B_BUSY)
vprint(NULL, bp->b_vp);
}
}
#endif
}
return nbusy;
}
#define KERN_BUFSLOP 20
static int
sysctl_dobuf(SYSCTLFN_ARGS)
{
struct buf *bp;
char *dp;
u_int i, elem_size;
size_t len, buflen, needed;
int error, s;
dp = oldp;
len = buflen = oldp != NULL ? *oldlenp : 0;
error = 0;
needed = 0;
elem_size = sizeof(struct buf);
s = splbio();
simple_lock(&bqueue_slock);
for (i = 0; i < BQUEUES; i++) {
TAILQ_FOREACH(bp, &bufqueues[i], b_freelist) {
if (len >= sizeof(elem_size)) {
error = copyout(bp, dp, elem_size);
if (error)
goto cleanup;
dp += elem_size;
len -= elem_size;
}
needed += elem_size;
}
}
cleanup:
simple_unlock(&bqueue_slock);
splx(s);
if (oldp != NULL) {
*oldlenp = (char *)dp - (char *)oldp;
if (needed > *oldlenp)
error = ENOMEM;
} else {
needed += KERN_BUFSLOP;
*oldlenp = needed;
}
return (error);
}
static int sysctlnum_bufcache, sysctlnum_bufmemhiwater, sysctlnum_bufmemlowater;
static int
sysctl_bufvm_update(SYSCTLFN_ARGS)
{
int t, error;
struct sysctlnode node;
node = *rnode;
node.sysctl_data = &t;
t = *(int*)rnode->sysctl_data;
error = sysctl_lookup(SYSCTLFN_CALL(&node));
if (error || newp == NULL)
return (error);
if (rnode->sysctl_num == sysctlnum_bufcache) {
if (t < 0 || t > 100)
return (EINVAL);
bufcache = t;
bufmem_hiwater = buf_memcalc();
bufmem_lowater = (bufmem_hiwater >> 4);
} else if (rnode->sysctl_num == sysctlnum_bufmemlowater) {
bufmem_lowater = t;
} else if (rnode->sysctl_num == sysctlnum_bufmemhiwater) {
bufmem_hiwater = t;
} else
return (EINVAL);
/* Drain until below new high water mark */
while ((t = bufmem - bufmem_hiwater) >= 0) {
if (buf_drain(t / (2*1024)) <= 0)
break;
}
return 0;
}
SYSCTL_SETUP(sysctl_kern_buf_setup, "sysctl kern.buf subtree setup")
{
struct sysctlnode *rnode;
sysctl_createv(SYSCTL_PERMANENT,
CTLTYPE_NODE, "buf", NULL,
sysctl_dobuf, 0, NULL, 0,
CTL_KERN, KERN_BUF, CTL_EOL);
rnode = NULL;
if (sysctl_createv(SYSCTL_PERMANENT|SYSCTL_READWRITE,
CTLTYPE_INT, "bufcache", &rnode,
sysctl_bufvm_update, 0, &bufcache, 0,
CTL_VM, CTL_CREATE, CTL_EOL) == 0)
sysctlnum_bufcache = rnode->sysctl_num;
rnode = NULL;
if (sysctl_createv(SYSCTL_PERMANENT|SYSCTL_READWRITE,
CTLTYPE_INT, "bufmem_lowater", &rnode,
sysctl_bufvm_update, 0, &bufmem_lowater, 0,
CTL_VM, CTL_CREATE, CTL_EOL) == 0)
sysctlnum_bufmemlowater = rnode->sysctl_num;
rnode = NULL;
if (sysctl_createv(SYSCTL_PERMANENT|SYSCTL_READWRITE,
CTLTYPE_INT, "bufmem_hiwater", &rnode,
sysctl_bufvm_update, 0, &bufmem_hiwater, 0,
CTL_VM, CTL_CREATE, CTL_EOL) == 0)
sysctlnum_bufmemhiwater = rnode->sysctl_num;
}
#ifdef DEBUG
/*
* Print out statistics on the current allocation of the buffer pool.
* Can be enabled to print out on every ``sync'' by setting "syncprt"
* in vfs_syscalls.c using sysctl.
*/
void
vfs_bufstats(void)
{
int s, i, j, count;
struct buf *bp;
struct bqueues *dp;
int counts[(MAXBSIZE / PAGE_SIZE) + 1];
static char *bname[BQUEUES] = { "LOCKED", "LRU", "AGE" };
for (dp = bufqueues, i = 0; dp < &bufqueues[BQUEUES]; dp++, i++) {
count = 0;
for (j = 0; j <= MAXBSIZE/PAGE_SIZE; j++)
counts[j] = 0;
s = splbio();
TAILQ_FOREACH(bp, dp, b_freelist) {
counts[bp->b_bufsize/PAGE_SIZE]++;
count++;
}
splx(s);
printf("%s: total-%d", bname[i], count);
for (j = 0; j <= MAXBSIZE/PAGE_SIZE; j++)
if (counts[j] != 0)
printf(", %d-%d", j * PAGE_SIZE, counts[j]);
printf("\n");
}
}
#endif /* DEBUG */
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