NetBSD/sys/kern/vfs__bio.c

590 lines
15 KiB
C

/*
* Copyright (c) 1989, 1990, 1991, 1992 William F. Jolitz, TeleMuse
* All rights reserved.
*
* 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 software is a component of "386BSD" developed by
* William F. Jolitz, TeleMuse.
* 4. Neither the name of the developer nor the name "386BSD"
* may be used to endorse or promote products derived from this software
* without specific prior written permission.
*
* THIS SOFTWARE IS A COMPONENT OF 386BSD DEVELOPED BY WILLIAM F. JOLITZ
* AND IS INTENDED FOR RESEARCH AND EDUCATIONAL PURPOSES ONLY. THIS
* SOFTWARE SHOULD NOT BE CONSIDERED TO BE A COMMERCIAL PRODUCT.
* THE DEVELOPER URGES THAT USERS WHO REQUIRE A COMMERCIAL PRODUCT
* NOT MAKE USE THIS WORK.
*
* FOR USERS WHO WISH TO UNDERSTAND THE 386BSD SYSTEM DEVELOPED
* BY WILLIAM F. JOLITZ, WE RECOMMEND THE USER STUDY WRITTEN
* REFERENCES SUCH AS THE "PORTING UNIX TO THE 386" SERIES
* (BEGINNING JANUARY 1991 "DR. DOBBS JOURNAL", USA AND BEGINNING
* JUNE 1991 "UNIX MAGAZIN", GERMANY) BY WILLIAM F. JOLITZ AND
* LYNNE GREER JOLITZ, AS WELL AS OTHER BOOKS ON UNIX AND THE
* ON-LINE 386BSD USER MANUAL BEFORE USE. A BOOK DISCUSSING THE INTERNALS
* OF 386BSD ENTITLED "386BSD FROM THE INSIDE OUT" WILL BE AVAILABLE LATE 1992.
*
* THIS SOFTWARE IS PROVIDED BY THE DEVELOPER ``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 DEVELOPER 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.
*
* $Id: vfs__bio.c,v 1.3 1993/05/18 15:38:35 cgd Exp $
*/
#include "param.h"
#include "proc.h"
#include "vnode.h"
#include "buf.h"
#include "specdev.h"
#include "mount.h"
#include "malloc.h"
#include "vm/vm.h"
#include "resourcevar.h"
struct buf *getnewbuf(int);
extern vm_map_t buffer_map;
/*
* Initialize buffer headers and related structures.
*/
void bufinit()
{
struct bufhd *bh;
struct buf *bp;
/* first, make a null hash table */
for(bh = bufhash; bh < bufhash + BUFHSZ; bh++) {
bh->b_flags = 0;
bh->b_forw = (struct buf *)bh;
bh->b_back = (struct buf *)bh;
}
/* next, make a null set of free lists */
for(bp = bfreelist; bp < bfreelist + BQUEUES; bp++) {
bp->b_flags = 0;
bp->av_forw = bp;
bp->av_back = bp;
bp->b_forw = bp;
bp->b_back = bp;
}
/* finally, initialize each buffer header and stick on empty q */
for(bp = buf; bp < buf + nbuf ; bp++) {
bp->b_flags = B_HEAD | B_INVAL; /* we're just an empty header */
bp->b_dev = NODEV;
bp->b_vp = 0;
binstailfree(bp, bfreelist + BQ_EMPTY);
binshash(bp, bfreelist + BQ_EMPTY);
}
}
/*
* Find the block in the buffer pool.
* If the buffer is not present, allocate a new buffer and load
* its contents according to the filesystem fill routine.
*/
int
bread(struct vnode *vp, daddr_t blkno, int size, struct ucred *cred,
struct buf **bpp)
{
struct buf *bp;
int rv = 0;
bp = getblk (vp, blkno, size);
/* if not found in cache, do some I/O */
if ((bp->b_flags & B_CACHE) == 0 || (bp->b_flags & B_INVAL) != 0) {
bp->b_flags |= B_READ;
bp->b_flags &= ~(B_DONE|B_ERROR|B_INVAL);
if (cred != NOCRED) crhold(cred); /* 25 Apr 92*/
bp->b_rcred = cred;
VOP_STRATEGY(bp);
rv = biowait (bp);
}
*bpp = bp;
return (rv);
}
/*
* Operates like bread, but also starts I/O on the specified
* read-ahead block. [See page 55 of Bach's Book]
*/
int
breada(struct vnode *vp, daddr_t blkno, int size, daddr_t rablkno, int rabsize,
struct ucred *cred, struct buf **bpp)
{
struct buf *bp, *rabp;
int rv = 0, needwait = 0;
bp = getblk (vp, blkno, size);
/* if not found in cache, do some I/O */
if ((bp->b_flags & B_CACHE) == 0 || (bp->b_flags & B_INVAL) != 0) {
bp->b_flags |= B_READ;
bp->b_flags &= ~(B_DONE|B_ERROR|B_INVAL);
if (cred != NOCRED) crhold(cred); /* 25 Apr 92*/
bp->b_rcred = cred;
VOP_STRATEGY(bp);
needwait++;
}
rabp = getblk (vp, rablkno, rabsize);
/* if not found in cache, do some I/O (overlapped with first) */
if ((rabp->b_flags & B_CACHE) == 0 || (rabp->b_flags & B_INVAL) != 0) {
rabp->b_flags |= B_READ | B_ASYNC;
rabp->b_flags &= ~(B_DONE|B_ERROR|B_INVAL);
if (cred != NOCRED) crhold(cred); /* 25 Apr 92*/
rabp->b_rcred = cred;
VOP_STRATEGY(rabp);
} else
brelse(rabp);
/* wait for original I/O */
if (needwait)
rv = biowait (bp);
*bpp = bp;
return (rv);
}
/*
* Synchronous write.
* Release buffer on completion.
*/
int
bwrite(register struct buf *bp)
{
int rv;
if(bp->b_flags & B_INVAL) {
brelse(bp);
return (0);
} else {
int wasdelayed;
if(!(bp->b_flags & B_BUSY))
panic("bwrite: not busy");
wasdelayed = bp->b_flags & B_DELWRI;
bp->b_flags &= ~(B_READ|B_DONE|B_ERROR|B_ASYNC|B_DELWRI);
if(wasdelayed)
reassignbuf(bp, bp->b_vp);
bp->b_flags |= B_DIRTY;
bp->b_vp->v_numoutput++;
VOP_STRATEGY(bp);
rv = biowait(bp);
brelse(bp);
return (rv);
}
}
/*
* 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.
*/
void
bdwrite(register struct buf *bp)
{
if(!(bp->b_flags & B_BUSY))
panic("bdwrite: not busy");
if(bp->b_flags & B_INVAL) {
brelse(bp);
}
if(bp->b_flags & B_TAPE) {
bwrite(bp);
return;
}
bp->b_flags &= ~(B_READ|B_DONE);
bp->b_flags |= B_DIRTY|B_DELWRI;
reassignbuf(bp, bp->b_vp);
brelse(bp);
return;
}
/*
* Asynchronous write.
* Start I/O on a buffer, but do not wait for it to complete.
* The buffer is released when the I/O completes.
*/
void
bawrite(register struct buf *bp)
{
if(!(bp->b_flags & B_BUSY))
panic("bawrite: not busy");
if(bp->b_flags & B_INVAL)
brelse(bp);
else {
int wasdelayed;
wasdelayed = bp->b_flags & B_DELWRI;
bp->b_flags &= ~(B_READ|B_DONE|B_ERROR|B_DELWRI);
if(wasdelayed)
reassignbuf(bp, bp->b_vp);
bp->b_flags |= B_DIRTY | B_ASYNC;
bp->b_vp->v_numoutput++;
VOP_STRATEGY(bp);
}
}
/*
* Release a buffer.
* Even if the buffer is dirty, no I/O is started.
*/
void
brelse(register struct buf *bp)
{
int x;
/* anyone need a "free" block? */
x=splbio();
if ((bfreelist + BQ_AGE)->b_flags & B_WANTED) {
(bfreelist + BQ_AGE) ->b_flags &= ~B_WANTED;
wakeup(bfreelist);
}
/* anyone need this very block? */
if (bp->b_flags & B_WANTED) {
bp->b_flags &= ~B_WANTED;
wakeup(bp);
}
if (bp->b_flags & (B_INVAL|B_ERROR)) {
bp->b_flags |= B_INVAL;
bp->b_flags &= ~(B_DELWRI|B_CACHE);
if(bp->b_vp)
brelvp(bp);
}
/* enqueue */
/* just an empty buffer head ... */
/*if(bp->b_flags & B_HEAD)
binsheadfree(bp, bfreelist + BQ_EMPTY)*/
/* buffers with junk contents */
/*else*/ if(bp->b_flags & (B_ERROR|B_INVAL|B_NOCACHE))
binsheadfree(bp, bfreelist + BQ_AGE)
/* buffers with stale but valid contents */
else if(bp->b_flags & B_AGE)
binstailfree(bp, bfreelist + BQ_AGE)
/* buffers with valid and quite potentially reuseable contents */
else
binstailfree(bp, bfreelist + BQ_LRU)
/* unlock */
bp->b_flags &= ~B_BUSY;
splx(x);
}
int freebufspace;
int allocbufspace;
/*
* Find a buffer which is available for use.
* If free memory for buffer space and an empty header from the empty list,
* use that. Otherwise, select something from a free list.
* Preference is to AGE list, then LRU list.
*/
static struct buf *
getnewbuf(int sz)
{
struct buf *bp;
int x;
x = splbio();
start:
/* can we constitute a new buffer? */
if (freebufspace > sz
&& bfreelist[BQ_EMPTY].av_forw != (struct buf *)bfreelist+BQ_EMPTY) {
caddr_t addr;
/*#define notyet*/
#ifndef notyet
if ((addr = malloc (sz, M_TEMP, M_WAITOK)) == 0) goto tryfree;
#else /* notyet */
/* get new memory buffer */
if (round_page(sz) == sz)
addr = (caddr_t) kmem_alloc_wired_wait(buffer_map, sz);
else
addr = (caddr_t) malloc (sz, M_TEMP, M_WAITOK);
/*if ((addr = malloc (sz, M_TEMP, M_NOWAIT)) == 0) goto tryfree;*/
bzero(addr, sz);
#endif /* notyet */
freebufspace -= sz;
allocbufspace += sz;
bp = bfreelist[BQ_EMPTY].av_forw;
bp->b_flags = B_BUSY | B_INVAL;
bremfree(bp);
bp->b_un.b_addr = addr;
bp->b_bufsize = sz; /* 20 Aug 92*/
goto fillin;
}
tryfree:
if (bfreelist[BQ_AGE].av_forw != (struct buf *)bfreelist+BQ_AGE) {
bp = bfreelist[BQ_AGE].av_forw;
bremfree(bp);
} else if (bfreelist[BQ_LRU].av_forw != (struct buf *)bfreelist+BQ_LRU) {
bp = bfreelist[BQ_LRU].av_forw;
bremfree(bp);
} else {
/* wait for a free buffer of any kind */
(bfreelist + BQ_AGE)->b_flags |= B_WANTED;
sleep(bfreelist, PRIBIO);
splx(x);
return (0);
}
/* if we are a delayed write, convert to an async write! */
if (bp->b_flags & B_DELWRI) {
bp->b_flags |= B_BUSY;
bawrite (bp);
goto start;
}
if(bp->b_vp)
brelvp(bp);
/* we are not free, nor do we contain interesting data */
if (bp->b_rcred != NOCRED) crfree(bp->b_rcred); /* 25 Apr 92*/
if (bp->b_wcred != NOCRED) crfree(bp->b_wcred);
bp->b_flags = B_BUSY;
fillin:
bremhash(bp);
splx(x);
bp->b_dev = NODEV;
bp->b_vp = NULL;
bp->b_blkno = bp->b_lblkno = 0;
bp->b_iodone = 0;
bp->b_error = 0;
bp->b_wcred = bp->b_rcred = NOCRED;
if (bp->b_bufsize != sz)
allocbuf(bp, sz);
bp->b_bcount = bp->b_bufsize = sz;
bp->b_dirtyoff = bp->b_dirtyend = 0;
return (bp);
}
/*
* Check to see if a block is currently memory resident.
*/
struct buf *
incore(struct vnode *vp, daddr_t blkno)
{
struct buf *bh;
struct buf *bp;
bh = BUFHASH(vp, blkno);
/* Search hash chain */
bp = bh->b_forw;
while (bp != (struct buf *) bh) {
/* hit */
if (bp->b_lblkno == blkno && bp->b_vp == vp
&& (bp->b_flags & B_INVAL) == 0)
return (bp);
bp = bp->b_forw;
}
return(0);
}
/*
* 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(register struct vnode *vp, daddr_t blkno, int size)
{
struct buf *bp, *bh;
int x;
for (;;) {
if (bp = incore(vp, blkno)) {
x = splbio();
if (bp->b_flags & B_BUSY) {
bp->b_flags |= B_WANTED;
sleep (bp, PRIBIO);
splx(x);
continue;
}
bp->b_flags |= B_BUSY | B_CACHE;
bremfree(bp);
if (size > bp->b_bufsize)
panic("now what do we do?");
/* if (bp->b_bufsize != size) allocbuf(bp, size); */
} else {
if((bp = getnewbuf(size)) == 0) continue;
bp->b_blkno = bp->b_lblkno = blkno;
bgetvp(vp, bp);
x = splbio();
bh = BUFHASH(vp, blkno);
binshash(bp, bh);
bp->b_flags = B_BUSY;
}
splx(x);
return (bp);
}
}
/*
* Get an empty, disassociated buffer of given size.
*/
struct buf *
geteblk(int size)
{
struct buf *bp;
int x;
while ((bp = getnewbuf(size)) == 0)
;
x = splbio();
binshash(bp, bfreelist + BQ_AGE);
splx(x);
return (bp);
}
/*
* Exchange a buffer's underlying buffer storage for one of different
* size, taking care to maintain contents appropriately. When buffer
* increases in size, caller is responsible for filling out additional
* contents. When buffer shrinks in size, data is lost, so caller must
* first return it to backing store before shrinking the buffer, as
* no implied I/O will be done.
*
* Expanded buffer is returned as value.
*/
void
allocbuf(register struct buf *bp, int size)
{
caddr_t newcontents;
/* get new memory buffer */
#ifndef notyet
newcontents = (caddr_t) malloc (size, M_TEMP, M_WAITOK);
#else /* notyet */
if (round_page(size) == size)
newcontents = (caddr_t) kmem_alloc_wired_wait(buffer_map, size);
else
newcontents = (caddr_t) malloc (size, M_TEMP, M_WAITOK);
#endif /* notyet */
/* copy the old into the new, up to the maximum that will fit */
bcopy (bp->b_un.b_addr, newcontents, min(bp->b_bufsize, size));
/* return old contents to free heap */
#ifndef notyet
free (bp->b_un.b_addr, M_TEMP);
#else /* notyet */
if (round_page(bp->b_bufsize) == bp->b_bufsize)
kmem_free_wakeup(buffer_map, bp->b_un.b_addr, bp->b_bufsize);
else
free (bp->b_un.b_addr, M_TEMP);
#endif /* notyet */
/* adjust buffer cache's idea of memory allocated to buffer contents */
freebufspace -= size - bp->b_bufsize;
allocbufspace += size - bp->b_bufsize;
/* update buffer header */
bp->b_un.b_addr = newcontents;
bp->b_bcount = bp->b_bufsize = size;
}
/*
* Patiently await operations to complete on this buffer.
* When they do, extract error value and return it.
* Extract and return any errors associated with the I/O.
* If an invalid block, force it off the lookup hash chains.
*/
int
biowait(register struct buf *bp)
{
int x;
x = splbio();
while ((bp->b_flags & B_DONE) == 0)
sleep((caddr_t)bp, PRIBIO);
if((bp->b_flags & B_ERROR) || bp->b_error) {
if ((bp->b_flags & B_INVAL) == 0) {
bp->b_flags |= B_INVAL;
bremhash(bp);
binshash(bp, bfreelist + BQ_AGE);
}
if (!bp->b_error)
bp->b_error = EIO;
else
bp->b_flags |= B_ERROR;
splx(x);
return (bp->b_error);
} else {
splx(x);
return (0);
}
}
/*
* Finish up operations on a buffer, calling an optional
* function (if requested), and releasing the buffer if
* marked asynchronous. Then mark this buffer done so that
* others biowait()'ing for it will notice when they are
* woken up from sleep().
*/
int
biodone(register struct buf *bp)
{
int x;
x = splbio();
if (bp->b_flags & B_CALL) (*bp->b_iodone)(bp);
bp->b_flags &= ~B_CALL;
if ((bp->b_flags & (B_READ|B_DIRTY)) == B_DIRTY) {
bp->b_flags &= ~B_DIRTY;
vwakeup(bp);
}
if (bp->b_flags & B_ASYNC)
brelse(bp);
bp->b_flags &= ~B_ASYNC;
bp->b_flags |= B_DONE;
wakeup(bp);
splx(x);
}