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提交 902b13f5 创建 作者: rtm's avatar rtm
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simplify ide queuing

nits in comments
上级 2bc72bdd
隐藏空白字符变更
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正在显示 包含 79 行增加 和 89 行删除
bio.c
浏览文件 @ 902b13f5
......@@ -4,15 +4,14 @@
// holding cached copies of disk block contents.
// Each buf has two state bits B_BUSY and B_VALID.
// If B_BUSY is set, it means that some code is currently
// editing buf, so other code is not allowed to look at it.
// modifying buf, so other code is not allowed to look at it.
// To wait for a buffer that is B_BUSY, sleep on buf.
// (See bget below.)
//
// If B_VALID is set, it means that the memory contents
// have been initialized by reading them off the disk.
// (Conversely, if B_VALID is not set, the memory contents
// If B_VALID is set, it means that the sector in b->data is
// the same as on the disk. If B_VALID is not set, the contents
// of buf must be initialized, often by calling bread,
// before being used.)
// before being used.
//
// After making changes to a buf's memory, call bwrite to flush
// the changes out to disk, to keep the disk and memory copies
......@@ -79,7 +78,6 @@ bget(uint dev, uint sector)
goto loop;
}
b->flags |= B_BUSY;
// b->flags &= ~B_VALID; // Force reread from disk
release(&buf_table_lock);
return b;
}
......@@ -98,7 +96,8 @@ bget(uint dev, uint sector)
panic("bget: no buffers");
}
// Read buf's contents from disk.
// Return a B_BUSY buf with the contents of the indicated
// disk sector.
struct buf*
bread(uint dev, uint sector)
{
......@@ -108,7 +107,8 @@ bread(uint dev, uint sector)
if(b->flags & B_VALID)
return b;
ide_rw(dev & 0xff, sector, b->data, 1, 1);
b->flags &= ~B_WRITE;
ide_rw(b);
b->flags |= B_VALID;
return b;
......@@ -121,7 +121,8 @@ bwrite(struct buf *b)
{
if((b->flags & B_BUSY) == 0)
panic("bwrite");
ide_rw(b->dev & 0xff, b->sector, b->data, 1, 0);
b->flags |= B_WRITE;
ide_rw(b);
b->flags |= B_VALID;
}
......
buf.h
浏览文件 @ 902b13f5
......@@ -2,9 +2,12 @@ struct buf {
int flags;
uint dev;
uint sector;
struct buf *prev;
struct buf *prev; // LRU cache list
struct buf *next;
struct buf *qnext; // disk queue
int done;
uchar data[512];
};
#define B_BUSY 0x1 // buffer is locked by some process
#define B_VALID 0x2 // buffer contains the data of the sector
#define B_WRITE 0x4 // asking device driver to write, else read
defs.h
浏览文件 @ 902b13f5
......@@ -55,7 +55,7 @@ int writei(struct inode*, char*, uint, uint);
// ide.c
void ide_init(void);
void ide_intr(void);
void ide_rw(int, uint, void*, uint, int);
void ide_rw(struct buf *);
// ioapic.c
void ioapic_enable(int irq, int cpu);
......
fs.c
浏览文件 @ 902b13f5
......@@ -6,7 +6,7 @@
// + Directories: inode with special contents (list of other inodes!)
// + Names: paths like /usr/rtm/xv6/fs.c for convenient naming.
//
// Disk layout is: superblock, inodes, disk bitmap, data blocks.
// Disk layout is: superblock, inodes, block not-free bitmap, data blocks.
//
// This file contains the low-level file system manipulation
// routines. The (higher-level) system call implementations
......@@ -51,7 +51,7 @@ balloc(uint dev)
bi = b % BPB;
m = 0x1 << (bi % 8);
if((bp->data[bi/8] & m) == 0) { // is block free?
bp->data[bi/8] |= 0x1 << (bi % 8);
bp->data[bi/8] |= m;
bwrite(bp); // mark it allocated on disk
brelse(bp);
return b;
......@@ -81,6 +81,8 @@ bfree(int dev, uint b)
bp = bread(dev, BBLOCK(b, ninodes));
bi = b % BPB;
m = 0x1 << (bi % 8);
if((bp->data[bi/8] & m) == 0)
panic("freeing free block");
bp->data[bi/8] &= ~m;
bwrite(bp); // mark it free on disk
brelse(bp);
......@@ -93,18 +95,17 @@ bfree(int dev, uint b)
// on-disk structures to provide a place for synchronizing access
// to inodes shared between multiple processes.
//
// ip->ref counts the number of references to this
// ip->ref counts the number of pointer references to this cached
// inode; references are typically kept in struct file and in cp->cwd.
// When ip->ref falls to zero, the inode is no longer cached.
// It is an error to use an inode without holding a reference to it.
//
// Inodes can be marked busy, just like bufs, meaning
// that some process has exclusive use of the inode.
// Inodes can be locked with I_BUSY (like bufs and B_BUSY).
// Processes are only allowed to read and write inode
// metadata and contents when holding the inode's lock.
// Because inodes locks are held during disk accesses,
// they are implemented using a flag, as in the buffer cache,
// not using spin locks. Callers are responsible for locking
// Because inode locks are held during disk accesses,
// they are implemented using a flag rather than with
// spin locks. Callers are responsible for locking
// inodes before passing them to routines in this file; leaving
// this responsibility with the caller makes it possible for them
// to create arbitrarily-sized atomic operations.
......@@ -112,7 +113,8 @@ bfree(int dev, uint b)
// To give maximum control over locking to the callers,
// the routines in this file that return inode pointers
// return pointers to *unlocked* inodes. It is the callers'
// responsibility to lock them before using them.
// responsibility to lock them before using them. A non-zero
// ip->ref keeps these unlocked inodes in the cache.
struct {
struct spinlock lock;
......
ide.c
浏览文件 @ 902b13f5
......@@ -8,6 +8,7 @@
#include "x86.h"
#include "traps.h"
#include "spinlock.h"
#include "buf.h"
#define IDE_BSY 0x80
#define IDE_DRDY 0x40
......@@ -18,28 +19,17 @@
#define IDE_CMD_WRITE 0x30
// IDE request queue.
// The next request will be stored in request[head],
// and the request currently being served by the disk
// is request[tail].
// ide_queue points to the buf now being read/written to the disk.
// ide_queue->qnext points to the next buf to be processed.
// Must hold ide_lock while manipulating queue.
struct ide_request {
int diskno;
uint secno;
void *addr;
uint nsecs;
uint read;
int done;
};
static struct ide_request request[NREQUEST];
static int head, tail;
static struct spinlock ide_lock;
static struct buf *ide_queue;
static int disk_1_present;
static int disk_queue;
static int ide_probe_disk1(void);
static void ide_start_request();
//PAGEBREAK: 10
// Wait for IDE disk to become ready.
......@@ -93,80 +83,75 @@ void
ide_intr(void)
{
acquire(&ide_lock);
request[tail].done = 1;
wakeup(&request[tail]);
if(ide_queue){
//cprintf("intr %x\n", ide_queue);
if((ide_queue->flags & B_WRITE) == 0)
if(ide_wait_ready(1) >= 0)
insl(0x1F0, ide_queue->data, 512/4);
ide_queue->done = 1;
wakeup(ide_queue);
ide_queue = ide_queue->qnext;
ide_start_request();
} else {
cprintf("stray ide interrupt\n");
}
release(&ide_lock);
}
// Start the next request in the queue.
// Caller must hold ide_lock.
static void
ide_start_request (void)
{
struct ide_request *r;
if(head != tail) {
r = &request[tail];
if(ide_queue){
ide_wait_ready(0);
//cprintf("start %x\n", ide_queue);
outb(0x3f6, 0); // generate interrupt
outb(0x1F2, r->nsecs);
outb(0x1F3, r->secno & 0xFF);
outb(0x1F4, (r->secno >> 8) & 0xFF);
outb(0x1F5, (r->secno >> 16) & 0xFF);
outb(0x1F6, 0xE0 | ((r->diskno&1)<<4) | ((r->secno>>24)&0x0F));
if(r->read)
outb(0x1F7, IDE_CMD_READ);
else {
outb(0x1F2, 1); // number of sectors
outb(0x1F3, ide_queue->sector & 0xFF);
outb(0x1F4, (ide_queue->sector >> 8) & 0xFF);
outb(0x1F5, (ide_queue->sector >> 16) & 0xFF);
outb(0x1F6, 0xE0 |
((ide_queue->dev & 1)<<4) |
((ide_queue->sector>>24)&0x0F));
if(ide_queue->flags & B_WRITE){
outb(0x1F7, IDE_CMD_WRITE);
outsl(0x1F0, r->addr, 512/4);
outsl(0x1F0, ide_queue->data, 512/4);
} else {
outb(0x1F7, IDE_CMD_READ);
}
}
}
//PAGEBREAK: 30
// Run an entire disk operation.
// Queue up a disk operation and wait for it to finish.
// b must have B_BUSY set.
void
ide_rw(int diskno, uint secno, void *addr, uint nsecs, int read)
ide_rw(struct buf *b)
{
struct ide_request *r;
struct buf **pp;
if(diskno && !disk_1_present)
if((b->dev & 0xff) && !disk_1_present)
panic("ide disk 1 not present");
acquire(&ide_lock);
// Add request to queue.
while((head + 1) % NREQUEST == tail)
sleep(&disk_queue, &ide_lock);
r = &request[head];
r->secno = secno;
r->addr = addr;
r->nsecs = nsecs;
r->diskno = diskno;
r->read = read;
r->done = 0;
head = (head + 1) % NREQUEST;
// Start request if necessary.
ide_start_request();
// Wait for request to finish.
while(!r->done)
sleep(r, &ide_lock);
// Finish request.
if(read){
if(ide_wait_ready(1) >= 0)
insl(0x1F0, addr, 512/4);
}
// Remove request from queue.
if((head + 1) % NREQUEST == tail)
wakeup(&disk_queue);
tail = (tail + 1) % NREQUEST;
b->done = 0;
b->qnext = 0;
// Start next request in queue, if any.
ide_start_request();
// cprintf("enqueue %x %x\n", b, ide_queue);
// append b to ide_queue
pp = &ide_queue;
while(*pp)
pp = &(*pp)->qnext;
*pp = b;
if(ide_queue == b)
ide_start_request();
while(!b->done)
sleep(b, &ide_lock);
release(&ide_lock);
}
kalloc.c
浏览文件 @ 902b13f5
......@@ -95,7 +95,7 @@ kalloc(int n)
char *p;
struct run *r, **rr;
if(n % PAGE)
if(n % PAGE || n <= 0)
panic("kalloc");
acquire(&kalloc_lock);
......
param.h
浏览文件 @ 902b13f5
......@@ -5,7 +5,6 @@
#define NOFILE 16 // open files per process
#define NFILE 100 // open files per system
#define NBUF 10 // size of disk block cache
#define NREQUEST NBUF // outstanding disk requests
#define NINODE 50 // maximum number of active i-nodes
#define NDEV 10 // maximum major device number
#define ROOTDEV 1 // device number of file system root disk
syscall.c
浏览文件 @ 902b13f5
......@@ -49,7 +49,7 @@ fetchstr(struct proc *p, uint addr, char **pp)
return -1;
}
// Fetch the argno'th word-sized system call argument as an integer.
// Fetch the argno'th 32-bit system call argument.
int
argint(int argno, int *ip)
{
......
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