156 lines
2.7 KiB
C
156 lines
2.7 KiB
C
//
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// File descriptors
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//
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#include "types.h"
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#include "defs.h"
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#include "param.h"
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#include "fs.h"
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#include "file.h"
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#include "spinlock.h"
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struct devsw devsw[NDEV];
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struct {
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struct spinlock lock;
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struct file file[NFILE];
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} ftable;
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void
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fileinit(void)
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{
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initlock(&ftable.lock, "ftable");
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}
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// Allocate a file structure.
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struct file*
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filealloc(void)
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{
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struct file *f;
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acquire(&ftable.lock);
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for(f = ftable.file; f < ftable.file + NFILE; f++){
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if(f->ref == 0){
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f->ref = 1;
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release(&ftable.lock);
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return f;
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}
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}
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release(&ftable.lock);
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return 0;
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}
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// Increment ref count for file f.
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struct file*
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filedup(struct file *f)
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{
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acquire(&ftable.lock);
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if(f->ref < 1)
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panic("filedup");
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f->ref++;
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release(&ftable.lock);
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return f;
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}
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// Close file f. (Decrement ref count, close when reaches 0.)
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void
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fileclose(struct file *f)
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{
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struct file ff;
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acquire(&ftable.lock);
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if(f->ref < 1)
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panic("fileclose");
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if(--f->ref > 0){
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release(&ftable.lock);
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return;
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}
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ff = *f;
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f->ref = 0;
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f->type = FD_NONE;
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release(&ftable.lock);
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if(ff.type == FD_PIPE)
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pipeclose(ff.pipe, ff.writable);
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else if(ff.type == FD_INODE){
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begin_trans();
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iput(ff.ip);
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commit_trans();
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}
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}
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// Get metadata about file f.
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int
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filestat(struct file *f, struct stat *st)
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{
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if(f->type == FD_INODE){
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ilock(f->ip);
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stati(f->ip, st);
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iunlock(f->ip);
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return 0;
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}
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return -1;
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}
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// Read from file f.
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int
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fileread(struct file *f, char *addr, int n)
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{
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int r;
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if(f->readable == 0)
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return -1;
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if(f->type == FD_PIPE)
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return piperead(f->pipe, addr, n);
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if(f->type == FD_INODE){
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ilock(f->ip);
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if((r = readi(f->ip, addr, f->off, n)) > 0)
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f->off += r;
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iunlock(f->ip);
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return r;
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}
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panic("fileread");
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}
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//PAGEBREAK!
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// Write to file f.
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int
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filewrite(struct file *f, char *addr, int n)
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{
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int r;
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if(f->writable == 0)
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return -1;
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if(f->type == FD_PIPE)
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return pipewrite(f->pipe, addr, n);
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if(f->type == FD_INODE){
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// write a few blocks at a time to avoid exceeding
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// the maximum log transaction size, including
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// i-node, indirect block, allocation blocks,
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// and 2 blocks of slop for non-aligned writes.
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// this really belongs lower down, since writei()
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// might be writing a device like the console.
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int max = ((LOGSIZE-1-1-2) / 2) * 512;
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int i = 0;
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while(i < n){
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int n1 = n - i;
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if(n1 > max)
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n1 = max;
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begin_trans();
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ilock(f->ip);
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if ((r = writei(f->ip, addr + i, f->off, n1)) > 0)
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f->off += r;
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iunlock(f->ip);
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commit_trans();
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if(r < 0)
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break;
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if(r != n1)
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panic("short filewrite");
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i += r;
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}
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return i == n ? n : -1;
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}
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panic("filewrite");
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}
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