a start at concurrent FS system calls
This commit is contained in:
Robert Morris
parent
2c56547272
commit
71453f72f2
4
defs.h
4
defs.h
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@ -81,8 +81,8 @@ void microdelay(int);
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// log.c
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void initlog(void);
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void log_write(struct buf*);
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void begin_trans();
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void commit_trans();
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void begin_op();
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void end_op();
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// mp.c
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extern int ismp;
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8
exec.c
8
exec.c
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@ -18,9 +18,9 @@ exec(char *path, char **argv)
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struct proghdr ph;
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pde_t *pgdir, *oldpgdir;
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begin_trans();
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begin_op();
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if((ip = namei(path)) == 0){
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commit_trans();
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end_op();
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return -1;
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}
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ilock(ip);
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@ -50,7 +50,7 @@ exec(char *path, char **argv)
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goto bad;
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}
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iunlockput(ip);
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commit_trans();
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end_op();
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ip = 0;
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// Allocate two pages at the next page boundary.
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@ -101,7 +101,7 @@ exec(char *path, char **argv)
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freevm(pgdir);
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if(ip){
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iunlockput(ip);
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commit_trans();
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end_op();
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}
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return -1;
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}
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8
file.c
8
file.c
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@ -72,9 +72,9 @@ fileclose(struct file *f)
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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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begin_op();
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iput(ff.ip);
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commit_trans();
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end_op();
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}
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}
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@ -136,12 +136,12 @@ filewrite(struct file *f, char *addr, int n)
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if(n1 > max)
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n1 = max;
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begin_trans();
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begin_op();
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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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end_op();
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if(r < 0)
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break;
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78
log.c
78
log.c
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@ -5,18 +5,22 @@
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#include "fs.h"
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#include "buf.h"
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// Simple logging. Each file system system call
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// should be surrounded with begin_trans() and commit_trans() calls.
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// Simple logging that allows concurrent FS system calls.
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//
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// The log holds at most one transaction at a time. Commit forces
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// the log (with commit record) to disk, then installs the affected
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// blocks to disk, then erases the log. begin_trans() ensures that
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// only one system call can be in a transaction; others must wait.
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// A log transaction contains the updates of *multiple* FS system
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// calls. The logging systems only commits when there are
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// no FS system calls active. Thus there is never
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// any reasoning required about whether a commit might
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// write an uncommitted system call's updates to disk.
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//
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// Allowing only one transaction at a time means that the file
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// system code doesn't have to worry about the possibility of
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// one transaction reading a block that another one has modified,
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// for example an i-node block.
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// A system call should call begin_op()/end_op() to mark
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// its start and end. Usually begin_op() just increments
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// the count of in-progress FS system calls and returns.
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// But if it thinks the log is close to running out, it
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// blocks this system call, and causes the system to wait
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// until end_op() indicates there are no executing FS
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// system calls, at which point the last end_op() commits
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// all the system calls' writes.
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//
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// The log is a physical re-do log containing disk blocks.
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// The on-disk log format:
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@ -38,13 +42,15 @@ struct log {
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struct spinlock lock;
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int start;
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int size;
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int busy; // a transaction is active
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int outstanding; // how many FS sys calls are executing.
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int committing; // in commit(), please wait.
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int dev;
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struct logheader lh;
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};
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struct log log;
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static void recover_from_log(void);
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static void commit();
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void
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initlog(void)
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@ -117,19 +123,52 @@ recover_from_log(void)
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write_head(); // clear the log
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}
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// an FS system call should call begin_op() when it starts.
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void
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begin_trans(void)
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begin_op(void)
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{
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acquire(&log.lock);
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while (log.busy) {
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while(1){
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if(log.committing){
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sleep(&log, &log.lock);
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}
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log.busy = 1;
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} else {
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// XXX wait (for a commit) if log is longish.
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// need to reserve to avoid over-commit of log space.
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log.outstanding += 1;
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release(&log.lock);
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break;
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}
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}
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}
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// an FS system call should call end_op() after it finishes.
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// can't write the disk &c while holding locks, thus do_commit.
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void
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commit_trans(void)
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end_op(void)
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{
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int do_commit = 0;
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acquire(&log.lock);
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log.outstanding -= 1;
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if(log.committing)
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panic("log.committing");
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if(log.outstanding == 0){
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do_commit = 1;
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log.committing = 1;
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}
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release(&log.lock);
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if(do_commit){
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commit();
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acquire(&log.lock);
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log.committing = 0;
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wakeup(&log);
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release(&log.lock);
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}
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}
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static void
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commit()
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{
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if (log.lh.n > 0) {
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write_head(); // Write header to disk -- the real commit
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@ -137,11 +176,6 @@ commit_trans(void)
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log.lh.n = 0;
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write_head(); // Erase the transaction from the log
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}
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acquire(&log.lock);
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log.busy = 0;
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wakeup(&log);
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release(&log.lock);
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}
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// Caller has modified b->data and is done with the buffer.
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@ -159,7 +193,7 @@ log_write(struct buf *b)
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if (log.lh.n >= LOGSIZE || log.lh.n >= log.size - 1)
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panic("too big a transaction");
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if (!log.busy)
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if (log.outstanding < 1)
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panic("write outside of trans");
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for (i = 0; i < log.lh.n; i++) {
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4
proc.c
4
proc.c
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@ -186,9 +186,9 @@ exit(void)
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}
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}
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begin_trans();
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begin_op();
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iput(proc->cwd);
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commit_trans();
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end_op();
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proc->cwd = 0;
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acquire(&ptable.lock);
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50
sysfile.c
50
sysfile.c
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@ -121,16 +121,16 @@ sys_link(void)
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if(argstr(0, &old) < 0 || argstr(1, &new) < 0)
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return -1;
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begin_trans();
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begin_op();
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if((ip = namei(old)) == 0){
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commit_trans();
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end_op();
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return -1;
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}
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ilock(ip);
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if(ip->type == T_DIR){
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iunlockput(ip);
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commit_trans();
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end_op();
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return -1;
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}
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@ -148,7 +148,7 @@ sys_link(void)
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iunlockput(dp);
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iput(ip);
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commit_trans();
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end_op();
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return 0;
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@ -157,7 +157,7 @@ bad:
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ip->nlink--;
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iupdate(ip);
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iunlockput(ip);
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commit_trans();
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end_op();
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return -1;
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}
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@ -189,9 +189,9 @@ sys_unlink(void)
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if(argstr(0, &path) < 0)
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return -1;
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begin_trans();
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begin_op();
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if((dp = nameiparent(path, name)) == 0){
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commit_trans();
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end_op();
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return -1;
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}
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@ -225,13 +225,13 @@ sys_unlink(void)
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iupdate(ip);
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iunlockput(ip);
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commit_trans();
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end_op();
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return 0;
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bad:
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iunlockput(dp);
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commit_trans();
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end_op();
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return -1;
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}
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@ -291,23 +291,23 @@ sys_open(void)
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if(argstr(0, &path) < 0 || argint(1, &omode) < 0)
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return -1;
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begin_trans();
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begin_op();
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if(omode & O_CREATE){
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ip = create(path, T_FILE, 0, 0);
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if(ip == 0){
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commit_trans();
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end_op();
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return -1;
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}
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} else {
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if((ip = namei(path)) == 0){
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commit_trans();
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end_op();
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return -1;
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}
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ilock(ip);
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if(ip->type == T_DIR && omode != O_RDONLY){
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iunlockput(ip);
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commit_trans();
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end_op();
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return -1;
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}
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}
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@ -316,11 +316,11 @@ sys_open(void)
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if(f)
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fileclose(f);
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iunlockput(ip);
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commit_trans();
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end_op();
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return -1;
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}
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iunlock(ip);
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commit_trans();
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end_op();
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f->type = FD_INODE;
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f->ip = ip;
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@ -336,13 +336,13 @@ sys_mkdir(void)
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char *path;
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struct inode *ip;
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begin_trans();
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begin_op();
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if(argstr(0, &path) < 0 || (ip = create(path, T_DIR, 0, 0)) == 0){
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commit_trans();
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end_op();
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return -1;
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}
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iunlockput(ip);
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commit_trans();
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end_op();
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return 0;
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}
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@ -354,16 +354,16 @@ sys_mknod(void)
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int len;
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int major, minor;
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begin_trans();
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begin_op();
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if((len=argstr(0, &path)) < 0 ||
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argint(1, &major) < 0 ||
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argint(2, &minor) < 0 ||
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(ip = create(path, T_DEV, major, minor)) == 0){
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commit_trans();
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end_op();
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return -1;
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}
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iunlockput(ip);
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commit_trans();
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end_op();
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return 0;
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}
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@ -373,20 +373,20 @@ sys_chdir(void)
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char *path;
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struct inode *ip;
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begin_trans();
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begin_op();
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if(argstr(0, &path) < 0 || (ip = namei(path)) == 0){
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commit_trans();
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end_op();
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return -1;
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}
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ilock(ip);
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if(ip->type != T_DIR){
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iunlockput(ip);
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commit_trans();
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end_op();
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return -1;
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}
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iunlock(ip);
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iput(proc->cwd);
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commit_trans();
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end_op();
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proc->cwd = ip;
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return 0;
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}
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