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xv6-cs450
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log write() data 

usertest for big write()s
push begin_trans/commit_trans down into syscalls
This commit is contained in:
Robert Morris 2011-08-12 09:25:39 -04:00
parent bd71a45046
commit 2e59046362
7 changed files with 143 additions and 43 deletions
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29
file.c
View File

@ -67,8 +67,11 @@ fileclose(struct file *f)
if(ff.type == FD_PIPE)
pipeclose(ff.pipe, ff.writable);
else if(ff.type == FD_INODE)
else if(ff.type == FD_INODE){
begin_trans();
iput(ff.ip);
commit_trans();
}
}
// Get metadata about file f.
@ -116,10 +119,30 @@ filewrite(struct file *f, char *addr, int n)
return pipewrite(f->pipe, addr, n);
if(f->type == FD_INODE){
ilock(f->ip);
if((r = writei(f->ip, addr, f->off, n)) > 0)
// write a few blocks at a time to avoid exceeding
// the maximum log transaction size, including
// i-node, indirect block, allocation blocks,
// and 2 blocks of slop for non-aligned writes.
// this really belongs lower down, since writei()
// might be writing a device like the console.
int max = ((LOGSIZE-1-1-2) / 2) * 512;
int i = 0;
while(i < n){
int n1 = n - i;
if(n1 > max)
n1 = max;
begin_trans();
r = writei(f->ip, addr + i, f->off, n1);
commit_trans();
if(r < 0)
break;
if(r != n1)
panic("short filewrite");
f->off += r;
i += r;
}
iunlock(f->ip);
return r;
return i == n ? n : -1;
}
panic("filewrite");
}

4
fs.c
View File

@ -437,13 +437,13 @@ writei(struct inode *ip, char *src, uint off, uint n)
if(off > ip->size || off + n < off)
return -1;
if(off + n > MAXFILE*BSIZE)
n = MAXFILE*BSIZE - off;
return -1;
for(tot=0; tot<n; tot+=m, off+=m, src+=m){
bp = bread(ip->dev, bmap(ip, off/BSIZE));
m = min(n - tot, BSIZE - off%BSIZE);
memmove(bp->data + off%BSIZE, src, m);
bwrite(bp);
log_write(bp);
brelse(bp);
}

86
log.c
View File

@ -8,18 +8,36 @@
#include "fs.h"
#include "buf.h"
// Dirt simple "logging" supporting only one transaction. All file system calls
// that potentially write a block should be wrapped in begin_trans and commit_trans,
// so that there is never more than one transaction. This serializes all file system
// operations that potentially write, but simplifies recovery (only the last
// one transaction to recover) and concurrency (don't have to worry about reading a modified
// block from a transaction that hasn't committed yet).
// Simple logging. Each system call that might write the file system
// should be surrounded with begin_trans() and commit_trans() calls.
//
// The log holds at most one transaction at a time. Commit forces
// the log (with commit record) to disk, then installs the affected
// blocks to disk, then erases the log. begin_trans() ensures that
// only one system call can be in a transaction; others must wait.
//
// Allowing only one transaction at a time means that the file
// system code doesn't have to worry about the possibility of
// one transaction reading a block that another one has modified,
// for example an i-node block.
//
// Read-only system calls don't need to use transactions, though
// this means that they may observe uncommitted data. I-node
// and buffer locks prevent read-only calls from seeing inconsistent data.
//
// The log is a physical re-do log containing disk blocks.
// The on-disk log format:
// header block, containing sector #s for block A, B, C, ...
// block A
// block B
// block C
// ...
// Log appends are synchronous.
// The header of the log. If head == 0, there are no log entries. All entries till head
// are committed. sector[] records the home sector for each block in the log
// (i.e., physical logging).
// Contents of the header block, used for both the on-disk header block
// and to keep track in memory of logged sector #s before commit.
struct logheader {
int head;
int n;
int sector[LOGSIZE];
};
@ -55,10 +73,10 @@ install_trans(void)
{
int tail;
if (log.lh.head > 0)
cprintf("install_trans %d\n", log.lh.head);
for (tail = 0; tail < log.lh.head; tail++) {
cprintf("put entry %d to disk block %d\n", tail, log.lh.sector[tail]);
//if (log.lh.n > 0)
// cprintf("install_trans %d\n", log.lh.n);
for (tail = 0; tail < log.lh.n; tail++) {
// cprintf("put entry %d to disk block %d\n", tail, log.lh.sector[tail]);
struct buf *lbuf = bread(log.dev, log.start+tail+1); // read i'th block from log
struct buf *dbuf = bread(log.dev, log.lh.sector[tail]); // read dst block
memmove(dbuf->data, lbuf->data, BSIZE);
@ -75,27 +93,27 @@ read_head(void)
struct buf *buf = bread(log.dev, log.start);
struct logheader *lh = (struct logheader *) (buf->data);
int i;
log.lh.head = lh->head;
for (i = 0; i < log.lh.head; i++) {
log.lh.n = lh->n;
for (i = 0; i < log.lh.n; i++) {
log.lh.sector[i] = lh->sector[i];
}
brelse(buf);
if (log.lh.head > 0)
cprintf("read_head: %d\n", log.lh.head);
//if (log.lh.n > 0)
// cprintf("read_head: %d\n", log.lh.n);
}
// Write the in-memory log header to disk, committing log entries till head
static void
write_head(void)
{
if (log.lh.head > 0)
cprintf("write_head: %d\n", log.lh.head);
// if (log.lh.n > 0)
// cprintf("write_head: %d\n", log.lh.n);
struct buf *buf = bread(log.dev, log.start);
struct logheader *hb = (struct logheader *) (buf->data);
int i;
hb->head = log.lh.head;
for (i = 0; i < log.lh.head; i++) {
hb->n = log.lh.n;
for (i = 0; i < log.lh.n; i++) {
hb->sector[i] = log.lh.sector[i];
}
bwrite(buf);
@ -107,7 +125,7 @@ recover_from_log(void)
{
read_head();
install_trans(); // Install all transactions till head
log.lh.head = 0;
log.lh.n = 0;
write_head(); // Reclaim log
}
@ -127,7 +145,7 @@ commit_trans(void)
{
write_head(); // This causes all blocks till log.head to be commited
install_trans(); // Install all the transactions till head
log.lh.head = 0;
log.lh.n = 0;
write_head(); // Reclaim log
acquire(&log.lock);
@ -136,21 +154,27 @@ commit_trans(void)
release(&log.lock);
}
// Write buffer into the log at log.head and record the block number log.lh.entry, but
// don't write the log header (which would commit the write).
// Caller has modified b->data and is done with the buffer.
// Append the block to the log and record the block number,
// but don't write the log header (which would commit the write).
// log_write() replaces bwrite(); a typical use is:
// bp = bread(...)
// modify bp->data[]
// log_write(bp)
// brelse(bp)
void
log_write(struct buf *b)
{
int i;
if (log.lh.head >= LOGSIZE)
if (log.lh.n >= LOGSIZE || log.lh.n >= log.size - 1)
panic("too big a transaction");
if (!log.intrans)
panic("write outside of trans");
cprintf("log_write: %d %d\n", b->sector, log.lh.head);
// cprintf("log_write: %d %d\n", b->sector, log.lh.n);
for (i = 0; i < log.lh.head; i++) {
for (i = 0; i < log.lh.n; i++) {
if (log.lh.sector[i] == b->sector) // log absorbtion?
break;
}
@ -159,6 +183,6 @@ log_write(struct buf *b)
memmove(lbuf->data, b->data, BSIZE);
bwrite(lbuf);
brelse(lbuf);
if (i == log.lh.head)
log.lh.head++;
if (i == log.lh.n)
log.lh.n++;
}

2
param.h
View File

@ -8,5 +8,5 @@
#define NDEV 10 // maximum major device number
#define ROOTDEV 1 // device number of file system root disk
#define MAXARG 32 // max exec arguments
#define LOGSIZE 10 // size of log
#define LOGSIZE 10 // max data sectors in on-disk log

2
syscall.c
View File

@ -141,9 +141,7 @@ syscall(void)
if(num >= 0 && num < SYS_open && syscalls[num]) {
proc->tf->eax = syscalls[num]();
} else if (num >= SYS_open && num < NELEM(syscalls) && syscalls[num]) {
begin_trans();
proc->tf->eax = syscalls[num]();
commit_trans();
} else {
cprintf("%d %s: unknown sys call %d\n",
proc->pid, proc->name, num);

30
sysfile.c
View File

@ -121,6 +121,9 @@ sys_link(void)
iunlockput(ip);
return -1;
}
begin_trans();
ip->nlink++;
iupdate(ip);
iunlock(ip);
@ -134,6 +137,9 @@ sys_link(void)
}
iunlockput(dp);
iput(ip);
commit_trans();
return 0;
bad:
@ -141,6 +147,7 @@ bad:
ip->nlink--;
iupdate(ip);
iunlockput(ip);
commit_trans();
return -1;
}
@ -195,6 +202,8 @@ sys_unlink(void)
return -1;
}
begin_trans();
memset(&de, 0, sizeof(de));
if(writei(dp, (char*)&de, off, sizeof(de)) != sizeof(de))
panic("unlink: writei");
@ -207,6 +216,9 @@ sys_unlink(void)
ip->nlink--;
iupdate(ip);
iunlockput(ip);
commit_trans();
return 0;
}
@ -251,6 +263,7 @@ create(char *path, short type, short major, short minor)
panic("create: dirlink");
iunlockput(dp);
return ip;
}
@ -265,7 +278,10 @@ sys_open(void)
if(argstr(0, &path) < 0 || argint(1, &omode) < 0)
return -1;
if(omode & O_CREATE){
if((ip = create(path, T_FILE, 0, 0)) == 0)
begin_trans();
ip = create(path, T_FILE, 0, 0);
commit_trans();
if(ip == 0)
return -1;
} else {
if((ip = namei(path)) == 0)
@ -299,9 +315,13 @@ sys_mkdir(void)
char *path;
struct inode *ip;
if(argstr(0, &path) < 0 || (ip = create(path, T_DIR, 0, 0)) == 0)
begin_trans();
if(argstr(0, &path) < 0 || (ip = create(path, T_DIR, 0, 0)) == 0){
commit_trans();
return -1;
}
iunlockput(ip);
commit_trans();
return 0;
}
@ -313,12 +333,16 @@ sys_mknod(void)
int len;
int major, minor;
begin_trans();
if((len=argstr(0, &path)) < 0 ||
argint(1, &major) < 0 ||
argint(2, &minor) < 0 ||
(ip = create(path, T_DEV, major, minor)) == 0)
(ip = create(path, T_DEV, major, minor)) == 0){
commit_trans();
return -1;
}
iunlockput(ip);
commit_trans();
return 0;
}

33
usertests.c
View File

@ -7,7 +7,7 @@
#include "traps.h"
#include "memlayout.h"
char buf[2048];
char buf[8192];
char name[3];
char *echoargv[] = { "echo", "ALL", "TESTS", "PASSED", 0 };
int stdout = 1;
@ -968,6 +968,36 @@ subdir(void)
printf(1, "subdir ok\n");
}
// test writes that are larger than the log.
void
bigwrite(void)
{
int fd, sz;
printf(1, "bigwrite test\n");
unlink("bigwrite");
for(sz = 499; sz < 12*512; sz += 471){
fd = open("bigwrite", O_CREATE | O_RDWR);
if(fd < 0){
printf(1, "cannot create bigwrite\n");
exit();
}
int i;
for(i = 0; i < 2; i++){
int cc = write(fd, buf, sz);
if(cc != sz){
printf(1, "write(%d) ret %d\n", sz, cc);
exit();
}
}
close(fd);
unlink("bigwrite");
}
printf(1, "bigwrite ok\n");
}
void
bigfile(void)
{
@ -1467,6 +1497,7 @@ main(int argc, char *argv[])
}
close(open("usertests.ran", O_CREATE));
bigwrite();
bigargtest();
bsstest();
sbrktest();