From 2c56547272e43b483d560a61692f1e24926a82fb Mon Sep 17 00:00:00 2001
From: Robert Morris <rtm@csail.mit.edu>
Date: Mon, 4 Aug 2014 13:06:48 -0400
Subject: [PATCH] every iput() and namei() must be inside a transaction
---
exec.c | 10 ++++-
fs.c | 3 ++
log.c | 6 +--
proc.c | 2 +
sysfile.c | 35 ++++++++++++-----
usertests.c | 106 +++++++++++++++++++++++++++++++++++++++++++++++++++-
6 files changed, 145 insertions(+), 17 deletions(-)
diff --git a/exec.c b/exec.c
index a85e203..7eaef5b 100644
--- a/exec.c
+++ b/exec.c
@@ -18,8 +18,11 @@ exec(char *path, char **argv)
struct proghdr ph;
pde_t *pgdir, *oldpgdir;
- if((ip = namei(path)) == 0)
+ begin_trans();
+ if((ip = namei(path)) == 0){
+ commit_trans();
return -1;
+ }
ilock(ip);
pgdir = 0;
@@ -47,6 +50,7 @@ exec(char *path, char **argv)
goto bad;
}
iunlockput(ip);
+ commit_trans();
ip = 0;
// Allocate two pages at the next page boundary.
@@ -95,7 +99,9 @@ exec(char *path, char **argv)
bad:
if(pgdir)
freevm(pgdir);
- if(ip)
+ if(ip){
iunlockput(ip);
+ commit_trans();
+ }
return -1;
}
diff --git a/fs.c b/fs.c
index 9d6dfd1..7621d08 100644
--- a/fs.c
+++ b/fs.c
@@ -314,6 +314,8 @@ iunlock(struct inode *ip)
// be recycled.
// If that was the last reference and the inode has no links
// to it, free the inode (and its content) on disk.
+// All calls to iput() must be inside a transaction in
+// case it has to free the inode.
void
iput(struct inode *ip)
{
@@ -601,6 +603,7 @@ skipelem(char *path, char *name)
// Look up and return the inode for a path name.
// If parent != 0, return the inode for the parent and copy the final
// path element into name, which must have room for DIRSIZ bytes.
+// Must be called inside a transaction since it calls iput().
static struct inode*
namex(char *path, int nameiparent, char *name)
{
diff --git a/log.c b/log.c
index 1814edc..95cc4d5 100644
--- a/log.c
+++ b/log.c
@@ -5,7 +5,7 @@
#include "fs.h"
#include "buf.h"
-// Simple logging. Each system call that might write the file system
+// Simple logging. Each file system system call
// should be surrounded with begin_trans() and commit_trans() calls.
//
// The log holds at most one transaction at a time. Commit forces
@@ -18,10 +18,6 @@
// 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, ...
diff --git a/proc.c b/proc.c
index e19539c..db0e9c7 100644
--- a/proc.c
+++ b/proc.c
@@ -186,7 +186,9 @@ exit(void)
}
}
+ begin_trans();
iput(proc->cwd);
+ commit_trans();
proc->cwd = 0;
acquire(&ptable.lock);
diff --git a/sysfile.c b/sysfile.c
index 64f2b33..095fca7 100644
--- a/sysfile.c
+++ b/sysfile.c
@@ -120,10 +120,12 @@ sys_link(void)
if(argstr(0, &old) < 0 || argstr(1, &new) < 0)
return -1;
- if((ip = namei(old)) == 0)
- return -1;
begin_trans();
+ if((ip = namei(old)) == 0){
+ commit_trans();
+ return -1;
+ }
ilock(ip);
if(ip->type == T_DIR){
@@ -186,10 +188,12 @@ sys_unlink(void)
if(argstr(0, &path) < 0)
return -1;
- if((dp = nameiparent(path, name)) == 0)
- return -1;
begin_trans();
+ if((dp = nameiparent(path, name)) == 0){
+ commit_trans();
+ return -1;
+ }
ilock(dp);
@@ -286,18 +290,24 @@ sys_open(void)
if(argstr(0, &path) < 0 || argint(1, &omode) < 0)
return -1;
+
+ begin_trans();
+
if(omode & O_CREATE){
- begin_trans();
ip = create(path, T_FILE, 0, 0);
- commit_trans();
- if(ip == 0)
+ if(ip == 0){
+ commit_trans();
return -1;
+ }
} else {
- if((ip = namei(path)) == 0)
+ if((ip = namei(path)) == 0){
+ commit_trans();
return -1;
+ }
ilock(ip);
if(ip->type == T_DIR && omode != O_RDONLY){
iunlockput(ip);
+ commit_trans();
return -1;
}
}
@@ -306,9 +316,11 @@ sys_open(void)
if(f)
fileclose(f);
iunlockput(ip);
+ commit_trans();
return -1;
}
iunlock(ip);
+ commit_trans();
f->type = FD_INODE;
f->ip = ip;
@@ -361,15 +373,20 @@ sys_chdir(void)
char *path;
struct inode *ip;
- if(argstr(0, &path) < 0 || (ip = namei(path)) == 0)
+ begin_trans();
+ if(argstr(0, &path) < 0 || (ip = namei(path)) == 0){
+ commit_trans();
return -1;
+ }
ilock(ip);
if(ip->type != T_DIR){
iunlockput(ip);
+ commit_trans();
return -1;
}
iunlock(ip);
iput(proc->cwd);
+ commit_trans();
proc->cwd = ip;
return 0;
}
diff --git a/usertests.c b/usertests.c
index 92b9136..5a78c7c 100644
--- a/usertests.c
+++ b/usertests.c
@@ -13,6 +13,106 @@ char name[3];
char *echoargv[] = { "echo", "ALL", "TESTS", "PASSED", 0 };
int stdout = 1;
+// does chdir() call iput(p->cwd) in a transaction?
+void
+iputtest(void)
+{
+ printf(stdout, "iput test\n");
+
+ if(mkdir("iputdir") < 0){
+ printf(stdout, "mkdir failed\n");
+ exit();
+ }
+ if(chdir("iputdir") < 0){
+ printf(stdout, "chdir iputdir failed\n");
+ exit();
+ }
+ if(unlink("../iputdir") < 0){
+ printf(stdout, "unlink ../iputdir failed\n");
+ exit();
+ }
+ if(chdir("/") < 0){
+ printf(stdout, "chdir / failed\n");
+ exit();
+ }
+ printf(stdout, "iput test ok\n");
+}
+
+// does exit() call iput(p->cwd) in a transaction?
+void
+exitiputtest(void)
+{
+ int pid;
+
+ printf(stdout, "exitiput test\n");
+
+ pid = fork();
+ if(pid < 0){
+ printf(stdout, "fork failed\n");
+ exit();
+ }
+ if(pid == 0){
+ if(mkdir("iputdir") < 0){
+ printf(stdout, "mkdir failed\n");
+ exit();
+ }
+ if(chdir("iputdir") < 0){
+ printf(stdout, "child chdir failed\n");
+ exit();
+ }
+ if(unlink("../iputdir") < 0){
+ printf(stdout, "unlink ../iputdir failed\n");
+ exit();
+ }
+ exit();
+ }
+ wait();
+ printf(stdout, "exitiput test ok\n");
+}
+
+// does the error path in open() for attempt to write a
+// directory call iput() in a transaction?
+// needs a hacked kernel that pauses just after the namei()
+// call in sys_open():
+// if((ip = namei(path)) == 0)
+// return -1;
+// {
+// int i;
+// for(i = 0; i < 10000; i++)
+// yield();
+// }
+void
+openiputtest(void)
+{
+ int pid;
+
+ printf(stdout, "openiput test\n");
+ if(mkdir("oidir") < 0){
+ printf(stdout, "mkdir oidir failed\n");
+ exit();
+ }
+ pid = fork();
+ if(pid < 0){
+ printf(stdout, "fork failed\n");
+ exit();
+ }
+ if(pid == 0){
+ int fd = open("oidir", O_RDWR);
+ if(fd >= 0){
+ printf(stdout, "open directory for write succeeded\n");
+ exit();
+ }
+ exit();
+ }
+ sleep(1);
+ if(unlink("oidir") != 0){
+ printf(stdout, "unlink failed\n");
+ exit();
+ }
+ wait();
+ printf(stdout, "openiput test ok\n");
+}
+
// simple file system tests
void
@@ -187,7 +287,7 @@ void dirtest(void)
printf(stdout, "unlink dir0 failed\n");
exit();
}
- printf(stdout, "mkdir test\n");
+ printf(stdout, "mkdir test ok\n");
}
void
@@ -1628,6 +1728,10 @@ main(int argc, char *argv[])
writetest1();
createtest();
+ openiputtest();
+ exitiputtest();
+ iputtest();
+
mem();
pipe1();
preempt();
--
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