From 211ff0c67ea6737853cf932313cf4e27cc15f55c Mon Sep 17 00:00:00 2001
From: rtm <rtm>
Date: Sun, 13 Aug 2006 12:22:44 +0000
Subject: [PATCH] namei returns locked parent dir inode for create / unlink
don't hold fd table lock across idecref() (latter does block i/o) idecref
calls iput() in case last ref -> freeing inode dir size is 512 * # blocks, so
readi/writei &c work unlink deletes dirent even if ip->nlink > 0
---
Notes | 15 ++++++
defs.h | 2 +-
fd.c | 20 ++++---
fs.c | 153 ++++++++++++++++++++++++++++------------------------
fsvar.h | 4 ++
syscall.c | 6 +--
usertests.c | 2 +-
7 files changed, 120 insertions(+), 82 deletions(-)
diff --git a/Notes b/Notes
index 386bc2f..4bb9552 100644
--- a/Notes
+++ b/Notes
@@ -365,3 +365,18 @@ two bugs in unlink: don't just return if nlink > 0,
and search for name, not inum
is there a create/create race for same file name?
resulting in two entries w/ same name in directory?
+
+namei
+ return just inode
+ return offset in dir where found, w/ dir locked, for unlink
+ return dir locked, for mknod
+
+is the offset alone useful? how do I read/write it?
+
+test: one process unlinks a file while another links to it
+test: simultaneous create of same file
+test: one process opens a file while another deletes it
+
+oy, mkfs wants dir size to be last written entry, but i
+ want it to be nblocks*512
+ maybe fix kernel code to handle former
diff --git a/defs.h b/defs.h
index c8e1870..da47691 100644
--- a/defs.h
+++ b/defs.h
@@ -116,7 +116,7 @@ void ilock(struct inode *ip);
void iunlock(struct inode *ip);
void idecref(struct inode *ip);
void iput(struct inode *ip);
-struct inode * namei(char *path, uint *);
+struct inode * namei(char *path, int, uint *);
void stati(struct inode *ip, struct stat *st);
int readi(struct inode *ip, char *xdst, uint off, uint n);
int writei(struct inode *ip, char *addr, uint off, uint n);
diff --git a/fd.c b/fd.c
index c5c3e57..25a51fb 100644
--- a/fd.c
+++ b/fd.c
@@ -108,18 +108,22 @@ fd_close(struct fd *fd)
panic("fd_close");
if(--fd->ref == 0){
- if(fd->type == FD_PIPE){
- pipe_close(fd->pipe, fd->writeable);
- } else if(fd->type == FD_FILE){
- idecref(fd->ip);
+ struct fd dummy = *fd;
+
+ fd->ref = 0;
+ fd->type = FD_CLOSED;
+ release(&fd_table_lock);
+
+ if(dummy.type == FD_PIPE){
+ pipe_close(dummy.pipe, dummy.writeable);
+ } else if(dummy.type == FD_FILE){
+ idecref(dummy.ip);
} else {
panic("fd_close");
}
- fd->ref = 0;
- fd->type = FD_CLOSED;
+ } else {
+ release(&fd_table_lock);
}
-
- release(&fd_table_lock);
}
int
diff --git a/fs.c b/fs.c
index dbecb41..37b964d 100644
--- a/fs.c
+++ b/fs.c
@@ -286,14 +286,8 @@ iput(struct inode *ip)
void
idecref(struct inode *ip)
{
- acquire(&inode_table_lock);
-
- if(ip->count < 1)
- panic("idecref");
-
- ip->count -= 1;
-
- release(&inode_table_lock);
+ ilock(ip);
+ iput(ip);
}
void
@@ -376,34 +370,37 @@ writei(struct inode *ip, char *addr, uint off, uint n)
}
}
+// look up a path name, in one of three modes.
+// NAMEI_LOOKUP: return locked target inode.
+// NAMEI_CREATE: return locked parent inode.
+// but return 0 if name does exist.
+// NAMEI_DELETE: return locked parent inode, offset of dirent in *ret_off.
+// return 0 if name doesn't exist.
struct inode *
-namei(char *path, uint *ret_pinum)
+namei(char *path, int mode, uint *ret_off)
{
struct inode *dp;
- char *cp = path;
+ char *cp = path, *cp1;
uint off, dev;
struct buf *bp;
struct dirent *ep;
- int i;
+ int i, atend;
unsigned ninum;
- unsigned pinum;
-
+
dp = iget(rootdev, 1);
- pinum = dp->inum;
while(*cp == '/')
cp++;
while(1){
- if(*cp == '\0') {
- if (ret_pinum)
- *ret_pinum = pinum;
- return dp;
+ if(*cp == '\0'){
+ if(mode == NAMEI_LOOKUP)
+ return dp;
+ iput(dp);
+ return 0;
}
if(dp->type != T_DIR){
- if (ret_pinum)
- *ret_pinum = pinum;
iput(dp);
return 0;
}
@@ -419,6 +416,7 @@ namei(char *path, uint *ret_pinum)
if(cp[i] != ep->name[i])
break;
if((cp[i] == '\0' || cp[i] == '/') && (i >= DIRSIZ || ep->name[i] == '\0')){
+ off += (uchar*)ep - bp->data;
ninum = ep->inum;
brelse(bp);
cp += i;
@@ -427,14 +425,22 @@ namei(char *path, uint *ret_pinum)
}
brelse(bp);
}
+ atend = 1;
+ for(cp1 = cp; *cp1; cp1++)
+ if(*cp1 == '/')
+ atend = 0;
+ if(mode == NAMEI_CREATE && atend)
+ return dp;
+
iput(dp);
- if (ret_pinum)
- *ret_pinum = pinum;
return 0;
found:
+ if(mode == NAMEI_DELETE && *cp == '\0'){
+ *ret_off = off;
+ return dp;
+ }
dev = dp->dev;
- pinum = dp->inum;
iput(dp);
dp = iget(dev, ninum);
if(dp->type == 0 || dp->nlink < 1)
@@ -453,6 +459,9 @@ wdir(struct inode *dp, char *name, uint ino)
int i;
int lb;
+ if(dp->size % BSIZE)
+ dp->size += (BSIZE - dp->size % BSIZE);
+
for(off = 0; off < dp->size; off += BSIZE) {
bp = bread(dp->dev, bmap(dp, off / BSIZE));
for(ep = (struct dirent *) bp->data;
@@ -469,14 +478,16 @@ wdir(struct inode *dp, char *name, uint ino)
}
dp->addrs[lb] = balloc(dp->dev);
bp = bread(dp->dev, dp->addrs[lb]);
+ memset(bp->data, 0, BSIZE);
ep = (struct dirent *) (bp->data);
+ dp->size += BSIZE;
+
found:
ep->inum = ino;
for(i = 0; i < DIRSIZ && name[i]; i++)
ep->name[i] = name[i];
for( ; i < DIRSIZ; i++)
ep->name[i] = '\0';
- dp->size += sizeof(struct dirent);
bwrite (bp, bmap(dp, off/BSIZE)); // write directory block
brelse(bp);
iupdate(dp);
@@ -486,15 +497,12 @@ struct inode *
mknod(char *cp, short type, short major, short minor)
{
struct inode *ip, *dp;
- uint pinum = 0;
cprintf("mknod: %s %d %d %d\n", cp, type, major, minor);
- if ((ip = namei(cp, &pinum)) != 0) {
- iput(ip);
+ if ((dp = namei(cp, NAMEI_CREATE, 0)) == 0)
return 0;
- }
- dp = iget(rootdev, pinum);
+
ip = ialloc(dp->dev, type);
if (ip == 0) {
iput(dp);
@@ -515,74 +523,81 @@ mknod(char *cp, short type, short major, short minor)
int
unlink(char *cp)
{
- struct inode *ip;
- struct inode *dp;
- struct dirent *ep = 0;
- int off;
- struct buf *bp = 0;
- uint pinum;
-
+ struct inode *ip, *dp;
+ struct dirent de;
+ uint off, inum, cc;
- if ((ip = namei(cp, &pinum)) == 0) {
+ cprintf("unlink(%s)\n", cp);
+
+ if ((dp = namei(cp, NAMEI_DELETE, &off)) == 0) {
cprintf("unlink(%s) it doesn't exist\n", cp);
return -1;
}
- ip->nlink--;
- if (ip->nlink > 0) {
- iput(ip);
- return 0;
+ if((cc = readi(dp, (char*)&de, off, sizeof(de))) != sizeof(de) ||
+ de.inum == 0){
+ cprintf("off %d dp->size %d cc %d de.inum %d",
+ off, dp->size, cc, de.inum);
+ panic("unlink no entry");
}
+ inum = de.inum;
+ cprintf("dinum %d off %d de %s/%d\n",
+ dp->inum, off, de.name, de.inum);
- dp = iget(rootdev, pinum);
- for(off = 0; off < dp->size; off += BSIZE) {
- bp = bread(dp->dev, bmap(dp, off / BSIZE));
- for(ep = (struct dirent *) bp->data;
- ep < (struct dirent *) (bp->data + BSIZE);
- ep++){
- if(ep->inum == ip->inum) {
- goto found;
- }
- }
- brelse(bp);
- }
- panic("unlink: entry doesn't exist\n");
+ memset(&de, 0, sizeof(de));
+ if(writei(dp, (char*)&de, off, sizeof(de)) != sizeof(de))
+ panic("unlink dir write");
- found:
- ep->inum = 0;
- memset(ep->name, '\0', DIRSIZ);
- bwrite (bp, bmap(dp, off/BSIZE)); // write directory block
- brelse(bp);
- dp->size -= sizeof(struct dirent);
- iupdate (dp);
+ iupdate(dp);
iput(dp);
+
+ ip = iget(dp->dev, inum);
+ if(ip == 0)
+ panic("unlink no inode");
+
+ ip->nlink--;
+
+ iupdate(ip);
iput(ip);
+
return 0;
}
int
link(char *name1, char *name2)
{
- struct inode *ip, *dp, *xip;
- uint pinum = 0;
+ struct inode *ip, *dp;
cprintf("link(%s, %s)\n", name1, name2);
- if ((xip = namei(name2, &pinum)) != 0) {
- cprintf(" failed %s exists\n", name2);
- iput(xip);
+ if ((ip = namei(name1, NAMEI_LOOKUP, 0)) == 0){
+ cprintf(" failed %s does not exist\n", name1);
+ return -1;
+ }
+ if(ip->type == T_DIR){
+ cprintf(" failed %s is a dir\n", name1);
+ iput(ip);
return -1;
}
- if ((ip = namei(name1, &pinum)) == 0){
- cprintf(" failed %s does not exist\n", name1);
+ iunlock(ip);
+
+ if ((dp = namei(name2, NAMEI_CREATE, 0)) == 0) {
+ cprintf(" failed %s exists\n", name2);
+ idecref(ip);
+ return -1;
+ }
+ if(dp->dev != ip->dev){
+ cprintf(" cross-device link\n");
+ idecref(ip);
+ iput(dp);
return -1;
}
+ ilock(ip);
ip->nlink += 1;
iupdate (ip);
- dp = iget(rootdev, pinum);
wdir(dp, name2, ip->inum);
iput(dp);
iput(ip);
diff --git a/fsvar.h b/fsvar.h
index ef678dd..6f4e68a 100644
--- a/fsvar.h
+++ b/fsvar.h
@@ -14,3 +14,7 @@ struct inode {
};
extern uint rootdev;
+
+#define NAMEI_LOOKUP 1
+#define NAMEI_CREATE 2
+#define NAMEI_DELETE 3
diff --git a/syscall.c b/syscall.c
index 4505c89..71a7013 100644
--- a/syscall.c
+++ b/syscall.c
@@ -228,7 +228,7 @@ sys_open(void)
return -1;
if((l = checkstring(arg0)) < 0)
return -1;
- if((ip = namei(cp->mem + arg0, 0)) == 0) {
+ if((ip = namei(cp->mem + arg0, NAMEI_LOOKUP, 0)) == 0) {
if (arg1 & O_CREATE) {
if (l >= DIRSIZ)
return -1;
@@ -356,7 +356,7 @@ sys_exec(void)
return -1;
if(checkstring(arg0) < 0)
return -1;
- ip = namei(cp->mem + arg0, 0);
+ ip = namei(cp->mem + arg0, NAMEI_LOOKUP, 0);
if(ip == 0)
return -1;
@@ -494,7 +494,7 @@ sys_block(void)
ip->type, ip->nlink, ip->size, ip->addrs[0]);
iput(ip);
- ip = namei(".././//./../usertests", 0);
+ ip = namei(".././//./../usertests", NAMEI_LOOKUP, 0);
if(ip){
cprintf("namei(usertests): %d %d %d %d %d %d %d %d\n",
ip->dev, ip->inum, ip->count, ip->busy,
diff --git a/usertests.c b/usertests.c
index 2d6b065..c3e9113 100644
--- a/usertests.c
+++ b/usertests.c
@@ -231,7 +231,7 @@ void
createdelete()
{
int pid, i, fd;
- int n = 10; // for now, fit in one directory block
+ int n = 20;
char name[32];
pid = fork();
--
GitLab