I have run 2.4.19-pre4-ac1 with path_lookup on an 8-way SMP and
it looks good. Here is the latest version of path_lookup for
your recently announced pre4-ac1 kernel.
This is a cleanup precursor to a fast_walk patch I wrote based on
suggestions from Al Viro to decrease cacheline bouncing of a global
reference counter during path lookup of dentries in the cache.
That patch has shown 50% reduction in BKL contention on an 8-way
SMP running dbench. Incidentally, it has also shown a 90% reduction in
dcache_lock contention on a 16-way NUMA-Q building the kernel.
Results and patch coming soon.
This patch included simply cleans up source code by changing the many calls
of the form: if(path_init) error = path_walk to one function path_lookup.
By wrapping path_init with path_lookup I will be able to control which
filesystems use the fast_walk mechanism.
Linus has already accepted this patch from Al Viro in 2.5.6, his comments:
<viro@math.psu.edu> (02/03/02 1.375.1.84)
[PATCH] path_lookup()
New helper:
path_lookup(name, flags, nd)
{
int err = 0;
if (path_init(name, flags, nd))
err = path_walk(name, nd);
return err;
}
Places doing that by hand converted to calling it.
Actually, quite a few of them were doing equivalent of __user_walk()
(getname() and if it was successful - call path_lookup() and putname()).
Converted to calling __user_walk().
Please consider this patch for inclusion in your 2.4.19 tree.
Following is the linux-2.4.19-pre4-ac1 version. Also available at:
http://prdownloads.sf.net/lse/path_lookupA5-2.4.19-pre4-ac1.patch
Hanna Linder
hannal@us.ibm.com
IBM Linux Technology Center
------
diff -Nru -X dontdiff linux-2.4.19-pre4-ac1/fs/exec.c linux-path_lookup/fs/exec.c
--- linux-2.4.19-pre4-ac1/fs/exec.c Tue Mar 26 10:38:34 2002
+++ linux-path_lookup/fs/exec.c Tue Mar 26 10:33:01 2002
@@ -351,8 +351,7 @@
struct file *file;
int err = 0;
- if (path_init(name, LOOKUP_FOLLOW|LOOKUP_POSITIVE, &nd))
- err = path_walk(name, &nd);
+ err = path_lookup(name, LOOKUP_FOLLOW|LOOKUP_POSITIVE, &nd);
file = ERR_PTR(err);
if (!err) {
inode = nd.dentry->d_inode;
diff -Nru -X dontdiff linux-2.4.19-pre4-ac1/fs/namei.c linux-path_lookup/fs/namei.c
--- linux-2.4.19-pre4-ac1/fs/namei.c Tue Mar 26 10:37:25 2002
+++ linux-path_lookup/fs/namei.c Tue Mar 26 10:33:01 2002
@@ -739,6 +739,16 @@
}
/* SMP-safe */
+int path_lookup(const char *path, unsigned flags, struct nameidata *nd)
+{
+ int error = 0;
+ if (path_init(path, flags, nd))
+ error = path_walk(path, nd);
+ return error;
+}
+
+
+/* SMP-safe */
int path_init(const char *name, unsigned int flags, struct nameidata *nd)
{
nd->last_type = LAST_ROOT; /* if there are only slashes... */
@@ -844,8 +854,7 @@
err = PTR_ERR(tmp);
if (!IS_ERR(tmp)) {
err = 0;
- if (path_init(tmp, flags, nd))
- err = path_walk(tmp, nd);
+ err = path_lookup(tmp, flags, nd);
putname(tmp);
}
return err;
@@ -999,8 +1008,7 @@
* The simplest case - just a plain lookup.
*/
if (!(flag & O_CREAT)) {
- if (path_init(pathname, lookup_flags(flag), nd))
- error = path_walk(pathname, nd);
+ error = path_lookup(pathname, lookup_flags(flag), nd);
if (error)
return error;
dentry = nd->dentry;
@@ -1010,8 +1018,7 @@
/*
* Create - we need to know the parent.
*/
- if (path_init(pathname, LOOKUP_PARENT, nd))
- error = path_walk(pathname, nd);
+ error = path_lookup(pathname, LOOKUP_PARENT, nd);
if (error)
return error;
@@ -1263,8 +1270,7 @@
if (IS_ERR(tmp))
return PTR_ERR(tmp);
- if (path_init(tmp, LOOKUP_PARENT, &nd))
- error = path_walk(tmp, &nd);
+ error = path_lookup(tmp, LOOKUP_PARENT, &nd);
if (error)
goto out;
dentry = lookup_create(&nd, 0);
@@ -1332,8 +1338,7 @@
struct dentry *dentry;
struct nameidata nd;
- if (path_init(tmp, LOOKUP_PARENT, &nd))
- error = path_walk(tmp, &nd);
+ error = path_lookup(tmp, LOOKUP_PARENT, &nd);
if (error)
goto out;
dentry = lookup_create(&nd, 1);
@@ -1427,8 +1432,7 @@
if(IS_ERR(name))
return PTR_ERR(name);
- if (path_init(name, LOOKUP_PARENT, &nd))
- error = path_walk(name, &nd);
+ error = path_lookup(name, LOOKUP_PARENT, &nd);
if (error)
goto exit;
@@ -1496,8 +1500,7 @@
if(IS_ERR(name))
return PTR_ERR(name);
- if (path_init(name, LOOKUP_PARENT, &nd))
- error = path_walk(name, &nd);
+ error = path_lookup(name, LOOKUP_PARENT, &nd);
if (error)
goto exit;
error = -EISDIR;
@@ -1568,8 +1571,7 @@
struct dentry *dentry;
struct nameidata nd;
- if (path_init(to, LOOKUP_PARENT, &nd))
- error = path_walk(to, &nd);
+ error = path_lookup(to, LOOKUP_PARENT, &nd);
if (error)
goto out;
dentry = lookup_create(&nd, 0);
@@ -1639,25 +1641,18 @@
asmlinkage long sys_link(const char * oldname, const char * newname)
{
int error;
- char * from;
char * to;
- from = getname(oldname);
- if(IS_ERR(from))
- return PTR_ERR(from);
to = getname(newname);
error = PTR_ERR(to);
if (!IS_ERR(to)) {
struct dentry *new_dentry;
struct nameidata nd, old_nd;
- error = 0;
- if (path_init(from, LOOKUP_POSITIVE, &old_nd))
- error = path_walk(from, &old_nd);
+ error = __user_walk(oldname, LOOKUP_POSITIVE, &old_nd);
if (error)
goto exit;
- if (path_init(to, LOOKUP_PARENT, &nd))
- error = path_walk(to, &nd);
+ error = path_lookup(to, LOOKUP_PARENT, &nd);
if (error)
goto out;
error = -EXDEV;
@@ -1677,8 +1672,6 @@
exit:
putname(to);
}
- putname(from);
-
return error;
}
@@ -1857,14 +1850,11 @@
struct dentry * old_dentry, *new_dentry;
struct nameidata oldnd, newnd;
- if (path_init(oldname, LOOKUP_PARENT, &oldnd))
- error = path_walk(oldname, &oldnd);
-
+ error = path_lookup(oldname, LOOKUP_PARENT, &oldnd);
if (error)
goto exit;
- if (path_init(newname, LOOKUP_PARENT, &newnd))
- error = path_walk(newname, &newnd);
+ error = path_lookup(newname, LOOKUP_PARENT, &newnd);
if (error)
goto exit1;
diff -Nru -X dontdiff linux-2.4.19-pre4-ac1/fs/namespace.c linux-path_lookup/fs/namespace.c
--- linux-2.4.19-pre4-ac1/fs/namespace.c Tue Mar 26 10:38:36 2002
+++ linux-path_lookup/fs/namespace.c Tue Mar 26 10:33:01 2002
@@ -364,17 +364,9 @@
asmlinkage long sys_umount(char * name, int flags)
{
struct nameidata nd;
- char *kname;
int retval;
- kname = getname(name);
- retval = PTR_ERR(kname);
- if (IS_ERR(kname))
- goto out;
- retval = 0;
- if (path_init(kname, LOOKUP_POSITIVE|LOOKUP_FOLLOW, &nd))
- retval = path_walk(kname, &nd);
- putname(kname);
+ retval = __user_walk(name, LOOKUP_POSITIVE|LOOKUP_FOLLOW, &nd);
if (retval)
goto out;
retval = -EINVAL;
@@ -501,8 +493,7 @@
return err;
if (!old_name || !*old_name)
return -EINVAL;
- if (path_init(old_name, LOOKUP_POSITIVE|LOOKUP_FOLLOW, &old_nd))
- err = path_walk(old_name, &old_nd);
+ err = path_lookup(old_name, LOOKUP_POSITIVE|LOOKUP_FOLLOW, &old_nd);
if (err)
return err;
@@ -568,8 +559,7 @@
return -EPERM;
if (!old_name || !*old_name)
return -EINVAL;
- if (path_init(old_name, LOOKUP_POSITIVE|LOOKUP_FOLLOW, &old_nd))
- err = path_walk(old_name, &old_nd);
+ err = path_lookup(old_name, LOOKUP_POSITIVE|LOOKUP_FOLLOW, &old_nd);
if (err)
return err;
@@ -726,8 +716,7 @@
flags &= ~(MS_NOSUID|MS_NOEXEC|MS_NODEV);
/* ... and get the mountpoint */
- if (path_init(dir_name, LOOKUP_FOLLOW|LOOKUP_POSITIVE, &nd))
- retval = path_walk(dir_name, &nd);
+ retval = path_lookup(dir_name, LOOKUP_FOLLOW|LOOKUP_POSITIVE, &nd);
if (retval)
return retval;
@@ -826,7 +815,6 @@
{
struct vfsmount *tmp;
struct nameidata new_nd, old_nd, parent_nd, root_parent, user_nd;
- char *name;
int error;
if (!capable(CAP_SYS_ADMIN))
@@ -834,28 +822,14 @@
lock_kernel();
- name = getname(new_root);
- error = PTR_ERR(name);
- if (IS_ERR(name))
- goto out0;
- error = 0;
- if (path_init(name, LOOKUP_POSITIVE|LOOKUP_FOLLOW|LOOKUP_DIRECTORY, &new_nd))
- error = path_walk(name, &new_nd);
- putname(name);
+ error = __user_walk(new_root, LOOKUP_POSITIVE|LOOKUP_FOLLOW|LOOKUP_DIRECTORY, &new_nd);
if (error)
goto out0;
error = -EINVAL;
if (!check_mnt(new_nd.mnt))
goto out1;
- name = getname(put_old);
- error = PTR_ERR(name);
- if (IS_ERR(name))
- goto out1;
- error = 0;
- if (path_init(name, LOOKUP_POSITIVE|LOOKUP_FOLLOW|LOOKUP_DIRECTORY, &old_nd))
- error = path_walk(name, &old_nd);
- putname(name);
+ error = __user_walk(put_old, LOOKUP_POSITIVE|LOOKUP_FOLLOW|LOOKUP_DIRECTORY, &old_nd);
if (error)
goto out1;
diff -Nru -X dontdiff linux-2.4.19-pre4-ac1/fs/open.c linux-path_lookup/fs/open.c
--- linux-2.4.19-pre4-ac1/fs/open.c Tue Mar 26 10:38:36 2002
+++ linux-path_lookup/fs/open.c Tue Mar 26 10:33:01 2002
@@ -384,17 +384,8 @@
{
int error;
struct nameidata nd;
- char *name;
- name = getname(filename);
- error = PTR_ERR(name);
- if (IS_ERR(name))
- goto out;
-
- error = 0;
- if (path_init(name,LOOKUP_POSITIVE|LOOKUP_FOLLOW|LOOKUP_DIRECTORY,&nd))
- error = path_walk(name, &nd);
- putname(name);
+ error = __user_walk(filename,LOOKUP_POSITIVE|LOOKUP_FOLLOW|LOOKUP_DIRECTORY,&nd);
if (error)
goto out;
@@ -444,17 +435,9 @@
{
int error;
struct nameidata nd;
- char *name;
-
- name = getname(filename);
- error = PTR_ERR(name);
- if (IS_ERR(name))
- goto out;
- path_init(name, LOOKUP_POSITIVE | LOOKUP_FOLLOW |
+ error = __user_walk(filename, LOOKUP_POSITIVE | LOOKUP_FOLLOW |
LOOKUP_DIRECTORY | LOOKUP_NOALT, &nd);
- error = path_walk(name, &nd);
- putname(name);
if (error)
goto out;
diff -Nru -X dontdiff linux-2.4.19-pre4-ac1/fs/super.c linux-path_lookup/fs/super.c
--- linux-2.4.19-pre4-ac1/fs/super.c Tue Mar 26 10:38:36 2002
+++ linux-path_lookup/fs/super.c Tue Mar 26 10:33:01 2002
@@ -575,8 +575,7 @@
/* What device it is? */
if (!dev_name || !*dev_name)
return ERR_PTR(-EINVAL);
- if (path_init(dev_name, LOOKUP_FOLLOW|LOOKUP_POSITIVE, &nd))
- error = path_walk(dev_name, &nd);
+ error = path_lookup(dev_name, LOOKUP_FOLLOW|LOOKUP_POSITIVE, &nd);
if (error)
return ERR_PTR(error);
inode = nd.dentry->d_inode;
diff -Nru -X dontdiff linux-2.4.19-pre4-ac1/include/linux/fs.h linux-path_lookup/include/linux/fs.h
--- linux-2.4.19-pre4-ac1/include/linux/fs.h Tue Mar 26 10:38:37 2002
+++ linux-path_lookup/include/linux/fs.h Tue Mar 26 10:33:01 2002
@@ -1348,6 +1348,7 @@
extern int FASTCALL(__user_walk(const char *, unsigned, struct nameidata *));
extern int FASTCALL(path_init(const char *, unsigned, struct nameidata *));
extern int FASTCALL(path_walk(const char *, struct nameidata *));
+extern int FASTCALL(path_lookup(const char *, unsigned, struct nameidata *));
extern int FASTCALL(link_path_walk(const char *, struct nameidata *));
extern void path_release(struct nameidata *);
extern int follow_down(struct vfsmount **, struct dentry **);
-
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