Patch from Maneesh Soni <maneesh@in.ibm.com>
dcache_rcu-2 is for reversing fast_walk code introduced in 2.5.11.
fast_walk code hold the dcache_lock for longer durations.
namei.c | 138 ++++++++++++++++++++++------------------------------------
namespace.c | 4 -
linux/namei.h | 2
3 files changed, 54 insertions(+), 90 deletions(-)
diff -puN fs/namei.c~dcache_rcu-fast_walk-revert fs/namei.c
--- 25/fs/namei.c~dcache_rcu-fast_walk-revert 2003-02-04 22:02:53.000000000 -0800
+++ 25-akpm/fs/namei.c 2003-02-04 22:02:53.000000000 -0800
@@ -286,27 +286,6 @@ static struct dentry * cached_lookup(str
return dentry;
}
-/*for fastwalking*/
-static inline void unlock_nd(struct nameidata *nd)
-{
- struct vfsmount *mnt = nd->old_mnt;
- struct dentry *dentry = nd->old_dentry;
- mntget(nd->mnt);
- dget_locked(nd->dentry);
- nd->old_mnt = NULL;
- nd->old_dentry = NULL;
- spin_unlock(&dcache_lock);
- dput(dentry);
- mntput(mnt);
-}
-
-static inline void lock_nd(struct nameidata *nd)
-{
- spin_lock(&dcache_lock);
- nd->old_mnt = nd->mnt;
- nd->old_dentry = nd->dentry;
-}
-
/*
* Short-cut version of permission(), for calling by
* path_walk(), when dcache lock is held. Combines parts
@@ -451,11 +430,18 @@ static int follow_mount(struct vfsmount
{
int res = 0;
while (d_mountpoint(*dentry)) {
- struct vfsmount *mounted = lookup_mnt(*mnt, *dentry);
- if (!mounted)
+ struct vfsmount *mounted;
+ spin_lock(&dcache_lock);
+ mounted = lookup_mnt(*mnt, *dentry);
+ if (!mounted) {
+ spin_unlock(&dcache_lock);
break;
- *mnt = mounted;
- *dentry = mounted->mnt_root;
+ }
+ *mnt = mntget(mounted);
+ spin_unlock(&dcache_lock);
+ dput(*dentry);
+ mntput(mounted->mnt_parent);
+ *dentry = dget(mounted->mnt_root);
res = 1;
}
return res;
@@ -488,17 +474,32 @@ static inline void follow_dotdot(struct
{
while(1) {
struct vfsmount *parent;
+ struct dentry *old = *dentry;
+
+ read_lock(¤t->fs->lock);
if (*dentry == current->fs->root &&
- *mnt == current->fs->rootmnt)
+ *mnt == current->fs->rootmnt) {
+ read_unlock(¤t->fs->lock);
break;
+ }
+ read_unlock(¤t->fs->lock);
+ spin_lock(&dcache_lock);
if (*dentry != (*mnt)->mnt_root) {
- *dentry = (*dentry)->d_parent;
+ *dentry = dget((*dentry)->d_parent);
+ spin_unlock(&dcache_lock);
+ dput(old);
break;
}
- parent=(*mnt)->mnt_parent;
- if (parent == *mnt)
+ parent = (*mnt)->mnt_parent;
+ if (parent == *mnt) {
+ spin_unlock(&dcache_lock);
break;
- *dentry=(*mnt)->mnt_mountpoint;
+ }
+ mntget(parent);
+ *dentry = dget((*mnt)->mnt_mountpoint);
+ spin_unlock(&dcache_lock);
+ dput(old);
+ mntput(*mnt);
*mnt = parent;
}
follow_mount(mnt, dentry);
@@ -515,14 +516,13 @@ struct path {
* It _is_ time-critical.
*/
static int do_lookup(struct nameidata *nd, struct qstr *name,
- struct path *path, struct path *cached_path,
- int flags)
+ struct path *path, int flags)
{
struct vfsmount *mnt = nd->mnt;
- struct dentry *dentry = __d_lookup(nd->dentry, name);
+ struct dentry *dentry = d_lookup(nd->dentry, name);
if (!dentry)
- goto dcache_miss;
+ goto need_lookup;
if (dentry->d_op && dentry->d_op->d_revalidate)
goto need_revalidate;
done:
@@ -530,36 +530,21 @@ done:
path->dentry = dentry;
return 0;
-dcache_miss:
- unlock_nd(nd);
-
need_lookup:
dentry = real_lookup(nd->dentry, name, LOOKUP_CONTINUE);
if (IS_ERR(dentry))
goto fail;
- mntget(mnt);
-relock:
- dput(cached_path->dentry);
- mntput(cached_path->mnt);
- cached_path->mnt = mnt;
- cached_path->dentry = dentry;
- lock_nd(nd);
goto done;
need_revalidate:
- mntget(mnt);
- dget_locked(dentry);
- unlock_nd(nd);
if (dentry->d_op->d_revalidate(dentry, flags))
- goto relock;
+ goto done;
if (d_invalidate(dentry))
- goto relock;
+ goto done;
dput(dentry);
- mntput(mnt);
goto need_lookup;
fail:
- lock_nd(nd);
return PTR_ERR(dentry);
}
@@ -573,7 +558,7 @@ fail:
*/
int link_path_walk(const char * name, struct nameidata *nd)
{
- struct path next, pinned = {NULL, NULL};
+ struct path next;
struct inode *inode;
int err;
unsigned int lookup_flags = nd->flags;
@@ -594,10 +579,8 @@ int link_path_walk(const char * name, st
unsigned int c;
err = exec_permission_lite(inode);
- if (err == -EAGAIN) {
- unlock_nd(nd);
+ if (err == -EAGAIN) {
err = permission(inode, MAY_EXEC);
- lock_nd(nd);
}
if (err)
break;
@@ -648,7 +631,7 @@ int link_path_walk(const char * name, st
break;
}
/* This does the actual lookups.. */
- err = do_lookup(nd, &this, &next, &pinned, LOOKUP_CONTINUE);
+ err = do_lookup(nd, &this, &next, LOOKUP_CONTINUE);
if (err)
break;
/* Check mountpoints.. */
@@ -657,21 +640,18 @@ int link_path_walk(const char * name, st
err = -ENOENT;
inode = next.dentry->d_inode;
if (!inode)
- break;
+ goto out_dput;
err = -ENOTDIR;
if (!inode->i_op)
- break;
+ goto out_dput;
if (inode->i_op->follow_link) {
mntget(next.mnt);
- dget_locked(next.dentry);
- unlock_nd(nd);
err = do_follow_link(next.dentry, nd);
dput(next.dentry);
mntput(next.mnt);
if (err)
goto return_err;
- lock_nd(nd);
err = -ENOENT;
inode = nd->dentry->d_inode;
if (!inode)
@@ -680,6 +660,7 @@ int link_path_walk(const char * name, st
if (!inode->i_op)
break;
} else {
+ dput(nd->dentry);
nd->mnt = next.mnt;
nd->dentry = next.dentry;
}
@@ -711,7 +692,7 @@ last_component:
if (err < 0)
break;
}
- err = do_lookup(nd, &this, &next, &pinned, 0);
+ err = do_lookup(nd, &this, &next, 0);
if (err)
break;
follow_mount(&next.mnt, &next.dentry);
@@ -719,16 +700,14 @@ last_component:
if ((lookup_flags & LOOKUP_FOLLOW)
&& inode && inode->i_op && inode->i_op->follow_link) {
mntget(next.mnt);
- dget_locked(next.dentry);
- unlock_nd(nd);
err = do_follow_link(next.dentry, nd);
dput(next.dentry);
mntput(next.mnt);
if (err)
goto return_err;
inode = nd->dentry->d_inode;
- lock_nd(nd);
} else {
+ dput(nd->dentry);
nd->mnt = next.mnt;
nd->dentry = next.dentry;
}
@@ -751,23 +730,19 @@ lookup_parent:
else if (this.len == 2 && this.name[1] == '.')
nd->last_type = LAST_DOTDOT;
return_base:
- unlock_nd(nd);
- dput(pinned.dentry);
- mntput(pinned.mnt);
return 0;
+out_dput:
+ dput(next.dentry);
+ break;
}
- unlock_nd(nd);
path_release(nd);
return_err:
- dput(pinned.dentry);
- mntput(pinned.mnt);
return err;
}
int path_walk(const char * name, struct nameidata *nd)
{
current->total_link_count = 0;
- lock_nd(nd);
return link_path_walk(name, nd);
}
@@ -855,28 +830,24 @@ int path_lookup(const char *name, unsign
{
nd->last_type = LAST_ROOT; /* if there are only slashes... */
nd->flags = flags;
+
+ read_lock(¤t->fs->lock);
if (*name=='/') {
- read_lock(¤t->fs->lock);
if (current->fs->altroot && !(nd->flags & LOOKUP_NOALT)) {
nd->mnt = mntget(current->fs->altrootmnt);
nd->dentry = dget(current->fs->altroot);
read_unlock(¤t->fs->lock);
if (__emul_lookup_dentry(name,nd))
return 0;
- } else {
- read_unlock(¤t->fs->lock);
}
- spin_lock(&dcache_lock);
- nd->mnt = current->fs->rootmnt;
- nd->dentry = current->fs->root;
+ nd->mnt = mntget(current->fs->rootmnt);
+ nd->dentry = dget(current->fs->root);
}
else{
- spin_lock(&dcache_lock);
- nd->mnt = current->fs->pwdmnt;
- nd->dentry = current->fs->pwd;
+ nd->mnt = mntget(current->fs->pwdmnt);
+ nd->dentry = dget(current->fs->pwd);
}
- nd->old_mnt = NULL;
- nd->old_dentry = NULL;
+ read_unlock(¤t->fs->lock);
current->total_link_count = 0;
return link_path_walk(name, nd);
}
@@ -2129,7 +2100,6 @@ __vfs_follow_link(struct nameidata *nd,
/* weird __emul_prefix() stuff did it */
goto out;
}
- lock_nd(nd);
res = link_path_walk(link, nd);
out:
if (current->link_count || res || nd->last_type!=LAST_NORM)
diff -puN fs/namespace.c~dcache_rcu-fast_walk-revert fs/namespace.c
--- 25/fs/namespace.c~dcache_rcu-fast_walk-revert 2003-02-04 22:02:53.000000000 -0800
+++ 25-akpm/fs/namespace.c 2003-02-04 22:02:53.000000000 -0800
@@ -892,12 +892,10 @@ void set_fs_root(struct fs_struct *fs, s
struct dentry *old_root;
struct vfsmount *old_rootmnt;
write_lock(&fs->lock);
- spin_lock(&dcache_lock);
old_root = fs->root;
old_rootmnt = fs->rootmnt;
fs->rootmnt = mntget(mnt);
fs->root = dget(dentry);
- spin_unlock(&dcache_lock);
write_unlock(&fs->lock);
if (old_root) {
dput(old_root);
@@ -916,12 +914,10 @@ void set_fs_pwd(struct fs_struct *fs, st
struct vfsmount *old_pwdmnt;
write_lock(&fs->lock);
- spin_lock(&dcache_lock);
old_pwd = fs->pwd;
old_pwdmnt = fs->pwdmnt;
fs->pwdmnt = mntget(mnt);
fs->pwd = dget(dentry);
- spin_unlock(&dcache_lock);
write_unlock(&fs->lock);
if (old_pwd) {
diff -puN include/linux/namei.h~dcache_rcu-fast_walk-revert include/linux/namei.h
--- 25/include/linux/namei.h~dcache_rcu-fast_walk-revert 2003-02-04 22:02:53.000000000 -0800
+++ 25-akpm/include/linux/namei.h 2003-02-04 22:02:53.000000000 -0800
@@ -11,8 +11,6 @@ struct nameidata {
struct qstr last;
unsigned int flags;
int last_type;
- struct dentry *old_dentry;
- struct vfsmount *old_mnt;
};
/*
_