[PATCH 2/7] vfs: add helpers to get root and pwd

From: Miklos Szeredi
Date: Tue Aug 10 2010 - 05:44:37 EST

From: Miklos Szeredi <mszeredi@xxxxxxx>

Add three helpers that retrieve a refcounted copy of the root and cwd
from the supplied fs_struct.

get_fs_root()
get_fs_pwd()
get_fs_root_and_pwd()

Signed-off-by: Miklos Szeredi <mszeredi@xxxxxxx>
---
fs/cachefiles/daemon.c | 14 ++------------
fs/dcache.c | 12 ++----------
fs/fs_struct.c | 7 +------
fs/namei.c | 15 +++------------
fs/namespace.c | 5 +----
fs/proc/base.c | 22 +++++++++++-----------
include/linux/fs_struct.h | 27 +++++++++++++++++++++++++++
kernel/auditsc.c | 9 ++-------
8 files changed, 49 insertions(+), 62 deletions(-)

Index: linux-2.6/fs/fs_struct.c
===================================================================
--- linux-2.6.orig/fs/fs_struct.c 2010-07-06 17:59:05.000000000 +0200
+++ linux-2.6/fs/fs_struct.c 2010-07-06 18:08:06.000000000 +0200
@@ -106,12 +106,7 @@ struct fs_struct *copy_fs_struct(struct
fs->in_exec = 0;
rwlock_init(&fs->lock);
fs->umask = old->umask;
- read_lock(&old->lock);
- fs->root = old->root;
- path_get(&old->root);
- fs->pwd = old->pwd;
- path_get(&old->pwd);
- read_unlock(&old->lock);
+ get_fs_root_and_pwd(old, &fs->root, &fs->pwd);
}
return fs;
}
Index: linux-2.6/include/linux/fs_struct.h
===================================================================
--- linux-2.6.orig/include/linux/fs_struct.h 2010-07-06 17:59:05.000000000 +0200
+++ linux-2.6/include/linux/fs_struct.h 2010-07-06 18:08:06.000000000 +0200
@@ -21,4 +21,31 @@ extern void free_fs_struct(struct fs_str
extern void daemonize_fs_struct(void);
extern int unshare_fs_struct(void);

+static inline void get_fs_root(struct fs_struct *fs, struct path *root)
+{
+ read_lock(&fs->lock);
+ *root = fs->root;
+ path_get(root);
+ read_unlock(&fs->lock);
+}
+
+static inline void get_fs_pwd(struct fs_struct *fs, struct path *pwd)
+{
+ read_lock(&fs->lock);
+ *pwd = fs->pwd;
+ path_get(pwd);
+ read_unlock(&fs->lock);
+}
+
+static inline void get_fs_root_and_pwd(struct fs_struct *fs, struct path *root,
+ struct path *pwd)
+{
+ read_lock(&fs->lock);
+ *root = fs->root;
+ path_get(root);
+ *pwd = fs->pwd;
+ path_get(pwd);
+ read_unlock(&fs->lock);
+}
+
#endif /* _LINUX_FS_STRUCT_H */
Index: linux-2.6/fs/dcache.c
===================================================================
--- linux-2.6.orig/fs/dcache.c 2010-07-06 17:59:05.000000000 +0200
+++ linux-2.6/fs/dcache.c 2010-07-06 18:08:06.000000000 +0200
@@ -2012,10 +2012,7 @@ char *d_path(const struct path *path, ch
if (path->dentry->d_op && path->dentry->d_op->d_dname)
return path->dentry->d_op->d_dname(path->dentry, buf, buflen);

- read_lock(&current->fs->lock);
- root = current->fs->root;
- path_get(&root);
- read_unlock(&current->fs->lock);
+ get_fs_root(current->fs, &root);
spin_lock(&dcache_lock);
tmp = root;
res = __d_path(path, &tmp, buf, buflen);
@@ -2110,12 +2107,7 @@ SYSCALL_DEFINE2(getcwd, char __user *, b
if (!page)
return -ENOMEM;

- read_lock(&current->fs->lock);
- pwd = current->fs->pwd;
- path_get(&pwd);
- root = current->fs->root;
- path_get(&root);
- read_unlock(&current->fs->lock);
+ get_fs_root_and_pwd(current->fs, &root, &pwd);

error = -ENOENT;
spin_lock(&dcache_lock);
Index: linux-2.6/fs/proc/base.c
===================================================================
--- linux-2.6.orig/fs/proc/base.c 2010-07-06 17:59:05.000000000 +0200
+++ linux-2.6/fs/proc/base.c 2010-07-06 18:08:06.000000000 +0200
@@ -148,18 +148,13 @@ static unsigned int pid_entry_count_dirs
return count;
}

-static int get_fs_path(struct task_struct *task, struct path *path, bool root)
+static int get_task_root(struct task_struct *task, struct path *root)
{
- struct fs_struct *fs;
int result = -ENOENT;

task_lock(task);
- fs = task->fs;
- if (fs) {
- read_lock(&fs->lock);
- *path = root ? fs->root : fs->pwd;
- path_get(path);
- read_unlock(&fs->lock);
+ if (task->fs) {
+ get_fs_root(task->fs, root);
result = 0;
}
task_unlock(task);
@@ -172,7 +167,12 @@ static int proc_cwd_link(struct inode *i
int result = -ENOENT;

if (task) {
- result = get_fs_path(task, path, 0);
+ task_lock(task);
+ if (task->fs) {
+ get_fs_pwd(task->fs, path);
+ result = 0;
+ }
+ task_unlock(task);
put_task_struct(task);
}
return result;
@@ -184,7 +184,7 @@ static int proc_root_link(struct inode *
int result = -ENOENT;

if (task) {
- result = get_fs_path(task, path, 1);
+ result = get_task_root(task, path);
put_task_struct(task);
}
return result;
@@ -589,7 +589,7 @@ static int mounts_open_common(struct ino
get_mnt_ns(ns);
}
rcu_read_unlock();
- if (ns && get_fs_path(task, &root, 1) == 0)
+ if (ns && get_task_root(task, &root) == 0)
ret = 0;
put_task_struct(task);
}
Index: linux-2.6/fs/cachefiles/daemon.c
===================================================================
--- linux-2.6.orig/fs/cachefiles/daemon.c 2010-07-06 18:08:00.000000000 +0200
+++ linux-2.6/fs/cachefiles/daemon.c 2010-07-06 18:08:06.000000000 +0200
@@ -552,7 +552,6 @@ static int cachefiles_daemon_tag(struct
*/
static int cachefiles_daemon_cull(struct cachefiles_cache *cache, char *args)
{
- struct fs_struct *fs;
struct path path;
const struct cred *saved_cred;
int ret;
@@ -573,11 +572,7 @@ static int cachefiles_daemon_cull(struct
}

/* extract the directory dentry from the cwd */
- fs = current->fs;
- read_lock(&fs->lock);
- path = fs->pwd;
- path_get(&path);
- read_unlock(&fs->lock);
+ get_fs_pwd(current->fs, &path);

if (!S_ISDIR(path.dentry->d_inode->i_mode))
goto notdir;
@@ -629,7 +624,6 @@ inval:
*/
static int cachefiles_daemon_inuse(struct cachefiles_cache *cache, char *args)
{
- struct fs_struct *fs;
struct path path;
const struct cred *saved_cred;
int ret;
@@ -650,11 +644,7 @@ static int cachefiles_daemon_inuse(struc
}

/* extract the directory dentry from the cwd */
- fs = current->fs;
- read_lock(&fs->lock);
- path = fs->pwd;
- path_get(&path);
- read_unlock(&fs->lock);
+ get_fs_pwd(current->fs, &path);

if (!S_ISDIR(path.dentry->d_inode->i_mode))
goto notdir;
Index: linux-2.6/fs/namei.c
===================================================================
--- linux-2.6.orig/fs/namei.c 2010-07-06 17:59:05.000000000 +0200
+++ linux-2.6/fs/namei.c 2010-07-06 18:08:06.000000000 +0200
@@ -484,13 +484,8 @@ ok:

static __always_inline void set_root(struct nameidata *nd)
{
- if (!nd->root.mnt) {
- struct fs_struct *fs = current->fs;
- read_lock(&fs->lock);
- nd->root = fs->root;
- path_get(&nd->root);
- read_unlock(&fs->lock);
- }
+ if (!nd->root.mnt)
+ get_fs_root(current->fs, &nd->root);
}

static int link_path_walk(const char *, struct nameidata *);
@@ -1016,11 +1011,7 @@ static int path_init(int dfd, const char
nd->path = nd->root;
path_get(&nd->root);
} else if (dfd == AT_FDCWD) {
- struct fs_struct *fs = current->fs;
- read_lock(&fs->lock);
- nd->path = fs->pwd;
- path_get(&fs->pwd);
- read_unlock(&fs->lock);
+ get_fs_pwd(current->fs, &nd->path);
} else {
struct dentry *dentry;

Index: linux-2.6/kernel/auditsc.c
===================================================================
--- linux-2.6.orig/kernel/auditsc.c 2010-07-06 17:59:05.000000000 +0200
+++ linux-2.6/kernel/auditsc.c 2010-07-06 18:08:06.000000000 +0200
@@ -1837,13 +1837,8 @@ void __audit_getname(const char *name)
context->names[context->name_count].ino = (unsigned long)-1;
context->names[context->name_count].osid = 0;
++context->name_count;
- if (!context->pwd.dentry) {
- read_lock(&current->fs->lock);
- context->pwd = current->fs->pwd;
- path_get(&current->fs->pwd);
- read_unlock(&current->fs->lock);
- }
-
+ if (!context->pwd.dentry)
+ get_fs_pwd(current->fs, &context->pwd);
}

/* audit_putname - intercept a putname request
Index: linux-2.6/fs/namespace.c
===================================================================
--- linux-2.6.orig/fs/namespace.c 2010-07-06 17:59:05.000000000 +0200
+++ linux-2.6/fs/namespace.c 2010-07-06 18:08:06.000000000 +0200
@@ -2208,10 +2208,7 @@ SYSCALL_DEFINE2(pivot_root, const char _
goto out1;
}

- read_lock(&current->fs->lock);
- root = current->fs->root;
- path_get(&current->fs->root);
- read_unlock(&current->fs->lock);
+ get_fs_root(current->fs, &root);
down_write(&namespace_sem);
mutex_lock(&old.dentry->d_inode->i_mutex);
error = -EINVAL;

--
--
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