[patch 39/58] Take fs_struct handling to new file (fs/fs_struct.c)

From: Greg KH
Date: Wed May 06 2009 - 18:11:01 EST

2.6.29-stable review patch. If anyone has any objections, please let us know.

------------------

From: Al Viro <viro@xxxxxxxxxxxxxxxxxx>

commit 3e93cd671813e204c258f1e6c797959920cf7772 upstream.

Pure code move; two new helper functions for nfsd and daemonize
(unshare_fs_struct() and daemonize_fs_struct() resp.; for now -
the same code as used to be in callers). unshare_fs_struct()
exported (for nfsd, as copy_fs_struct()/exit_fs() used to be),
copy_fs_struct() and exit_fs() don't need exports anymore.

Signed-off-by: Al Viro <viro@xxxxxxxxxxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxx>

---
fs/Makefile | 2
fs/fs_struct.c | 141 ++++++++++++++++++++++++++++++++++++++++++++++
fs/internal.h | 6 +
fs/namei.c | 7 --
fs/namespace.c | 68 ----------------------
fs/nfsd/nfssvc.c | 7 --
include/linux/fs_struct.h | 2
kernel/exit.c | 31 ----------
kernel/fork.c | 29 ---------
9 files changed, 155 insertions(+), 138 deletions(-)

--- /dev/null
+++ b/fs/fs_struct.c
@@ -0,0 +1,141 @@
+#include <linux/module.h>
+#include <linux/sched.h>
+#include <linux/fs.h>
+#include <linux/path.h>
+#include <linux/slab.h>
+
+/*
+ * Replace the fs->{rootmnt,root} with {mnt,dentry}. Put the old values.
+ * It can block.
+ */
+void set_fs_root(struct fs_struct *fs, struct path *path)
+{
+ struct path old_root;
+
+ write_lock(&fs->lock);
+ old_root = fs->root;
+ fs->root = *path;
+ path_get(path);
+ write_unlock(&fs->lock);
+ if (old_root.dentry)
+ path_put(&old_root);
+}
+
+/*
+ * Replace the fs->{pwdmnt,pwd} with {mnt,dentry}. Put the old values.
+ * It can block.
+ */
+void set_fs_pwd(struct fs_struct *fs, struct path *path)
+{
+ struct path old_pwd;
+
+ write_lock(&fs->lock);
+ old_pwd = fs->pwd;
+ fs->pwd = *path;
+ path_get(path);
+ write_unlock(&fs->lock);
+
+ if (old_pwd.dentry)
+ path_put(&old_pwd);
+}
+
+void chroot_fs_refs(struct path *old_root, struct path *new_root)
+{
+ struct task_struct *g, *p;
+ struct fs_struct *fs;
+ int count = 0;
+
+ read_lock(&tasklist_lock);
+ do_each_thread(g, p) {
+ task_lock(p);
+ fs = p->fs;
+ if (fs) {
+ write_lock(&fs->lock);
+ if (fs->root.dentry == old_root->dentry
+ && fs->root.mnt == old_root->mnt) {
+ path_get(new_root);
+ fs->root = *new_root;
+ count++;
+ }
+ if (fs->pwd.dentry == old_root->dentry
+ && fs->pwd.mnt == old_root->mnt) {
+ path_get(new_root);
+ fs->pwd = *new_root;
+ count++;
+ }
+ write_unlock(&fs->lock);
+ }
+ task_unlock(p);
+ } while_each_thread(g, p);
+ read_unlock(&tasklist_lock);
+ while (count--)
+ path_put(old_root);
+}
+
+void put_fs_struct(struct fs_struct *fs)
+{
+ /* No need to hold fs->lock if we are killing it */
+ if (atomic_dec_and_test(&fs->count)) {
+ path_put(&fs->root);
+ path_put(&fs->pwd);
+ kmem_cache_free(fs_cachep, fs);
+ }
+}
+
+void exit_fs(struct task_struct *tsk)
+{
+ struct fs_struct * fs = tsk->fs;
+
+ if (fs) {
+ task_lock(tsk);
+ tsk->fs = NULL;
+ task_unlock(tsk);
+ put_fs_struct(fs);
+ }
+}
+
+struct fs_struct *copy_fs_struct(struct fs_struct *old)
+{
+ struct fs_struct *fs = kmem_cache_alloc(fs_cachep, GFP_KERNEL);
+ /* We don't need to lock fs - think why ;-) */
+ if (fs) {
+ atomic_set(&fs->count, 1);
+ 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);
+ }
+ return fs;
+}
+
+int unshare_fs_struct(void)
+{
+ struct fs_struct *fsp = copy_fs_struct(current->fs);
+ if (!fsp)
+ return -ENOMEM;
+ exit_fs(current);
+ current->fs = fsp;
+ return 0;
+}
+EXPORT_SYMBOL_GPL(unshare_fs_struct);
+
+/* to be mentioned only in INIT_TASK */
+struct fs_struct init_fs = {
+ .count = ATOMIC_INIT(1),
+ .lock = __RW_LOCK_UNLOCKED(init_fs.lock),
+ .umask = 0022,
+};
+
+void daemonize_fs_struct(void)
+{
+ struct fs_struct *fs;
+
+ exit_fs(current); /* current->fs->count--; */
+ fs = &init_fs;
+ current->fs = fs;
+ atomic_inc(&fs->count);
+}
--- a/fs/internal.h
+++ b/fs/internal.h
@@ -11,6 +11,7 @@

struct super_block;
struct linux_binprm;
+struct path;

/*
* block_dev.c
@@ -60,3 +61,8 @@ extern void umount_tree(struct vfsmount
extern struct vfsmount *copy_tree(struct vfsmount *, struct dentry *, int);

extern void __init mnt_init(void);
+
+/*
+ * fs_struct.c
+ */
+extern void chroot_fs_refs(struct path *, struct path *);
--- a/fs/Makefile
+++ b/fs/Makefile
@@ -11,7 +11,7 @@ obj-y := open.o read_write.o file_table.
attr.o bad_inode.o file.o filesystems.o namespace.o \
seq_file.o xattr.o libfs.o fs-writeback.o \
pnode.o drop_caches.o splice.o sync.o utimes.o \
- stack.o
+ stack.o fs_struct.o

ifeq ($(CONFIG_BLOCK),y)
obj-y += buffer.o bio.o block_dev.o direct-io.o mpage.o ioprio.o
--- a/fs/namei.c
+++ b/fs/namei.c
@@ -2891,10 +2891,3 @@ EXPORT_SYMBOL(vfs_symlink);
EXPORT_SYMBOL(vfs_unlink);
EXPORT_SYMBOL(dentry_unhash);
EXPORT_SYMBOL(generic_readlink);
-
-/* to be mentioned only in INIT_TASK */
-struct fs_struct init_fs = {
- .count = ATOMIC_INIT(1),
- .lock = __RW_LOCK_UNLOCKED(init_fs.lock),
- .umask = 0022,
-};
--- a/fs/namespace.c
+++ b/fs/namespace.c
@@ -2089,74 +2089,6 @@ out1:
}

/*
- * Replace the fs->{rootmnt,root} with {mnt,dentry}. Put the old values.
- * It can block. Requires the big lock held.
- */
-void set_fs_root(struct fs_struct *fs, struct path *path)
-{
- struct path old_root;
-
- write_lock(&fs->lock);
- old_root = fs->root;
- fs->root = *path;
- path_get(path);
- write_unlock(&fs->lock);
- if (old_root.dentry)
- path_put(&old_root);
-}
-
-/*
- * Replace the fs->{pwdmnt,pwd} with {mnt,dentry}. Put the old values.
- * It can block. Requires the big lock held.
- */
-void set_fs_pwd(struct fs_struct *fs, struct path *path)
-{
- struct path old_pwd;
-
- write_lock(&fs->lock);
- old_pwd = fs->pwd;
- fs->pwd = *path;
- path_get(path);
- write_unlock(&fs->lock);
-
- if (old_pwd.dentry)
- path_put(&old_pwd);
-}
-
-static void chroot_fs_refs(struct path *old_root, struct path *new_root)
-{
- struct task_struct *g, *p;
- struct fs_struct *fs;
- int count = 0;
-
- read_lock(&tasklist_lock);
- do_each_thread(g, p) {
- task_lock(p);
- fs = p->fs;
- if (fs) {
- write_lock(&fs->lock);
- if (fs->root.dentry == old_root->dentry
- && fs->root.mnt == old_root->mnt) {
- path_get(new_root);
- fs->root = *new_root;
- count++;
- }
- if (fs->pwd.dentry == old_root->dentry
- && fs->pwd.mnt == old_root->mnt) {
- path_get(new_root);
- fs->pwd = *new_root;
- count++;
- }
- write_unlock(&fs->lock);
- }
- task_unlock(p);
- } while_each_thread(g, p);
- read_unlock(&tasklist_lock);
- while (count--)
- path_put(old_root);
-}
-
-/*
* pivot_root Semantics:
* Moves the root file system of the current process to the directory put_old,
* makes new_root as the new root file system of the current process, and sets
--- a/fs/nfsd/nfssvc.c
+++ b/fs/nfsd/nfssvc.c
@@ -404,7 +404,6 @@ static int
nfsd(void *vrqstp)
{
struct svc_rqst *rqstp = (struct svc_rqst *) vrqstp;
- struct fs_struct *fsp;
int err, preverr = 0;

/* Lock module and set up kernel thread */
@@ -413,13 +412,11 @@ nfsd(void *vrqstp)
/* At this point, the thread shares current->fs
* with the init process. We need to create files with a
* umask of 0 instead of init's umask. */
- fsp = copy_fs_struct(current->fs);
- if (!fsp) {
+ if (unshare_fs_struct() < 0) {
printk("Unable to start nfsd thread: out of memory\n");
goto out;
}
- exit_fs(current);
- current->fs = fsp;
+
current->fs->umask = 0;

/*
--- a/include/linux/fs_struct.h
+++ b/include/linux/fs_struct.h
@@ -20,5 +20,7 @@ extern void set_fs_root(struct fs_struct
extern void set_fs_pwd(struct fs_struct *, struct path *);
extern struct fs_struct *copy_fs_struct(struct fs_struct *);
extern void put_fs_struct(struct fs_struct *);
+extern void daemonize_fs_struct(void);
+extern int unshare_fs_struct(void);

#endif /* _LINUX_FS_STRUCT_H */
--- a/kernel/exit.c
+++ b/kernel/exit.c
@@ -429,7 +429,6 @@ EXPORT_SYMBOL(disallow_signal);
void daemonize(const char *name, ...)
{
va_list args;
- struct fs_struct *fs;
sigset_t blocked;

va_start(args, name);
@@ -462,11 +461,7 @@ void daemonize(const char *name, ...)

/* Become as one with the init task */

- exit_fs(current); /* current->fs->count--; */
- fs = init_task.fs;
- current->fs = fs;
- atomic_inc(&fs->count);
-
+ daemonize_fs_struct();
exit_files(current);
current->files = init_task.files;
atomic_inc(&current->files->count);
@@ -565,30 +560,6 @@ void exit_files(struct task_struct *tsk)
}
}

-void put_fs_struct(struct fs_struct *fs)
-{
- /* No need to hold fs->lock if we are killing it */
- if (atomic_dec_and_test(&fs->count)) {
- path_put(&fs->root);
- path_put(&fs->pwd);
- kmem_cache_free(fs_cachep, fs);
- }
-}
-
-void exit_fs(struct task_struct *tsk)
-{
- struct fs_struct * fs = tsk->fs;
-
- if (fs) {
- task_lock(tsk);
- tsk->fs = NULL;
- task_unlock(tsk);
- put_fs_struct(fs);
- }
-}
-
-EXPORT_SYMBOL_GPL(exit_fs);
-
#ifdef CONFIG_MM_OWNER
/*
* Task p is exiting and it owned mm, lets find a new owner for it
--- a/kernel/fork.c
+++ b/kernel/fork.c
@@ -676,38 +676,13 @@ fail_nomem:
return retval;
}

-static struct fs_struct *__copy_fs_struct(struct fs_struct *old)
-{
- struct fs_struct *fs = kmem_cache_alloc(fs_cachep, GFP_KERNEL);
- /* We don't need to lock fs - think why ;-) */
- if (fs) {
- atomic_set(&fs->count, 1);
- 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);
- }
- return fs;
-}
-
-struct fs_struct *copy_fs_struct(struct fs_struct *old)
-{
- return __copy_fs_struct(old);
-}
-
-EXPORT_SYMBOL_GPL(copy_fs_struct);
-
static int copy_fs(unsigned long clone_flags, struct task_struct *tsk)
{
if (clone_flags & CLONE_FS) {
atomic_inc(&current->fs->count);
return 0;
}
- tsk->fs = __copy_fs_struct(current->fs);
+ tsk->fs = copy_fs_struct(current->fs);
if (!tsk->fs)
return -ENOMEM;
return 0;
@@ -1545,7 +1520,7 @@ static int unshare_fs(unsigned long unsh

if ((unshare_flags & CLONE_FS) &&
(fs && atomic_read(&fs->count) > 1)) {
- *new_fsp = __copy_fs_struct(current->fs);
+ *new_fsp = copy_fs_struct(current->fs);
if (!*new_fsp)
return -ENOMEM;
}


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