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Subject[PATCH RT 13/25][RFC 3.0.23-rt39-rc1] fs: fs_struct use seqlock
From: Thomas Gleixner <tglx@linutronix.de>

Replace the open coded seqlock with a real one, so RT can handle it.

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Cc: stable-rt@vger.kernel.org
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
---
fs/exec.c | 4 +-
fs/fhandle.c | 4 +-
fs/fs_struct.c | 46 +++++++++++++++++---------------------------
fs/namei.c | 14 ++++++------
include/linux/fs_struct.h | 16 ++++++--------
kernel/fork.c | 10 ++++----
6 files changed, 41 insertions(+), 53 deletions(-)
diff --git a/fs/exec.c b/fs/exec.c
index 709557e..3116940 100644
--- a/fs/exec.c
+++ b/fs/exec.c
@@ -1230,7 +1230,7 @@ int check_unsafe_exec(struct linux_binprm *bprm)
bprm->unsafe = tracehook_unsafe_exec(p);

n_fs = 1;
- spin_lock(&p->fs->lock);
+ seq_spin_lock(&p->fs->lock);
rcu_read_lock();
for (t = next_thread(p); t != p; t = next_thread(t)) {
if (t->fs == p->fs)
@@ -1247,7 +1247,7 @@ int check_unsafe_exec(struct linux_binprm *bprm)
res = 1;
}
}
- spin_unlock(&p->fs->lock);
+ seq_spin_unlock(&p->fs->lock);

return res;
}
diff --git a/fs/fhandle.c b/fs/fhandle.c
index 6b08864..9f437ac 100644
--- a/fs/fhandle.c
+++ b/fs/fhandle.c
@@ -115,10 +115,10 @@ static struct vfsmount *get_vfsmount_from_fd(int fd)

if (fd == AT_FDCWD) {
struct fs_struct *fs = current->fs;
- spin_lock(&fs->lock);
+ seq_spin_lock(&fs->lock);
path = fs->pwd;
mntget(path.mnt);
- spin_unlock(&fs->lock);
+ seq_spin_unlock(&fs->lock);
} else {
int fput_needed;
struct file *file = fget_light(fd, &fput_needed);
diff --git a/fs/fs_struct.c b/fs/fs_struct.c
index 78b519c..84db5f1 100644
--- a/fs/fs_struct.c
+++ b/fs/fs_struct.c
@@ -26,13 +26,11 @@ void set_fs_root(struct fs_struct *fs, struct path *path)
{
struct path old_root;

- spin_lock(&fs->lock);
- write_seqcount_begin(&fs->seq);
+ write_seqlock(&fs->lock);
old_root = fs->root;
fs->root = *path;
path_get_longterm(path);
- write_seqcount_end(&fs->seq);
- spin_unlock(&fs->lock);
+ write_sequnlock(&fs->lock);
if (old_root.dentry)
path_put_longterm(&old_root);
}
@@ -45,13 +43,11 @@ void set_fs_pwd(struct fs_struct *fs, struct path *path)
{
struct path old_pwd;

- spin_lock(&fs->lock);
- write_seqcount_begin(&fs->seq);
+ write_seqlock(&fs->lock);
old_pwd = fs->pwd;
fs->pwd = *path;
path_get_longterm(path);
- write_seqcount_end(&fs->seq);
- spin_unlock(&fs->lock);
+ write_sequnlock(&fs->lock);

if (old_pwd.dentry)
path_put_longterm(&old_pwd);
@@ -68,8 +64,7 @@ void chroot_fs_refs(struct path *old_root, struct path *new_root)
task_lock(p);
fs = p->fs;
if (fs) {
- spin_lock(&fs->lock);
- write_seqcount_begin(&fs->seq);
+ write_seqlock(&fs->lock);
if (fs->root.dentry == old_root->dentry
&& fs->root.mnt == old_root->mnt) {
path_get_longterm(new_root);
@@ -82,8 +77,7 @@ void chroot_fs_refs(struct path *old_root, struct path *new_root)
fs->pwd = *new_root;
count++;
}
- write_seqcount_end(&fs->seq);
- spin_unlock(&fs->lock);
+ write_sequnlock(&fs->lock);
}
task_unlock(p);
} while_each_thread(g, p);
@@ -106,12 +100,10 @@ void exit_fs(struct task_struct *tsk)
if (fs) {
int kill;
task_lock(tsk);
- spin_lock(&fs->lock);
- write_seqcount_begin(&fs->seq);
+ write_seqlock(&fs->lock);
tsk->fs = NULL;
kill = !--fs->users;
- write_seqcount_end(&fs->seq);
- spin_unlock(&fs->lock);
+ write_sequnlock(&fs->lock);
task_unlock(tsk);
if (kill)
free_fs_struct(fs);
@@ -125,16 +117,15 @@ struct fs_struct *copy_fs_struct(struct fs_struct *old)
if (fs) {
fs->users = 1;
fs->in_exec = 0;
- spin_lock_init(&fs->lock);
- seqcount_init(&fs->seq);
+ seqlock_init(&fs->lock);
fs->umask = old->umask;

- spin_lock(&old->lock);
+ seq_spin_lock(&old->lock);
fs->root = old->root;
path_get_longterm(&fs->root);
fs->pwd = old->pwd;
path_get_longterm(&fs->pwd);
- spin_unlock(&old->lock);
+ seq_spin_unlock(&old->lock);
}
return fs;
}
@@ -149,10 +140,10 @@ int unshare_fs_struct(void)
return -ENOMEM;

task_lock(current);
- spin_lock(&fs->lock);
+ seq_spin_lock(&fs->lock);
kill = !--fs->users;
current->fs = new_fs;
- spin_unlock(&fs->lock);
+ seq_spin_unlock(&fs->lock);
task_unlock(current);

if (kill)
@@ -171,8 +162,7 @@ EXPORT_SYMBOL(current_umask);
/* to be mentioned only in INIT_TASK */
struct fs_struct init_fs = {
.users = 1,
- .lock = __SPIN_LOCK_UNLOCKED(init_fs.lock),
- .seq = SEQCNT_ZERO,
+ .lock = __SEQLOCK_UNLOCKED(init_fs.lock),
.umask = 0022,
};

@@ -185,14 +175,14 @@ void daemonize_fs_struct(void)

task_lock(current);

- spin_lock(&init_fs.lock);
+ seq_spin_lock(&init_fs.lock);
init_fs.users++;
- spin_unlock(&init_fs.lock);
+ seq_spin_unlock(&init_fs.lock);

- spin_lock(&fs->lock);
+ seq_spin_lock(&fs->lock);
current->fs = &init_fs;
kill = !--fs->users;
- spin_unlock(&fs->lock);
+ seq_spin_unlock(&fs->lock);

task_unlock(current);
if (kill)
diff --git a/fs/namei.c b/fs/namei.c
index f7593c0..b364372 100644
--- a/fs/namei.c
+++ b/fs/namei.c
@@ -424,7 +424,7 @@ static int unlazy_walk(struct nameidata *nd, struct dentry *dentry)
BUG_ON(!(nd->flags & LOOKUP_RCU));
if (nd->root.mnt && !(nd->flags & LOOKUP_ROOT)) {
want_root = 1;
- spin_lock(&fs->lock);
+ seq_spin_lock(&fs->lock);
if (nd->root.mnt != fs->root.mnt ||
nd->root.dentry != fs->root.dentry)
goto err_root;
@@ -454,7 +454,7 @@ static int unlazy_walk(struct nameidata *nd, struct dentry *dentry)
spin_unlock(&parent->d_lock);
if (want_root) {
path_get(&nd->root);
- spin_unlock(&fs->lock);
+ seq_spin_unlock(&fs->lock);
}
mntget(nd->path.mnt);

@@ -469,7 +469,7 @@ err_parent:
spin_unlock(&parent->d_lock);
err_root:
if (want_root)
- spin_unlock(&fs->lock);
+ seq_spin_unlock(&fs->lock);
return -ECHILD;
}

@@ -619,10 +619,10 @@ static __always_inline void set_root_rcu(struct nameidata *nd)
unsigned seq;

do {
- seq = read_seqcount_begin(&fs->seq);
+ seq = read_seqbegin(&fs->lock);
nd->root = fs->root;
nd->seq = __read_seqcount_begin(&nd->root.dentry->d_seq);
- } while (read_seqcount_retry(&fs->seq, seq));
+ } while (read_seqretry(&fs->lock, seq));
}
}

@@ -1501,10 +1501,10 @@ static int path_init(int dfd, const char *name, unsigned int flags,
rcu_read_lock();

do {
- seq = read_seqcount_begin(&fs->seq);
+ seq = read_seqbegin(&fs->lock);
nd->path = fs->pwd;
nd->seq = __read_seqcount_begin(&nd->path.dentry->d_seq);
- } while (read_seqcount_retry(&fs->seq, seq));
+ } while (read_seqretry(&fs->lock, seq));
} else {
get_fs_pwd(current->fs, &nd->path);
}
diff --git a/include/linux/fs_struct.h b/include/linux/fs_struct.h
index 003dc0f..f748403 100644
--- a/include/linux/fs_struct.h
+++ b/include/linux/fs_struct.h
@@ -2,13 +2,11 @@
#define _LINUX_FS_STRUCT_H

#include <linux/path.h>
-#include <linux/spinlock.h>
#include <linux/seqlock.h>

struct fs_struct {
int users;
- spinlock_t lock;
- seqcount_t seq;
+ seqlock_t lock;
int umask;
int in_exec;
struct path root, pwd;
@@ -26,29 +24,29 @@ extern int unshare_fs_struct(void);

static inline void get_fs_root(struct fs_struct *fs, struct path *root)
{
- spin_lock(&fs->lock);
+ seq_spin_lock(&fs->lock);
*root = fs->root;
path_get(root);
- spin_unlock(&fs->lock);
+ seq_spin_unlock(&fs->lock);
}

static inline void get_fs_pwd(struct fs_struct *fs, struct path *pwd)
{
- spin_lock(&fs->lock);
+ seq_spin_lock(&fs->lock);
*pwd = fs->pwd;
path_get(pwd);
- spin_unlock(&fs->lock);
+ seq_spin_unlock(&fs->lock);
}

static inline void get_fs_root_and_pwd(struct fs_struct *fs, struct path *root,
struct path *pwd)
{
- spin_lock(&fs->lock);
+ seq_spin_lock(&fs->lock);
*root = fs->root;
path_get(root);
*pwd = fs->pwd;
path_get(pwd);
- spin_unlock(&fs->lock);
+ seq_spin_unlock(&fs->lock);
}

#endif /* _LINUX_FS_STRUCT_H */
diff --git a/kernel/fork.c b/kernel/fork.c
index 0429130..1643f63 100644
--- a/kernel/fork.c
+++ b/kernel/fork.c
@@ -856,13 +856,13 @@ static int copy_fs(unsigned long clone_flags, struct task_struct *tsk)
struct fs_struct *fs = current->fs;
if (clone_flags & CLONE_FS) {
/* tsk->fs is already what we want */
- spin_lock(&fs->lock);
+ seq_spin_lock(&fs->lock);
if (fs->in_exec) {
- spin_unlock(&fs->lock);
+ seq_spin_unlock(&fs->lock);
return -EAGAIN;
}
fs->users++;
- spin_unlock(&fs->lock);
+ seq_spin_unlock(&fs->lock);
return 0;
}
tsk->fs = copy_fs_struct(fs);
@@ -1729,13 +1729,13 @@ SYSCALL_DEFINE1(unshare, unsigned long, unshare_flags)

if (new_fs) {
fs = current->fs;
- spin_lock(&fs->lock);
+ seq_spin_lock(&fs->lock);
current->fs = new_fs;
if (--fs->users)
new_fs = NULL;
else
new_fs = fs;
- spin_unlock(&fs->lock);
+ seq_spin_unlock(&fs->lock);
}

if (new_fd) {
--
1.7.8.3



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