[patch 06/10] fs: cleanup files_lock locking

From: Nick Piggin
Date: Tue Aug 17 2010 - 14:52:05 EST

fs: cleanup files_lock locking

Lock tty_files with a new spinlock, tty_files_lock; provide helpers to
manipulate the per-sb files list; unexport the files_lock spinlock.

Cc: linux-kernel@xxxxxxxxxxxxxxx
Cc: Christoph Hellwig <hch@xxxxxxxxxxxxx>
Cc: Alan Cox <alan@xxxxxxxxxxxxxxxxxxx>
Acked-by: Andi Kleen <ak@xxxxxxxxxxxxxxx>
Acked-by: Greg Kroah-Hartman <gregkh@xxxxxxx>
Signed-off-by: Nick Piggin <npiggin@xxxxxxxxx>

---
drivers/char/pty.c | 6 +++++-
drivers/char/tty_io.c | 26 ++++++++++++++++++--------
fs/file_table.c | 42 ++++++++++++++++++------------------------
fs/open.c | 4 ++--
include/linux/fs.h | 7 ++-----
include/linux/tty.h | 1 +
security/selinux/hooks.c | 4 ++--
7 files changed, 48 insertions(+), 42 deletions(-)

Index: linux-2.6/security/selinux/hooks.c
===================================================================
--- linux-2.6.orig/security/selinux/hooks.c 2010-08-18 04:04:01.000000000 +1000
+++ linux-2.6/security/selinux/hooks.c 2010-08-18 04:05:10.000000000 +1000
@@ -2170,7 +2170,7 @@ static inline void flush_unauthorized_fi

tty = get_current_tty();
if (tty) {
- file_list_lock();
+ spin_lock(&tty_files_lock);
if (!list_empty(&tty->tty_files)) {
struct inode *inode;

@@ -2186,7 +2186,7 @@ static inline void flush_unauthorized_fi
drop_tty = 1;
}
}
- file_list_unlock();
+ spin_unlock(&tty_files_lock);
tty_kref_put(tty);
}
/* Reset controlling tty. */
Index: linux-2.6/drivers/char/pty.c
===================================================================
--- linux-2.6.orig/drivers/char/pty.c 2010-08-18 04:04:01.000000000 +1000
+++ linux-2.6/drivers/char/pty.c 2010-08-18 04:05:10.000000000 +1000
@@ -676,7 +676,11 @@ static int ptmx_open(struct inode *inode

set_bit(TTY_PTY_LOCK, &tty->flags); /* LOCK THE SLAVE */
filp->private_data = tty;
- file_move(filp, &tty->tty_files);
+
+ file_sb_list_del(filp); /* __dentry_open has put it on the sb list */
+ spin_lock(&tty_files_lock);
+ list_add(&filp->f_u.fu_list, &tty->tty_files);
+ spin_unlock(&tty_files_lock);

retval = devpts_pty_new(inode, tty->link);
if (retval)
Index: linux-2.6/drivers/char/tty_io.c
===================================================================
--- linux-2.6.orig/drivers/char/tty_io.c 2010-08-18 04:04:01.000000000 +1000
+++ linux-2.6/drivers/char/tty_io.c 2010-08-18 04:05:10.000000000 +1000
@@ -136,6 +136,9 @@ LIST_HEAD(tty_drivers); /* linked list
DEFINE_MUTEX(tty_mutex);
EXPORT_SYMBOL(tty_mutex);

+/* Spinlock to protect the tty->tty_files list */
+DEFINE_SPINLOCK(tty_files_lock);
+
static ssize_t tty_read(struct file *, char __user *, size_t, loff_t *);
static ssize_t tty_write(struct file *, const char __user *, size_t, loff_t *);
ssize_t redirected_tty_write(struct file *, const char __user *,
@@ -235,11 +238,11 @@ static int check_tty_count(struct tty_st
struct list_head *p;
int count = 0;

- file_list_lock();
+ spin_lock(&tty_files_lock);
list_for_each(p, &tty->tty_files) {
count++;
}
- file_list_unlock();
+ spin_unlock(&tty_files_lock);
if (tty->driver->type == TTY_DRIVER_TYPE_PTY &&
tty->driver->subtype == PTY_TYPE_SLAVE &&
tty->link && tty->link->count)
@@ -519,7 +522,7 @@ void __tty_hangup(struct tty_struct *tty
workqueue with the lock held */
check_tty_count(tty, "tty_hangup");

- file_list_lock();
+ spin_lock(&tty_files_lock);
/* This breaks for file handles being sent over AF_UNIX sockets ? */
list_for_each_entry(filp, &tty->tty_files, f_u.fu_list) {
if (filp->f_op->write == redirected_tty_write)
@@ -530,7 +533,7 @@ void __tty_hangup(struct tty_struct *tty
__tty_fasync(-1, filp, 0); /* can't block */
filp->f_op = &hung_up_tty_fops;
}
- file_list_unlock();
+ spin_unlock(&tty_files_lock);

tty_ldisc_hangup(tty);

@@ -1424,9 +1427,9 @@ static void release_one_tty(struct work_
tty_driver_kref_put(driver);
module_put(driver->owner);

- file_list_lock();
+ spin_lock(&tty_files_lock);
list_del_init(&tty->tty_files);
- file_list_unlock();
+ spin_unlock(&tty_files_lock);

put_pid(tty->pgrp);
put_pid(tty->session);
@@ -1671,7 +1674,10 @@ int tty_release(struct inode *inode, str
* - do_tty_hangup no longer sees this file descriptor as
* something that needs to be handled for hangups.
*/
- file_kill(filp);
+ spin_lock(&tty_files_lock);
+ BUG_ON(list_empty(&filp->f_u.fu_list));
+ list_del_init(&filp->f_u.fu_list);
+ spin_unlock(&tty_files_lock);
filp->private_data = NULL;

/*
@@ -1840,7 +1846,11 @@ got_driver:
}

filp->private_data = tty;
- file_move(filp, &tty->tty_files);
+ BUG_ON(list_empty(&filp->f_u.fu_list));
+ file_sb_list_del(filp); /* __dentry_open has put it on the sb list */
+ spin_lock(&tty_files_lock);
+ list_add(&filp->f_u.fu_list, &tty->tty_files);
+ spin_unlock(&tty_files_lock);
check_tty_count(tty, "tty_open");
if (tty->driver->type == TTY_DRIVER_TYPE_PTY &&
tty->driver->subtype == PTY_TYPE_MASTER)
Index: linux-2.6/fs/file_table.c
===================================================================
--- linux-2.6.orig/fs/file_table.c 2010-08-18 04:04:01.000000000 +1000
+++ linux-2.6/fs/file_table.c 2010-08-18 04:05:09.000000000 +1000
@@ -32,8 +32,7 @@ struct files_stat_struct files_stat = {
.max_files = NR_FILE
};

-/* public. Not pretty! */
-__cacheline_aligned_in_smp DEFINE_SPINLOCK(files_lock);
+static __cacheline_aligned_in_smp DEFINE_SPINLOCK(files_lock);

/* SLAB cache for file structures */
static struct kmem_cache *filp_cachep __read_mostly;
@@ -249,7 +248,7 @@ static void __fput(struct file *file)
cdev_put(inode->i_cdev);
fops_put(file->f_op);
put_pid(file->f_owner.pid);
- file_kill(file);
+ file_sb_list_del(file);
if (file->f_mode & FMODE_WRITE)
drop_file_write_access(file);
file->f_path.dentry = NULL;
@@ -328,31 +327,29 @@ struct file *fget_light(unsigned int fd,
return file;
}

-
void put_filp(struct file *file)
{
if (atomic_long_dec_and_test(&file->f_count)) {
security_file_free(file);
- file_kill(file);
+ file_sb_list_del(file);
file_free(file);
}
}

-void file_move(struct file *file, struct list_head *list)
+void file_sb_list_add(struct file *file, struct super_block *sb)
{
- if (!list)
- return;
- file_list_lock();
- list_move(&file->f_u.fu_list, list);
- file_list_unlock();
+ spin_lock(&files_lock);
+ BUG_ON(!list_empty(&file->f_u.fu_list));
+ list_add(&file->f_u.fu_list, &sb->s_files);
+ spin_unlock(&files_lock);
}

-void file_kill(struct file *file)
+void file_sb_list_del(struct file *file)
{
if (!list_empty(&file->f_u.fu_list)) {
- file_list_lock();
+ spin_lock(&files_lock);
list_del_init(&file->f_u.fu_list);
- file_list_unlock();
+ spin_unlock(&files_lock);
}
}

@@ -361,7 +358,7 @@ int fs_may_remount_ro(struct super_block
struct file *file;

/* Check that no files are currently opened for writing. */
- file_list_lock();
+ spin_lock(&files_lock);
list_for_each_entry(file, &sb->s_files, f_u.fu_list) {
struct inode *inode = file->f_path.dentry->d_inode;

@@ -373,10 +370,10 @@ int fs_may_remount_ro(struct super_block
if (S_ISREG(inode->i_mode) && (file->f_mode & FMODE_WRITE))
goto too_bad;
}
- file_list_unlock();
+ spin_unlock(&files_lock);
return 1; /* Tis' cool bro. */
too_bad:
- file_list_unlock();
+ spin_unlock(&files_lock);
return 0;
}

@@ -392,7 +389,7 @@ void mark_files_ro(struct super_block *s
struct file *f;

retry:
- file_list_lock();
+ spin_lock(&files_lock);
list_for_each_entry(f, &sb->s_files, f_u.fu_list) {
struct vfsmount *mnt;
if (!S_ISREG(f->f_path.dentry->d_inode->i_mode))
@@ -408,16 +405,13 @@ retry:
continue;
file_release_write(f);
mnt = mntget(f->f_path.mnt);
- file_list_unlock();
- /*
- * This can sleep, so we can't hold
- * the file_list_lock() spinlock.
- */
+ /* This can sleep, so we can't hold the spinlock. */
+ spin_unlock(&files_lock);
mnt_drop_write(mnt);
mntput(mnt);
goto retry;
}
- file_list_unlock();
+ spin_unlock(&files_lock);
}

void __init files_init(unsigned long mempages)
Index: linux-2.6/fs/open.c
===================================================================
--- linux-2.6.orig/fs/open.c 2010-08-18 04:04:01.000000000 +1000
+++ linux-2.6/fs/open.c 2010-08-18 04:04:29.000000000 +1000
@@ -675,7 +675,7 @@ static struct file *__dentry_open(struct
f->f_path.mnt = mnt;
f->f_pos = 0;
f->f_op = fops_get(inode->i_fop);
- file_move(f, &inode->i_sb->s_files);
+ file_sb_list_add(f, inode->i_sb);

error = security_dentry_open(f, cred);
if (error)
@@ -721,7 +721,7 @@ cleanup_all:
mnt_drop_write(mnt);
}
}
- file_kill(f);
+ file_sb_list_del(f);
f->f_path.dentry = NULL;
f->f_path.mnt = NULL;
cleanup_file:
Index: linux-2.6/include/linux/fs.h
===================================================================
--- linux-2.6.orig/include/linux/fs.h 2010-08-18 04:04:01.000000000 +1000
+++ linux-2.6/include/linux/fs.h 2010-08-18 04:05:10.000000000 +1000
@@ -953,9 +953,6 @@ struct file {
unsigned long f_mnt_write_state;
#endif
};
-extern spinlock_t files_lock;
-#define file_list_lock() spin_lock(&files_lock);
-#define file_list_unlock() spin_unlock(&files_lock);

#define get_file(x) atomic_long_inc(&(x)->f_count)
#define fput_atomic(x) atomic_long_add_unless(&(x)->f_count, -1, 1)
@@ -2197,8 +2194,8 @@ static inline void insert_inode_hash(str
__insert_inode_hash(inode, inode->i_ino);
}

-extern void file_move(struct file *f, struct list_head *list);
-extern void file_kill(struct file *f);
+extern void file_sb_list_add(struct file *f, struct super_block *sb);
+extern void file_sb_list_del(struct file *f);
#ifdef CONFIG_BLOCK
extern void submit_bio(int, struct bio *);
extern int bdev_read_only(struct block_device *);
Index: linux-2.6/include/linux/tty.h
===================================================================
--- linux-2.6.orig/include/linux/tty.h 2010-08-18 04:04:01.000000000 +1000
+++ linux-2.6/include/linux/tty.h 2010-08-18 04:05:10.000000000 +1000
@@ -470,6 +470,7 @@ extern struct tty_struct *tty_pair_get_t
extern struct tty_struct *tty_pair_get_pty(struct tty_struct *tty);

extern struct mutex tty_mutex;
+extern spinlock_t tty_files_lock;

extern void tty_write_unlock(struct tty_struct *tty);
extern int tty_write_lock(struct tty_struct *tty, int ndelay);


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