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Date: Mon, 27 Apr 2009 08:37:46 +1000 (EST)
From: James Morris <jmorris@...ei.org>
To: npiggin@...e.de
cc: Al Viro <viro@...IV.linux.org.uk>, linux-fsdevel@...r.kernel.org,
linux-kernel@...r.kernel.org, Alan Cox <alan@...rguk.ukuu.org.uk>,
Stephen Smalley <sds@...ho.nsa.gov>,
Eric Paris <eparis@...hat.com>
Subject: Re: [patch 5/5] fs: cleanup files_lock
On Sun, 26 Apr 2009, npiggin@...e.de wrote:
> 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: Alan Cox <alan@...rguk.ukuu.org.uk>
> Signed-off-by: Nick Piggin <npiggin@...e.de>
The SELinux tty part looks fine to me.
Acked-by: James Morris <jmorris@...ei.org>
> ---
> drivers/char/pty.c | 6 +++++-
> drivers/char/tty_io.c | 26 ++++++++++++++++++--------
> fs/file_table.c | 44 +++++++++++++++++++-------------------------
> fs/open.c | 4 ++--
> include/linux/fs.h | 8 +++-----
> include/linux/tty.h | 1 +
> security/selinux/hooks.c | 4 ++--
> 7 files changed, 50 insertions(+), 43 deletions(-)
>
> Index: linux-2.6/drivers/char/pty.c
> ===================================================================
> --- linux-2.6.orig/drivers/char/pty.c
> +++ linux-2.6/drivers/char/pty.c
> @@ -662,7 +662,11 @@ static int __ptmx_open(struct inode *ino
>
> 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
> +++ linux-2.6/drivers/char/tty_io.c
> @@ -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)
> @@ -554,7 +557,7 @@ static void do_tty_hangup(struct work_st
> spin_unlock(&redirect_lock);
>
> check_tty_count(tty, "do_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)
> @@ -565,7 +568,7 @@ static void do_tty_hangup(struct work_st
> tty_fasync(-1, filp, 0); /* can't block */
> filp->f_op = &hung_up_tty_fops;
> }
> - file_list_unlock();
> + spin_unlock(&tty_files_lock);
> /*
> * FIXME! What are the locking issues here? This may me overdoing
> * things... This question is especially important now that we've
> @@ -1467,9 +1470,9 @@ static void release_one_tty(struct kref
> 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);
>
> free_tty_struct(tty);
> }
> @@ -1678,7 +1681,10 @@ void tty_release_dev(struct file *filp)
> * - 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;
>
> /*
> @@ -1836,7 +1842,11 @@ got_driver:
> return PTR_ERR(tty);
>
> 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
> +++ linux-2.6/fs/file_table.c
> @@ -30,8 +30,7 @@ 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;
> @@ -285,7 +284,7 @@ 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;
> @@ -347,31 +346,29 @@ 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);
> }
> }
>
> @@ -380,7 +377,7 @@ 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;
>
> @@ -392,10 +389,10 @@ 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;
> }
>
> @@ -406,12 +403,12 @@ too_bad:
> * All files are marked read-only. We don't care about pending
> * delete files so this should be used in 'force' mode only.
> */
> -static void mark_files_ro(struct super_block *sb)
> +void mark_files_ro(struct super_block *sb)
> {
> 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))
> @@ -425,16 +422,13 @@ 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
> +++ linux-2.6/fs/open.c
> @@ -828,7 +828,7 @@ 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)
> @@ -873,7 +873,7 @@ 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
> +++ linux-2.6/include/linux/fs.h
> @@ -934,9 +934,6 @@ 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 file_count(x) atomic_long_read(&(x)->f_count)
> @@ -2021,6 +2018,7 @@ extern const struct file_operations read
> extern const struct file_operations write_pipefifo_fops;
> extern const struct file_operations rdwr_pipefifo_fops;
>
> +extern void mark_files_ro(struct super_block *sb);
> extern int fs_may_remount_ro(struct super_block *);
>
> #ifdef CONFIG_BLOCK
> @@ -2172,8 +2170,8 @@ static inline void insert_inode_hash(str
> }
>
> extern struct file * get_empty_filp(void);
> -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
> struct bio;
> extern void submit_bio(int, struct bio *);
> Index: linux-2.6/security/selinux/hooks.c
> ===================================================================
> --- linux-2.6.orig/security/selinux/hooks.c
> +++ linux-2.6/security/selinux/hooks.c
> @@ -2244,7 +2244,7 @@ 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;
>
> @@ -2260,7 +2260,7 @@ 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/include/linux/tty.h
> ===================================================================
> --- linux-2.6.orig/include/linux/tty.h
> +++ linux-2.6/include/linux/tty.h
> @@ -426,6 +426,7 @@ extern void tty_release_dev(struct file
> extern int tty_init_termios(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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>
--
James Morris
<jmorris@...ei.org>
--
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