From 8ead9dd54716d1e05e129959f702fcc1786f82b4 Mon Sep 17 00:00:00 2001 From: Linus Torvalds Date: Mon, 25 Apr 2016 20:04:08 -0700 Subject: [PATCH] devpts: more pty driver interface cleanups This is more prep-work for the upcoming pty changes. Still just code cleanup with no actual semantic changes. This removes a bunch pointless complexity by just having the slave pty side remember the dentry associated with the devpts slave rather than the inode. That allows us to remove all the "look up the dentry" code for when we want to remove it again. Together with moving the tty pointer from "inode->i_private" to "dentry->d_fsdata" and getting rid of pointless inode locking, this removes about 30 lines of code. Not only is the end result smaller, it's simpler and easier to understand. The old code, for example, depended on the d_find_alias() to not just find the dentry, but also to check that it is still hashed, which in turn validated the tty pointer in the inode. That is a _very_ roundabout way to say "invalidate the cached tty pointer when the dentry is removed". The new code just does dentry->d_fsdata = NULL; in devpts_pty_kill() instead, invalidating the tty pointer rather more directly and obviously. Don't do something complex and subtle when the obvious straightforward approach will do. The rest of the patch (ie apart from code deletion and the above tty pointer clearing) is just switching the calling convention to pass the dentry or file pointer around instead of the inode. Cc: Eric Biederman Cc: Peter Anvin Cc: Andy Lutomirski Cc: Al Viro Cc: Peter Hurley Cc: Serge Hallyn Cc: Willy Tarreau Cc: Aurelien Jarno Cc: Alan Cox Cc: Jann Horn Cc: Greg KH Cc: Jiri Slaby Cc: Florian Weimer Signed-off-by: Linus Torvalds --- drivers/tty/pty.c | 18 ++++++------- drivers/tty/tty_io.c | 6 ++--- fs/devpts/inode.c | 53 +++++++++----------------------------- include/linux/devpts_fs.h | 6 ++--- include/linux/tty_driver.h | 4 +-- 5 files changed, 28 insertions(+), 59 deletions(-) diff --git a/drivers/tty/pty.c b/drivers/tty/pty.c index 0058d9fbf931..cf0dc51a2690 100644 --- a/drivers/tty/pty.c +++ b/drivers/tty/pty.c @@ -626,7 +626,7 @@ static int pty_unix98_ioctl(struct tty_struct *tty, */ static struct tty_struct *ptm_unix98_lookup(struct tty_driver *driver, - struct inode *ptm_inode, int idx) + struct file *file, int idx) { /* Master must be open via /dev/ptmx */ return ERR_PTR(-EIO); @@ -642,12 +642,12 @@ static struct tty_struct *ptm_unix98_lookup(struct tty_driver *driver, */ static struct tty_struct *pts_unix98_lookup(struct tty_driver *driver, - struct inode *pts_inode, int idx) + struct file *file, int idx) { struct tty_struct *tty; mutex_lock(&devpts_mutex); - tty = devpts_get_priv(pts_inode); + tty = devpts_get_priv(file->f_path.dentry); mutex_unlock(&devpts_mutex); /* Master must be open before slave */ if (!tty) @@ -722,7 +722,7 @@ static int ptmx_open(struct inode *inode, struct file *filp) { struct pts_fs_info *fsi; struct tty_struct *tty; - struct inode *slave_inode; + struct dentry *dentry; int retval; int index; @@ -769,14 +769,12 @@ static int ptmx_open(struct inode *inode, struct file *filp) tty_add_file(tty, filp); - slave_inode = devpts_pty_new(fsi, - MKDEV(UNIX98_PTY_SLAVE_MAJOR, index), index, - tty->link); - if (IS_ERR(slave_inode)) { - retval = PTR_ERR(slave_inode); + dentry = devpts_pty_new(fsi, index, tty->link); + if (IS_ERR(dentry)) { + retval = PTR_ERR(dentry); goto err_release; } - tty->link->driver_data = slave_inode; + tty->link->driver_data = dentry; retval = ptm_driver->ops->open(tty, filp); if (retval) diff --git a/drivers/tty/tty_io.c b/drivers/tty/tty_io.c index 9b04d72e752e..24d5491ef0da 100644 --- a/drivers/tty/tty_io.c +++ b/drivers/tty/tty_io.c @@ -1367,12 +1367,12 @@ static ssize_t tty_line_name(struct tty_driver *driver, int index, char *p) * Locking: tty_mutex must be held. If the tty is found, bump the tty kref. */ static struct tty_struct *tty_driver_lookup_tty(struct tty_driver *driver, - struct inode *inode, int idx) + struct file *file, int idx) { struct tty_struct *tty; if (driver->ops->lookup) - tty = driver->ops->lookup(driver, inode, idx); + tty = driver->ops->lookup(driver, file, idx); else tty = driver->ttys[idx]; @@ -2040,7 +2040,7 @@ static struct tty_struct *tty_open_by_driver(dev_t device, struct inode *inode, } /* check whether we're reopening an existing tty */ - tty = tty_driver_lookup_tty(driver, inode, index); + tty = tty_driver_lookup_tty(driver, filp, index); if (IS_ERR(tty)) { mutex_unlock(&tty_mutex); goto out; diff --git a/fs/devpts/inode.c b/fs/devpts/inode.c index 0af8e7d70d27..0b2954d7172d 100644 --- a/fs/devpts/inode.c +++ b/fs/devpts/inode.c @@ -604,8 +604,7 @@ void devpts_put_ref(struct pts_fs_info *fsi) * * The created inode is returned. Remove it from /dev/pts/ by devpts_pty_kill. */ -struct inode *devpts_pty_new(struct pts_fs_info *fsi, dev_t device, int index, - void *priv) +struct dentry *devpts_pty_new(struct pts_fs_info *fsi, int index, void *priv) { struct dentry *dentry; struct super_block *sb; @@ -629,25 +628,21 @@ struct inode *devpts_pty_new(struct pts_fs_info *fsi, dev_t device, int index, inode->i_uid = opts->setuid ? opts->uid : current_fsuid(); inode->i_gid = opts->setgid ? opts->gid : current_fsgid(); inode->i_mtime = inode->i_atime = inode->i_ctime = CURRENT_TIME; - init_special_inode(inode, S_IFCHR|opts->mode, device); - inode->i_private = priv; + init_special_inode(inode, S_IFCHR|opts->mode, MKDEV(UNIX98_PTY_SLAVE_MAJOR, index)); sprintf(s, "%d", index); - inode_lock(d_inode(root)); - dentry = d_alloc_name(root, s); if (dentry) { + dentry->d_fsdata = priv; d_add(dentry, inode); fsnotify_create(d_inode(root), dentry); } else { iput(inode); - inode = ERR_PTR(-ENOMEM); + dentry = ERR_PTR(-ENOMEM); } - inode_unlock(d_inode(root)); - - return inode; + return dentry; } /** @@ -656,24 +651,10 @@ struct inode *devpts_pty_new(struct pts_fs_info *fsi, dev_t device, int index, * * Returns whatever was passed as priv in devpts_pty_new for a given inode. */ -void *devpts_get_priv(struct inode *pts_inode) +void *devpts_get_priv(struct dentry *dentry) { - struct dentry *dentry; - void *priv = NULL; - - BUG_ON(pts_inode->i_rdev == MKDEV(TTYAUX_MAJOR, PTMX_MINOR)); - - /* Ensure dentry has not been deleted by devpts_pty_kill() */ - dentry = d_find_alias(pts_inode); - if (!dentry) - return NULL; - - if (pts_inode->i_sb->s_magic == DEVPTS_SUPER_MAGIC) - priv = pts_inode->i_private; - - dput(dentry); - - return priv; + WARN_ON_ONCE(dentry->d_sb->s_magic != DEVPTS_SUPER_MAGIC); + return dentry->d_fsdata; } /** @@ -682,24 +663,14 @@ void *devpts_get_priv(struct inode *pts_inode) * * This is an inverse operation of devpts_pty_new. */ -void devpts_pty_kill(struct inode *inode) +void devpts_pty_kill(struct dentry *dentry) { - struct super_block *sb = pts_sb_from_inode(inode); - struct dentry *root = sb->s_root; - struct dentry *dentry; + WARN_ON_ONCE(dentry->d_sb->s_magic != DEVPTS_SUPER_MAGIC); - BUG_ON(inode->i_rdev == MKDEV(TTYAUX_MAJOR, PTMX_MINOR)); - - inode_lock(d_inode(root)); - - dentry = d_find_alias(inode); - - drop_nlink(inode); + dentry->d_fsdata = NULL; + drop_nlink(dentry->d_inode); d_delete(dentry); dput(dentry); /* d_alloc_name() in devpts_pty_new() */ - dput(dentry); /* d_find_alias above */ - - inode_unlock(d_inode(root)); } static int __init init_devpts_fs(void) diff --git a/include/linux/devpts_fs.h b/include/linux/devpts_fs.h index 358a4db72a27..5871f292b596 100644 --- a/include/linux/devpts_fs.h +++ b/include/linux/devpts_fs.h @@ -27,11 +27,11 @@ int devpts_new_index(struct pts_fs_info *); void devpts_kill_index(struct pts_fs_info *, int); /* mknod in devpts */ -struct inode *devpts_pty_new(struct pts_fs_info *, dev_t, int, void *); +struct dentry *devpts_pty_new(struct pts_fs_info *, int, void *); /* get private structure */ -void *devpts_get_priv(struct inode *pts_inode); +void *devpts_get_priv(struct dentry *); /* unlink */ -void devpts_pty_kill(struct inode *inode); +void devpts_pty_kill(struct dentry *); #endif diff --git a/include/linux/tty_driver.h b/include/linux/tty_driver.h index 161052477f77..b742b5e47cc2 100644 --- a/include/linux/tty_driver.h +++ b/include/linux/tty_driver.h @@ -7,7 +7,7 @@ * defined; unless noted otherwise, they are optional, and can be * filled in with a null pointer. * - * struct tty_struct * (*lookup)(struct tty_driver *self, int idx) + * struct tty_struct * (*lookup)(struct tty_driver *self, struct file *, int idx) * * Return the tty device corresponding to idx, NULL if there is not * one currently in use and an ERR_PTR value on error. Called under @@ -250,7 +250,7 @@ struct serial_icounter_struct; struct tty_operations { struct tty_struct * (*lookup)(struct tty_driver *driver, - struct inode *inode, int idx); + struct file *filp, int idx); int (*install)(struct tty_driver *driver, struct tty_struct *tty); void (*remove)(struct tty_driver *driver, struct tty_struct *tty); int (*open)(struct tty_struct * tty, struct file * filp); -- 2.20.1