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convert devpts 

Two kinds of objects there - ptmx and everything else (pty).  The former is
created on mount and kept until the fs shutdown; the latter get created
and removed by tty layer (the references are borrowed into tty->driver_data).
The reference to ptmx dentry is also kept, but we only ever use it to
find ptmx inode on remount.

* turn d_add() into d_make_persistent() + dput()  both in mknod_ptmx() and
in devpts_pty_new().

* turn dput() to d_make_discardable() in devpts_pty_kill().

* switch mknod_ptmx() to simple_{start,done}_creating().

* instead of storing in pts_fs_info a reference to ptmx dentry, store a reference
to its inode, seeing that this is what we use it for.

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
This commit is contained in:
Al Viro 2024-02-26 02:34:49 -05:00
parent b83431564d
commit b4a76faf9d
1 changed files with 21 additions and 36 deletions
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57
fs/devpts/inode.c
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@ -102,7 +102,7 @@ struct pts_fs_info {
struct ida allocated_ptys;
struct pts_mount_opts mount_opts;
struct super_block *sb;
struct dentry *ptmx_dentry;
struct inode *ptmx_inode; // borrowed
};
static inline struct pts_fs_info *DEVPTS_SB(struct super_block *sb)
@ -259,7 +259,6 @@ static int devpts_parse_param(struct fs_context *fc, struct fs_parameter *param)
static int mknod_ptmx(struct super_block *sb, struct fs_context *fc)
{
int mode;
int rc = -ENOMEM;
struct dentry *dentry;
struct inode *inode;
struct dentry *root = sb->s_root;
@ -268,18 +267,10 @@ static int mknod_ptmx(struct super_block *sb, struct fs_context *fc)
kuid_t ptmx_uid = current_fsuid();
kgid_t ptmx_gid = current_fsgid();
inode_lock(d_inode(root));
/* If we have already created ptmx node, return */
if (fsi->ptmx_dentry) {
rc = 0;
goto out;
}
dentry = d_alloc_name(root, "ptmx");
if (!dentry) {
dentry = simple_start_creating(root, "ptmx");
if (IS_ERR(dentry)) {
pr_err("Unable to alloc dentry for ptmx node\n");
goto out;
return PTR_ERR(dentry);
}
/*
@ -287,9 +278,9 @@ static int mknod_ptmx(struct super_block *sb, struct fs_context *fc)
*/
inode = new_inode(sb);
if (!inode) {
simple_done_creating(dentry);
pr_err("Unable to alloc inode for ptmx node\n");
dput(dentry);
goto out;
return -ENOMEM;
}
inode->i_ino = 2;
@ -299,23 +290,18 @@ static int mknod_ptmx(struct super_block *sb, struct fs_context *fc)
init_special_inode(inode, mode, MKDEV(TTYAUX_MAJOR, 2));
inode->i_uid = ptmx_uid;
inode->i_gid = ptmx_gid;
fsi->ptmx_inode = inode;
d_add(dentry, inode);
d_make_persistent(dentry, inode);
fsi->ptmx_dentry = dentry;
rc = 0;
out:
inode_unlock(d_inode(root));
return rc;
simple_done_creating(dentry);
return 0;
}
static void update_ptmx_mode(struct pts_fs_info *fsi)
{
struct inode *inode;
if (fsi->ptmx_dentry) {
inode = d_inode(fsi->ptmx_dentry);
inode->i_mode = S_IFCHR|fsi->mount_opts.ptmxmode;
}
fsi->ptmx_inode->i_mode = S_IFCHR|fsi->mount_opts.ptmxmode;
}
static int devpts_reconfigure(struct fs_context *fc)
@ -461,7 +447,7 @@ static void devpts_kill_sb(struct super_block *sb)
if (fsi)
ida_destroy(&fsi->allocated_ptys);
kfree(fsi);
kill_litter_super(sb);
kill_anon_super(sb);
}
static struct file_system_type devpts_fs_type = {
@ -534,16 +520,15 @@ struct dentry *devpts_pty_new(struct pts_fs_info *fsi, int index, void *priv)
sprintf(s, "%d", index);
dentry = d_alloc_name(root, s);
if (dentry) {
dentry->d_fsdata = priv;
d_add(dentry, inode);
fsnotify_create(d_inode(root), dentry);
} else {
if (!dentry) {
iput(inode);
dentry = ERR_PTR(-ENOMEM);
return ERR_PTR(-ENOMEM);
}
return dentry;
dentry->d_fsdata = priv;
d_make_persistent(dentry, inode);
fsnotify_create(d_inode(root), dentry);
dput(dentry);
return dentry; // borrowed
}
/**
@ -573,7 +558,7 @@ void devpts_pty_kill(struct dentry *dentry)
drop_nlink(dentry->d_inode);
d_drop(dentry);
fsnotify_unlink(d_inode(dentry->d_parent), dentry);
dput(dentry); /* d_alloc_name() in devpts_pty_new() */
d_make_discardable(dentry);
}
static int __init init_devpts_fs(void)