[PATCH 09/75] Per-mount allocated_ptys

Alan Cox
2009-01-02T13:41:06Z

From: Sukadev Bhattiprolu <sukadev@linux.vnet.ibm.com>

To enable multiple mounts of devpts, 'allocated_ptys' must be a per-mount
variable rather than a global variable. Move 'allocated_ptys' into the
super_block's s_fs_info.

Changelog[v2]:
Define and use DEVPTS_SB() wrapper.

Signed-off-by: Sukadev Bhattiprolu <sukadev@linux.vnet.ibm.com>
Signed-off-by: Alan Cox <alan@redhat.com>
---

fs/devpts/inode.c | 55 ++++++++++++++++++++++++++++++++++++++++++++++-------
1 files changed, 48 insertions(+), 7 deletions(-)

diff --git a/fs/devpts/inode.c b/fs/devpts/inode.c
index f96e10a..49d879d 100644
--- a/fs/devpts/inode.c
+++ b/fs/devpts/inode.c
@@ -30,7 +30,6 @@
#define PTMX_MINOR 2

extern int pty_limit; /* Config limit on Unix98 ptys */
-static DEFINE_IDA(allocated_ptys);
static DEFINE_MUTEX(allocated_ptys_lock);

static struct vfsmount *devpts_mnt;
@@ -55,6 +54,15 @@ static const match_table_t tokens = {
{Opt_err, NULL}
};

+struct pts_fs_info {
+ struct ida allocated_ptys;
+};
+
+static inline struct pts_fs_info *DEVPTS_SB(struct super_block *sb)
+{
+ return sb->s_fs_info;
+}
+
static inline struct super_block *pts_sb_from_inode(struct inode *inode)
{
if (inode->i_sb->s_magic == DEVPTS_SUPER_MAGIC)
@@ -126,6 +134,19 @@ static const struct super_operations devpts_sops = {
.show_options = devpts_show_options,
};

+static void *new_pts_fs_info(void)
+{
+ struct pts_fs_info *fsi;
+
+ fsi = kzalloc(sizeof(struct pts_fs_info), GFP_KERNEL);
+ if (!fsi)
+ return NULL;
+
+ ida_init(&fsi->allocated_ptys);
+
+ return fsi;
+}
+
static int
devpts_fill_super(struct super_block *s, void *data, int silent)
{
@@ -137,9 +158,13 @@ devpts_fill_super(struct super_block *s, void *data, int silent)
s->s_op = &devpts_sops;
s->s_time_gran = 1;

+ s->s_fs_info = new_pts_fs_info();
+ if (!s->s_fs_info)
+ goto fail;
+
inode = new_inode(s);
if (!inode)
- goto fail;
+ goto free_fsi;
inode->i_ino = 1;
inode->i_mtime = inode->i_atime = inode->i_ctime = CURRENT_TIME;
inode->i_blocks = 0;
@@ -155,6 +180,9 @@ devpts_fill_super(struct super_block *s, void *data, int silent)

printk("devpts: get root dentry failed\n");
iput(inode);
+
+free_fsi:
+ kfree(s->s_fs_info);
fail:
return -ENOMEM;
}
@@ -165,11 +193,19 @@ static int devpts_get_sb(struct file_system_type *fs_type,
return get_sb_single(fs_type, flags, data, devpts_fill_super, mnt);
}

+static void devpts_kill_sb(struct super_block *sb)
+{
+ struct pts_fs_info *fsi = DEVPTS_SB(sb);
+
+ kfree(fsi);
+ kill_anon_super(sb);
+}
+
static struct file_system_type devpts_fs_type = {
.owner = THIS_MODULE,
.name = "devpts",
.get_sb = devpts_get_sb,
- .kill_sb = kill_anon_super,
+ .kill_sb = devpts_kill_sb,
};

/*
@@ -179,16 +215,18 @@ static struct file_system_type devpts_fs_type = {

int devpts_new_index(struct inode *ptmx_inode)
{
+ struct super_block *sb = pts_sb_from_inode(ptmx_inode);
+ struct pts_fs_info *fsi = DEVPTS_SB(sb);
int index;
int ida_ret;

retry:
- if (!ida_pre_get(&allocated_ptys, GFP_KERNEL)) {
+ if (!ida_pre_get(&fsi->allocated_ptys, GFP_KERNEL)) {
return -ENOMEM;
}

mutex_lock(&allocated_ptys_lock);
- ida_ret = ida_get_new(&allocated_ptys, &index);
+ ida_ret = ida_get_new(&fsi->allocated_ptys, &index);
if (ida_ret < 0) {
mutex_unlock(&allocated_ptys_lock);
if (ida_ret == -EAGAIN)
@@ -197,7 +235,7 @@ retry:
}

if (index >= pty_limit) {
- ida_remove(&allocated_ptys, index);
+ ida_remove(&fsi->allocated_ptys, index);
mutex_unlock(&allocated_ptys_lock);
return -EIO;
}
@@ -207,8 +245,11 @@ retry:

void devpts_kill_index(struct inode *ptmx_inode, int idx)
{
+ struct super_block *sb = pts_sb_from_inode(ptmx_inode);
+ struct pts_fs_info *fsi = DEVPTS_SB(sb);
+
mutex_lock(&allocated_ptys_lock);
- ida_remove(&allocated_ptys, idx);
+ ida_remove(&fsi->allocated_ptys, idx);
mutex_unlock(&allocated_ptys_lock);
}