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devtmpfs: replace ->mount with ->get_tree in public instance

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To finalize mount API conversion, remove the ->mount op from the public
instance in favor of ->get_tree etc. Copy most ops from the underlying
ops vector (whether it's shmem or ramfs) and substitute our own
->get_tree which simply takes an extra reference on the existing internal
mount as before.

Thanks to Al for the fs_context_for_reconfigure() idea.

Cc: Al Viro <viro@zeniv.linux.org.uk>
Cc: Neil Brown <neilb@suse.de>
Signed-off-by: Eric Sandeen <sandeen@redhat.com>
Link: https://lore.kernel.org/r/20250205213931.74614-4-sandeen@redhat.com
Signed-off-by: Christian Brauner <brauner@kernel.org>
This commit is contained in:
Eric Sandeen
2025-02-05 15:34:31 -06:00
committed by Christian Brauner
parent cc0876f817
commit cb0e0a8bf4
1 changed files with 64 additions and 17 deletions
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81
drivers/base/devtmpfs.c
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@@ -63,22 +63,6 @@ __setup("devtmpfs.mount=", mount_param);
static struct vfsmount *mnt;
static struct dentry *public_dev_mount(struct file_system_type *fs_type, int flags,
const char *dev_name, void *data)
{
struct super_block *s = mnt->mnt_sb;
int err;
atomic_inc(&s->s_active);
down_write(&s->s_umount);
err = reconfigure_single(s, flags, data);
if (err < 0) {
deactivate_locked_super(s);
return ERR_PTR(err);
}
return dget(s->s_root);
}
static struct file_system_type internal_fs_type = {
.name = "devtmpfs",
#ifdef CONFIG_TMPFS
@@ -89,9 +73,40 @@ static struct file_system_type internal_fs_type = {
.kill_sb = kill_litter_super,
};
/* Simply take a ref on the existing mount */
static int devtmpfs_get_tree(struct fs_context *fc)
{
struct super_block *sb = mnt->mnt_sb;
atomic_inc(&sb->s_active);
down_write(&sb->s_umount);
fc->root = dget(sb->s_root);
return 0;
}
/* Ops are filled in during init depending on underlying shmem or ramfs type */
struct fs_context_operations devtmpfs_context_ops = {};
/* Call the underlying initialization and set to our ops */
static int devtmpfs_init_fs_context(struct fs_context *fc)
{
int ret;
#ifdef CONFIG_TMPFS
ret = shmem_init_fs_context(fc);
#else
ret = ramfs_init_fs_context(fc);
#endif
if (ret < 0)
return ret;
fc->ops = &devtmpfs_context_ops;
return 0;
}
static struct file_system_type dev_fs_type = {
.name = "devtmpfs",
.mount = public_dev_mount,
.init_fs_context = devtmpfs_init_fs_context,
};
static int devtmpfs_submit_req(struct req *req, const char *tmp)
@@ -442,6 +457,31 @@ static int __ref devtmpfsd(void *p)
return 0;
}
/*
* Get the underlying (shmem/ramfs) context ops to build ours
*/
static int devtmpfs_configure_context(void)
{
struct fs_context *fc;
fc = fs_context_for_reconfigure(mnt->mnt_root, mnt->mnt_sb->s_flags,
MS_RMT_MASK);
if (IS_ERR(fc))
return PTR_ERR(fc);
/* Set up devtmpfs_context_ops based on underlying type */
devtmpfs_context_ops.free = fc->ops->free;
devtmpfs_context_ops.dup = fc->ops->dup;
devtmpfs_context_ops.parse_param = fc->ops->parse_param;
devtmpfs_context_ops.parse_monolithic = fc->ops->parse_monolithic;
devtmpfs_context_ops.get_tree = &devtmpfs_get_tree;
devtmpfs_context_ops.reconfigure = fc->ops->reconfigure;
put_fs_context(fc);
return 0;
}
/*
* Create devtmpfs instance, driver-core devices will add their device
* nodes here.
@@ -456,6 +496,13 @@ int __init devtmpfs_init(void)
pr_err("unable to create devtmpfs %ld\n", PTR_ERR(mnt));
return PTR_ERR(mnt);
}
err = devtmpfs_configure_context();
if (err) {
pr_err("unable to configure devtmpfs type %d\n", err);
return err;
}
err = register_filesystem(&dev_fs_type);
if (err) {
pr_err("unable to register devtmpfs type %d\n", err);