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new helpers: vfs_create_mount(), fc_mount()

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Create a new helper, vfs_create_mount(), that creates a detached vfsmount
object from an fs_context that has a superblock attached to it.

Almost all uses will be paired with immediately preceding vfs_get_tree();
add a helper for such combination.

Switch vfs_kern_mount() to use this.

NOTE: mild behaviour change; passing NULL as 'device name' to
something like procfs will change /proc/*/mountstats - "device none"
instead on "no device".  That is consistent with /proc/mounts et.al.

[do'h - EXPORT_SYMBOL_GPL slipped in by mistake; removed]
[AV -- remove confused comment from vfs_create_mount()]
[AV -- removed the second argument]

Reviewed-by: David Howells <dhowells@redhat.com>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
This commit is contained in:
Al Viro 2018-11-04 06:48:34 -05:00
parent 9bc61ab18b
commit 8f2918898e
2 changed files with 55 additions and 24 deletions
repo.diff.show_diff_stats Download patch file Download diff file Expand all files Collapse all files

76
fs/namespace.c
View file

@ -941,12 +941,59 @@ static struct mount *skip_mnt_tree(struct mount *p)
return p;
}
/**
* vfs_create_mount - Create a mount for a configured superblock
* @fc: The configuration context with the superblock attached
*
* Create a mount to an already configured superblock. If necessary, the
* caller should invoke vfs_get_tree() before calling this.
*
* Note that this does not attach the mount to anything.
*/
struct vfsmount *vfs_create_mount(struct fs_context *fc)
{
struct mount *mnt;
if (!fc->root)
return ERR_PTR(-EINVAL);
mnt = alloc_vfsmnt(fc->source ?: "none");
if (!mnt)
return ERR_PTR(-ENOMEM);
if (fc->sb_flags & SB_KERNMOUNT)
mnt->mnt.mnt_flags = MNT_INTERNAL;
atomic_inc(&fc->root->d_sb->s_active);
mnt->mnt.mnt_sb = fc->root->d_sb;
mnt->mnt.mnt_root = dget(fc->root);
mnt->mnt_mountpoint = mnt->mnt.mnt_root;
mnt->mnt_parent = mnt;
lock_mount_hash();
list_add_tail(&mnt->mnt_instance, &mnt->mnt.mnt_sb->s_mounts);
unlock_mount_hash();
return &mnt->mnt;
}
EXPORT_SYMBOL(vfs_create_mount);
struct vfsmount *fc_mount(struct fs_context *fc)
{
int err = vfs_get_tree(fc);
if (!err) {
up_write(&fc->root->d_sb->s_umount);
return vfs_create_mount(fc);
}
return ERR_PTR(err);
}
EXPORT_SYMBOL(fc_mount);
struct vfsmount *vfs_kern_mount(struct file_system_type *type,
int flags, const char *name,
void *data)
{
struct fs_context *fc;
struct mount *mnt;
struct vfsmount *mnt;
int ret = 0;
if (!type)
@ -964,31 +1011,12 @@ struct vfsmount *vfs_kern_mount(struct file_system_type *type,
if (!ret)
ret = parse_monolithic_mount_data(fc, data);
if (!ret)
ret = vfs_get_tree(fc);
if (ret) {
put_fs_context(fc);
return ERR_PTR(ret);
}
up_write(&fc->root->d_sb->s_umount);
mnt = alloc_vfsmnt(name);
if (!mnt) {
put_fs_context(fc);
return ERR_PTR(-ENOMEM);
}
mnt = fc_mount(fc);
else
mnt = ERR_PTR(ret);
if (flags & SB_KERNMOUNT)
mnt->mnt.mnt_flags = MNT_INTERNAL;
atomic_inc(&fc->root->d_sb->s_active);
mnt->mnt.mnt_root = dget(fc->root);
mnt->mnt.mnt_sb = fc->root->d_sb;
mnt->mnt_mountpoint = mnt->mnt.mnt_root;
mnt->mnt_parent = mnt;
lock_mount_hash();
list_add_tail(&mnt->mnt_instance, &fc->root->d_sb->s_mounts);
unlock_mount_hash();
put_fs_context(fc);
return &mnt->mnt;
return mnt;
}
EXPORT_SYMBOL_GPL(vfs_kern_mount);

3
include/linux/mount.h
View file

@ -21,6 +21,7 @@ struct super_block;
struct vfsmount;
struct dentry;
struct mnt_namespace;
struct fs_context;
#define MNT_NOSUID 0x01
#define MNT_NODEV 0x02
@ -88,6 +89,8 @@ struct path;
extern struct vfsmount *clone_private_mount(const struct path *path);
struct file_system_type;
extern struct vfsmount *fc_mount(struct fs_context *fc);
extern struct vfsmount *vfs_create_mount(struct fs_context *fc);
extern struct vfsmount *vfs_kern_mount(struct file_system_type *type,
int flags, const char *name,
void *data);