On Mon, 12 Jul 2010, Aneesh Kumar K.V wrote:
> This enables to use linkat to create hardlinks from a
> file descriptor pointing to the file. This can be used
> with open_by_handle syscall that returns a file descriptor.
This needs more thought, filesystems don't usually tolerate
resurrecting a file which has already been unlinked (i_nlink == 0).
Thanks,
Miklos
>
> Signed-off-by: Aneesh Kumar K.V <aneesh.kumar@xxxxxxxxxxxxxxxxxx>
> ---
> fs/namei.c | 34 +++++++++++++++++++++++++---------
> 1 files changed, 25 insertions(+), 9 deletions(-)
>
> diff --git a/fs/namei.c b/fs/namei.c
> index a6a8093..9a7b71a 100644
> --- a/fs/namei.c
> +++ b/fs/namei.c
> @@ -2553,16 +2553,28 @@ SYSCALL_DEFINE5(linkat, int, olddfd, const char __user *, oldname,
> {
> struct dentry *new_dentry;
> struct nameidata nd;
> - struct path old_path;
> - int error;
> + struct path old_path, *old_pathp;
> + struct file *file = NULL;
> + int error, fput_needed;
> char *to;
>
> if ((flags & ~AT_SYMLINK_FOLLOW) != 0)
> return -EINVAL;
>
> - error = user_path_at(olddfd, oldname,
> - flags & AT_SYMLINK_FOLLOW ? LOOKUP_FOLLOW : 0,
> - &old_path);
> + if (oldname == NULL && olddfd != AT_FDCWD) {
> + file = fget_light(olddfd, &fput_needed);
> + if (file) {
> + old_pathp = &file->f_path;
> + error = 0;
> + } else
> + error = -EBADF;
> + } else {
> + error = user_path_at(olddfd, oldname,
> + flags & AT_SYMLINK_FOLLOW ?
> + LOOKUP_FOLLOW : 0,
> + &old_path);
> + old_pathp = &old_path;
> + }
> if (error)
> return error;
>
> @@ -2570,7 +2582,7 @@ SYSCALL_DEFINE5(linkat, int, olddfd, const char __user *, oldname,
> if (error)
> goto out;
> error = -EXDEV;
> - if (old_path.mnt != nd.path.mnt)
> + if (old_pathp->mnt != nd.path.mnt)
> goto out_release;
> new_dentry = lookup_create(&nd, 0);
> error = PTR_ERR(new_dentry);
> @@ -2579,10 +2591,11 @@ SYSCALL_DEFINE5(linkat, int, olddfd, const char __user *, oldname,
> error = mnt_want_write(nd.path.mnt);
> if (error)
> goto out_dput;
> - error = security_path_link(old_path.dentry, &nd.path, new_dentry);
> + error = security_path_link(old_pathp->dentry, &nd.path, new_dentry);
> if (error)
> goto out_drop_write;
> - error = vfs_link(old_path.dentry, nd.path.dentry->d_inode, new_dentry);
> + error = vfs_link(old_pathp->dentry,
> + nd.path.dentry->d_inode, new_dentry);
> out_drop_write:
> mnt_drop_write(nd.path.mnt);
> out_dput:
> @@ -2593,7 +2606,10 @@ out_release:
> path_put(&nd.path);
> putname(to);
> out:
> - path_put(&old_path);
> + if (file)
> + fput_light(file, fput_needed);
> + else
> + path_put(&old_path);
>
> return error;
> }
> --
> 1.7.2.rc1
>
> --
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