io_uring: add support for IORING_OP_LINKAT

IORING_OP_LINKAT behaves like linkat(2) and takes the same flags and
arguments.

In some internal places 'hardlink' is used instead of 'link' to avoid
confusion with the SQE links. Name 'link' conflicts with the existing
'link' member of io_kiocb.

Acked-by: Linus Torvalds <torvalds@linux-foundation.org>
Suggested-by: Christian Brauner <christian.brauner@ubuntu.com>
Link: https://lore.kernel.org/io-uring/20210514145259.wtl4xcsp52woi6ab@wittgenstein/
Signed-off-by: Dmitry Kadashev <dkadashev@gmail.com>
Acked-by: Christian Brauner <christian.brauner@ubuntu.com>
Link: https://lore.kernel.org/r/20210708063447.3556403-12-dkadashev@gmail.com
[axboe: add splice_fd_in check]
Signed-off-by: Jens Axboe <axboe@kernel.dk>

diff --git a/fs/internal.h b/fs/internal.h
index 2f9750a..2bb4446 100644 (file)
--- a/fs/internal.h
+++ b/fs/internal.h
@@ -78,6 +78,8 @@ int do_renameat2(int olddfd, struct filename *oldname, int newdfd,
                 struct filename *newname, unsigned int flags);
 int do_mkdirat(int dfd, struct filename *name, umode_t mode);
 int do_symlinkat(struct filename *from, int newdfd, struct filename *to);
+int do_linkat(int olddfd, struct filename *old, int newdfd,
+                       struct filename *new, int flags);
 
 /*
  * namespace.c

diff --git a/fs/io_uring.c b/fs/io_uring.c
index 33941df..a89bbff 100644 (file)
--- a/fs/io_uring.c
+++ b/fs/io_uring.c
@@ -676,6 +676,15 @@ struct io_symlink {
        struct filename                 *newpath;
 };
 
+struct io_hardlink {
+       struct file                     *file;
+       int                             old_dfd;
+       int                             new_dfd;
+       struct filename                 *oldpath;
+       struct filename                 *newpath;
+       int                             flags;
+};
+
 struct io_completion {
        struct file                     *file;
        u32                             cflags;
@@ -837,6 +846,7 @@ struct io_kiocb {
                struct io_unlink        unlink;
                struct io_mkdir         mkdir;
                struct io_symlink       symlink;
+               struct io_hardlink      hardlink;
                /* use only after cleaning per-op data, see io_clean_op() */
                struct io_completion    compl;
        };
@@ -1050,6 +1060,7 @@ static const struct io_op_def io_op_defs[] = {
        [IORING_OP_UNLINKAT] = {},
        [IORING_OP_MKDIRAT] = {},
        [IORING_OP_SYMLINKAT] = {},
+       [IORING_OP_LINKAT] = {},
 };
 
 /* requests with any of those set should undergo io_disarm_next() */
@@ -3713,6 +3724,57 @@ static int io_symlinkat(struct io_kiocb *req, int issue_flags)
        return 0;
 }
 
+static int io_linkat_prep(struct io_kiocb *req,
+                           const struct io_uring_sqe *sqe)
+{
+       struct io_hardlink *lnk = &req->hardlink;
+       const char __user *oldf, *newf;
+
+       if (unlikely(req->ctx->flags & IORING_SETUP_IOPOLL))
+               return -EINVAL;
+       if (sqe->ioprio || sqe->rw_flags || sqe->buf_index || sqe->splice_fd_in)
+               return -EINVAL;
+       if (unlikely(req->flags & REQ_F_FIXED_FILE))
+               return -EBADF;
+
+       lnk->old_dfd = READ_ONCE(sqe->fd);
+       lnk->new_dfd = READ_ONCE(sqe->len);
+       oldf = u64_to_user_ptr(READ_ONCE(sqe->addr));
+       newf = u64_to_user_ptr(READ_ONCE(sqe->addr2));
+       lnk->flags = READ_ONCE(sqe->hardlink_flags);
+
+       lnk->oldpath = getname(oldf);
+       if (IS_ERR(lnk->oldpath))
+               return PTR_ERR(lnk->oldpath);
+
+       lnk->newpath = getname(newf);
+       if (IS_ERR(lnk->newpath)) {
+               putname(lnk->oldpath);
+               return PTR_ERR(lnk->newpath);
+       }
+
+       req->flags |= REQ_F_NEED_CLEANUP;
+       return 0;
+}
+
+static int io_linkat(struct io_kiocb *req, int issue_flags)
+{
+       struct io_hardlink *lnk = &req->hardlink;
+       int ret;
+
+       if (issue_flags & IO_URING_F_NONBLOCK)
+               return -EAGAIN;
+
+       ret = do_linkat(lnk->old_dfd, lnk->oldpath, lnk->new_dfd,
+                               lnk->newpath, lnk->flags);
+
+       req->flags &= ~REQ_F_NEED_CLEANUP;
+       if (ret < 0)
+               req_set_fail(req);
+       io_req_complete(req, ret);
+       return 0;
+}
+
 static int io_shutdown_prep(struct io_kiocb *req,
                            const struct io_uring_sqe *sqe)
 {
@@ -6114,6 +6176,8 @@ static int io_req_prep(struct io_kiocb *req, const struct io_uring_sqe *sqe)
                return io_mkdirat_prep(req, sqe);
        case IORING_OP_SYMLINKAT:
                return io_symlinkat_prep(req, sqe);
+       case IORING_OP_LINKAT:
+               return io_linkat_prep(req, sqe);
        }
 
        printk_once(KERN_WARNING "io_uring: unhandled opcode %d\n",
@@ -6284,6 +6348,10 @@ static void io_clean_op(struct io_kiocb *req)
                        putname(req->symlink.oldpath);
                        putname(req->symlink.newpath);
                        break;
+               case IORING_OP_LINKAT:
+                       putname(req->hardlink.oldpath);
+                       putname(req->hardlink.newpath);
+                       break;
                }
        }
        if ((req->flags & REQ_F_POLLED) && req->apoll) {
@@ -6418,6 +6486,9 @@ static int io_issue_sqe(struct io_kiocb *req, unsigned int issue_flags)
        case IORING_OP_SYMLINKAT:
                ret = io_symlinkat(req, issue_flags);
                break;
+       case IORING_OP_LINKAT:
+               ret = io_linkat(req, issue_flags);
+               break;
        default:
                ret = -EINVAL;
                break;

diff --git a/fs/namei.c b/fs/namei.c
index 803fc95..0718e1e 100644 (file)
--- a/fs/namei.c
+++ b/fs/namei.c
@@ -4368,7 +4368,7 @@ EXPORT_SYMBOL(vfs_link);
  * with linux 2.0, and to avoid hard-linking to directories
  * and other special files.  --ADM
  */
-static int do_linkat(int olddfd, struct filename *old, int newdfd,
+int do_linkat(int olddfd, struct filename *old, int newdfd,
              struct filename *new, int flags)
 {
        struct user_namespace *mnt_userns;

diff --git a/include/uapi/linux/io_uring.h b/include/uapi/linux/io_uring.h
index 61fd347..10eb38d 100644 (file)
--- a/include/uapi/linux/io_uring.h
+++ b/include/uapi/linux/io_uring.h
@@ -44,6 +44,7 @@ struct io_uring_sqe {
                __u32           splice_flags;
                __u32           rename_flags;
                __u32           unlink_flags;
+               __u32           hardlink_flags;
        };
        __u64   user_data;      /* data to be passed back at completion time */
        /* pack this to avoid bogus arm OABI complaints */
@@ -135,6 +136,7 @@ enum {
        IORING_OP_UNLINKAT,
        IORING_OP_MKDIRAT,
        IORING_OP_SYMLINKAT,
+       IORING_OP_LINKAT,
 
        /* this goes last, obviously */
        IORING_OP_LAST,