Unrot uml mconsole a bit

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>

diff --git a/arch/um/drivers/mconsole_kern.c b/arch/um/drivers/mconsole_kern.c
index 51069245b79a207274547c51ce904206f5ffb939..3b3c36601a7b39e3634458eb11c5b0245261cb3e 100644 (file)
--- a/arch/um/drivers/mconsole_kern.c
+++ b/arch/um/drivers/mconsole_kern.c
@@ -125,50 +125,36 @@ void mconsole_log(struct mc_request *req)
 void mconsole_proc(struct mc_request *req)
 {
        struct nameidata nd;
-       struct file_system_type *proc;
-       struct super_block *super;
+       struct vfsmount *mnt = current->nsproxy->pid_ns->proc_mnt;
        struct file *file;
        int n, err;
        char *ptr = req->request.data, *buf;
+       mm_segment_t old_fs = get_fs();
 
        ptr += strlen("proc");
        ptr = skip_spaces(ptr);
 
-       proc = get_fs_type("proc");
-       if (proc == NULL) {
-               mconsole_reply(req, "procfs not registered", 1, 0);
+       err = vfs_path_lookup(mnt->mnt_root, mnt, ptr, LOOKUP_FOLLOW, &nd);
+       if (err) {
+               mconsole_reply(req, "Failed to look up file", 1, 0);
                goto out;
        }
 
-       super = (*proc->get_sb)(proc, 0, NULL, NULL);
-       put_filesystem(proc);
-       if (super == NULL) {
-               mconsole_reply(req, "Failed to get procfs superblock", 1, 0);
+       err = may_open(&nd.path, MAY_READ, FMODE_READ);
+       if (result) {
+               mconsole_reply(req, "Failed to open file", 1, 0);
+               path_put(&nd.path);
                goto out;
        }
-       up_write(&super->s_umount);
-
-       nd.path.dentry = super->s_root;
-       nd.path.mnt = NULL;
-       nd.flags = O_RDONLY + 1;
-       nd.last_type = LAST_ROOT;
-
-       /* START: it was experienced that the stability problems are closed
-        * if commenting out these two calls + the below read cycle. To
-        * make UML crash again, it was enough to readd either one.*/
-       err = link_path_walk(ptr, &nd);
-       if (err) {
-               mconsole_reply(req, "Failed to look up file", 1, 0);
-               goto out_kill;
-       }
 
        file = dentry_open(nd.path.dentry, nd.path.mnt, O_RDONLY,
                           current_cred());
+       err = PTR_ERR(file);
        if (IS_ERR(file)) {
                mconsole_reply(req, "Failed to open file", 1, 0);
-               goto out_kill;
+               path_put(&nd.path);
+               goto out;
        }
-       /*END*/
 
        buf = kmalloc(PAGE_SIZE, GFP_KERNEL);
        if (buf == NULL) {
@@ -176,10 +162,13 @@ void mconsole_proc(struct mc_request *req)
                goto out_fput;
        }
 
-       if ((file->f_op != NULL) && (file->f_op->read != NULL)) {
+       if (file->f_op->read) {
                do {
-                       n = (*file->f_op->read)(file, buf, PAGE_SIZE - 1,
-                                               &file->f_pos);
+                       loff_t pos;
+                       set_fs(KERNEL_DS);
+                       n = vfs_read(file, buf, PAGE_SIZE - 1, &pos);
+                       file_pos_write(file, pos);
+                       set_fs(old_fs);
                        if (n >= 0) {
                                buf[n] = '\0';
                                mconsole_reply(req, buf, 0, (n > 0));
@@ -197,8 +186,6 @@ void mconsole_proc(struct mc_request *req)
        kfree(buf);
  out_fput:
        fput(file);
- out_kill:
-       deactivate_super(super);
  out: ;
 }
 #endif