memcg_write_event_control(): switch to CLASS(fd)

some reordering required - take both fdget() to the point before
the allocations, with matching move of fdput() to the very end
of failure exit(s); after that it converts trivially.

simplify the cleanups that involve css_put(), while we are at it...

Reviewed-by: Christian Brauner <brauner@kernel.org>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>

diff --git a/mm/memcontrol-v1.c b/mm/memcontrol-v1.c
index 81d8819f13cdbf0c1a6a6c584fa6a633253a00ed..bc54cff7615fcab3468b8eb77a5eaebebf49db7c 100644 (file)
--- a/mm/memcontrol-v1.c
+++ b/mm/memcontrol-v1.c
@@ -1911,8 +1911,6 @@ static ssize_t memcg_write_event_control(struct kernfs_open_file *of,
        struct mem_cgroup_event *event;
        struct cgroup_subsys_state *cfile_css;
        unsigned int efd, cfd;
-       struct fd efile;
-       struct fd cfile;
        struct dentry *cdentry;
        const char *name;
        char *endp;
@@ -1936,6 +1934,12 @@ static ssize_t memcg_write_event_control(struct kernfs_open_file *of,
        else
                return -EINVAL;
 
+       CLASS(fd, efile)(efd);
+       if (fd_empty(efile))
+               return -EBADF;
+
+       CLASS(fd, cfile)(cfd);
+
        event = kzalloc(sizeof(*event), GFP_KERNEL);
        if (!event)
                return -ENOMEM;
@@ -1946,20 +1950,13 @@ static ssize_t memcg_write_event_control(struct kernfs_open_file *of,
        init_waitqueue_func_entry(&event->wait, memcg_event_wake);
        INIT_WORK(&event->remove, memcg_event_remove);
 
-       efile = fdget(efd);
-       if (!fd_file(efile)) {
-               ret = -EBADF;
-               goto out_kfree;
-       }
-
        event->eventfd = eventfd_ctx_fileget(fd_file(efile));
        if (IS_ERR(event->eventfd)) {
                ret = PTR_ERR(event->eventfd);
-               goto out_put_efile;
+               goto out_kfree;
        }
 
-       cfile = fdget(cfd);
-       if (!fd_file(cfile)) {
+       if (fd_empty(cfile)) {
                ret = -EBADF;
                goto out_put_eventfd;
        }
@@ -1968,7 +1965,7 @@ static ssize_t memcg_write_event_control(struct kernfs_open_file *of,
        /* AV: shouldn't we check that it's been opened for read instead? */
        ret = file_permission(fd_file(cfile), MAY_READ);
        if (ret < 0)
-               goto out_put_cfile;
+               goto out_put_eventfd;
 
        /*
         * The control file must be a regular cgroup1 file. As a regular cgroup
@@ -1977,7 +1974,7 @@ static ssize_t memcg_write_event_control(struct kernfs_open_file *of,
        cdentry = fd_file(cfile)->f_path.dentry;
        if (cdentry->d_sb->s_type != &cgroup_fs_type || !d_is_reg(cdentry)) {
                ret = -EINVAL;
-               goto out_put_cfile;
+               goto out_put_eventfd;
        }
 
        /*
@@ -2010,7 +2007,7 @@ static ssize_t memcg_write_event_control(struct kernfs_open_file *of,
                event->unregister_event = memsw_cgroup_usage_unregister_event;
        } else {
                ret = -EINVAL;
-               goto out_put_cfile;
+               goto out_put_eventfd;
        }
 
        /*
@@ -2022,11 +2019,9 @@ static ssize_t memcg_write_event_control(struct kernfs_open_file *of,
                                               &memory_cgrp_subsys);
        ret = -EINVAL;
        if (IS_ERR(cfile_css))
-               goto out_put_cfile;
-       if (cfile_css != css) {
-               css_put(cfile_css);
-               goto out_put_cfile;
-       }
+               goto out_put_eventfd;
+       if (cfile_css != css)
+               goto out_put_css;
 
        ret = event->register_event(memcg, event->eventfd, buf);
        if (ret)
@@ -2037,23 +2032,14 @@ static ssize_t memcg_write_event_control(struct kernfs_open_file *of,
        spin_lock_irq(&memcg->event_list_lock);
        list_add(&event->list, &memcg->event_list);
        spin_unlock_irq(&memcg->event_list_lock);
-
-       fdput(cfile);
-       fdput(efile);
-
        return nbytes;
 
 out_put_css:
-       css_put(css);
-out_put_cfile:
-       fdput(cfile);
+       css_put(cfile_css);
 out_put_eventfd:
        eventfd_ctx_put(event->eventfd);
-out_put_efile:
-       fdput(efile);
 out_kfree:
        kfree(event);
-
        return ret;
 }