[PATCH v3 26/28] memcg_write_event_control(): switch to CLASS(fd)

Al Viro
2024-11-02T05:08:32Z

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>
---
mm/memcontrol-v1.c | 44 +++++++++++++++-----------------------------
1 file changed, 15 insertions(+), 29 deletions(-)

diff --git a/mm/memcontrol-v1.c b/mm/memcontrol-v1.c
index 81d8819f13cd..bc54cff7615f 100644
--- 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;
}

--
2.39.5