The commit is pushed to "branch-rh10-6.12.0-55.13.1.3.x.vz10-ovz" and will
appear at [email protected]:openvz/vzkernel.git
after rh10-6.12.0-55.13.1.3.25.vz10
------>
commit a05a668cf1c9f8c7bff5e89a4a6bbcd43271593a
Author: Pavel Tikhomirov <[email protected]>
Date: Mon Dec 15 19:21:56 2025 +0800
cgroup-v2: Fix error handling in cgroup_controllers_hidden_write()
Currently if there is a population error, we can end up with partially
applied mask, which is not what we want, let's do a proper cleanup.
Split cgroup_apply_hidden() into two separate helpers for showing and
hiding: cgroup_unhide() and cgroup_hide(). As cgroup_hide() never fails
we can easily use it for both hiding on success path and cleanup on
error path of cgroup_unhide() with restored old mask.
While on it let's add small comments to those helpers.
https://virtuozzo.atlassian.net/browse/VSTOR-119803
Fixes: fbc4461a215c ("cgroup-v2: Add a new API to hide cgroup files per
controller")
Co-developed-by: Konstantin Khorenko <[email protected]>
Signed-off-by: Pavel Tikhomirov <[email protected]>
Feature: ve: ve generic structures
---
kernel/cgroup/cgroup.c | 52 ++++++++++++++++++++++++++++++++++++++++++++------
1 file changed, 46 insertions(+), 6 deletions(-)
diff --git a/kernel/cgroup/cgroup.c b/kernel/cgroup/cgroup.c
index eb2b64f7da37b..92abecb000b19 100644
--- a/kernel/cgroup/cgroup.c
+++ b/kernel/cgroup/cgroup.c
@@ -3896,7 +3896,11 @@ static ssize_t cgroup_subtree_control_write(struct
kernfs_open_file *of,
return ret ?: nbytes;
}
-static int cgroup_apply_hidden(struct cgroup *cgrp)
+/*
+ * cgroup_unhide() - Apply cleared bits in hidden_ss_mask to the cgroup
+ * directory by populating files for visible controllers.
+ */
+static int cgroup_unhide(struct cgroup *cgrp)
{
struct cgroup_subsys *ss;
int ssid;
@@ -3916,14 +3920,36 @@ static int cgroup_apply_hidden(struct cgroup *cgrp)
ret = css_populate_dir(css);
if (ret)
return ret;
- } else {
+ }
+ }
+
+ return 0;
+}
+
+/*
+ * cgroup_hide() - Apply set bits in hidden_ss_mask to the cgroup
+ * directory by clearing files for hidden controllers.
+ */
+static void cgroup_hide(struct cgroup *cgrp)
+{
+ struct cgroup_subsys *ss;
+ int ssid;
+
+ for_each_subsys(ss, ssid) {
+ struct cgroup_subsys_state *css = cgroup_css(cgrp, ss);
+
+ if (!(cgroup_ss_mask(cgrp) & (1 << ss->id)))
+ continue;
+
+ if (!css)
+ continue;
+
+ if (!css_visible(css)) {
css_clear_dir(css);
if (ss->css_reset)
ss->css_reset(css);
}
}
-
- return 0;
}
/* change the hidden controllers for a cgroup in the default hierarchy */
@@ -3933,6 +3959,7 @@ static ssize_t cgroup_controllers_hidden_write(struct
kernfs_open_file *of,
{
struct cgroup_subsys *ss;
u16 hide = 0, show = 0;
+ u16 old_hidden_ss_mask;
struct cgroup *cgrp;
int ssid, ret;
char *tok;
@@ -3988,10 +4015,23 @@ static ssize_t cgroup_controllers_hidden_write(struct
kernfs_open_file *of,
goto out_unlock;
}
- cgrp->hidden_ss_mask |= hide;
+ /*
+ * This is similar to cgroup_apply_control_enable(). We first try to
+ * populate dirs for controllers being shown, and on success, hide the
+ * controllers being hidden. On error we restore the old mask and hide
+ * any dirs that might have been populated in cgroup_unhide().
+ */
+ old_hidden_ss_mask = cgroup_hidden_ss_mask(cgrp);
cgrp->hidden_ss_mask &= ~show;
- ret = cgroup_apply_hidden(cgrp);
+ ret = cgroup_unhide(cgrp);
+ if (ret)
+ /* Restore old mask on failure */
+ cgrp->hidden_ss_mask = old_hidden_ss_mask;
+ else
+ cgrp->hidden_ss_mask |= hide;
+
+ cgroup_hide(cgrp);
if (ret)
goto out_unlock;
_______________________________________________
Devel mailing list
[email protected]
https://lists.openvz.org/mailman/listinfo/devel
