From: Nick Rosbrook <nick.rosbrook@canonical.com>
Date: Mon, 28 Nov 2022 16:13:08 +0000 (-0500)
Subject: oomd: only check prefix_uid when uid != 0
X-Git-Tag: v253-rc1~402^2~2
X-Git-Url: http://git-history.diyao.me/?a=commitdiff_plain;h=66bc4f6fb1a9354ec21c9fbe48b7b6c82c7717a2;p=systemd%2F.git

oomd: only check prefix_uid when uid != 0

If the cgroup is owned by root there is no need to get prefix_uid. Only
check prefix_uid when uid != 0, and then set MANAGED_OOM_PREFERENCE_NONE
and return early if uid != prefix_uid.
---

diff --git a/src/oom/oomd-util.c b/src/oom/oomd-util.c
index 70a1dc941e..7291e044eb 100644
--- a/src/oom/oomd-util.c
+++ b/src/oom/oomd-util.c
@@ -145,7 +145,7 @@ bool oomd_swap_free_below(const OomdSystemContext *ctx, int threshold_permyriad)
 }
 
 int oomd_fetch_cgroup_oom_preference(OomdCGroupContext *ctx, const char *prefix) {
-        uid_t uid, prefix_uid;
+        uid_t uid;
         int r;
 
         assert(ctx);
@@ -160,28 +160,34 @@ int oomd_fetch_cgroup_oom_preference(OomdCGroupContext *ctx, const char *prefix)
         if (r < 0)
                 return log_debug_errno(r, "Failed to get owner/group from %s: %m", ctx->path);
 
-        r = cg_get_owner(SYSTEMD_CGROUP_CONTROLLER, prefix, &prefix_uid);
-        if (r < 0)
-                return log_debug_errno(r, "Failed to get owner/group from %s: %m", ctx->path);
+        if (uid != 0) {
+                uid_t prefix_uid;
 
-        if (uid == prefix_uid || uid == 0) {
-                /* Ignore most errors when reading the xattr since it is usually unset and cgroup xattrs are only used
-                 * as an optional feature of systemd-oomd (and the system might not even support them). */
-                r = cg_get_xattr_bool(SYSTEMD_CGROUP_CONTROLLER, ctx->path, "user.oomd_avoid");
-                if (r == -ENOMEM)
-                        return log_oom_debug();
-                if (r < 0 && !ERRNO_IS_XATTR_ABSENT(r))
-                        log_debug_errno(r, "Failed to get xattr user.oomd_avoid, ignoring: %m");
-                ctx->preference = r > 0 ? MANAGED_OOM_PREFERENCE_AVOID : ctx->preference;
+                r = cg_get_owner(SYSTEMD_CGROUP_CONTROLLER, prefix, &prefix_uid);
+                if (r < 0)
+                        return log_debug_errno(r, "Failed to get owner/group from %s: %m", prefix);
 
-                r = cg_get_xattr_bool(SYSTEMD_CGROUP_CONTROLLER, ctx->path, "user.oomd_omit");
-                if (r == -ENOMEM)
-                        return log_oom_debug();
-                if (r < 0 && !ERRNO_IS_XATTR_ABSENT(r))
-                        log_debug_errno(r, "Failed to get xattr user.oomd_omit, ignoring: %m");
-                ctx->preference = r > 0 ? MANAGED_OOM_PREFERENCE_OMIT : ctx->preference;
-        } else
-                ctx->preference = MANAGED_OOM_PREFERENCE_NONE;
+                if (uid != prefix_uid) {
+                        ctx->preference = MANAGED_OOM_PREFERENCE_NONE;
+                        return 0;
+                }
+        }
+
+        /* Ignore most errors when reading the xattr since it is usually unset and cgroup xattrs are only used
+         * as an optional feature of systemd-oomd (and the system might not even support them). */
+        r = cg_get_xattr_bool(SYSTEMD_CGROUP_CONTROLLER, ctx->path, "user.oomd_avoid");
+        if (r == -ENOMEM)
+                return log_oom_debug();
+        if (r < 0 && !ERRNO_IS_XATTR_ABSENT(r))
+                log_debug_errno(r, "Failed to get xattr user.oomd_avoid, ignoring: %m");
+        ctx->preference = r > 0 ? MANAGED_OOM_PREFERENCE_AVOID : ctx->preference;
+
+        r = cg_get_xattr_bool(SYSTEMD_CGROUP_CONTROLLER, ctx->path, "user.oomd_omit");
+        if (r == -ENOMEM)
+                return log_oom_debug();
+        if (r < 0 && !ERRNO_IS_XATTR_ABSENT(r))
+                log_debug_errno(r, "Failed to get xattr user.oomd_omit, ignoring: %m");
+        ctx->preference = r > 0 ? MANAGED_OOM_PREFERENCE_OMIT : ctx->preference;
 
         return 0;
 }