From 30f4834c5bc7769bdc4d88f1115b7b16f850f289 Mon Sep 17 00:00:00 2001
From: "fupan.lfp" <fupan.lfp@antgroup.com>
Date: Fri, 21 May 2021 17:55:44 +0800
Subject: [PATCH] cgroup: fix the issue of set mem.limit and mem.swap

When update memory limit, we should adapt the write sequence
for memory and swap memory, so it won't fail because
the new value and the old value don't fit kernel's
validation.

Fixes: #1917

Signed-off-by: fupan.lfp <fupan.lfp@antgroup.com>
---
 src/agent/rustjail/src/cgroups/fs/mod.rs | 38 +++++++++++++++++++-----
 1 file changed, 31 insertions(+), 7 deletions(-)

diff --git a/src/agent/rustjail/src/cgroups/fs/mod.rs b/src/agent/rustjail/src/cgroups/fs/mod.rs
index 7f41cb4ddb..04aa575379 100644
--- a/src/agent/rustjail/src/cgroups/fs/mod.rs
+++ b/src/agent/rustjail/src/cgroups/fs/mod.rs
@@ -349,14 +349,34 @@ fn set_memory_resources(cg: &cgroups::Cgroup, memory: &LinuxMemory, update: bool
         mem_controller.set_kmem_limit(-1)?;
     }
 
-    set_resource!(mem_controller, set_limit, memory, limit);
-    set_resource!(mem_controller, set_soft_limit, memory, reservation);
-    set_resource!(mem_controller, set_kmem_limit, memory, kernel);
-    set_resource!(mem_controller, set_tcp_limit, memory, kernel_tcp);
+    // If the memory update is set to -1 we should also
+    // set swap to -1, it means unlimited memory.
+    let mut swap = memory.swap.unwrap_or(0);
+    if memory.limit == Some(-1) {
+        swap = -1;
+    }
 
-    if let Some(swap) = memory.swap {
-        // set memory swap
-        let swap = if cg.v2() {
+    if memory.limit.is_some() && swap != 0 {
+        let memstat = get_memory_stats(cg)
+            .into_option()
+            .ok_or_else(|| anyhow!("failed to get the cgroup memory stats"))?;
+        let memusage = memstat.get_usage();
+
+        // When update memory limit, the kernel would check the current memory limit
+        // set against the new swap setting, if the current memory limit is large than
+        // the new swap, then set limit first, otherwise the kernel would complain and
+        // refused to set; on the other hand, if the current memory limit is smaller than
+        // the new swap, then we should set the swap first and then set the memor limit.
+        if swap == -1 || memusage.get_limit() < swap as u64 {
+            mem_controller.set_memswap_limit(swap)?;
+            set_resource!(mem_controller, set_limit, memory, limit);
+        } else {
+            set_resource!(mem_controller, set_limit, memory, limit);
+            mem_controller.set_memswap_limit(swap)?;
+        }
+    } else {
+        set_resource!(mem_controller, set_limit, memory, limit);
+        swap = if cg.v2() {
             convert_memory_swap_to_v2_value(swap, memory.limit.unwrap_or(0))?
         } else {
             swap
@@ -366,6 +386,10 @@ fn set_memory_resources(cg: &cgroups::Cgroup, memory: &LinuxMemory, update: bool
         }
     }
 
+    set_resource!(mem_controller, set_soft_limit, memory, reservation);
+    set_resource!(mem_controller, set_kmem_limit, memory, kernel);
+    set_resource!(mem_controller, set_tcp_limit, memory, kernel_tcp);
+
     if let Some(swappiness) = memory.swappiness {
         if (0..=100).contains(&swappiness) {
             mem_controller.set_swappiness(swappiness as u64)?;