From 639c98f5ad3b73358a41338b81f4af2fa7696f6e Mon Sep 17 00:00:00 2001
From: Giuseppe Scrivano <gscrivan@redhat.com>
Date: Sun, 10 Jul 2022 00:57:09 +0200
Subject: [PATCH] cgroup: add fallback to io.weight

copy the same fallback runc has.

If io.bfq.weight doesn't exist, then fallback to using io.weight with
a conversion.

Signed-off-by: Giuseppe Scrivano <gscrivan@redhat.com>
---
 crun.1                         |  6 ++++++
 crun.1.md                      |  2 ++
 src/libcrun/cgroup-resources.c | 30 +++++++++++++++++++++++++++---
 3 files changed, 35 insertions(+), 3 deletions(-)

diff --git a/crun.1 b/crun.1
index c9790165cf..a8bc0853d7 100644
--- a/crun.1
+++ b/crun.1
@@ -879,6 +879,12 @@ l l l l .
 \fB\fCOCI (x)\fR	\fB\fCcgroup 2 value (y)\fR	\fB\fCconversion\fR	\fB\fCcomment\fR
 weight	io.bfq.weight	y = x	
 weight_device	io.bfq.weight	y = x	
+weight	io.weight (fallback)	y = 1 + (x-10)*9999/990	T{
+convert linearly from [10-1000] to [1-10000]
+T}
+weight_device	io.weight (fallback)	y = 1 + (x-10)*9999/990	T{
+convert linearly from [10-1000] to [1-10000]
+T}
 rbps	io.max	y=x	
 wbps	io.max	y=x	
 riops	io.max	y=x	
diff --git a/crun.1.md b/crun.1.md
index e48cfd92e9..c4d2ca662e 100644
--- a/crun.1.md
+++ b/crun.1.md
@@ -676,6 +676,8 @@ they are converted when needed from the cgroup v1 configuration.
 |---|---|---|---|
 | weight | io.bfq.weight | y = x ||
 | weight_device | io.bfq.weight | y = x ||
+| weight | io.weight (fallback) | y = 1 + (x-10)*9999/990 | convert linearly from [10-1000] to [1-10000] |
+| weight_device | io.weight (fallback) | y = 1 + (x-10)*9999/990 | convert linearly from [10-1000] to [1-10000] |
 | rbps | io.max | y=x ||
 | wbps | io.max | y=x ||
 | riops | io.max |y=x ||
diff --git a/src/libcrun/cgroup-resources.c b/src/libcrun/cgroup-resources.c
index eb5bb40a97..53c4f122fa 100644
--- a/src/libcrun/cgroup-resources.c
+++ b/src/libcrun/cgroup-resources.c
@@ -212,9 +212,33 @@ write_blkio_resources (int dirfd, bool cgroup2, runtime_spec_schema_config_linux
       uint32_t val = blkio->weight;
 
       len = sprintf (fmt_buf, "%" PRIu32, val);
-      ret = write_cgroup_file (dirfd, cgroup2 ? "io.bfq.weight" : "blkio.weight", fmt_buf, len, err);
-      if (UNLIKELY (ret < 0))
-        return ret;
+      if (! cgroup2)
+        {
+          ret = write_cgroup_file (dirfd, "blkio.weight", fmt_buf, len, err);
+          if (UNLIKELY (ret < 0))
+            return ret;
+        }
+      else
+        {
+          ret = write_cgroup_file (dirfd, "io.bfq.weight", fmt_buf, len, err);
+          if (UNLIKELY (ret < 0))
+            {
+              if (crun_error_get_errno (err) == ENOENT)
+                {
+                  crun_error_release (err);
+
+                  /* convert linearly from [10-1000] to [1-10000] */
+                  val = 1 + (val - 10) * 9999 / 990;
+
+                  len = sprintf (fmt_buf, "%" PRIu32, val);
+
+                  ret = write_cgroup_file (dirfd, "io.weight", fmt_buf, len, err);
+                }
+
+              if (UNLIKELY (ret < 0))
+                return ret;
+            }
+        }
     }
   if (blkio->leaf_weight)
     {