memcg-introduce-non-blocking-limit-setting-option-v3

add more explanation in doc and commit message on O_NONBLOCK side-effects
(Johannes)

Link: https://lkml.kernel.org/r/20250506232833.3109790-1-shakeel.butt@linux.dev
Signed-off-by: Shakeel Butt <shakeel.butt@linux.dev>
Acked-by: Roman Gushchin <roman.gushchin@linux.dev>
Acked-by: Johannes Weiner <hannes@cmpxchg.org>
Cc: Greg Thelen <gthelen@google.com>
Cc: Michal Hocko <mhocko@kernel.org>
Cc: Michal Koutný <mkoutny@suse.com>
Cc: Muchun Song <muchun.song@linux.dev>
Cc: Tejun Heo <tj@kernel.org>
Cc: Yosry Ahmed <yosry.ahmed@linux.dev>
Cc: Christian Brauner <brauner@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

1 files changed, 22 insertions, 12 deletions

diff --git a/Documentation/admin-guide/cgroup-v2.rst b/Documentation/admin-guide/cgroup-v2.rst
index b34f1dd969e0..d537f3d3fed9 100644
--- a/Documentation/admin-guide/cgroup-v2.rst
+++ b/Documentation/admin-guide/cgroup-v2.rst
@@ -1299,12 +1299,17 @@ PAGE_SIZE multiple when read back.
 	monitors the limited cgroup to alleviate heavy reclaim
 	pressure.
 
-        If memory.high is opened with O_NONBLOCK then the synchronous
-        reclaim is bypassed. This is useful for admin processes that
-        need to dynamically adjust the job's memory limits without
-        expending their own CPU resources on memory reclamation. The
-        job will trigger the reclaim and/or get throttled on its
-        next charge request.
+	If memory.high is opened with O_NONBLOCK then the synchronous
+	reclaim is bypassed. This is useful for admin processes that
+	need to dynamically adjust the job's memory limits without
+	expending their own CPU resources on memory reclamation. The
+	job will trigger the reclaim and/or get throttled on its
+	next charge request.
+
+	Please note that with O_NONBLOCK, there is a chance that the
+	target memory cgroup may take indefinite amount of time to
+	reduce usage below the limit due to delayed charge request or
+	busy-hitting its memory to slow down reclaim.
 
   memory.max
 	A read-write single value file which exists on non-root
@@ -1323,12 +1328,17 @@ PAGE_SIZE multiple when read back.
 	Caller could retry them differently, return into userspace
 	as -ENOMEM or silently ignore in cases like disk readahead.
 
-        If memory.max is opened with O_NONBLOCK, then the synchronous
-        reclaim and oom-kill are bypassed. This is useful for admin
-        processes that need to dynamically adjust the job's memory limits
-        without expending their own CPU resources on memory reclamation.
-        The job will trigger the reclaim and/or oom-kill on its next
-        charge request.
+	If memory.max is opened with O_NONBLOCK, then the synchronous
+	reclaim and oom-kill are bypassed. This is useful for admin
+	processes that need to dynamically adjust the job's memory limits
+	without expending their own CPU resources on memory reclamation.
+	The job will trigger the reclaim and/or oom-kill on its next
+	charge request.
+
+	Please note that with O_NONBLOCK, there is a chance that the
+	target memory cgroup may take indefinite amount of time to
+	reduce usage below the limit due to delayed charge request or
+	busy-hitting its memory to slow down reclaim.
 
   memory.reclaim
 	A write-only nested-keyed file which exists for all cgroups.