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authorMichal Hocko <mhocko@suse.com>2023-09-21 10:38:29 +0300
committerAndrew Morton <akpm@linux-foundation.org>2023-09-30 03:20:47 +0300
commit4597648fddeadef5877610d693af11906aa666ac (patch)
tree516a3ba84c21dee04c7eb9eb4e8cd5878a8e37ed /mm
parentca56489c2f1df516801eeff06129d2e9e282ab7b (diff)
downloadlinux-4597648fddeadef5877610d693af11906aa666ac.tar.xz
mm, memcg: reconsider kmem.limit_in_bytes deprecation
This reverts commits 86327e8eb94c ("memcg: drop kmem.limit_in_bytes") and partially reverts 58056f77502f ("memcg, kmem: further deprecate kmem.limit_in_bytes") which have incrementally removed support for the kernel memory accounting hard limit. Unfortunately it has turned out that there is still userspace depending on the existence of memory.kmem.limit_in_bytes [1]. The underlying functionality is not really required but the non-existent file just confuses the userspace which fails in the result. The patch to fix this on the userspace side has been submitted but it is hard to predict how it will propagate through the maze of 3rd party consumers of the software. Now, reverting alone 86327e8eb94c is not an option because there is another set of userspace which cannot cope with ENOTSUPP returned when writing to the file. Therefore we have to go and revisit 58056f77502f as well. There are two ways to go ahead. Either we give up on the deprecation and fully revert 58056f77502f as well or we can keep kmem.limit_in_bytes but make the write a noop and warn about the fact. This should work for both known breaking workloads which depend on the existence but do not depend on the hard limit enforcement. Note to backporters to stable trees. a8c49af3be5f ("memcg: add per-memcg total kernel memory stat") introduced in 4.18 has added memcg_account_kmem so the accounting is not done by obj_cgroup_charge_pages directly for v1 anymore. Prior kernels need to add it explicitly (thanks to Johannes for pointing this out). [akpm@linux-foundation.org: fix build - remove unused local] Link: http://lkml.kernel.org/r/20230920081101.GA12096@linuxonhyperv3.guj3yctzbm1etfxqx2vob5hsef.xx.internal.cloudapp.net [1] Link: https://lkml.kernel.org/r/ZRE5VJozPZt9bRPy@dhcp22.suse.cz Fixes: 86327e8eb94c ("memcg: drop kmem.limit_in_bytes") Fixes: 58056f77502f ("memcg, kmem: further deprecate kmem.limit_in_bytes") Signed-off-by: Michal Hocko <mhocko@suse.com> Acked-by: Shakeel Butt <shakeelb@google.com> Acked-by: Johannes Weiner <hannes@cmpxchg.org> Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org> Cc: Jeremi Piotrowski <jpiotrowski@linux.microsoft.com> Cc: Muchun Song <muchun.song@linux.dev> Cc: Roman Gushchin <roman.gushchin@linux.dev> Cc: Tejun heo <tj@kernel.org> Cc: <stable@vger.kernel.org> Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Diffstat (limited to 'mm')
-rw-r--r--mm/memcontrol.c13
1 files changed, 13 insertions, 0 deletions
diff --git a/mm/memcontrol.c b/mm/memcontrol.c
index d13dde2f8b56..5b009b233ab8 100644
--- a/mm/memcontrol.c
+++ b/mm/memcontrol.c
@@ -3867,6 +3867,13 @@ static ssize_t mem_cgroup_write(struct kernfs_open_file *of,
case _MEMSWAP:
ret = mem_cgroup_resize_max(memcg, nr_pages, true);
break;
+ case _KMEM:
+ pr_warn_once("kmem.limit_in_bytes is deprecated and will be removed. "
+ "Writing any value to this file has no effect. "
+ "Please report your usecase to linux-mm@kvack.org if you "
+ "depend on this functionality.\n");
+ ret = 0;
+ break;
case _TCP:
ret = memcg_update_tcp_max(memcg, nr_pages);
break;
@@ -5078,6 +5085,12 @@ static struct cftype mem_cgroup_legacy_files[] = {
},
#endif
{
+ .name = "kmem.limit_in_bytes",
+ .private = MEMFILE_PRIVATE(_KMEM, RES_LIMIT),
+ .write = mem_cgroup_write,
+ .read_u64 = mem_cgroup_read_u64,
+ },
+ {
.name = "kmem.usage_in_bytes",
.private = MEMFILE_PRIVATE(_KMEM, RES_USAGE),
.read_u64 = mem_cgroup_read_u64,