Applications can currently escape their cgroup memory containment when zram is used. This patchset adds per-cgroup limiting of zram compressed memory to fix it. As we know, zram can be used in two ways, direct and indirect, this patchset can charge memory in both cases. Direct zram usage by process within a cgroup will fail to charge if there is no memory. Indirect zram usage by process within a cgroup via swap in PF_MEMALLOC context, will charge successfully. This allows some limit overrun, but not enough to matter in practice.Charge compressed page once, mean a page will be freed.the size of compressed page is less than or equal to the page to be freed. The numbers of excess depend on the compression ratio only. The maximum amount will not exceed 400KB, and will be smaller than the hard limit finally, So not an unbounded way. Changes from V1: - remove memalloc_noreclaim_save in zram_recompress() - add gfp_t flag in obj_cgroup_charge_zram() V1's link: https://lore.kernel.org/all/20230707044613.1169103-1-hezhongkun.hzk@xxxxxxxxxxxxx/ The first patch charged in zsmalloc, now aborted: https://lore.kernel.org/all/20230615034830.1361853-1-hezhongkun.hzk@xxxxxxxxxxxxx/ We charge compressed memory directly in the zram module instead of in the zsmalloc module because zsmallc may be used by zswap, zswap objects has been charged once in the zswap module, so zsmallc will double charge. Summarize the previous discussion: [1]Michal's concern is that the hard limit reclaim would fail. Chage compressed page once, mean a page will be freed, so allows some limit overrun not exceed 400KB. [2]David's concern is that if there is a page in the BIO that is not charged,we can not charge the compressed page for the fs->zram and whether the recompress case is charged. As i can see, page caches are alloced by user with cgroup. For the corner case, ZERO_PAGE will not take up space after compression. Besides,the recompress case is charged. Zhongkun He (2): memcg: Add support for zram object charge zram: charge the compressed RAM to the page's memcgroup drivers/block/zram/zram_drv.c | 46 +++++++++++++++++++++++++++++++++++ drivers/block/zram/zram_drv.h | 1 + include/linux/memcontrol.h | 12 +++++++++ mm/memcontrol.c | 24 ++++++++++++++++++ 4 files changed, 83 insertions(+) -- 2.25.1
