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![Qi Zheng](/assets/img/avatar_default.png)
Now there are no readers of shrinker_rwsem, so we can simply replace it with mutex lock. [akpm@linux-foundation.org: update the fix to alloc_shrinker_info()] Link: https://lkml.kernel.org/r/20230911094444.68966-46-zhengqi.arch@bytedance.com Signed-off-by: Qi Zheng <zhengqi.arch@bytedance.com> Reviewed-by: Muchun Song <songmuchun@bytedance.com> Cc: Abhinav Kumar <quic_abhinavk@quicinc.com> Cc: Alasdair Kergon <agk@redhat.com> Cc: Alexander Viro <viro@zeniv.linux.org.uk> Cc: Alyssa Rosenzweig <alyssa.rosenzweig@collabora.com> Cc: Andreas Dilger <adilger.kernel@dilger.ca> Cc: Andreas Gruenbacher <agruenba@redhat.com> Cc: Anna Schumaker <anna@kernel.org> Cc: Arnd Bergmann <arnd@arndb.de> Cc: Bob Peterson <rpeterso@redhat.com> Cc: Borislav Petkov <bp@alien8.de> Cc: Carlos Llamas <cmllamas@google.com> Cc: Chandan Babu R <chandan.babu@oracle.com> Cc: Chao Yu <chao@kernel.org> Cc: Chris Mason <clm@fb.com> Cc: Christian Brauner <brauner@kernel.org> Cc: Christian Koenig <christian.koenig@amd.com> Cc: Chuck Lever <cel@kernel.org> Cc: Coly Li <colyli@suse.de> Cc: Dai Ngo <Dai.Ngo@oracle.com> Cc: Daniel Vetter <daniel@ffwll.ch> Cc: Daniel Vetter <daniel.vetter@ffwll.ch> Cc: "Darrick J. Wong" <djwong@kernel.org> Cc: Dave Chinner <david@fromorbit.com> Cc: Dave Hansen <dave.hansen@linux.intel.com> Cc: David Airlie <airlied@gmail.com> Cc: David Hildenbrand <david@redhat.com> Cc: David Sterba <dsterba@suse.com> Cc: Dmitry Baryshkov <dmitry.baryshkov@linaro.org> Cc: Gao Xiang <hsiangkao@linux.alibaba.com> Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org> Cc: Huang Rui <ray.huang@amd.com> Cc: Ingo Molnar <mingo@redhat.com> Cc: Jaegeuk Kim <jaegeuk@kernel.org> Cc: Jani Nikula <jani.nikula@linux.intel.com> Cc: Jan Kara <jack@suse.cz> Cc: Jason Wang <jasowang@redhat.com> Cc: Jeff Layton <jlayton@kernel.org> Cc: Jeffle Xu <jefflexu@linux.alibaba.com> Cc: Joel Fernandes (Google) <joel@joelfernandes.org> Cc: Joonas Lahtinen <joonas.lahtinen@linux.intel.com> Cc: Josef Bacik <josef@toxicpanda.com> Cc: Juergen Gross <jgross@suse.com> Cc: Kent Overstreet <kent.overstreet@gmail.com> Cc: Kirill Tkhai <tkhai@ya.ru> Cc: Marijn Suijten <marijn.suijten@somainline.org> Cc: "Michael S. Tsirkin" <mst@redhat.com> Cc: Mike Snitzer <snitzer@kernel.org> Cc: Minchan Kim <minchan@kernel.org> Cc: Nadav Amit <namit@vmware.com> Cc: Neil Brown <neilb@suse.de> Cc: Oleksandr Tyshchenko <oleksandr_tyshchenko@epam.com> Cc: Olga Kornievskaia <kolga@netapp.com> Cc: Paul E. McKenney <paulmck@kernel.org> Cc: Richard Weinberger <richard@nod.at> Cc: Rob Clark <robdclark@gmail.com> Cc: Rob Herring <robh@kernel.org> Cc: Rodrigo Vivi <rodrigo.vivi@intel.com> Cc: Roman Gushchin <roman.gushchin@linux.dev> Cc: Sean Paul <sean@poorly.run> Cc: Sergey Senozhatsky <senozhatsky@chromium.org> Cc: Song Liu <song@kernel.org> Cc: Stefano Stabellini <sstabellini@kernel.org> Cc: Steven Price <steven.price@arm.com> Cc: "Theodore Ts'o" <tytso@mit.edu> Cc: Thomas Gleixner <tglx@linutronix.de> Cc: Tomeu Vizoso <tomeu.vizoso@collabora.com> Cc: Tom Talpey <tom@talpey.com> Cc: Trond Myklebust <trond.myklebust@hammerspace.com> Cc: Tvrtko Ursulin <tvrtko.ursulin@linux.intel.com> Cc: Vlastimil Babka <vbabka@suse.cz> Cc: Xuan Zhuo <xuanzhuo@linux.alibaba.com> Cc: Yue Hu <huyue2@coolpad.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
809 lines
21 KiB
C
809 lines
21 KiB
C
// SPDX-License-Identifier: GPL-2.0
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#include <linux/memcontrol.h>
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#include <linux/rwsem.h>
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#include <linux/shrinker.h>
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#include <linux/rculist.h>
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#include <trace/events/vmscan.h>
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#include "internal.h"
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LIST_HEAD(shrinker_list);
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DEFINE_MUTEX(shrinker_mutex);
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#ifdef CONFIG_MEMCG
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static int shrinker_nr_max;
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static inline int shrinker_unit_size(int nr_items)
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{
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return (DIV_ROUND_UP(nr_items, SHRINKER_UNIT_BITS) * sizeof(struct shrinker_info_unit *));
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}
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static inline void shrinker_unit_free(struct shrinker_info *info, int start)
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{
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struct shrinker_info_unit **unit;
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int nr, i;
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if (!info)
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return;
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unit = info->unit;
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nr = DIV_ROUND_UP(info->map_nr_max, SHRINKER_UNIT_BITS);
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for (i = start; i < nr; i++) {
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if (!unit[i])
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break;
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kfree(unit[i]);
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unit[i] = NULL;
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}
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}
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static inline int shrinker_unit_alloc(struct shrinker_info *new,
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struct shrinker_info *old, int nid)
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{
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struct shrinker_info_unit *unit;
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int nr = DIV_ROUND_UP(new->map_nr_max, SHRINKER_UNIT_BITS);
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int start = old ? DIV_ROUND_UP(old->map_nr_max, SHRINKER_UNIT_BITS) : 0;
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int i;
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for (i = start; i < nr; i++) {
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unit = kzalloc_node(sizeof(*unit), GFP_KERNEL, nid);
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if (!unit) {
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shrinker_unit_free(new, start);
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return -ENOMEM;
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}
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new->unit[i] = unit;
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}
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return 0;
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}
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void free_shrinker_info(struct mem_cgroup *memcg)
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{
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struct mem_cgroup_per_node *pn;
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struct shrinker_info *info;
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int nid;
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for_each_node(nid) {
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pn = memcg->nodeinfo[nid];
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info = rcu_dereference_protected(pn->shrinker_info, true);
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shrinker_unit_free(info, 0);
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kvfree(info);
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rcu_assign_pointer(pn->shrinker_info, NULL);
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}
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}
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int alloc_shrinker_info(struct mem_cgroup *memcg)
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{
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struct shrinker_info *info;
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int nid, ret = 0;
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int array_size = 0;
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mutex_lock(&shrinker_mutex);
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array_size = shrinker_unit_size(shrinker_nr_max);
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for_each_node(nid) {
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info = kvzalloc_node(sizeof(*info) + array_size, GFP_KERNEL, nid);
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if (!info)
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goto err;
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info->map_nr_max = shrinker_nr_max;
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if (shrinker_unit_alloc(info, NULL, nid))
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goto err;
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rcu_assign_pointer(memcg->nodeinfo[nid]->shrinker_info, info);
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}
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mutex_unlock(&shrinker_mutex);
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return ret;
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err:
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mutex_unlock(&shrinker_mutex);
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free_shrinker_info(memcg);
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return -ENOMEM;
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}
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static struct shrinker_info *shrinker_info_protected(struct mem_cgroup *memcg,
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int nid)
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{
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return rcu_dereference_protected(memcg->nodeinfo[nid]->shrinker_info,
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lockdep_is_held(&shrinker_mutex));
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}
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static int expand_one_shrinker_info(struct mem_cgroup *memcg, int new_size,
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int old_size, int new_nr_max)
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{
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struct shrinker_info *new, *old;
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struct mem_cgroup_per_node *pn;
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int nid;
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for_each_node(nid) {
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pn = memcg->nodeinfo[nid];
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old = shrinker_info_protected(memcg, nid);
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/* Not yet online memcg */
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if (!old)
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return 0;
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/* Already expanded this shrinker_info */
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if (new_nr_max <= old->map_nr_max)
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continue;
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new = kvmalloc_node(sizeof(*new) + new_size, GFP_KERNEL, nid);
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if (!new)
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return -ENOMEM;
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new->map_nr_max = new_nr_max;
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memcpy(new->unit, old->unit, old_size);
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if (shrinker_unit_alloc(new, old, nid)) {
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kvfree(new);
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return -ENOMEM;
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}
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rcu_assign_pointer(pn->shrinker_info, new);
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kvfree_rcu(old, rcu);
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}
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return 0;
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}
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static int expand_shrinker_info(int new_id)
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{
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int ret = 0;
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int new_nr_max = round_up(new_id + 1, SHRINKER_UNIT_BITS);
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int new_size, old_size = 0;
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struct mem_cgroup *memcg;
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if (!root_mem_cgroup)
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goto out;
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lockdep_assert_held(&shrinker_mutex);
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new_size = shrinker_unit_size(new_nr_max);
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old_size = shrinker_unit_size(shrinker_nr_max);
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memcg = mem_cgroup_iter(NULL, NULL, NULL);
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do {
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ret = expand_one_shrinker_info(memcg, new_size, old_size,
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new_nr_max);
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if (ret) {
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mem_cgroup_iter_break(NULL, memcg);
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goto out;
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}
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} while ((memcg = mem_cgroup_iter(NULL, memcg, NULL)) != NULL);
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out:
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if (!ret)
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shrinker_nr_max = new_nr_max;
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return ret;
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}
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static inline int shrinker_id_to_index(int shrinker_id)
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{
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return shrinker_id / SHRINKER_UNIT_BITS;
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}
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static inline int shrinker_id_to_offset(int shrinker_id)
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{
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return shrinker_id % SHRINKER_UNIT_BITS;
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}
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static inline int calc_shrinker_id(int index, int offset)
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{
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return index * SHRINKER_UNIT_BITS + offset;
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}
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void set_shrinker_bit(struct mem_cgroup *memcg, int nid, int shrinker_id)
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{
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if (shrinker_id >= 0 && memcg && !mem_cgroup_is_root(memcg)) {
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struct shrinker_info *info;
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struct shrinker_info_unit *unit;
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rcu_read_lock();
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info = rcu_dereference(memcg->nodeinfo[nid]->shrinker_info);
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unit = info->unit[shrinker_id_to_index(shrinker_id)];
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if (!WARN_ON_ONCE(shrinker_id >= info->map_nr_max)) {
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/* Pairs with smp mb in shrink_slab() */
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smp_mb__before_atomic();
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set_bit(shrinker_id_to_offset(shrinker_id), unit->map);
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}
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rcu_read_unlock();
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}
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}
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static DEFINE_IDR(shrinker_idr);
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static int shrinker_memcg_alloc(struct shrinker *shrinker)
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{
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int id, ret = -ENOMEM;
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if (mem_cgroup_disabled())
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return -ENOSYS;
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mutex_lock(&shrinker_mutex);
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id = idr_alloc(&shrinker_idr, shrinker, 0, 0, GFP_KERNEL);
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if (id < 0)
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goto unlock;
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if (id >= shrinker_nr_max) {
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if (expand_shrinker_info(id)) {
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idr_remove(&shrinker_idr, id);
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goto unlock;
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}
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}
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shrinker->id = id;
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ret = 0;
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unlock:
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mutex_unlock(&shrinker_mutex);
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return ret;
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}
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static void shrinker_memcg_remove(struct shrinker *shrinker)
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{
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int id = shrinker->id;
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BUG_ON(id < 0);
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lockdep_assert_held(&shrinker_mutex);
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idr_remove(&shrinker_idr, id);
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}
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static long xchg_nr_deferred_memcg(int nid, struct shrinker *shrinker,
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struct mem_cgroup *memcg)
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{
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struct shrinker_info *info;
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struct shrinker_info_unit *unit;
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long nr_deferred;
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rcu_read_lock();
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info = rcu_dereference(memcg->nodeinfo[nid]->shrinker_info);
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unit = info->unit[shrinker_id_to_index(shrinker->id)];
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nr_deferred = atomic_long_xchg(&unit->nr_deferred[shrinker_id_to_offset(shrinker->id)], 0);
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rcu_read_unlock();
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return nr_deferred;
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}
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static long add_nr_deferred_memcg(long nr, int nid, struct shrinker *shrinker,
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struct mem_cgroup *memcg)
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{
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struct shrinker_info *info;
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struct shrinker_info_unit *unit;
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long nr_deferred;
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rcu_read_lock();
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info = rcu_dereference(memcg->nodeinfo[nid]->shrinker_info);
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unit = info->unit[shrinker_id_to_index(shrinker->id)];
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nr_deferred =
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atomic_long_add_return(nr, &unit->nr_deferred[shrinker_id_to_offset(shrinker->id)]);
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rcu_read_unlock();
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return nr_deferred;
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}
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void reparent_shrinker_deferred(struct mem_cgroup *memcg)
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{
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int nid, index, offset;
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long nr;
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struct mem_cgroup *parent;
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struct shrinker_info *child_info, *parent_info;
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struct shrinker_info_unit *child_unit, *parent_unit;
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parent = parent_mem_cgroup(memcg);
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if (!parent)
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parent = root_mem_cgroup;
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/* Prevent from concurrent shrinker_info expand */
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mutex_lock(&shrinker_mutex);
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for_each_node(nid) {
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child_info = shrinker_info_protected(memcg, nid);
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parent_info = shrinker_info_protected(parent, nid);
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for (index = 0; index < shrinker_id_to_index(child_info->map_nr_max); index++) {
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child_unit = child_info->unit[index];
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parent_unit = parent_info->unit[index];
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for (offset = 0; offset < SHRINKER_UNIT_BITS; offset++) {
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nr = atomic_long_read(&child_unit->nr_deferred[offset]);
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atomic_long_add(nr, &parent_unit->nr_deferred[offset]);
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}
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}
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}
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mutex_unlock(&shrinker_mutex);
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}
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#else
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static int shrinker_memcg_alloc(struct shrinker *shrinker)
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{
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return -ENOSYS;
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}
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static void shrinker_memcg_remove(struct shrinker *shrinker)
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{
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}
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static long xchg_nr_deferred_memcg(int nid, struct shrinker *shrinker,
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struct mem_cgroup *memcg)
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{
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return 0;
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}
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static long add_nr_deferred_memcg(long nr, int nid, struct shrinker *shrinker,
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struct mem_cgroup *memcg)
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{
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return 0;
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}
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#endif /* CONFIG_MEMCG */
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static long xchg_nr_deferred(struct shrinker *shrinker,
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struct shrink_control *sc)
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{
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int nid = sc->nid;
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if (!(shrinker->flags & SHRINKER_NUMA_AWARE))
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nid = 0;
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if (sc->memcg &&
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(shrinker->flags & SHRINKER_MEMCG_AWARE))
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return xchg_nr_deferred_memcg(nid, shrinker,
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sc->memcg);
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return atomic_long_xchg(&shrinker->nr_deferred[nid], 0);
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}
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static long add_nr_deferred(long nr, struct shrinker *shrinker,
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struct shrink_control *sc)
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{
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int nid = sc->nid;
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if (!(shrinker->flags & SHRINKER_NUMA_AWARE))
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nid = 0;
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if (sc->memcg &&
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(shrinker->flags & SHRINKER_MEMCG_AWARE))
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return add_nr_deferred_memcg(nr, nid, shrinker,
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sc->memcg);
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return atomic_long_add_return(nr, &shrinker->nr_deferred[nid]);
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}
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#define SHRINK_BATCH 128
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static unsigned long do_shrink_slab(struct shrink_control *shrinkctl,
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struct shrinker *shrinker, int priority)
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{
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unsigned long freed = 0;
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unsigned long long delta;
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long total_scan;
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long freeable;
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long nr;
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long new_nr;
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long batch_size = shrinker->batch ? shrinker->batch
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: SHRINK_BATCH;
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long scanned = 0, next_deferred;
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freeable = shrinker->count_objects(shrinker, shrinkctl);
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if (freeable == 0 || freeable == SHRINK_EMPTY)
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return freeable;
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/*
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* copy the current shrinker scan count into a local variable
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* and zero it so that other concurrent shrinker invocations
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* don't also do this scanning work.
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*/
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nr = xchg_nr_deferred(shrinker, shrinkctl);
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if (shrinker->seeks) {
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delta = freeable >> priority;
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delta *= 4;
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do_div(delta, shrinker->seeks);
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} else {
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/*
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* These objects don't require any IO to create. Trim
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* them aggressively under memory pressure to keep
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* them from causing refetches in the IO caches.
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*/
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delta = freeable / 2;
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}
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total_scan = nr >> priority;
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total_scan += delta;
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total_scan = min(total_scan, (2 * freeable));
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trace_mm_shrink_slab_start(shrinker, shrinkctl, nr,
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freeable, delta, total_scan, priority);
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/*
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* Normally, we should not scan less than batch_size objects in one
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* pass to avoid too frequent shrinker calls, but if the slab has less
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* than batch_size objects in total and we are really tight on memory,
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* we will try to reclaim all available objects, otherwise we can end
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* up failing allocations although there are plenty of reclaimable
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* objects spread over several slabs with usage less than the
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* batch_size.
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*
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* We detect the "tight on memory" situations by looking at the total
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* number of objects we want to scan (total_scan). If it is greater
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* than the total number of objects on slab (freeable), we must be
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* scanning at high prio and therefore should try to reclaim as much as
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* possible.
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*/
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while (total_scan >= batch_size ||
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total_scan >= freeable) {
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unsigned long ret;
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unsigned long nr_to_scan = min(batch_size, total_scan);
|
|
|
|
shrinkctl->nr_to_scan = nr_to_scan;
|
|
shrinkctl->nr_scanned = nr_to_scan;
|
|
ret = shrinker->scan_objects(shrinker, shrinkctl);
|
|
if (ret == SHRINK_STOP)
|
|
break;
|
|
freed += ret;
|
|
|
|
count_vm_events(SLABS_SCANNED, shrinkctl->nr_scanned);
|
|
total_scan -= shrinkctl->nr_scanned;
|
|
scanned += shrinkctl->nr_scanned;
|
|
|
|
cond_resched();
|
|
}
|
|
|
|
/*
|
|
* The deferred work is increased by any new work (delta) that wasn't
|
|
* done, decreased by old deferred work that was done now.
|
|
*
|
|
* And it is capped to two times of the freeable items.
|
|
*/
|
|
next_deferred = max_t(long, (nr + delta - scanned), 0);
|
|
next_deferred = min(next_deferred, (2 * freeable));
|
|
|
|
/*
|
|
* move the unused scan count back into the shrinker in a
|
|
* manner that handles concurrent updates.
|
|
*/
|
|
new_nr = add_nr_deferred(next_deferred, shrinker, shrinkctl);
|
|
|
|
trace_mm_shrink_slab_end(shrinker, shrinkctl->nid, freed, nr, new_nr, total_scan);
|
|
return freed;
|
|
}
|
|
|
|
#ifdef CONFIG_MEMCG
|
|
static unsigned long shrink_slab_memcg(gfp_t gfp_mask, int nid,
|
|
struct mem_cgroup *memcg, int priority)
|
|
{
|
|
struct shrinker_info *info;
|
|
unsigned long ret, freed = 0;
|
|
int offset, index = 0;
|
|
|
|
if (!mem_cgroup_online(memcg))
|
|
return 0;
|
|
|
|
/*
|
|
* lockless algorithm of memcg shrink.
|
|
*
|
|
* The shrinker_info may be freed asynchronously via RCU in the
|
|
* expand_one_shrinker_info(), so the rcu_read_lock() needs to be used
|
|
* to ensure the existence of the shrinker_info.
|
|
*
|
|
* The shrinker_info_unit is never freed unless its corresponding memcg
|
|
* is destroyed. Here we already hold the refcount of memcg, so the
|
|
* memcg will not be destroyed, and of course shrinker_info_unit will
|
|
* not be freed.
|
|
*
|
|
* So in the memcg shrink:
|
|
* step 1: use rcu_read_lock() to guarantee existence of the
|
|
* shrinker_info.
|
|
* step 2: after getting shrinker_info_unit we can safely release the
|
|
* RCU lock.
|
|
* step 3: traverse the bitmap and calculate shrinker_id
|
|
* step 4: use rcu_read_lock() to guarantee existence of the shrinker.
|
|
* step 5: use shrinker_id to find the shrinker, then use
|
|
* shrinker_try_get() to guarantee existence of the shrinker,
|
|
* then we can release the RCU lock to do do_shrink_slab() that
|
|
* may sleep.
|
|
* step 6: do shrinker_put() paired with step 5 to put the refcount,
|
|
* if the refcount reaches 0, then wake up the waiter in
|
|
* shrinker_free() by calling complete().
|
|
* Note: here is different from the global shrink, we don't
|
|
* need to acquire the RCU lock to guarantee existence of
|
|
* the shrinker, because we don't need to use this
|
|
* shrinker to traverse the next shrinker in the bitmap.
|
|
* step 7: we have already exited the read-side of rcu critical section
|
|
* before calling do_shrink_slab(), the shrinker_info may be
|
|
* released in expand_one_shrinker_info(), so go back to step 1
|
|
* to reacquire the shrinker_info.
|
|
*/
|
|
again:
|
|
rcu_read_lock();
|
|
info = rcu_dereference(memcg->nodeinfo[nid]->shrinker_info);
|
|
if (unlikely(!info))
|
|
goto unlock;
|
|
|
|
if (index < shrinker_id_to_index(info->map_nr_max)) {
|
|
struct shrinker_info_unit *unit;
|
|
|
|
unit = info->unit[index];
|
|
|
|
rcu_read_unlock();
|
|
|
|
for_each_set_bit(offset, unit->map, SHRINKER_UNIT_BITS) {
|
|
struct shrink_control sc = {
|
|
.gfp_mask = gfp_mask,
|
|
.nid = nid,
|
|
.memcg = memcg,
|
|
};
|
|
struct shrinker *shrinker;
|
|
int shrinker_id = calc_shrinker_id(index, offset);
|
|
|
|
rcu_read_lock();
|
|
shrinker = idr_find(&shrinker_idr, shrinker_id);
|
|
if (unlikely(!shrinker || !shrinker_try_get(shrinker))) {
|
|
clear_bit(offset, unit->map);
|
|
rcu_read_unlock();
|
|
continue;
|
|
}
|
|
rcu_read_unlock();
|
|
|
|
/* Call non-slab shrinkers even though kmem is disabled */
|
|
if (!memcg_kmem_online() &&
|
|
!(shrinker->flags & SHRINKER_NONSLAB))
|
|
continue;
|
|
|
|
ret = do_shrink_slab(&sc, shrinker, priority);
|
|
if (ret == SHRINK_EMPTY) {
|
|
clear_bit(offset, unit->map);
|
|
/*
|
|
* After the shrinker reported that it had no objects to
|
|
* free, but before we cleared the corresponding bit in
|
|
* the memcg shrinker map, a new object might have been
|
|
* added. To make sure, we have the bit set in this
|
|
* case, we invoke the shrinker one more time and reset
|
|
* the bit if it reports that it is not empty anymore.
|
|
* The memory barrier here pairs with the barrier in
|
|
* set_shrinker_bit():
|
|
*
|
|
* list_lru_add() shrink_slab_memcg()
|
|
* list_add_tail() clear_bit()
|
|
* <MB> <MB>
|
|
* set_bit() do_shrink_slab()
|
|
*/
|
|
smp_mb__after_atomic();
|
|
ret = do_shrink_slab(&sc, shrinker, priority);
|
|
if (ret == SHRINK_EMPTY)
|
|
ret = 0;
|
|
else
|
|
set_shrinker_bit(memcg, nid, shrinker_id);
|
|
}
|
|
freed += ret;
|
|
shrinker_put(shrinker);
|
|
}
|
|
|
|
index++;
|
|
goto again;
|
|
}
|
|
unlock:
|
|
rcu_read_unlock();
|
|
return freed;
|
|
}
|
|
#else /* !CONFIG_MEMCG */
|
|
static unsigned long shrink_slab_memcg(gfp_t gfp_mask, int nid,
|
|
struct mem_cgroup *memcg, int priority)
|
|
{
|
|
return 0;
|
|
}
|
|
#endif /* CONFIG_MEMCG */
|
|
|
|
/**
|
|
* shrink_slab - shrink slab caches
|
|
* @gfp_mask: allocation context
|
|
* @nid: node whose slab caches to target
|
|
* @memcg: memory cgroup whose slab caches to target
|
|
* @priority: the reclaim priority
|
|
*
|
|
* Call the shrink functions to age shrinkable caches.
|
|
*
|
|
* @nid is passed along to shrinkers with SHRINKER_NUMA_AWARE set,
|
|
* unaware shrinkers will receive a node id of 0 instead.
|
|
*
|
|
* @memcg specifies the memory cgroup to target. Unaware shrinkers
|
|
* are called only if it is the root cgroup.
|
|
*
|
|
* @priority is sc->priority, we take the number of objects and >> by priority
|
|
* in order to get the scan target.
|
|
*
|
|
* Returns the number of reclaimed slab objects.
|
|
*/
|
|
unsigned long shrink_slab(gfp_t gfp_mask, int nid, struct mem_cgroup *memcg,
|
|
int priority)
|
|
{
|
|
unsigned long ret, freed = 0;
|
|
struct shrinker *shrinker;
|
|
|
|
/*
|
|
* The root memcg might be allocated even though memcg is disabled
|
|
* via "cgroup_disable=memory" boot parameter. This could make
|
|
* mem_cgroup_is_root() return false, then just run memcg slab
|
|
* shrink, but skip global shrink. This may result in premature
|
|
* oom.
|
|
*/
|
|
if (!mem_cgroup_disabled() && !mem_cgroup_is_root(memcg))
|
|
return shrink_slab_memcg(gfp_mask, nid, memcg, priority);
|
|
|
|
/*
|
|
* lockless algorithm of global shrink.
|
|
*
|
|
* In the unregistration setp, the shrinker will be freed asynchronously
|
|
* via RCU after its refcount reaches 0. So both rcu_read_lock() and
|
|
* shrinker_try_get() can be used to ensure the existence of the shrinker.
|
|
*
|
|
* So in the global shrink:
|
|
* step 1: use rcu_read_lock() to guarantee existence of the shrinker
|
|
* and the validity of the shrinker_list walk.
|
|
* step 2: use shrinker_try_get() to try get the refcount, if successful,
|
|
* then the existence of the shrinker can also be guaranteed,
|
|
* so we can release the RCU lock to do do_shrink_slab() that
|
|
* may sleep.
|
|
* step 3: *MUST* to reacquire the RCU lock before calling shrinker_put(),
|
|
* which ensures that neither this shrinker nor the next shrinker
|
|
* will be freed in the next traversal operation.
|
|
* step 4: do shrinker_put() paired with step 2 to put the refcount,
|
|
* if the refcount reaches 0, then wake up the waiter in
|
|
* shrinker_free() by calling complete().
|
|
*/
|
|
rcu_read_lock();
|
|
list_for_each_entry_rcu(shrinker, &shrinker_list, list) {
|
|
struct shrink_control sc = {
|
|
.gfp_mask = gfp_mask,
|
|
.nid = nid,
|
|
.memcg = memcg,
|
|
};
|
|
|
|
if (!shrinker_try_get(shrinker))
|
|
continue;
|
|
|
|
rcu_read_unlock();
|
|
|
|
ret = do_shrink_slab(&sc, shrinker, priority);
|
|
if (ret == SHRINK_EMPTY)
|
|
ret = 0;
|
|
freed += ret;
|
|
|
|
rcu_read_lock();
|
|
shrinker_put(shrinker);
|
|
}
|
|
|
|
rcu_read_unlock();
|
|
cond_resched();
|
|
return freed;
|
|
}
|
|
|
|
struct shrinker *shrinker_alloc(unsigned int flags, const char *fmt, ...)
|
|
{
|
|
struct shrinker *shrinker;
|
|
unsigned int size;
|
|
va_list ap;
|
|
int err;
|
|
|
|
shrinker = kzalloc(sizeof(struct shrinker), GFP_KERNEL);
|
|
if (!shrinker)
|
|
return NULL;
|
|
|
|
va_start(ap, fmt);
|
|
err = shrinker_debugfs_name_alloc(shrinker, fmt, ap);
|
|
va_end(ap);
|
|
if (err)
|
|
goto err_name;
|
|
|
|
shrinker->flags = flags | SHRINKER_ALLOCATED;
|
|
shrinker->seeks = DEFAULT_SEEKS;
|
|
|
|
if (flags & SHRINKER_MEMCG_AWARE) {
|
|
err = shrinker_memcg_alloc(shrinker);
|
|
if (err == -ENOSYS) {
|
|
/* Memcg is not supported, fallback to non-memcg-aware shrinker. */
|
|
shrinker->flags &= ~SHRINKER_MEMCG_AWARE;
|
|
goto non_memcg;
|
|
}
|
|
|
|
if (err)
|
|
goto err_flags;
|
|
|
|
return shrinker;
|
|
}
|
|
|
|
non_memcg:
|
|
/*
|
|
* The nr_deferred is available on per memcg level for memcg aware
|
|
* shrinkers, so only allocate nr_deferred in the following cases:
|
|
* - non-memcg-aware shrinkers
|
|
* - !CONFIG_MEMCG
|
|
* - memcg is disabled by kernel command line
|
|
*/
|
|
size = sizeof(*shrinker->nr_deferred);
|
|
if (flags & SHRINKER_NUMA_AWARE)
|
|
size *= nr_node_ids;
|
|
|
|
shrinker->nr_deferred = kzalloc(size, GFP_KERNEL);
|
|
if (!shrinker->nr_deferred)
|
|
goto err_flags;
|
|
|
|
return shrinker;
|
|
|
|
err_flags:
|
|
shrinker_debugfs_name_free(shrinker);
|
|
err_name:
|
|
kfree(shrinker);
|
|
return NULL;
|
|
}
|
|
EXPORT_SYMBOL_GPL(shrinker_alloc);
|
|
|
|
void shrinker_register(struct shrinker *shrinker)
|
|
{
|
|
if (unlikely(!(shrinker->flags & SHRINKER_ALLOCATED))) {
|
|
pr_warn("Must use shrinker_alloc() to dynamically allocate the shrinker");
|
|
return;
|
|
}
|
|
|
|
mutex_lock(&shrinker_mutex);
|
|
list_add_tail_rcu(&shrinker->list, &shrinker_list);
|
|
shrinker->flags |= SHRINKER_REGISTERED;
|
|
shrinker_debugfs_add(shrinker);
|
|
mutex_unlock(&shrinker_mutex);
|
|
|
|
init_completion(&shrinker->done);
|
|
/*
|
|
* Now the shrinker is fully set up, take the first reference to it to
|
|
* indicate that lookup operations are now allowed to use it via
|
|
* shrinker_try_get().
|
|
*/
|
|
refcount_set(&shrinker->refcount, 1);
|
|
}
|
|
EXPORT_SYMBOL_GPL(shrinker_register);
|
|
|
|
static void shrinker_free_rcu_cb(struct rcu_head *head)
|
|
{
|
|
struct shrinker *shrinker = container_of(head, struct shrinker, rcu);
|
|
|
|
kfree(shrinker->nr_deferred);
|
|
kfree(shrinker);
|
|
}
|
|
|
|
void shrinker_free(struct shrinker *shrinker)
|
|
{
|
|
struct dentry *debugfs_entry = NULL;
|
|
int debugfs_id;
|
|
|
|
if (!shrinker)
|
|
return;
|
|
|
|
if (shrinker->flags & SHRINKER_REGISTERED) {
|
|
/* drop the initial refcount */
|
|
shrinker_put(shrinker);
|
|
/*
|
|
* Wait for all lookups of the shrinker to complete, after that,
|
|
* no shrinker is running or will run again, then we can safely
|
|
* free it asynchronously via RCU and safely free the structure
|
|
* where the shrinker is located, such as super_block etc.
|
|
*/
|
|
wait_for_completion(&shrinker->done);
|
|
}
|
|
|
|
mutex_lock(&shrinker_mutex);
|
|
if (shrinker->flags & SHRINKER_REGISTERED) {
|
|
/*
|
|
* Now we can safely remove it from the shrinker_list and then
|
|
* free it.
|
|
*/
|
|
list_del_rcu(&shrinker->list);
|
|
debugfs_entry = shrinker_debugfs_detach(shrinker, &debugfs_id);
|
|
shrinker->flags &= ~SHRINKER_REGISTERED;
|
|
}
|
|
|
|
shrinker_debugfs_name_free(shrinker);
|
|
|
|
if (shrinker->flags & SHRINKER_MEMCG_AWARE)
|
|
shrinker_memcg_remove(shrinker);
|
|
mutex_unlock(&shrinker_mutex);
|
|
|
|
if (debugfs_entry)
|
|
shrinker_debugfs_remove(debugfs_entry, debugfs_id);
|
|
|
|
call_rcu(&shrinker->rcu, shrinker_free_rcu_cb);
|
|
}
|
|
EXPORT_SYMBOL_GPL(shrinker_free);
|