[PATCH OLK-6.6 0/2] fix deadlock in cgroup1_writeback
*** BLURB HERE *** Chen Ridong (2): cgroup_writeback: Revert "fix deadlock in cgroup1_writeback" cgroup_writeback: fix deadlock in cgroup1_writeback mm/backing-dev.c | 2 ++ mm/memcontrol.c | 24 +++++++++--------------- 2 files changed, 11 insertions(+), 15 deletions(-) -- 2.34.1
hulk inclusion category: bugfix bugzilla: https://gitee.com/openeuler/kernel/issues/I99KM6 -------------------------------- "fix deadlock in cgroup1_writeback" will lead to softlockup for deleting cgroup_mutex lead to blkcg->memcg_list unprotected. so revert "cgroup_writeback: fix deadlock in cgroup1_writeback". Signed-off-by: Chen Ridong <chenridong@huawei.com> --- mm/backing-dev.c | 2 ++ mm/memcontrol.c | 21 ++++++--------------- 2 files changed, 8 insertions(+), 15 deletions(-) diff --git a/mm/backing-dev.c b/mm/backing-dev.c index bfb2c50b0354..d70f8420c805 100644 --- a/mm/backing-dev.c +++ b/mm/backing-dev.c @@ -1221,6 +1221,8 @@ void wb_attach_memcg_to_blkcg(struct cgroup_subsys_state *memcg_css, if (!cgroup1_writeback) return; + lockdep_assert_held(&cgroup_mutex); + css_get(blkcg_css); memcg->wb_blk_css = blkcg_css; if (pre_blkcss == NULL) diff --git a/mm/memcontrol.c b/mm/memcontrol.c index 5613bf6c1d7d..0f1813deb527 100644 --- a/mm/memcontrol.c +++ b/mm/memcontrol.c @@ -6042,22 +6042,15 @@ static int wb_blkio_show(struct seq_file *m, void *v) if (!path) return -ENOMEM; - rcu_read_lock(); + mutex_lock(&cgroup_mutex); blkcg_css = memcg->wb_blk_css; - if (!css_tryget_online(blkcg_css)) { - kfree(path); - rcu_read_unlock(); - - return -EINVAL; - } blkcg_cgroup = blkcg_css->cgroup; blkcg_id = cgroup_ino(blkcg_cgroup); cgroup_path(blkcg_cgroup, path, PATH_MAX); + mutex_unlock(&cgroup_mutex); seq_printf(m, "wb_blkio_path:%s\n", path); seq_printf(m, "wb_blkio_ino:%lu\n", blkcg_id); kfree(path); - css_put(blkcg_css); - rcu_read_unlock(); return 0; } @@ -6080,24 +6073,22 @@ static ssize_t wb_blkio_write(struct kernfs_open_file *of, char *buf, if (ret) return ret; - rcu_read_lock(); + mutex_lock(&cgroup_mutex); root = blkcg_root_css->cgroup->root; blk_cgroup = __cgroup_get_from_id(root, cgrp_id); if (IS_ERR(blk_cgroup)) { - rcu_read_unlock(); + mutex_unlock(&cgroup_mutex); return -EINVAL; } blkcg_css = cgroup_tryget_css(blk_cgroup, &io_cgrp_subsys); - if (!blkcg_css) { - ret = -EINVAL; + if (!blkcg_css) goto out_unlock; - } wb_attach_memcg_to_blkcg(memcg_css, blkcg_css); css_put(blkcg_css); out_unlock: cgroup_put(blk_cgroup); - rcu_read_unlock(); + mutex_unlock(&cgroup_mutex); return ret < 0 ? ret : nbytes; } -- 2.34.1
hulk inclusion category: bugfix bugzilla: https://gitee.com/openeuler/kernel/issues/I99KM6 -------------------------------- When read/write memory.wb_blkio_ino of a memcg, and delete the memcg at the same time, it could cause deadlock as below: CPU0 CPU1 rlock(kn->active#4); lock(cgroup_mutex); lock(kn->active#4); lock(cgroup_mutex); Therefore, use cgroup_kn_lock_live to replace cgroup_mutex in reading/writing memory.wb_blkio_ino. cgroup_kn_lock_live is locking helper for cgroup kernfs methods. Fixes: cf4973d8f67c ("cgroup: support cgroup writeback on cgroupv1") Signed-off-by: Chen Ridong <chenridong@huawei.com> --- mm/memcontrol.c | 13 ++++++++----- 1 file changed, 8 insertions(+), 5 deletions(-) diff --git a/mm/memcontrol.c b/mm/memcontrol.c index 0f1813deb527..df2d73ad85cf 100644 --- a/mm/memcontrol.c +++ b/mm/memcontrol.c @@ -6029,6 +6029,7 @@ static ssize_t memcg_high_async_ratio_write(struct kernfs_open_file *of, static int wb_blkio_show(struct seq_file *m, void *v) { + struct kernfs_open_file *of = m->private; char *path; ino_t blkcg_id; struct cgroup *blkcg_cgroup; @@ -6042,12 +6043,13 @@ static int wb_blkio_show(struct seq_file *m, void *v) if (!path) return -ENOMEM; - mutex_lock(&cgroup_mutex); + if (!cgroup_kn_lock_live(of->kn, false)) + return -ENODEV; blkcg_css = memcg->wb_blk_css; blkcg_cgroup = blkcg_css->cgroup; blkcg_id = cgroup_ino(blkcg_cgroup); cgroup_path(blkcg_cgroup, path, PATH_MAX); - mutex_unlock(&cgroup_mutex); + cgroup_kn_unlock(of->kn); seq_printf(m, "wb_blkio_path:%s\n", path); seq_printf(m, "wb_blkio_ino:%lu\n", blkcg_id); kfree(path); @@ -6073,11 +6075,12 @@ static ssize_t wb_blkio_write(struct kernfs_open_file *of, char *buf, if (ret) return ret; - mutex_lock(&cgroup_mutex); + if (!cgroup_kn_lock_live(of->kn, false)) + return -ENODEV; root = blkcg_root_css->cgroup->root; blk_cgroup = __cgroup_get_from_id(root, cgrp_id); if (IS_ERR(blk_cgroup)) { - mutex_unlock(&cgroup_mutex); + cgroup_kn_unlock(of->kn); return -EINVAL; } blkcg_css = cgroup_tryget_css(blk_cgroup, &io_cgrp_subsys); @@ -6088,7 +6091,7 @@ static ssize_t wb_blkio_write(struct kernfs_open_file *of, char *buf, out_unlock: cgroup_put(blk_cgroup); - mutex_unlock(&cgroup_mutex); + cgroup_kn_unlock(of->kn); return ret < 0 ? ret : nbytes; } -- 2.34.1
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