[Devel] [PATCH RH7 v3] ub: correct _ub_get_css() retvalue for dying/stopped containers

Vasily Averin vvs at virtuozzo.com
Tue Sep 14 09:41:48 MSK 2021


Currently __ub_get_css(ub) for dying or stopped container returns
ub0-related css as failback. As result read from /proc/bc/<>/ files
can show ve0-related info.

With this patch, __ub_get_css() will return NULL in such cases,
and everyone who called of this function now handles this return value.

https://jira.sw.ru/browse/PSBM-123686
Signed-off-by: Vasily Averin <vvs at virtuozzo.com>
---
v2: removed an extra check in end of __ub_get_css(), thanks to eshatokhin@
v3: fixed goto label in ub_get_attach, thanks to eshatokhin@ again

 include/bc/beancounter.h | 10 +++++++-
 kernel/bc/beancounter.c  | 67 +++++++++++++++++++++++++++++++++++-------------
 kernel/bc/io_prio.c      | 13 ++++++++--
 kernel/bc/proc.c         |  3 +++
 kernel/bc/vm_pages.c     | 18 ++++++++++---
 5 files changed, 86 insertions(+), 25 deletions(-)

diff --git a/include/bc/beancounter.h b/include/bc/beancounter.h
index e4c5017..4b69a34 100644
--- a/include/bc/beancounter.h
+++ b/include/bc/beancounter.h
@@ -163,6 +163,10 @@ static __always_inline struct cgroup_subsys_state *__ub_get_css(struct user_bean
 	css = ACCESS_ONCE(ub->ub_bound_css[idx]);
 	if (likely(css && css_tryget(css))) {
 		rcu_read_unlock();
+		if ((ub != &ub0) && (css == ub0.ub_bound_css[idx])) {
+			css_put(css);
+			css = NULL;
+		}
 		return css;
 	}
 
@@ -183,7 +187,11 @@ static __always_inline struct cgroup_subsys_state *__ub_get_css(struct user_bean
 	if (css)
 		css_put(css);
 
-	css_get(root_css);
+	if (ub == &ub0)
+		css_get(root_css);
+	else
+		root_css = NULL;
+
 	return root_css;
 }
 
diff --git a/kernel/bc/beancounter.c b/kernel/bc/beancounter.c
index 5e04d6c..e4b0b23 100644
--- a/kernel/bc/beancounter.c
+++ b/kernel/bc/beancounter.c
@@ -117,34 +117,54 @@ int ub_attach_task(struct user_beancounter *ub, struct task_struct *tsk)
 {
 	int ret = 0;
 	struct user_beancounter *old_ub = tsk->task_bc.exec_ub;
-	struct cgroup_subsys_state *css;
+	struct cgroup_subsys_state *css, *com, *cob;
 
 	if (ub == old_ub)
 		goto out;
+
+	ret = -ENODEV;
+	com = ub_get_mem_css(old_ub);
+	if (!com)
+		goto out;
+
+	cob = ub_get_blkio_css(old_ub);
+	if (!cob)
+		goto fail_om;
+
 	css = ub_get_mem_css(ub);
+	if (!css)
+		goto fail_ob;
+
 	ret = cgroup_kernel_attach(css->cgroup, tsk);
 	css_put(css);
 	if (ret)
-		goto out;
+		goto fail_ob;
+
+	ret = -ENODEV;
 	css = ub_get_blkio_css(ub);
+	if (!css)
+		goto fail_blkio;
+
 	ret = cgroup_kernel_attach(css->cgroup, tsk);
 	css_put(css);
 	if (ret)
 		goto fail_blkio;
+
 	ret = cgroup_kernel_attach(ub->css.cgroup, tsk);
 	if (ret)
 		goto fail_ub;
+
+fail_ob:
+	css_put(cob);
+fail_om:
+	css_put(com);
 out:
 	return ret;
 fail_ub:
-	css = ub_get_blkio_css(old_ub);
-	cgroup_kernel_attach(css->cgroup, tsk);
-	css_put(css);
+	cgroup_kernel_attach(cob->cgroup, tsk);
 fail_blkio:
-	css = ub_get_mem_css(old_ub);
-	cgroup_kernel_attach(css->cgroup, tsk);
-	css_put(css);
-	goto out;
+	cgroup_kernel_attach(com->cgroup, tsk);
+	goto fail_ob;
 }
 
 extern void mem_cgroup_sync_beancounter(struct mem_cgroup *memcg,
@@ -167,6 +187,9 @@ int ub_update_memcg(struct user_beancounter *ub)
 	int ret;
 
 	css = ub_get_mem_css(ub);
+	if (!css)
+		return -ENODEV;
+
 	ret = mem_cgroup_apply_beancounter(mem_cgroup_from_cont(css->cgroup),
 					   ub);
 	css_put(css);
@@ -181,8 +204,10 @@ void ub_sync_pids(struct user_beancounter *ub)
 	struct cgroup_subsys_state *css;
 
 	css = ub_get_pids_css(ub);
-	pids_cgroup_sync_beancounter(pids_cgroup_from_cont(css->cgroup), ub);
-	css_put(css);
+	if (css) {
+		pids_cgroup_sync_beancounter(pids_cgroup_from_cont(css->cgroup), ub);
+		css_put(css);
+	}
 }
 
 /*
@@ -193,18 +218,22 @@ void ub_sync_memcg(struct user_beancounter *ub)
 	struct cgroup_subsys_state *css;
 
 	css = ub_get_mem_css(ub);
-	mem_cgroup_sync_beancounter(mem_cgroup_from_cont(css->cgroup), ub);
-	css_put(css);
+	if (css) {
+		mem_cgroup_sync_beancounter(mem_cgroup_from_cont(css->cgroup), ub);
+		css_put(css);
+	}
 }
 
 unsigned long ub_total_pages(struct user_beancounter *ub, bool swap)
 {
 	struct cgroup_subsys_state *css;
-	unsigned long ret;
+	unsigned long ret = 0;
 
 	css = ub_get_mem_css(ub);
-	ret = mem_cgroup_total_pages(mem_cgroup_from_cont(css->cgroup), swap);
-	css_put(css);
+	if (css) {
+		ret = mem_cgroup_total_pages(mem_cgroup_from_cont(css->cgroup), swap);
+		css_put(css);
+	}
 	return ret;
 }
 
@@ -576,11 +605,12 @@ static ssize_t ub_cgroup_read(struct cgroup *cg, struct cftype *cft,
 	struct cgroup_subsys_state *bound_css;
 	char *path;
 	int len;
-	ssize_t ret;
+	ssize_t ret = -ENOMEM;
 
 	bound_css = __ub_get_css(ub, cft->private);
+	if (!bound_css)
+		goto fail;
 
-	ret = -ENOMEM;
 	path = kmalloc(PATH_MAX + 1, GFP_KERNEL);
 	if (!path)
 		goto out;
@@ -594,6 +624,7 @@ static ssize_t ub_cgroup_read(struct cgroup *cg, struct cftype *cft,
 	kfree(path);
 out:
 	css_put(bound_css);
+fail:
 	return ret;
 }
 
diff --git a/kernel/bc/io_prio.c b/kernel/bc/io_prio.c
index 16f5024..01a6251 100644
--- a/kernel/bc/io_prio.c
+++ b/kernel/bc/io_prio.c
@@ -35,8 +35,12 @@ int ub_set_ioprio(int id, int ioprio)
 		goto out;
 
 	css = ub_get_blkio_css(ub);
+	if (!css)
+		goto put;
+	
 	ret = blkcg_set_weight(css->cgroup, ioprio_weight[ioprio]);
 	css_put(css);
+put:
 	put_beancounter(ub);
 out:
 	return ret;
@@ -59,8 +63,10 @@ static int bc_iostat(struct seq_file *f, struct user_beancounter *bc)
 			__ub_percpu_sum(bc, fuse_bytes) >> 9);
 
 	css = ub_get_blkio_css(bc);
-	blkcg_show_ub_iostat(css->cgroup, f);
-	css_put(css);
+	if (css) {
+		blkcg_show_ub_iostat(css->cgroup, f);
+		css_put(css);
+	}
 	return 0;
 }
 
@@ -146,6 +152,9 @@ static int bc_ioprio_show(struct seq_file *f, void *v)
 	bc = seq_beancounter(f);
 
 	css = ub_get_blkio_css(bc);
+	if (!css)
+		return 0;
+
 	weight = blkcg_get_weight(css->cgroup);
 	css_put(css);
 
diff --git a/kernel/bc/proc.c b/kernel/bc/proc.c
index efcfdbc..2251d6d 100644
--- a/kernel/bc/proc.c
+++ b/kernel/bc/proc.c
@@ -144,6 +144,9 @@ static int bc_proc_nodeinfo_show(struct seq_file *f, void *v)
 	unsigned long pages[NR_LRU_LISTS];
 
 	css = ub_get_mem_css(seq_beancounter(f));
+	if (!css)
+		return 0;
+
 	for_each_node_state(nid, N_HIGH_MEMORY) {
 		memset(pages, 0, sizeof(pages));
 		mem_cgroup_get_nr_pages(mem_cgroup_from_cont(css->cgroup),
diff --git a/kernel/bc/vm_pages.c b/kernel/bc/vm_pages.c
index e5019c0..7952da1 100644
--- a/kernel/bc/vm_pages.c
+++ b/kernel/bc/vm_pages.c
@@ -127,7 +127,7 @@ int ub_enough_memory(struct mm_struct *mm, long pages)
 	struct user_beancounter *ub;
 	struct cgroup_subsys_state *css;
 	unsigned long flags;
-	int ret;
+	int ret = -ENOMEM;
 
 	if (!mm)
 		return 0;
@@ -135,15 +135,16 @@ int ub_enough_memory(struct mm_struct *mm, long pages)
 	ub = mm->mm_ub;
 
 	if (ub->ub_parms[UB_PRIVVMPAGES].held >
-	    ub->ub_parms[UB_PRIVVMPAGES].barrier) {
-		ret = -ENOMEM;
+	    ub->ub_parms[UB_PRIVVMPAGES].barrier)
 		goto out;
-	}
 
 	if (ub == get_ub0() || ub_overcommit_memory)
 		return 0;
 
 	css = ub_get_mem_css(ub);
+	if (!css)
+		goto out;
+		
 	ret = mem_cgroup_enough_memory(mem_cgroup_from_cont(css->cgroup), pages);
 	css_put(css);
 out:
@@ -166,6 +167,9 @@ static int bc_fill_sysinfo(struct user_beancounter *ub,
 		return NOTIFY_DONE | NOTIFY_STOP_MASK;
 
 	css = ub_get_mem_css(ub);
+	if (!css)
+		return NOTIFY_BAD;
+
 	mem_cgroup_fill_sysinfo(mem_cgroup_from_cont(css->cgroup), si);
 	css_put(css);
 
@@ -185,6 +189,9 @@ static int bc_fill_meminfo(struct user_beancounter *ub,
 		goto out;
 
 	css = ub_get_mem_css(ub);
+	if (!css)
+		return NOTIFY_BAD;
+
 	mem_cgroup_fill_meminfo(mem_cgroup_from_cont(css->cgroup), mi);
 	css_put(css);
 
@@ -213,6 +220,9 @@ static int bc_fill_vmstat(struct user_beancounter *ub, unsigned long *stat)
 		return NOTIFY_OK;
 
 	css = ub_get_mem_css(ub);
+	if (!css)
+		return NOTIFY_BAD;
+
 	mem_cgroup_fill_vmstat(mem_cgroup_from_cont(css->cgroup), stat);
 	css_put(css);
 	return NOTIFY_OK;
-- 
1.8.3.1



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