[Devel] [PATCH VZ10 v5 3/9] ve/fs: Rework per-ve mount count
Vladimir Riabchun
vladimir.riabchun at virtuozzo.com
Sun Aug 2 14:40:33 MSK 2026
Previous approach with current mounts counter had an issue:
there was a gap between ve_mount_allowed check and ve_mount_nr_inc,
which could allow CT to have more mounts than expected.
Fix this by tracking the number of available mounts instead
of current ones. This also makes resources accounting
more consistent - we are using ***_avail_nr approach more.
One more issue with inconsistent ve value is fixed:
ve_mount_allowed always used ve from get_exec_env, but
ve_mount_nr_inc operated with owner_ve.
Now actual ve value is calculated in the beginning of alloc_vfsmnt.
To avoid incorrect accounting when is_pseudosuper is changed,
update avail_nr count without > 0 check if VE is ve0 or pseudosuper.
This also simplifies ve_mount_put, since increment is
now unconditional.
https://virtuozzo.atlassian.net/browse/VSTOR-135520
Feature: per-ve failcounters
Signed-off-by: Vladimir Riabchun <vladimir.riabchun at virtuozzo.com>
---
v4 -> v5:
- Dropped created_as_pseudosuper, now all mounts are accounted,
but for ve0 and pseudosuper mnt_avail_nr is allowed to go below 0.
fs/namespace.c | 71 +++++++++++++++++++++++++++-------------------
include/linux/ve.h | 2 +-
kernel/ve/ve.c | 12 ++++----
3 files changed, 49 insertions(+), 36 deletions(-)
diff --git a/fs/namespace.c b/fs/namespace.c
index cd6aa2127203..2550aeba2f1e 100644
--- a/fs/namespace.c
+++ b/fs/namespace.c
@@ -317,18 +317,21 @@ int mnt_get_count(struct mount *mnt)
#endif
}
-static inline int ve_mount_allowed(void);
-static inline void ve_mount_nr_inc(struct mount *mnt, struct ve_struct *ve);
-static inline void ve_mount_nr_dec(struct mount *mnt);
+static inline int ve_try_reserve_mount(struct ve_struct *ve);
+static inline void ve_mount_put(struct mount *mnt, struct ve_struct *ve);
static struct mount *alloc_vfsmnt(const char *name, struct ve_struct *owner_ve)
{
struct mount *mnt;
+ struct ve_struct *ve = owner_ve;
- if (!ve_mount_allowed()) {
+ if (!ve)
+ ve = get_exec_env();
+
+ if (!ve_try_reserve_mount(ve)) {
pr_warn_ratelimited(
"CT#%s reached the limit on mounts.\n",
- ve_name(get_exec_env()));
+ ve_name(ve));
return NULL;
}
@@ -336,6 +339,14 @@ static struct mount *alloc_vfsmnt(const char *name, struct ve_struct *owner_ve)
if (mnt) {
int err;
+#ifdef CONFIG_VE
+ /*
+ * Got ve reference in ve_try_reserve_mount, set mnt ve data
+ * here, so in case of error ve_mount_put sees correct info.
+ */
+ mnt->ve_owner = ve;
+#endif
+
err = mnt_alloc_id(mnt);
if (err)
goto out_free_cache;
@@ -370,7 +381,8 @@ static struct mount *alloc_vfsmnt(const char *name, struct ve_struct *owner_ve)
INIT_LIST_HEAD(&mnt->mnt_umounting);
INIT_HLIST_HEAD(&mnt->mnt_stuck_children);
mnt->mnt.mnt_idmap = &nop_mnt_idmap;
- ve_mount_nr_inc(mnt, owner_ve);
+ } else {
+ ve_mount_put(mnt, ve);
}
return mnt;
@@ -381,6 +393,8 @@ static struct mount *alloc_vfsmnt(const char *name, struct ve_struct *owner_ve)
out_free_id:
mnt_free_id(mnt);
out_free_cache:
+ /* Got ve reference in ve_try_reserve_mount */
+ ve_mount_put(mnt, ve);
kmem_cache_free(mnt_cache, mnt);
return NULL;
}
@@ -750,7 +764,7 @@ int sb_prepare_remount_readonly(struct super_block *sb)
static void free_vfsmnt(struct mount *mnt)
{
mnt_idmap_put(mnt_idmap(&mnt->mnt));
- ve_mount_nr_dec(mnt);
+ ve_mount_put(mnt, mnt->ve_owner);
kfree_const(mnt->mnt_devname);
#ifdef CONFIG_SMP
free_percpu(mnt->mnt_pcp);
@@ -3205,7 +3219,7 @@ int ve_devmnt_process(struct ve_struct *ve, dev_t dev, void **data_pp, int remou
if (devmnt->dev == dev) {
err = ve_devmnt_check(data, devmnt->allowed_options);
/*
- * In case of @is_pseudouser set, ie restore procedure,
+ * In case of @is_pseudosuper set, ie restore procedure,
* we don't check for allowed options filtering, since
* restore mode is special.
*/
@@ -3258,30 +3272,30 @@ int ve_devmnt_process(struct ve_struct *ve, dev_t dev, void **data_pp, int remou
return err;
}
-static inline int ve_mount_allowed(void)
-{
- struct ve_struct *ve = get_exec_env();
-
- return ve_is_super(ve) || ve->is_pseudosuper ||
- atomic_read(&ve->mnt_nr) < (int)sysctl_ve_mount_nr;
-}
-
-static inline void ve_mount_nr_inc(struct mount *mnt, struct ve_struct *ve)
+static inline int ve_try_reserve_mount(struct ve_struct *ve)
{
- if (!ve)
- ve = get_exec_env();
+ int ret = ve_is_super(ve) || ve->is_pseudosuper;
+ /* Ignore limits in ve0 and pseudosuper cases, but still count. */
+ if (ret)
+ atomic_dec(&ve->mnt_avail_nr);
+ else
+ ret = atomic_dec_if_positive(&ve->mnt_avail_nr) >= 0;
- mnt->ve_owner = get_ve(ve);
- atomic_inc(&ve->mnt_nr);
+ if (ret)
+ get_ve(ve);
+ return ret;
}
-static inline void ve_mount_nr_dec(struct mount *mnt)
+static inline void ve_mount_put(struct mount *mnt, struct ve_struct *ve)
{
- struct ve_struct *ve = mnt->ve_owner;
-
- atomic_dec(&ve->mnt_nr);
+ /*
+ * ve argument is needed to reuse this function in alloc_vfsmnt error path.
+ * Other users should pass mnt->ve_owner value.
+ */
+ atomic_inc(&ve->mnt_avail_nr);
put_ve(ve);
- mnt->ve_owner = NULL;
+ if (mnt)
+ mnt->ve_owner = NULL;
}
bool is_sb_ve_accessible(struct ve_struct *ve, struct super_block *sb)
@@ -3303,9 +3317,8 @@ bool is_sb_ve_accessible(struct ve_struct *ve, struct super_block *sb)
#else /* CONFIG_VE */
-static inline int ve_mount_allowed(void) { return 1; }
-static inline void ve_mount_nr_inc(struct mount *mnt, struct ve_struct *ve) { }
-static inline void ve_mount_nr_dec(struct mount *mnt) { }
+static inline int ve_try_reserve_mount(struct ve_struct *ve) { return 1; }
+static inline void ve_mount_put(struct mount *mnt, struct ve_struct *ve) { }
#endif /* CONFIG_VE */
static int ve_prepare_mount_options(struct fs_context *fc, void *data)
diff --git a/include/linux/ve.h b/include/linux/ve.h
index 3facbd1759df..cca0a2bc1aac 100644
--- a/include/linux/ve.h
+++ b/include/linux/ve.h
@@ -88,7 +88,7 @@ struct ve_struct {
atomic_t nd_neigh_nr;
unsigned long meminfo_val;
- atomic_t mnt_nr; /* number of present VE mounts */
+ atomic_t mnt_avail_nr; /* number of available VE mounts */
#ifdef CONFIG_COREDUMP
char core_pattern[CORENAME_MAX_SIZE];
diff --git a/kernel/ve/ve.c b/kernel/ve/ve.c
index dddf2393326d..3f66144eeb7e 100644
--- a/kernel/ve/ve.c
+++ b/kernel/ve/ve.c
@@ -81,7 +81,7 @@ struct ve_struct ve0 = {
.arp_neigh_nr = ATOMIC_INIT(0),
.nd_neigh_nr = ATOMIC_INIT(0),
- .mnt_nr = ATOMIC_INIT(0),
+ .mnt_avail_nr = ATOMIC_INIT(INT_MAX),
.meminfo_val = VE_MEMINFO_SYSTEM,
.umh_running_helpers = ATOMIC_INIT(0),
.umh_helpers_waitq = __WAIT_QUEUE_HEAD_INITIALIZER(ve0.umh_helpers_waitq),
@@ -778,7 +778,7 @@ static struct cgroup_subsys_state *ve_create(struct cgroup_subsys_state *parent_
atomic_set(&ve->arp_neigh_nr, 0);
atomic_set(&ve->nd_neigh_nr, 0);
- atomic_set(&ve->mnt_nr, 0);
+ atomic_set(&ve->mnt_avail_nr, sysctl_ve_mount_nr);
#ifdef CONFIG_COREDUMP
strcpy(ve->core_pattern, "core");
@@ -1055,9 +1055,9 @@ static u64 ve_netns_avail_nr_read(struct cgroup_subsys_state *css, struct cftype
return atomic_read(&css_to_ve(css)->netns_avail_nr);
}
-static u64 ve_mnt_nr_read(struct cgroup_subsys_state *css, struct cftype *cft)
+static s64 ve_mnt_avail_nr_read(struct cgroup_subsys_state *css, struct cftype *cft)
{
- return atomic_read(&css_to_ve(css)->mnt_nr);
+ return atomic_read(&css_to_ve(css)->mnt_avail_nr);
}
static u64 ve_netif_max_nr_read(struct cgroup_subsys_state *css, struct cftype *cft)
@@ -1617,8 +1617,8 @@ static struct cftype ve_cftypes[] = {
.read_u64 = ve_netns_avail_nr_read,
},
{
- .name = "mnt_nr",
- .read_u64 = ve_mnt_nr_read,
+ .name = "mnt_avail_nr",
+ .read_s64 = ve_mnt_avail_nr_read,
},
{
.name = "netif_max_nr",
--
2.47.1
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