[RFC PATCH v3 1/8] Use refcount_t for ucounts reference counting
From: Alexey Gladkov <hidden>
Date: 2021-01-15 15:00:09
Also in:
io-uring, lkml
Subsystem:
the rest · Maintainer:
Linus Torvalds
Signed-off-by: Alexey Gladkov <redacted> --- include/linux/user_namespace.h | 2 +- kernel/ucount.c | 20 +++++++------------- 2 files changed, 8 insertions(+), 14 deletions(-)
diff --git a/include/linux/user_namespace.h b/include/linux/user_namespace.h
index 64cf8ebdc4ec..f84fc2d9ce20 100644
--- a/include/linux/user_namespace.h
+++ b/include/linux/user_namespace.h@@ -92,7 +92,7 @@ struct ucounts { struct hlist_node node; struct user_namespace *ns; kuid_t uid; - int count; + refcount_t count; atomic_t ucount[UCOUNT_COUNTS]; };
diff --git a/kernel/ucount.c b/kernel/ucount.c
index 11b1596e2542..82acd2226460 100644
--- a/kernel/ucount.c
+++ b/kernel/ucount.c@@ -141,7 +141,8 @@ static struct ucounts *get_ucounts(struct user_namespace *ns, kuid_t uid) new->ns = ns; new->uid = uid; - new->count = 0; + + refcount_set(&new->count, 0); spin_lock_irq(&ucounts_lock); ucounts = find_ucounts(ns, uid, hashent);
@@ -152,10 +153,7 @@ static struct ucounts *get_ucounts(struct user_namespace *ns, kuid_t uid) ucounts = new; } } - if (ucounts->count == INT_MAX) - ucounts = NULL; - else - ucounts->count += 1; + refcount_inc(&ucounts->count); spin_unlock_irq(&ucounts_lock); return ucounts; }
@@ -164,15 +162,11 @@ static void put_ucounts(struct ucounts *ucounts) { unsigned long flags; - spin_lock_irqsave(&ucounts_lock, flags); - ucounts->count -= 1; - if (!ucounts->count) + if (refcount_dec_and_lock_irqsave(&ucounts->count, &ucounts_lock, &flags)) { hlist_del_init(&ucounts->node); - else - ucounts = NULL; - spin_unlock_irqrestore(&ucounts_lock, flags); - - kfree(ucounts); + spin_unlock_irqrestore(&ucounts_lock, flags); + kfree(ucounts); + } } static inline bool atomic_inc_below(atomic_t *v, int u)
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2.29.2