[3/4] ucounts: Add get_ucounts_or_wrap for clarity

Commit Message

Eric W. Biederman Oct. 18, 2021, 5:56 p.m. UTC

Add a helper function get_ucounts_or_wrap that is a trivial
wrapper around atomic_add_negative, that makes it clear
how atomic_add_negative is used in the context of ucounts.

Signed-off-by: "Eric W. Biederman" <[e-mail]>
---
 kernel/ucount.c | 14 ++++++++++----
 1 file changed, 10 insertions(+), 4 deletions(-)

Patch

diff --git a/kernel/ucount.c b/kernel/ucount.c
index 708d05164a7d..133b6044fda4 100644
--- a/kernel/ucount.c
+++ b/kernel/ucount.c
@@ -150,9 +150,15 @@  static void hlist_add_ucounts(struct ucounts *ucounts)
 	spin_unlock_irq(&ucounts_lock);
 }
 
+static inline bool get_ucounts_or_wrap(struct ucounts *ucounts)
+{
+	/* Returns true on a successful get, false if the count wraps. */
+	return !atomic_add_negative(1, &ucounts->count);
+}
+
 struct ucounts *get_ucounts(struct ucounts *ucounts)
 {
-	if (atomic_add_negative(1, &ucounts->count)) {
+	if (!get_ucounts_or_wrap(ucounts)) {
 		put_ucounts(ucounts);
 		ucounts = NULL;
 	}
@@ -163,7 +169,7 @@  struct ucounts *alloc_ucounts(struct user_namespace *ns, kuid_t uid)
 {
 	struct hlist_head *hashent = ucounts_hashentry(ns, uid);
 	struct ucounts *ucounts, *new;
-	long overflow;
+	bool wrapped;
 
 	spin_lock_irq(&ucounts_lock);
 	ucounts = find_ucounts(ns, uid, hashent);
@@ -188,9 +194,9 @@  struct ucounts *alloc_ucounts(struct user_namespace *ns, kuid_t uid)
 			return new;
 		}
 	}
-	overflow = atomic_add_negative(1, &ucounts->count);
+	wrapped = !get_ucounts_or_wrap(ucounts);
 	spin_unlock_irq(&ucounts_lock);
-	if (overflow) {
+	if (wrapped) {
 		put_ucounts(ucounts);
 		return NULL;
 	}