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ucounts: Add get_ucounts_or_wrap for clarity

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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.

Link: https://lkml.kernel.org/r/87pms2qkr9.fsf_-_@disp2133
Tested-by: Yu Zhao <yuzhao@google.com>
Reviewed-by: Alexey Gladkov <legion@kernel.org>
Signed-off-by: "Eric W. Biederman" <ebiederm@xmission.com>
This commit is contained in:
Eric W. Biederman 2021-10-16 14:05:34 -05:00
parent 5fc9e37cd5
commit da70d3109e
1 changed files with 10 additions and 4 deletions
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14
kernel/ucount.c
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@ -150,9 +150,15 @@ static void hlist_add_ucounts(struct ucounts *ucounts)
spin_unlock_irq(&ucounts_lock); 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) struct ucounts *get_ucounts(struct ucounts *ucounts)
{ {
if (atomic_add_negative(1, &ucounts->count)) { if (!get_ucounts_or_wrap(ucounts)) {
put_ucounts(ucounts); put_ucounts(ucounts);
ucounts = NULL; 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 hlist_head *hashent = ucounts_hashentry(ns, uid);
struct ucounts *ucounts, *new; struct ucounts *ucounts, *new;
long overflow; bool wrapped;
spin_lock_irq(&ucounts_lock); spin_lock_irq(&ucounts_lock);
ucounts = find_ucounts(ns, uid, hashent); ucounts = find_ucounts(ns, uid, hashent);
@ -188,9 +194,9 @@ struct ucounts *alloc_ucounts(struct user_namespace *ns, kuid_t uid)
return new; return new;
} }
} }
overflow = atomic_add_negative(1, &ucounts->count); wrapped = !get_ucounts_or_wrap(ucounts);
spin_unlock_irq(&ucounts_lock); spin_unlock_irq(&ucounts_lock);
if (overflow) { if (wrapped) {
put_ucounts(ucounts); put_ucounts(ucounts);
return NULL; return NULL;
} }