refcount: introduce __refcount_{add|inc}_not_zero_limited_acquire

Introduce functions to increase refcount but with a top limit above which
they will fail to increase (the limit is inclusive). Setting the limit to
INT_MAX indicates no limit.

Link: https://lkml.kernel.org/r/[e-mail]
Signed-off-by: Suren Baghdasaryan <[e-mail]>
Tested-by: Shivank Garg <[e-mail]>
Link: https://lkml.kernel.org/r/[e-mail]
Cc: Christian Brauner <[e-mail]>
Cc: David Hildenbrand <[e-mail]>
Cc: David Howells <[e-mail]>
Cc: Davidlohr Bueso <[e-mail]>
Cc: Hugh Dickins <[e-mail]>
Cc: Jann Horn <[e-mail]>
Cc: Johannes Weiner <[e-mail]>
Cc: Jonathan Corbet <[e-mail]>
Cc: Klara Modin <[e-mail]>
Cc: Liam R. Howlett <[e-mail]>
Cc: Lokesh Gidra <[e-mail]>
Cc: Lorenzo Stoakes <[e-mail]>
Cc: Mateusz Guzik <[e-mail]>
Cc: Matthew Wilcox <[e-mail]>
Cc: Mel Gorman <[e-mail]>
Cc: Michal Hocko <[e-mail]>
Cc: Minchan Kim <[e-mail]>
Cc: Oleg Nesterov <[e-mail]>
Cc: Pasha Tatashin <[e-mail]>
Cc: "Paul E . McKenney" <[e-mail]>
Cc: Peter Xu <[e-mail]>
Cc: Peter Zijlstra (Intel) <[e-mail]>
Cc: Shakeel Butt <[e-mail]>
Cc: Sourav Panda <[e-mail]>
Cc: Vlastimil Babka <[e-mail]>
Cc: Wei Yang <[e-mail]>
Cc: Will Deacon <[e-mail]>
Cc: Heiko Carstens <[e-mail]>
Cc: Stephen Rothwell <[e-mail]>
Signed-off-by: Andrew Morton <[e-mail]>

include/linux/refcount.h

···
 }
 
 static inline __must_check __signed_wrap
-bool __refcount_add_not_zero_acquire(int i, refcount_t *r, int *oldp)
+bool __refcount_add_not_zero_limited_acquire(int i, refcount_t *r, int *oldp,
+					     int limit)
 {
 	int old = refcount_read(r);
 
 	do {
 		if (!old)
 			break;
+
+		if (i > limit - old) {
+			if (oldp)
+				*oldp = old;
+			return false;
+		}
 	} while (!atomic_try_cmpxchg_acquire(&r->refs, &old, old + i));
 
 	if (oldp)
···
 		refcount_warn_saturate(r, REFCOUNT_ADD_NOT_ZERO_OVF);
 
 	return old;
+}
+
+static inline __must_check bool
+__refcount_inc_not_zero_limited_acquire(refcount_t *r, int *oldp, int limit)
+{
+	return __refcount_add_not_zero_limited_acquire(1, r, oldp, limit);
+}
+
+static inline __must_check __signed_wrap
+bool __refcount_add_not_zero_acquire(int i, refcount_t *r, int *oldp)
+{
+	return __refcount_add_not_zero_limited_acquire(i, r, oldp, INT_MAX);
 }
 
 /**