From: Suren Baghdasaryan <surenb@google.com>
Date: Thu, 13 Feb 2025 22:46:48 +0000 (-0800)
Subject: refcount: introduce __refcount_{add|inc}_not_zero_limited_acquire
X-Git-Url: https://www.infradead.org/git/?a=commitdiff_plain;h=6599861663bcb6b2a3a63d6b462897c8a858546c;p=users%2Fjedix%2Flinux-maple.git

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/20250213224655.1680278-12-surenb@google.com
Signed-off-by: Suren Baghdasaryan <surenb@google.com>
Tested-by: Shivank Garg <shivankg@amd.com>
  Link: https://lkml.kernel.org/r/5e19ec93-8307-47c2-bb13-3ddf7150624e@amd.com
Cc: Christian Brauner <brauner@kernel.org>
Cc: David Hildenbrand <david@redhat.com>
Cc: David Howells <dhowells@redhat.com>
Cc: Davidlohr Bueso <dave@stgolabs.net>
Cc: Hugh Dickins <hughd@google.com>
Cc: Jann Horn <jannh@google.com>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Jonathan Corbet <corbet@lwn.net>
Cc: Klara Modin <klarasmodin@gmail.com>
Cc: Liam R. Howlett <Liam.Howlett@Oracle.com>
Cc: Lokesh Gidra <lokeshgidra@google.com>
Cc: Lorenzo Stoakes <lorenzo.stoakes@oracle.com>
Cc: Mateusz Guzik <mjguzik@gmail.com>
Cc: Matthew Wilcox <willy@infradead.org>
Cc: Mel Gorman <mgorman@techsingularity.net>
Cc: Michal Hocko <mhocko@suse.com>
Cc: Minchan Kim <minchan@google.com>
Cc: Oleg Nesterov <oleg@redhat.com>
Cc: Pasha Tatashin <pasha.tatashin@soleen.com>
Cc: "Paul E . McKenney" <paulmck@kernel.org>
Cc: Peter Xu <peterx@redhat.com>
Cc: Peter Zijlstra (Intel) <peterz@infradead.org>
Cc: Shakeel Butt <shakeel.butt@linux.dev>
Cc: Sourav Panda <souravpanda@google.com>
Cc: Vlastimil Babka <vbabka@suse.cz>
Cc: Wei Yang <richard.weiyang@gmail.com>
Cc: Will Deacon <will@kernel.org>
Cc: Heiko Carstens <hca@linux.ibm.com>
Cc: Stephen Rothwell <sfr@canb.auug.org.au>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
---

diff --git a/include/linux/refcount.h b/include/linux/refcount.h
index 4589d2e7bfea..80dc023ac2bf 100644
--- a/include/linux/refcount.h
+++ b/include/linux/refcount.h
@@ -213,13 +213,20 @@ static inline __must_check bool refcount_add_not_zero(int i, refcount_t *r)
 }
 
 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)
@@ -231,6 +238,18 @@ bool __refcount_add_not_zero_acquire(int i, refcount_t *r, int *oldp)
 	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);
+}
+
 /**
  * refcount_add_not_zero_acquire - add a value to a refcount with acquire ordering unless it is 0
  *