+ refcount-introduce-__refcount_addinc_not_zero_limited_acquire.patch added to mm-unstable branch

+ refcount-introduce-__refcount_addinc_not_zero_limited_acquire.patch added to mm-unstable branch

[Andrew Morton]

The patch titled
     Subject: refcount: introduce __refcount_{add|inc}_not_zero_limited_acquire
has been added to the -mm mm-unstable branch.  Its filename is
     refcount-introduce-__refcount_addinc_not_zero_limited_acquire.patch

This patch will shortly appear at
     https://git.kernel.org/pub/scm/linux/kernel/git/akpm/25-new.git/tree/patches/refcount-introduce-__refcount_addinc_not_zero_limited_acquire.patch

This patch will later appear in the mm-unstable branch at
    git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm

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------------------------------------------------------
From: Suren Baghdasaryan <surenb@google.com>
Subject: refcount: introduce __refcount_{add|inc}_not_zero_limited_acquire
Date: Thu, 13 Feb 2025 14:46:48 -0800

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: Hillf Danton <hdanton@sina.com>
Cc: Hugh Dickens <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>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
---

 include/linux/refcount.h |   21 ++++++++++++++++++++-
 1 file changed, 20 insertions(+), 1 deletion(-)

--- a/include/linux/refcount.h~refcount-introduce-__refcount_addinc_not_zero_limited_acquire
+++ a/include/linux/refcount.h
@@ -213,13 +213,20 @@ static inline __must_check bool refcount
 }
 
 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
 	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
  *
_

Patches currently in -mm which might be from surenb@google.com are

alloc_tag-work-around-clang-14-issue-with-__builtin_object_size.patch
mm-avoid-extra-mem_alloc_profiling_enabled-checks.patch
alloc_tag-uninline-code-gated-by-mem_alloc_profiling_key-in-slab-allocator.patch
alloc_tag-uninline-code-gated-by-mem_alloc_profiling_key-in-page-allocator.patch
mm-introduce-vma_start_read_locked_nested-helpers.patch
mm-move-per-vma-lock-into-vm_area_struct.patch
mm-mark-vma-as-detached-until-its-added-into-vma-tree.patch
mm-introduce-vma_iter_store_attached-to-use-with-attached-vmas.patch
mm-mark-vmas-detached-upon-exit.patch
types-move-struct-rcuwait-into-typesh.patch
mm-allow-vma_start_read_locked-vma_start_read_locked_nested-to-fail.patch
mm-move-mmap_init_lock-out-of-the-header-file.patch
mm-uninline-the-main-body-of-vma_start_write.patch
refcount-provide-ops-for-cases-when-objects-memory-can-be-reused.patch
refcount-introduce-__refcount_addinc_not_zero_limited_acquire.patch
mm-replace-vm_lock-and-detached-flag-with-a-reference-count.patch
mm-move-lesser-used-vma_area_struct-members-into-the-last-cacheline.patch
mm-debug-print-vm_refcnt-state-when-dumping-the-vma.patch
mm-remove-extra-vma_numab_state_init-call.patch
mm-prepare-lock_vma_under_rcu-for-vma-reuse-possibility.patch
mm-make-vma-cache-slab_typesafe_by_rcu.patch
docs-mm-document-latest-changes-to-vm_lock.patch