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[188.141.5.72]) by smtp.gmail.com with ESMTPSA id 5b1f17b1804b1-4872718dfdfsm38161075e9.30.2026.03.28.10.01.05 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Sat, 28 Mar 2026 10:01:06 -0700 (PDT) From: David Carlier To: Andrew Morton , Peter Xu Cc: Mike Rapoport , linux-mm@kvack.org, linux-kernel@vger.kernel.org, David Carlier Subject: [PATCH 2/2] mm/userfaultfd: fix wrong likely() hint on mmap_changing check in move_pages() Date: Sat, 28 Mar 2026 17:01:01 +0000 Message-ID: <20260328170101.184163-2-devnexen@gmail.com> X-Mailer: git-send-email 2.53.0 In-Reply-To: <20260328170101.184163-1-devnexen@gmail.com> References: <20260328170101.184163-1-devnexen@gmail.com> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit The mmap_changing check in move_pages() uses likely() but the condition being true (concurrent mapping changes during UFFDIO_MOVE) is the exceptional case, not the common one. All other mmap_changing checks in the same file correctly use no branch hint or use unlikely(). Replace likely() with unlikely() to match the expected branch behavior. Signed-off-by: David Carlier --- mm/userfaultfd.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/mm/userfaultfd.c b/mm/userfaultfd.c index 2a6e034b15aa..dc1b3dd1aece 100644 --- a/mm/userfaultfd.c +++ b/mm/userfaultfd.c @@ -1872,7 +1872,7 @@ ssize_t move_pages(struct userfaultfd_ctx *ctx, unsigned long dst_start, /* Re-check after taking map_changing_lock */ err = -EAGAIN; down_read(&ctx->map_changing_lock); - if (likely(atomic_read(&ctx->mmap_changing))) + if (unlikely(atomic_read(&ctx->mmap_changing))) goto out_unlock; /* * Make sure the vma is not shared, that the src and dst remap -- 2.53.0