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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> MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Rspamd-Server: rspam12 X-Stat-Signature: 6xsfj55561rw3kzz4hmkt835pma3ddcp X-Rspamd-Queue-Id: 3CDB4140004 X-Rspam-User: X-HE-Tag: 1774717267-829882 X-HE-Meta: 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 prR5OjdW 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 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: 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