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([157.51.37.214]) by smtp.gmail.com with ESMTPSA id d9443c01a7336-2a93397ef6fsm27170315ad.95.2026.02.04.06.24.11 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Wed, 04 Feb 2026 06:24:13 -0800 (PST) From: Aswin Kumar To: linux-mm@kvack.org Cc: andrew.morton@linux-foundation.org, linux-kernel@vger.kernel.org, Aswin Kumar Subject: [PATCH] mm/userfaultfd: fix likely/unlikely annotation in move_pages() Date: Wed, 4 Feb 2026 14:23:50 +0000 Message-ID: <20260204142350.1642-1-aswinkumar3301@gmail.com> X-Mailer: git-send-email 2.43.0 MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Rspamd-Server: rspam01 X-Rspamd-Queue-Id: 7065240006 X-Stat-Signature: ji3jnd549mc5ndjsrkyajtoikdaize95 X-Rspam-User: X-HE-Tag: 1770215055-478738 X-HE-Meta: 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 lo0NGgoU 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 X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: All other userfaultfd paths use unlikely() for the mmap_changing check, since normally mmap is not changing. The move_pages() path incorrectly uses likely(), which is the opposite of the intended branch prediction hint. This is a performance-only fix - the logic is correct but the branch prediction annotation is wrong, potentially causing a minor performance penalty on the fast path. Fixes: e0a58ef0faa7 ("userfaultfd: UFFDIO_MOVE uABI") Signed-off-by: Aswin Kumar --- mm/userfaultfd.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/mm/userfaultfd.c b/mm/userfaultfd.c index e6dfd5f28..d27080348 100644 --- a/mm/userfaultfd.c +++ b/mm/userfaultfd.c @@ -1793,7 +1793,7 @@ 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 -- 2.43.0