From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-alma10-1.taild15c8.ts.net [100.103.45.18]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id D929F3BCD0E for ; Mon, 31 Aug 2026 22:35:59 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=100.103.45.18 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1788215761; cv=none; b=gNYLAWm4fKo3Pf7uPSPfJYeHpvSVDDPMmifizyJFMKaRGMejVC8t7gw4hfM7PfRNB4QEwd78Q/L+B3OH9PuEKxcR1hQEHAGgQp6ZYsdlhnezED9RD+lfeKFdetAkk820ahCkSdWTXlqje0bp65ru0HmDKbtprgtQSs/HY7YsBNU= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1788215761; c=relaxed/simple; bh=vsEjG0pzb/QoJGyb814Ww6uC1P3aIE3hc57W/TkxlIU=; h=Date:To:From:Subject:Message-Id; b=JdJ+MecYJm1kyPJQU/gpcsYXLR0no6hPRA4+0adE7IxM6zi3OWanRp7GdLo6+hLPYYr1k1szMMhs2+2sFlhsNIe5EudbGvV/dvPLly0jqsaRuH3Uq36D+YsJKi7K+PELBAIaF57bftislLNk/hehknI3P4J6HNZPRDcZNbjHq+E= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linux-foundation.org header.i=@linux-foundation.org header.b=VH5y4MD2; arc=none smtp.client-ip=100.103.45.18 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linux-foundation.org header.i=@linux-foundation.org header.b="VH5y4MD2" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 978191F000E9; Mon, 31 Aug 2026 22:35:59 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linux-foundation.org; s=korg; t=1788215759; bh=4fk8vvzZ14mkLkOAh29WBo6Gb51acLTDvK4cblnz5/g=; h=Date:To:From:Subject; b=VH5y4MD26vpXtZ0cg1Ovb7wcl9x/U/clM6H/XRPFqZQrIPuc7kYBJhYQnUUZZMXVu n+kedFTbzp8NSKAfu/SvspV8aV4Caf/p/wg9LlR9sSFrKeENpexiN7tW1dTneHxOlr 3EHjsoHhhaZedd2L/r8mTkJxhl7mnl+sP3gx/BOI= Date: Mon, 31 Aug 2026 15:35:59 -0700 To: mm-commits@vger.kernel.org,vbabka@kernel.org,tkjos@android.com,surenb@google.com,shakeel.butt@linux.dev,ljs@kernel.org,Liam.Howlett@oracle.com,gregkh@linuxfoundation.org,dsahern@kernel.org,davem@davemloft.net,cmllamas@google.com,christian@brauner.io,arve@android.com,aliceryhl@google.com,dave.hansen@linux.intel.com,akpm@linux-foundation.org From: Andrew Morton Subject: + tcp-remove-mmap_lock-fallback-path.patch added to mm-new branch Message-Id: <20260831223559.978191F000E9@smtp.kernel.org> Precedence: bulk X-Mailing-List: mm-commits@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: The patch titled Subject: tcp: remove mmap_lock fallback path has been added to the -mm mm-new branch. Its filename is tcp-remove-mmap_lock-fallback-path.patch This patch will shortly appear at https://git.kernel.org/pub/scm/linux/kernel/git/akpm/25-new.git/tree/patches/tcp-remove-mmap_lock-fallback-path.patch This patch will later appear in the mm-new branch at git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm Note, mm-new is a provisional staging ground for work-in-progress patches, and acceptance into mm-new is a notification for others take notice and to finish up reviews. Please do not hesitate to respond to review feedback and post updated versions to replace or incrementally fixup patches in mm-new. The mm-new branch of mm.git is not included in linux-next If a few days of testing in mm-new is successful, the patch will me moved into mm.git's mm-unstable branch, which is included in linux-next Before you just go and hit "reply", please: a) Consider who else should be cc'ed b) Prefer to cc a suitable mailing list as well c) Ideally: find the original patch on the mailing list and do a reply-to-all to that, adding suitable additional cc's *** Remember to use Documentation/process/submit-checklist.rst when testing your code *** The -mm tree is included into linux-next via various branches at git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm and is updated there most days ------------------------------------------------------ From: Dave Hansen Subject: tcp: remove mmap_lock fallback path Date: Mon, 31 Aug 2026 13:30:56 -0700 Previously, the per-VMA locking could fail in the face of writers which necessitates a fallback to mmap_lock. The new vma_start_read_unlocked() will wait for writers instead of failing. Use the new helper. Wait for writers. Remove the fallback to mmap_lock. The fallback removal does not affect NOMMU case because TCP_ZEROCOPY is gated on CONFIG_MMU. This really is a nice cleanup. It removes the need to pass the lock state back and forth to find_tcp_vma(). Link: https://lore.kernel.org/20260831203056.838265-6-surenb@google.com Signed-off-by: Dave Hansen Signed-off-by: Suren Baghdasaryan Acked-by: Lorenzo Stoakes Acked-by: Vlastimil Babka (SUSE) Tested-by: syzbot@syzkaller.appspotmail.com Cc: Liam R. Howlett Cc: Vlastimil Babka Cc: Shakeel Butt Cc: Greg Kroah-Hartman Cc: Arve Hjønnevåg Cc: Todd Kjos Cc: Christian Brauner Cc: Carlos Llamas Cc: Alice Ryhl Cc: David S. Miller Cc: David Ahern Signed-off-by: Andrew Morton --- net/ipv4/tcp.c | 31 +++++++++---------------------- 1 file changed, 9 insertions(+), 22 deletions(-) --- a/net/ipv4/tcp.c~tcp-remove-mmap_lock-fallback-path +++ a/net/ipv4/tcp.c @@ -2167,27 +2167,18 @@ static void tcp_zc_finalize_rx_tstamp(st } static struct vm_area_struct *find_tcp_vma(struct mm_struct *mm, - unsigned long address, - bool *mmap_locked) + unsigned long address) { - struct vm_area_struct *vma = lock_vma_under_rcu(mm, address); + struct vm_area_struct *vma = vma_start_read_unlocked(mm, address); - if (vma) { - if (vma->vm_ops != &tcp_vm_ops) { - vma_end_read(vma); - return NULL; - } - *mmap_locked = false; - return vma; - } + if (!vma) + return NULL; - mmap_read_lock(mm); - vma = vma_lookup(mm, address); - if (!vma || vma->vm_ops != &tcp_vm_ops) { - mmap_read_unlock(mm); + if (vma->vm_ops != &tcp_vm_ops) { + vma_end_read(vma); return NULL; } - *mmap_locked = true; + return vma; } @@ -2208,7 +2199,6 @@ static int tcp_zerocopy_receive(struct s u32 seq = tp->copied_seq; u32 total_bytes_to_map; int inq = tcp_inq(sk); - bool mmap_locked; int ret; zc->copybuf_len = 0; @@ -2233,7 +2223,7 @@ static int tcp_zerocopy_receive(struct s return 0; } - vma = find_tcp_vma(current->mm, address, &mmap_locked); + vma = find_tcp_vma(current->mm, address); if (!vma) return -EINVAL; @@ -2315,10 +2305,7 @@ static int tcp_zerocopy_receive(struct s zc, total_bytes_to_map); } out: - if (mmap_locked) - mmap_read_unlock(current->mm); - else - vma_end_read(vma); + vma_end_read(vma); /* Try to copy straggler data. */ if (!ret) copylen = tcp_zc_handle_leftover(zc, sk, skb, &seq, copybuf_len, tss); _ Patches currently in -mm which might be from dave.hansen@linux.intel.com are mm-make-per-vma-locks-available-universally.patch binder-make-shrinker-rely-solely-on-per-vma-lock.patch mm-add-rcu-based-vma-lookup-helper-that-waits-for-writers.patch binder-remove-mmap_lock-fallback.patch tcp-remove-mmap_lock-fallback-path.patch