From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 57EAEEB64D9 for ; Sun, 2 Jul 2023 17:55:06 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S229638AbjGBRzF (ORCPT ); Sun, 2 Jul 2023 13:55:05 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:44326 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229584AbjGBRzF (ORCPT ); Sun, 2 Jul 2023 13:55:05 -0400 Received: from dfw.source.kernel.org (dfw.source.kernel.org [139.178.84.217]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id F187BE5E for ; Sun, 2 Jul 2023 10:55:03 -0700 (PDT) Received: from smtp.kernel.org (relay.kernel.org [52.25.139.140]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature RSA-PSS (2048 bits)) (No client certificate requested) by dfw.source.kernel.org (Postfix) with ESMTPS id 90D3B60C7B for ; Sun, 2 Jul 2023 17:55:03 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id E3944C433C7; Sun, 2 Jul 2023 17:55:02 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linux-foundation.org; s=korg; t=1688320503; bh=2Ywr3J3TDaO+pt2G2jVCJ3cCtcdITUNyCQRIXMCJj3M=; h=Date:To:From:Subject:From; b=rQHUgb8tuUlzDb2Q+qSDu6EWD7X9vylA66/s7sgjtlwVNrJocKqKin0aPq1/GvT31 GRgf87s3761lgBdLsCAxqT1WX37H1Bb5cXG76fIy2RTKEQcrjcJ/Xj5dzZfCh7AD9R ouiDLCCKjy6pYx56tHqmWTyAq9CHbwFKGd1M4sbs= Date: Sun, 02 Jul 2023 10:55:02 -0700 To: mm-commits@vger.kernel.org, yuzhao@google.com, ying.huang@intel.com, willy@infradead.org, viro@zeniv.linux.org.uk, vbabka@suse.cz, punit.agrawal@bytedance.com, peterx@redhat.com, pasha.tatashin@soleen.com, minchan@google.com, michel@lespinasse.org, mhocko@suse.com, lstoakes@gmail.com, Liam.Howlett@oracle.com, ldufour@linux.ibm.com, josef@toxicpanda.com, jack@suse.cz, hughd@google.com, hdanton@sina.com, hch@lst.de, hannes@cmpxchg.org, dhowells@redhat.com, david@redhat.com, dave@stgolabs.net, brauner@kernel.org, apopple@nvidia.com, surenb@google.com, akpm@linux-foundation.org From: Andrew Morton Subject: + mm-handle-swap-page-faults-under-per-vma-lock.patch added to mm-unstable branch Message-Id: <20230702175502.E3944C433C7@smtp.kernel.org> Precedence: bulk Reply-To: linux-kernel@vger.kernel.org List-ID: X-Mailing-List: mm-commits@vger.kernel.org The patch titled Subject: mm: handle swap page faults under per-VMA lock has been added to the -mm mm-unstable branch. Its filename is mm-handle-swap-page-faults-under-per-vma-lock.patch This patch will shortly appear at https://git.kernel.org/pub/scm/linux/kernel/git/akpm/25-new.git/tree/patches/mm-handle-swap-page-faults-under-per-vma-lock.patch This patch will later appear in the mm-unstable branch at git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm 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 the mm-everything branch at git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm and is updated there every 2-3 working days ------------------------------------------------------ From: Suren Baghdasaryan Subject: mm: handle swap page faults under per-VMA lock Date: Fri, 30 Jun 2023 14:19:56 -0700 When page fault is handled under per-VMA lock protection, all swap page faults are retried with mmap_lock because folio_lock_or_retry has to drop and reacquire mmap_lock if folio could not be immediately locked. Follow the same pattern as mmap_lock to drop per-VMA lock when waiting for folio and retrying once folio is available. With this obstacle removed, enable do_swap_page to operate under per-VMA lock protection. Drivers implementing ops->migrate_to_ram might still rely on mmap_lock, therefore we have to fall back to mmap_lock in that particular case. Note that the only time do_swap_page calls synchronous swap_readpage is when SWP_SYNCHRONOUS_IO is set, which is only set for QUEUE_FLAG_SYNCHRONOUS devices: brd, zram and nvdimms (both btt and pmem). Therefore we don't sleep in this path, and there's no need to drop the mmap or per-VMA lock. Link: https://lkml.kernel.org/r/20230630211957.1341547-6-surenb@google.com Signed-off-by: Suren Baghdasaryan Tested-by: Alistair Popple Reviewed-by: Alistair Popple Acked-by: Peter Xu Cc: Al Viro Cc: Christian Brauner Cc: Christoph Hellwig Cc: David Hildenbrand Cc: David Howells Cc: Davidlohr Bueso Cc: Hillf Danton Cc: "Huang, Ying" Cc: Hugh Dickins Cc: Jan Kara Cc: Johannes Weiner Cc: Josef Bacik Cc: Laurent Dufour Cc: Liam R. Howlett Cc: Lorenzo Stoakes Cc: Matthew Wilcox Cc: Michal Hocko Cc: Michel Lespinasse Cc: Minchan Kim Cc: Pavel Tatashin Cc: Punit Agrawal Cc: Vlastimil Babka Cc: Yu Zhao Signed-off-by: Andrew Morton --- include/linux/mm.h | 13 +++++++++++++ mm/filemap.c | 17 ++++++++--------- mm/memory.c | 16 ++++++++++------ 3 files changed, 31 insertions(+), 15 deletions(-) --- a/include/linux/mm.h~mm-handle-swap-page-faults-under-per-vma-lock +++ a/include/linux/mm.h @@ -720,6 +720,14 @@ static inline void vma_mark_detached(str vma->detached = detached; } +static inline void release_fault_lock(struct vm_fault *vmf) +{ + if (vmf->flags & FAULT_FLAG_VMA_LOCK) + vma_end_read(vmf->vma); + else + mmap_read_unlock(vmf->vma->vm_mm); +} + struct vm_area_struct *lock_vma_under_rcu(struct mm_struct *mm, unsigned long address); @@ -735,6 +743,11 @@ static inline void vma_assert_write_lock static inline void vma_mark_detached(struct vm_area_struct *vma, bool detached) {} +static inline void release_fault_lock(struct vm_fault *vmf) +{ + mmap_read_unlock(vmf->vma->vm_mm); +} + #endif /* CONFIG_PER_VMA_LOCK */ /* --- a/mm/filemap.c~mm-handle-swap-page-faults-under-per-vma-lock +++ a/mm/filemap.c @@ -1671,27 +1671,26 @@ static int __folio_lock_async(struct fol * Return values: * 0 - folio is locked. * non-zero - folio is not locked. - * mmap_lock has been released (mmap_read_unlock(), unless flags had both - * FAULT_FLAG_ALLOW_RETRY and FAULT_FLAG_RETRY_NOWAIT set, in - * which case mmap_lock is still held. + * mmap_lock or per-VMA lock has been released (mmap_read_unlock() or + * vma_end_read()), unless flags had both FAULT_FLAG_ALLOW_RETRY and + * FAULT_FLAG_RETRY_NOWAIT set, in which case the lock is still held. * * If neither ALLOW_RETRY nor KILLABLE are set, will always return 0 - * with the folio locked and the mmap_lock unperturbed. + * with the folio locked and the mmap_lock/per-VMA lock is left unperturbed. */ vm_fault_t __folio_lock_or_retry(struct folio *folio, struct vm_fault *vmf) { - struct mm_struct *mm = vmf->vma->vm_mm; unsigned int flags = vmf->flags; if (fault_flag_allow_retry_first(flags)) { /* - * CAUTION! In this case, mmap_lock is not released - * even though return VM_FAULT_RETRY. + * CAUTION! In this case, mmap_lock/per-VMA lock is not + * released even though returning VM_FAULT_RETRY. */ if (flags & FAULT_FLAG_RETRY_NOWAIT) return VM_FAULT_RETRY; - mmap_read_unlock(mm); + release_fault_lock(vmf); if (flags & FAULT_FLAG_KILLABLE) folio_wait_locked_killable(folio); else @@ -1703,7 +1702,7 @@ vm_fault_t __folio_lock_or_retry(struct ret = __folio_lock_killable(folio); if (ret) { - mmap_read_unlock(mm); + release_fault_lock(vmf); return VM_FAULT_RETRY; } } else { --- a/mm/memory.c~mm-handle-swap-page-faults-under-per-vma-lock +++ a/mm/memory.c @@ -3732,12 +3732,6 @@ vm_fault_t do_swap_page(struct vm_fault if (!pte_unmap_same(vmf)) goto out; - if (vmf->flags & FAULT_FLAG_VMA_LOCK) { - ret = VM_FAULT_RETRY; - vma_end_read(vma); - goto out; - } - entry = pte_to_swp_entry(vmf->orig_pte); if (unlikely(non_swap_entry(entry))) { if (is_migration_entry(entry)) { @@ -3747,6 +3741,16 @@ vm_fault_t do_swap_page(struct vm_fault vmf->page = pfn_swap_entry_to_page(entry); ret = remove_device_exclusive_entry(vmf); } else if (is_device_private_entry(entry)) { + if (vmf->flags & FAULT_FLAG_VMA_LOCK) { + /* + * migrate_to_ram is not yet ready to operate + * under VMA lock. + */ + vma_end_read(vma); + ret = VM_FAULT_RETRY; + goto out; + } + vmf->page = pfn_swap_entry_to_page(entry); vmf->pte = pte_offset_map_lock(vma->vm_mm, vmf->pmd, vmf->address, &vmf->ptl); _ Patches currently in -mm which might be from surenb@google.com are swap-remove-remnants-of-polling-from-read_swap_cache_async.patch mm-add-missing-vm_fault_result_trace-name-for-vm_fault_completed.patch mm-drop-per-vma-lock-when-returning-vm_fault_retry-or-vm_fault_completed.patch mm-change-folio_lock_or_retry-to-use-vm_fault-directly.patch mm-handle-swap-page-faults-under-per-vma-lock.patch mm-handle-userfaults-under-vma-lock.patch