From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (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 C0B98217F2E for ; Fri, 27 Jun 2025 20:16:47 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=10.30.226.201 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1751055407; cv=none; b=WWAfMBC1Ec/cziOhNBQlwIQBUWxUlg5+tDT6BtXFUvb/e17vQS1SS9UtkTxmXoMrXDtmBow6FzZbt3ctpYNFV3B4XnLZCsmQRUdfxFlzKqNvOzet1jEq2IK6LuB9DSnb2jHEKdt0JYsI48ztZHSJ6e6Lr4brll99n6gGbJE7clc= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1751055407; c=relaxed/simple; bh=qoTesDHBNcTZ2z4igS/DbwAz9nEx/Aol5VK5S2TGq/8=; h=Date:To:From:Subject:Message-Id; b=As4MuMCCG/FvqxXbbESzeKWuIxM560m2RuzcztjSIB3WbKGmG87VgHQ4zNB6/sJOJDKRgCivzfi7scKEuAeSi+GD+5nHqCs/AM7+4ATIgNVkSufXwVhbQxyqjY6Plxj9m+QJSM8UOi+Qkbwy6w1GobFJnCAtNxgx9qQU7sFuIqU= 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=FkCjiJmt; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linux-foundation.org header.i=@linux-foundation.org header.b="FkCjiJmt" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 537C3C4CEEB; Fri, 27 Jun 2025 20:16:47 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linux-foundation.org; s=korg; t=1751055407; bh=qoTesDHBNcTZ2z4igS/DbwAz9nEx/Aol5VK5S2TGq/8=; h=Date:To:From:Subject:From; b=FkCjiJmtgY7Ji03VdiQ4HfZGvK74SalVi4H7tWFHAo3+pxEyBzxMCqXbods6huCyQ vfIkaFssepEUCC8dGSqpj3Pv1e5ote/cBQL5ZnM8dULeIGGIpr0vPiDb5Bg21hrAmY kPeCPO3Hl03MdQfsunH+Cr2/E+uqk5OvMauj6REo= Date: Fri, 27 Jun 2025 13:16:46 -0700 To: mm-commits@vger.kernel.org,willy@infradead.org,shikemeng@huaweicloud.com,nphamcs@gmail.com,hughd@google.com,dev.jain@arm.com,chrisl@kernel.org,bhe@redhat.com,baolin.wang@linux.alibaba.com,baohua@kernel.org,kasong@tencent.com,akpm@linux-foundation.org From: Andrew Morton Subject: + mm-shmem-swap-clean-up-swap-entry-splitting.patch added to mm-new branch Message-Id: <20250627201647.537C3C4CEEB@smtp.kernel.org> Precedence: bulk X-Mailing-List: mm-commits@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: The patch titled Subject: mm/shmem, swap: clean up swap entry splitting has been added to the -mm mm-new branch. Its filename is mm-shmem-swap-clean-up-swap-entry-splitting.patch This patch will shortly appear at https://git.kernel.org/pub/scm/linux/kernel/git/akpm/25-new.git/tree/patches/mm-shmem-swap-clean-up-swap-entry-splitting.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. 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: Kairui Song Subject: mm/shmem, swap: clean up swap entry splitting Date: Fri, 27 Jun 2025 14:20:17 +0800 Instead of keeping different paths of splitting the entry and recalculating the swap entry and index, do it in one place. Whenever swapin brought in a folio smaller than the entry, split the entry. And always recalculate the entry and index, in case it might read in a folio that's larger than the entry order. This removes duplicated code and function calls, and makes the code more robust. Link: https://lkml.kernel.org/r/20250627062020.534-5-ryncsn@gmail.com Signed-off-by: Kairui Song Cc: Baolin Wang Cc: Baoquan He Cc: Barry Song Cc: Chris Li Cc: Dev Jain Cc: Hugh Dickins Cc: Kemeng Shi Cc: Matthew Wilcox (Oracle) Cc: Nhat Pham Signed-off-by: Andrew Morton --- mm/shmem.c | 103 ++++++++++++++++++++------------------------------- 1 file changed, 41 insertions(+), 62 deletions(-) --- a/mm/shmem.c~mm-shmem-swap-clean-up-swap-entry-splitting +++ a/mm/shmem.c @@ -2178,8 +2178,12 @@ static void shmem_set_folio_swapin_error swap_free_nr(swap, nr_pages); } -static int shmem_split_large_entry(struct inode *inode, pgoff_t index, - swp_entry_t swap, gfp_t gfp) +/* + * Split an existing large swap entry. @index should point to one sub mapping + * slot within the entry @swap, this sub slot will be split into order 0. + */ +static int shmem_split_swap_entry(struct inode *inode, pgoff_t index, + swp_entry_t swap, gfp_t gfp) { struct address_space *mapping = inode->i_mapping; XA_STATE_ORDER(xas, &mapping->i_pages, index, 0); @@ -2250,7 +2254,7 @@ unlock: if (xas_error(&xas)) return xas_error(&xas); - return entry_order; + return 0; } /* @@ -2267,11 +2271,11 @@ static int shmem_swapin_folio(struct ino struct address_space *mapping = inode->i_mapping; struct mm_struct *fault_mm = vma ? vma->vm_mm : NULL; struct shmem_inode_info *info = SHMEM_I(inode); + int error, nr_pages, order, swap_order; struct swap_info_struct *si; struct folio *folio = NULL; bool skip_swapcache = false; swp_entry_t swap; - int error, nr_pages, order, split_order; VM_BUG_ON(!*foliop || !xa_is_value(*foliop)); swap = radix_to_swp_entry(*foliop); @@ -2321,70 +2325,43 @@ static int shmem_swapin_folio(struct ino goto failed; } - /* - * Now swap device can only swap in order 0 folio, then we - * should split the large swap entry stored in the pagecache - * if necessary. - */ - split_order = shmem_split_large_entry(inode, index, swap, gfp); - if (split_order < 0) { - error = split_order; - goto failed; - } - - /* - * If the large swap entry has already been split, it is - * necessary to recalculate the new swap entry based on - * the old order alignment. - */ - if (split_order > 0) { - pgoff_t offset = index - round_down(index, 1 << split_order); - - swap = swp_entry(swp_type(swap), swp_offset(swap) + offset); - } - /* Here we actually start the io */ folio = shmem_swapin_cluster(swap, gfp, info, index); if (!folio) { error = -ENOMEM; goto failed; } - } else if (order > folio_order(folio)) { - /* - * Swap readahead may swap in order 0 folios into swapcache - * asynchronously, while the shmem mapping can still stores - * large swap entries. In such cases, we should split the - * large swap entry to prevent possible data corruption. - */ - split_order = shmem_split_large_entry(inode, index, swap, gfp); - if (split_order < 0) { - folio_put(folio); - folio = NULL; - error = split_order; - goto failed; - } - - /* - * If the large swap entry has already been split, it is - * necessary to recalculate the new swap entry based on - * the old order alignment. - */ - if (split_order > 0) { - pgoff_t offset = index - round_down(index, 1 << split_order); - - swap = swp_entry(swp_type(swap), swp_offset(swap) + offset); - } - } else if (order < folio_order(folio)) { - swap.val = round_down(swap.val, 1 << folio_order(folio)); } alloced: + /* + * We need to split an existing large entry if swapin brought in a + * smaller folio due to various of reasons. + * + * And worth noting there is a special case: if there is a smaller + * cached folio that covers @swap, but not @index (it only covers + * first few sub entries of the large entry, but @index points to + * later parts), the swap cache lookup will still see this folio, + * And we need to split the large entry here. Later checks will fail, + * as it can't satisfy the swap requirement, and we will retry + * the swapin from beginning. + */ + swap_order = folio_order(folio); + if (order > swap_order) { + error = shmem_split_swap_entry(inode, index, swap, gfp); + if (error) + goto failed_nolock; + } + + index = round_down(index, 1 << swap_order); + swap.val = round_down(swap.val, 1 << swap_order); + /* We have to do this with folio locked to prevent races */ folio_lock(folio); if ((!skip_swapcache && !folio_test_swapcache(folio)) || folio->swap.val != swap.val) { error = -EEXIST; - goto unlock; + goto failed_unlock; } if (!folio_test_uptodate(folio)) { error = -EIO; @@ -2405,8 +2382,7 @@ alloced: goto failed; } - error = shmem_add_to_page_cache(folio, mapping, - round_down(index, nr_pages), + error = shmem_add_to_page_cache(folio, mapping, index, swp_to_radix_entry(swap), gfp); if (error) goto failed; @@ -2417,8 +2393,8 @@ alloced: folio_mark_accessed(folio); if (skip_swapcache) { + swapcache_clear(si, folio->swap, folio_nr_pages(folio)); folio->swap.val = 0; - swapcache_clear(si, swap, nr_pages); } else { delete_from_swap_cache(folio); } @@ -2434,13 +2410,16 @@ failed: if (error == -EIO) shmem_set_folio_swapin_error(inode, index, folio, swap, skip_swapcache); -unlock: - if (skip_swapcache) - swapcache_clear(si, swap, folio_nr_pages(folio)); - if (folio) { +failed_unlock: + if (folio) folio_unlock(folio); - folio_put(folio); +failed_nolock: + if (skip_swapcache) { + swapcache_clear(si, folio->swap, folio_nr_pages(folio)); + folio->swap.val = 0; } + if (folio) + folio_put(folio); put_swap_device(si); return error; } _ Patches currently in -mm which might be from kasong@tencent.com are mm-list_lru-refactor-the-locking-code.patch mm-shmem-swap-improve-cached-mthp-handling-and-fix-potential-hung.patch mm-shmem-swap-avoid-redundant-xarray-lookup-during-swapin.patch mm-shmem-swap-tidy-up-thp-swapin-checks.patch mm-shmem-swap-clean-up-swap-entry-splitting.patch mm-shmem-swap-never-use-swap-cache-and-readahead-for-swp_synchronous_io.patch mm-shmem-swap-fix-major-fault-counting.patch mm-shmem-swap-avoid-false-positive-swap-cache-lookup.patch