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 15869391827; Fri, 27 Mar 2026 12:23:48 +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=1774614229; cv=none; b=b/I+Y0GX1SKEXE8b+eDlmfTcGimm8M9sE+B5UiqrSH37YsbfhM72PoRum3bMgJ1/bHqNFhiadpGQFUcZ684/giRjOIqhmJB/FzaBIkpQK03PUcRWRSWzF9nsk3WRBs4lBgL+m43mlVNcu2L4kewrCCxV8RXBVzQ2nX5L7CXgQJY= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1774614229; c=relaxed/simple; bh=V8sGUJvbBSQZ15CzkQaKkEa1Er8HddnCsDI3BKLTvtU=; h=Date:From:To:Cc:Subject:Message-ID:References:MIME-Version: Content-Type:Content-Disposition:In-Reply-To; b=kmbY/r/LGFVEQaBiMvMemZALlxGTPJTAWlnlTbCaQCcJ9qdpLF1yi+Ec5jzoGoZHOBdbQGVGqxb6vtJhTecqOD2EYVcJg1eeeRh1kkhIWPh6zqTAmUCM7MmAZCpTudSZPgYqxSYtdW1tys+zXPQduzvaeLj4pRExAP8Ov4CEZm8= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=F8g4lx3T; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="F8g4lx3T" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 43B8CC2BC87; Fri, 27 Mar 2026 12:23:48 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1774614228; bh=V8sGUJvbBSQZ15CzkQaKkEa1Er8HddnCsDI3BKLTvtU=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=F8g4lx3TiflLWf5tCAz6PYcHqfwkdC2OZT6fbVgng80WiGZeUSPvNUYNoJG8K5b1k ctE+Y9mi2tJbXfyDuDYpL+MLulBxdZdLTJ7hf9Gv3NjsRIyv2n3D02pKsxew980YrY 4+aAgDeHNXTwUC9zVA8rD9RTvSfLv0b6MeQipBsM5cx/SVt0thD2DT5zRNOUOiBohx XMc2WXmuFzojQexEc+KdEdDUrkHdVKh24ktJCp5ilaCqdqttDpFSYHjHh2i73tnbQz gfZfOymgqxXaJrXm1saxMePV2fv6gwfSo+frkerGCyGdg58aV7PsrIPFpK3l/AGZwr 7gLG979b4EszA== Date: Fri, 27 Mar 2026 12:23:46 +0000 From: "Lorenzo Stoakes (Oracle)" To: Zi Yan Cc: "Matthew Wilcox (Oracle)" , Song Liu , Chris Mason , David Sterba , Alexander Viro , Christian Brauner , Jan Kara , Andrew Morton , David Hildenbrand , Baolin Wang , "Liam R. Howlett" , Nico Pache , Ryan Roberts , Dev Jain , Barry Song , Lance Yang , Vlastimil Babka , Mike Rapoport , Suren Baghdasaryan , Michal Hocko , Shuah Khan , linux-btrfs@vger.kernel.org, linux-kernel@vger.kernel.org, linux-fsdevel@vger.kernel.org, linux-mm@kvack.org, linux-kselftest@vger.kernel.org Subject: Re: [PATCH v1 03/10] mm: fs: remove filemap_nr_thps*() functions and their users Message-ID: References: <20260327014255.2058916-1-ziy@nvidia.com> <20260327014255.2058916-4-ziy@nvidia.com> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20260327014255.2058916-4-ziy@nvidia.com> On Thu, Mar 26, 2026 at 09:42:48PM -0400, Zi Yan wrote: > They are used by READ_ONLY_THP_FOR_FS to handle writes to FSes without > large folio support, so that read-only THPs created in these FSes are not > seen by the FSes when the underlying fd becomes writable. Now read-only PMD > THPs only appear in a FS with large folio support and the supported orders > include PMD_ORDRE. Typo: PMD_ORDRE -> PMD_ORDER > > Signed-off-by: Zi Yan This looks obviously-correct since this stuff wouldn't have been invoked for large folio file systems before + they already had to handle it separately, and this function is only tied to CONFIG_READ_ONLY_THP_FOR_FS (+ a quick grep suggests you didn't miss anything), so: Reviewed-by: Lorenzo Stoakes (Oracle) > --- > fs/open.c | 27 --------------------------- > include/linux/pagemap.h | 29 ----------------------------- > mm/filemap.c | 1 - > mm/huge_memory.c | 1 - > mm/khugepaged.c | 29 ++--------------------------- > 5 files changed, 2 insertions(+), 85 deletions(-) > > diff --git a/fs/open.c b/fs/open.c > index 91f1139591ab..cef382d9d8b8 100644 > --- a/fs/open.c > +++ b/fs/open.c > @@ -970,33 +970,6 @@ static int do_dentry_open(struct file *f, > if ((f->f_flags & O_DIRECT) && !(f->f_mode & FMODE_CAN_ODIRECT)) > return -EINVAL; > > - /* > - * XXX: Huge page cache doesn't support writing yet. Drop all page > - * cache for this file before processing writes. > - */ > - if (f->f_mode & FMODE_WRITE) { > - /* > - * Depends on full fence from get_write_access() to synchronize > - * against collapse_file() regarding i_writecount and nr_thps > - * updates. Ensures subsequent insertion of THPs into the page > - * cache will fail. > - */ > - if (filemap_nr_thps(inode->i_mapping)) { > - struct address_space *mapping = inode->i_mapping; > - > - filemap_invalidate_lock(inode->i_mapping); > - /* > - * unmap_mapping_range just need to be called once > - * here, because the private pages is not need to be > - * unmapped mapping (e.g. data segment of dynamic > - * shared libraries here). > - */ > - unmap_mapping_range(mapping, 0, 0, 0); > - truncate_inode_pages(mapping, 0); > - filemap_invalidate_unlock(inode->i_mapping); > - } > - } > - > return 0; > > cleanup_all: > diff --git a/include/linux/pagemap.h b/include/linux/pagemap.h > index ec442af3f886..dad3f8846cdc 100644 > --- a/include/linux/pagemap.h > +++ b/include/linux/pagemap.h > @@ -530,35 +530,6 @@ static inline size_t mapping_max_folio_size(const struct address_space *mapping) > return PAGE_SIZE << mapping_max_folio_order(mapping); > } > > -static inline int filemap_nr_thps(const struct address_space *mapping) > -{ > -#ifdef CONFIG_READ_ONLY_THP_FOR_FS > - return atomic_read(&mapping->nr_thps); > -#else > - return 0; > -#endif > -} > - > -static inline void filemap_nr_thps_inc(struct address_space *mapping) > -{ > -#ifdef CONFIG_READ_ONLY_THP_FOR_FS > - if (!mapping_large_folio_support(mapping)) > - atomic_inc(&mapping->nr_thps); > -#else > - WARN_ON_ONCE(mapping_large_folio_support(mapping) == 0); > -#endif > -} > - > -static inline void filemap_nr_thps_dec(struct address_space *mapping) > -{ > -#ifdef CONFIG_READ_ONLY_THP_FOR_FS > - if (!mapping_large_folio_support(mapping)) > - atomic_dec(&mapping->nr_thps); > -#else > - WARN_ON_ONCE(mapping_large_folio_support(mapping) == 0); > -#endif > -} > - > struct address_space *folio_mapping(const struct folio *folio); > > /** > diff --git a/mm/filemap.c b/mm/filemap.c > index 2b933a1da9bd..4248e7cdecf3 100644 > --- a/mm/filemap.c > +++ b/mm/filemap.c > @@ -189,7 +189,6 @@ static void filemap_unaccount_folio(struct address_space *mapping, > lruvec_stat_mod_folio(folio, NR_SHMEM_THPS, -nr); > } else if (folio_test_pmd_mappable(folio)) { > lruvec_stat_mod_folio(folio, NR_FILE_THPS, -nr); > - filemap_nr_thps_dec(mapping); > } > if (test_bit(AS_KERNEL_FILE, &folio->mapping->flags)) > mod_node_page_state(folio_pgdat(folio), > diff --git a/mm/huge_memory.c b/mm/huge_memory.c > index b2a6060b3c20..c7873dbdc470 100644 > --- a/mm/huge_memory.c > +++ b/mm/huge_memory.c > @@ -3833,7 +3833,6 @@ static int __folio_freeze_and_split_unmapped(struct folio *folio, unsigned int n > } else { > lruvec_stat_mod_folio(folio, > NR_FILE_THPS, -nr); > - filemap_nr_thps_dec(mapping); > } > } > } > diff --git a/mm/khugepaged.c b/mm/khugepaged.c > index 45b12ffb1550..8004ab8de6d2 100644 > --- a/mm/khugepaged.c > +++ b/mm/khugepaged.c > @@ -2104,20 +2104,8 @@ static enum scan_result collapse_file(struct mm_struct *mm, unsigned long addr, > goto xa_unlocked; > } > > - if (!is_shmem) { > - filemap_nr_thps_inc(mapping); > - /* > - * Paired with the fence in do_dentry_open() -> get_write_access() > - * to ensure i_writecount is up to date and the update to nr_thps > - * is visible. Ensures the page cache will be truncated if the > - * file is opened writable. > - */ > - smp_mb(); > - if (inode_is_open_for_write(mapping->host)) { > - result = SCAN_FAIL; > - filemap_nr_thps_dec(mapping); > - } > - } > + if (!is_shmem && inode_is_open_for_write(mapping->host)) > + result = SCAN_FAIL; > > xa_locked: > xas_unlock_irq(&xas); > @@ -2296,19 +2284,6 @@ static enum scan_result collapse_file(struct mm_struct *mm, unsigned long addr, > folio_putback_lru(folio); > folio_put(folio); > } > - /* > - * Undo the updates of filemap_nr_thps_inc for non-SHMEM > - * file only. This undo is not needed unless failure is > - * due to SCAN_COPY_MC. > - */ > - if (!is_shmem && result == SCAN_COPY_MC) { > - filemap_nr_thps_dec(mapping); > - /* > - * Paired with the fence in do_dentry_open() -> get_write_access() > - * to ensure the update to nr_thps is visible. > - */ > - smp_mb(); > - } > > new_folio->mapping = NULL; > > -- > 2.43.0 > Cheers, Lorenzo