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 mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 05ACFC433F5 for ; Mon, 25 Oct 2021 14:17:42 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id CE25760184 for ; Mon, 25 Oct 2021 14:17:41 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S233481AbhJYOUC (ORCPT ); Mon, 25 Oct 2021 10:20:02 -0400 Received: from m43-7.mailgun.net ([69.72.43.7]:29683 "EHLO m43-7.mailgun.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S231246AbhJYOUB (ORCPT ); Mon, 25 Oct 2021 10:20:01 -0400 DKIM-Signature: a=rsa-sha256; v=1; c=relaxed/relaxed; d=mg.codeaurora.org; q=dns/txt; s=smtp; t=1635171459; h=Content-Transfer-Encoding: Content-Type: In-Reply-To: MIME-Version: Date: Message-ID: From: References: Cc: To: Subject: Sender; bh=ItKDh1mkDQtGAfEBN4GBpR5aSRyrZPrxrTC2PSe9jwo=; b=JIzMJVJpukCTKl2Ux4mMM9SuqofXy46+OR+zr9VEs9BUBIy0/+LaiaU0keScHpHmCkuiEinF 1QWCH4HkakjJMM9W3UfsmLDtVQo6xVDkK9SorTqL2ql0shITK917DibsFayK5d5+IS4NRRFj uBWXe3BS0VTc1svHYNCNwgRsrZ8= X-Mailgun-Sending-Ip: 69.72.43.7 X-Mailgun-Sid: WyI0MWYwYSIsICJsaW51eC1rZXJuZWxAdmdlci5rZXJuZWwub3JnIiwgImJlOWU0YSJd Received: from smtp.codeaurora.org (ec2-35-166-182-171.us-west-2.compute.amazonaws.com [35.166.182.171]) by smtp-out-n01.prod.us-east-1.postgun.com with SMTP id 6176bc6959612e010077c047 (version=TLS1.2, cipher=TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256); Mon, 25 Oct 2021 14:17:13 GMT Sender: charante=codeaurora.org@mg.codeaurora.org Received: by smtp.codeaurora.org (Postfix, from userid 1001) id 16ADBC43616; Mon, 25 Oct 2021 14:17:13 +0000 (UTC) Received: from [192.168.29.110] (unknown [49.37.156.162]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) (Authenticated sender: charante) by smtp.codeaurora.org (Postfix) with ESMTPSA id 0BFCFC4360C; Mon, 25 Oct 2021 14:17:08 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.4.1 smtp.codeaurora.org 0BFCFC4360C Authentication-Results: aws-us-west-2-caf-mail-1.web.codeaurora.org; dmarc=none (p=none dis=none) header.from=codeaurora.org Authentication-Results: aws-us-west-2-caf-mail-1.web.codeaurora.org; spf=fail smtp.mailfrom=codeaurora.org Subject: Re: [PATCH] mm: shmem: implement POSIX_FADV_[WILL|DONT]NEED for shmem To: hughd@google.com, akpm@linux-foundation.org, vbabka@suse.cz, rientjes@google.com, david@redhat.com, mhocko@suse.com, linux-mm@kvack.org, ",surenb"@google.com Cc: linux-kernel@vger.kernel.org References: <1633701982-22302-1-git-send-email-charante@codeaurora.org> From: Charan Teja Kalla Message-ID: Date: Mon, 25 Oct 2021 19:47:06 +0530 User-Agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64; rv:78.0) Gecko/20100101 Thunderbird/78.13.0 MIME-Version: 1.0 In-Reply-To: <1633701982-22302-1-git-send-email-charante@codeaurora.org> Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 7bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Hello, Can you please provide your valuable feed back here. There are of great help to me. Thanks, Charan On 10/8/2021 7:36 PM, Charan Teja Reddy wrote: > Currently fadvise(2) is supported only for the files that doesn't > associated with noop_backing_dev_info thus for the files, like shmem, > fadvise results into NOP. But then there is file_operations->fadvise() > that lets the file systems to implement their own fadvise > implementation. Use this support to implement some of the POSIX_FADV_XXX > functionality for shmem files. > > This patch aims to implement POSIX_FADV_WILLNEED and POSIX_FADV_DONTNEED > advices to shmem files which can be helpful for the drivers who may want > to manage the shmem pages of the files that are created through > shmem_file_setup[_with_mnt](). An example usecase may be like, driver > can create the shmem file of the size equal to its requirements and > map the pages for DMA and then pass the fd to user. The user who knows > well about the usage of these pages can now decide when these pages are > not required push them to swap through DONTNEED thus free up memory well > in advance rather than relying on the reclaim and use WILLNEED when it > decide that they are useful in the near future. IOW, it lets the clients > to free up/read the memory when it wants to. Another usecase is that GEM > objets which are currenlty allocated and managed through shmem files can > use vfs_fadvise(DONT|WILLNEED) on shmem fd when the driver comes to > know(like through some hints from user space) that GEM objects are not > going to use/will need in the near future. > > Signed-off-by: Charan Teja Reddy > --- > mm/shmem.c | 139 +++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++ > 1 file changed, 139 insertions(+) > > diff --git a/mm/shmem.c b/mm/shmem.c > index 70d9ce2..ab7ea33 100644 > --- a/mm/shmem.c > +++ b/mm/shmem.c > @@ -38,6 +38,8 @@ > #include > #include > #include > +#include > +#include > > #include /* for arch/microblaze update_mmu_cache() */ > > @@ -2792,6 +2794,142 @@ static long shmem_fallocate(struct file *file, int mode, loff_t offset, > return error; > } > > +static int shmem_fadvise_dontneed(struct address_space *mapping, loff_t start, > + loff_t end) > +{ > + int ret; > + struct writeback_control wbc = { > + .sync_mode = WB_SYNC_NONE, > + .nr_to_write = LONG_MAX, > + .range_start = 0, > + .range_end = LLONG_MAX, > + .for_reclaim = 1, > + }; > + struct page *page; > + > + XA_STATE(xas, &mapping->i_pages, start); > + if (!shmem_mapping(mapping)) > + return -EINVAL; > + > + if (!total_swap_pages) > + return 0; > + > + lru_add_drain(); > + > + rcu_read_lock(); > + xas_for_each(&xas, page, end) { > + if (xas_retry(&xas, page)) > + continue; > + if (xa_is_value(page)) > + continue; > + if (isolate_lru_page(page)) > + continue; > + > + inc_node_page_state(page, NR_ISOLATED_ANON + > + page_is_file_lru(page)); > + lock_page(page); > + ClearPageDirty(page); > + SetPageReclaim(page); > + ret = shmem_writepage(page, &wbc); > + if (!PageWriteback(page)) > + ClearPageReclaim(page); > + if (ret) { > + unlock_page(page); > + putback_lru_page(page); > + dec_node_page_state(page, NR_ISOLATED_ANON + > + page_is_file_lru(page)); > + continue; > + } > + > + /* > + * shmem_writepage() place the page in the swapcache. > + * Delete the page from the swapcache and release the > + * page. > + */ > + lock_page(page); > + delete_from_swap_cache(page); > + unlock_page(page); > + dec_node_page_state(page, NR_ISOLATED_ANON + > + page_is_file_lru(page)); > + put_page(page); > + if (need_resched()) { > + xas_pause(&xas); > + cond_resched_rcu(); > + } > + } > + rcu_read_unlock(); > + > + return 0; > +} > + > +static int shmem_fadvise_willneed(struct address_space *mapping, > + pgoff_t start, pgoff_t long end) > +{ > + struct page *page; > + > + XA_STATE(xas, &mapping->i_pages, start); > + rcu_read_lock(); > + xas_for_each(&xas, page, end) { > + if (!xa_is_value(page)) > + continue; > + page = shmem_read_mapping_page(mapping, xas.xa_index); > + if (!IS_ERR(page)) > + put_page(page); > + > + if (need_resched()) { > + xas_pause(&xas); > + cond_resched_rcu(); > + } > + } > + rcu_read_unlock(); > + > + return 0; > +} > + > +static int shmem_fadvise(struct file *file, loff_t offset, loff_t len, int advice) > +{ > + loff_t endbyte; > + pgoff_t start_index; > + pgoff_t end_index; > + struct address_space *mapping; > + int ret = 0; > + > + mapping = file->f_mapping; > + if (!mapping || len < 0) > + return -EINVAL; > + > + endbyte = (u64)offset + (u64)len; > + if (!len || endbyte < len) > + endbyte = -1; > + else > + endbyte--; > + > + > + start_index = offset >> PAGE_SHIFT; > + end_index = endbyte >> PAGE_SHIFT; > + switch (advice) { > + case POSIX_FADV_DONTNEED: > + ret = shmem_fadvise_dontneed(mapping, start_index, end_index); > + break; > + case POSIX_FADV_WILLNEED: > + ret = shmem_fadvise_willneed(mapping, start_index, end_index); > + break; > + case POSIX_FADV_NORMAL: > + case POSIX_FADV_RANDOM: > + case POSIX_FADV_SEQUENTIAL: > + case POSIX_FADV_NOREUSE: > + /* > + * No bad return value, but ignore advice. May have to > + * implement in future. > + */ > + break; > + default: > + return -EINVAL; > + } > + > + return ret; > +} > + > static int shmem_statfs(struct dentry *dentry, struct kstatfs *buf) > { > struct shmem_sb_info *sbinfo = SHMEM_SB(dentry->d_sb); > @@ -3799,6 +3937,7 @@ static const struct file_operations shmem_file_operations = { > .splice_write = iter_file_splice_write, > .fallocate = shmem_fallocate, > #endif > + .fadvise = shmem_fadvise, > }; > > static const struct inode_operations shmem_inode_operations = { > -- The Qualcomm Innovation Center, Inc. is a member of the Code Aurora Forum, a Linux Foundation Collaborative Project