From patchwork Thu Dec 2 10:50:53 2021 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Charan Teja Kalla X-Patchwork-Id: 12652183 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 kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by smtp.lore.kernel.org (Postfix) with ESMTP id CA459C433EF for ; Thu, 2 Dec 2021 10:51:50 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id 5A10F6B0072; Thu, 2 Dec 2021 05:51:40 -0500 (EST) Received: by kanga.kvack.org (Postfix, from userid 40) id 529A76B0073; Thu, 2 Dec 2021 05:51:40 -0500 (EST) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 3CA8B6B0074; Thu, 2 Dec 2021 05:51:40 -0500 (EST) X-Delivered-To: linux-mm@kvack.org Received: from forelay.hostedemail.com (smtprelay0202.hostedemail.com [216.40.44.202]) by kanga.kvack.org (Postfix) with ESMTP id 2B06E6B0072 for ; Thu, 2 Dec 2021 05:51:40 -0500 (EST) Received: from smtpin11.hostedemail.com (10.5.19.251.rfc1918.com [10.5.19.251]) by forelay05.hostedemail.com (Postfix) with ESMTP id E4557183944A7 for ; Thu, 2 Dec 2021 10:51:29 +0000 (UTC) X-FDA: 78872537940.11.3EB2093 Received: from so254-9.mailgun.net (so254-9.mailgun.net [198.61.254.9]) by imf26.hostedemail.com (Postfix) with ESMTP id 54C2720019C0 for ; Thu, 2 Dec 2021 10:51:29 +0000 (UTC) DKIM-Signature: a=rsa-sha256; v=1; c=relaxed/relaxed; d=mg.codeaurora.org; q=dns/txt; s=smtp; t=1638442289; h=Message-Id: Date: Subject: Cc: To: From: Sender; bh=HIGcD/jaqNClG+MM4DCw3sUIoBAVcod6MlDO/qs3diw=; b=YcEkCp470mxL0YPoTjSoJPK/mAVVNd/w3LbecnZTfwppokG0OZb+W0uL2I95p9HnO2FN7/wI 1VKWlmYG80pO90ALIDe+pSsNQyn8Z2YaksC52rzHm613EUtNmnBsCMZYdgUTaYgaJtUcvtTY IItRTQ82poThcDfN8yOqSIqvXUE= X-Mailgun-Sending-Ip: 198.61.254.9 X-Mailgun-Sid: WyIwY2Q3OCIsICJsaW51eC1tbUBrdmFjay5vcmciLCAiYmU5ZTRhIl0= Received: from smtp.codeaurora.org (ec2-35-166-182-171.us-west-2.compute.amazonaws.com [35.166.182.171]) by smtp-out-n07.prod.us-west-2.postgun.com with SMTP id 61a8a5305daaeec797997f1e (version=TLS1.2, cipher=TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256); Thu, 02 Dec 2021 10:51:28 GMT Received: by smtp.codeaurora.org (Postfix, from userid 1001) id 2EF09C43616; Thu, 2 Dec 2021 10:51:28 +0000 (UTC) Received: from hu-charante-hyd.qualcomm.com (unknown [202.46.22.19]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-SHA256 (128/128 bits)) (No client certificate requested) (Authenticated sender: charante) by smtp.codeaurora.org (Postfix) with ESMTPSA id 21A62C4338F; Thu, 2 Dec 2021 10:51:23 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.4.1 smtp.codeaurora.org 21A62C4338F From: Charan Teja Reddy To: hughd@google.com, akpm@linux-foundation.org, vbabka@suse.cz, rientjes@google.com, david@redhat.com, mhocko@suse.com, surenb@google.com, linux-mm@kvack.org Cc: linux-kernel@vger.kernel.org, Charan Teja Reddy Subject: [PATCH v2] mm: shmem: implement POSIX_FADV_[WILL|DONT]NEED for shmem Date: Thu, 2 Dec 2021 16:20:53 +0530 Message-Id: <1638442253-1591-1-git-send-email-quic_charante@quicinc.com> X-Mailer: git-send-email 2.7.4 X-Rspamd-Server: rspam04 X-Rspamd-Queue-Id: 54C2720019C0 X-Stat-Signature: gk8u75n7ptxd5bra5j334fyzn73i3i6y Authentication-Results: imf26.hostedemail.com; dkim=pass header.d=mg.codeaurora.org header.s=smtp header.b=YcEkCp47; spf=pass (imf26.hostedemail.com: domain of "bounce+d06763.be9e4a-linux-mm=kvack.org@mg.codeaurora.org" designates 198.61.254.9 as permitted sender) smtp.mailfrom="bounce+d06763.be9e4a-linux-mm=kvack.org@mg.codeaurora.org"; dmarc=fail reason="SPF not aligned (relaxed), DKIM not aligned (relaxed)" header.from=quicinc.com (policy=none) X-HE-Tag: 1638442289-143184 X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: From: Charan Teja Reddy 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 --- Changes in V2: -- Rearranged the code to not to sleep with rcu_lock while using xas_() functionality. -- Addressed the comments from Suren. changes in V1: -- Created the interface for fadvise(2) to work on shmem files. -- https://patchwork.kernel.org/project/linux-mm/patch/1633701982-22302-1-git-send-email-charante@codeaurora.org/ mm/shmem.c | 167 +++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 167 insertions(+) diff --git a/mm/shmem.c b/mm/shmem.c index 70d9ce2..4c4685f 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 +2794,170 @@ static long shmem_fallocate(struct file *file, int mode, loff_t offset, return error; } +static void shmem_isolate_pages_range(struct address_space *mapping, loff_t start, + loff_t end, struct list_head *list) +{ + XA_STATE(xas, &mapping->i_pages, start); + struct page *page; + + rcu_read_lock(); + xas_for_each(&xas, page, end) { + if (xas_retry(&xas, page)) + continue; + if (xa_is_value(page)) + continue; + if (!get_page_unless_zero(page)) + continue; + if (isolate_lru_page(page)) + continue; + + list_add(&page->lru, list); + inc_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(); +} + +static int shmem_fadvise_dontneed(struct address_space *mapping, loff_t start, + loff_t end) +{ + int ret; + struct page *page; + LIST_HEAD(list); + + if (!shmem_mapping(mapping)) + return -EINVAL; + + if (!total_swap_pages) + return 0; + + lru_add_drain(); + shmem_isolate_pages_range(mapping, start, end, &list); + + while (!list_empty(&list)) { + page = lru_to_page(&list); + list_del(&page->lru); + lock_page(page); + if (clear_page_dirty_for_io(page)) { + struct writeback_control wbc = { + .sync_mode = WB_SYNC_NONE, + .nr_to_write = LONG_MAX, + .range_start = 0, + .range_end = LLONG_MAX, + .for_reclaim = 1, + }; + + SetPageReclaim(page); + ret = shmem_writepage(page, &wbc); + if (ret || PageWriteback(page)) { + if (ret) + unlock_page(page); + putback_lru_page(page); + dec_node_page_state(page, NR_ISOLATED_ANON + + page_is_file_lru(page)); + continue; + } + } + + if (!PageWriteback(page)) + ClearPageReclaim(page); + + /* + * shmem_writepage() place the page in the swapcache. + * Delete the page from the swapcache and release the + * page. + */ + dec_node_page_state(page, NR_ISOLATED_ANON + + page_is_file_lru(page)); + lock_page(page); + delete_from_swap_cache(page); + unlock_page(page); + put_page(page); + + } + + return 0; +} + +static int shmem_fadvise_willneed(struct address_space *mapping, + pgoff_t start, pgoff_t long end) +{ + XA_STATE(xas, &mapping->i_pages, start); + struct page *page; + + rcu_read_lock(); + page = xas_find(&xas, end); + rcu_read_unlock(); + + while (page) { + if (xa_is_value(page)) { + 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_read_lock(); + page = xas_next_entry(&xas, end); + 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 +3965,7 @@ 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 = {