From patchwork Fri Mar 11 10:43:51 2022 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Charan Teja Kalla X-Patchwork-Id: 12777817 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 B5EA2C433F5 for ; Fri, 11 Mar 2022 10:45:07 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id 0F9558D0005; Fri, 11 Mar 2022 05:45:07 -0500 (EST) Received: by kanga.kvack.org (Postfix, from userid 40) id 080BB8D0001; Fri, 11 Mar 2022 05:45:07 -0500 (EST) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id E8C358D0005; Fri, 11 Mar 2022 05:45:06 -0500 (EST) X-Delivered-To: linux-mm@kvack.org Received: from relay.hostedemail.com (relay.hostedemail.com [64.99.140.27]) by kanga.kvack.org (Postfix) with ESMTP id D66298D0001 for ; Fri, 11 Mar 2022 05:45:06 -0500 (EST) Received: from smtpin12.hostedemail.com (a10.router.float.18 [10.200.18.1]) by unirelay02.hostedemail.com (Postfix) with ESMTP id A4EE424F6D for ; Fri, 11 Mar 2022 10:45:06 +0000 (UTC) X-FDA: 79231773012.12.30FBB8A Received: from alexa-out-sd-01.qualcomm.com (alexa-out-sd-01.qualcomm.com [199.106.114.38]) by imf17.hostedemail.com (Postfix) with ESMTP id F0BC14001F for ; Fri, 11 Mar 2022 10:45:05 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=quicinc.com; i=@quicinc.com; q=dns/txt; s=qcdkim; t=1646995506; x=1678531506; h=from:to:cc:subject:date:message-id:in-reply-to: references:mime-version; bh=qyQGJ2He+N8AB6+cRhEVM5D86zlY5Me+dRbYbcq+MQQ=; b=wjc2AwIytEzBbYj7M7Y6igMdHuJNv6jWd5Dscew278G+bgXIAs5w2Vdh z17vuTH2D8udbbfKXKdbJHz5PUeODtBtlhWMtJ09byqahgRRFAe7v40zn UVNm5j/6hDsEquMajhbF+SUo2VyQ/WjjKaT6CVTw3LTyVGbbbD7REvM2f g=; Received: from unknown (HELO ironmsg-SD-alpha.qualcomm.com) ([10.53.140.30]) by alexa-out-sd-01.qualcomm.com with ESMTP; 11 Mar 2022 02:45:05 -0800 X-QCInternal: smtphost Received: from nasanex01c.na.qualcomm.com ([10.47.97.222]) by ironmsg-SD-alpha.qualcomm.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 11 Mar 2022 02:45:05 -0800 Received: from nalasex01a.na.qualcomm.com (10.47.209.196) by nasanex01c.na.qualcomm.com (10.47.97.222) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id 15.2.986.15; Fri, 11 Mar 2022 02:45:05 -0800 Received: from hu-charante-hyd.qualcomm.com (10.80.80.8) by nalasex01a.na.qualcomm.com (10.47.209.196) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id 15.2.986.15; Fri, 11 Mar 2022 02:45:00 -0800 From: Charan Teja Kalla To: , , , , , , , , , CC: , , Charan Teja Reddy Subject: [PATCH V5,1/2] mm: fadvise: move 'endbyte' calculations to helper function Date: Fri, 11 Mar 2022 16:13:51 +0530 Message-ID: <3dbba7655209709198b4e58ea677160732f3fb3f.1646987674.git.quic_charante@quicinc.com> X-Mailer: git-send-email 2.7.4 In-Reply-To: References: MIME-Version: 1.0 X-Originating-IP: [10.80.80.8] X-ClientProxiedBy: nasanex01b.na.qualcomm.com (10.46.141.250) To nalasex01a.na.qualcomm.com (10.47.209.196) X-Stat-Signature: 313qcj5zsqq3j5ooo76okp9ym558y7o7 Authentication-Results: imf17.hostedemail.com; dkim=pass header.d=quicinc.com header.s=qcdkim header.b=wjc2AwIy; spf=pass (imf17.hostedemail.com: domain of quic_charante@quicinc.com designates 199.106.114.38 as permitted sender) smtp.mailfrom=quic_charante@quicinc.com; dmarc=pass (policy=none) header.from=quicinc.com X-Rspam-User: X-Rspamd-Server: rspam11 X-Rspamd-Queue-Id: F0BC14001F X-HE-Tag: 1646995505-669081 X-Bogosity: Ham, tests=bogofilter, spamicity=0.000003, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: From: Charan Teja Reddy Move the 'endbyte' calculations that determines last byte that fadvise can to a helper function. This is a preparatory change made for shmem_fadvise() functionality in the next patch. No functional changes in this patch. Signed-off-by: Charan Teja Reddy --- Changes in V5: -- Moved the 'endbyte' calculation to a helper function. -- This patch is newly raised in V5 thus no change exists from v1 to v4. mm/fadvise.c | 11 +---------- mm/internal.h | 21 +++++++++++++++++++++ 2 files changed, 22 insertions(+), 10 deletions(-) diff --git a/mm/fadvise.c b/mm/fadvise.c index d6baa4f..086e929 100644 --- a/mm/fadvise.c +++ b/mm/fadvise.c @@ -65,16 +65,7 @@ int generic_fadvise(struct file *file, loff_t offset, loff_t len, int advice) return 0; } - /* - * Careful about overflows. Len == 0 means "as much as possible". Use - * unsigned math because signed overflows are undefined and UBSan - * complains. - */ - endbyte = (u64)offset + (u64)len; - if (!len || endbyte < len) - endbyte = -1; - else - endbyte--; /* inclusive */ + endbyte = fadvise_calc_endbyte(offset, len); switch (advice) { case POSIX_FADV_NORMAL: diff --git a/mm/internal.h b/mm/internal.h index d8030039..91bb17d 100644 --- a/mm/internal.h +++ b/mm/internal.h @@ -506,6 +506,27 @@ static inline void vunmap_range_noflush(unsigned long start, unsigned long end) #endif /* !CONFIG_MMU */ /* + * Helper function to get the endbyte of a file that fadvise can operate on. + */ +static inline loff_t fadvise_calc_endbyte(loff_t offset, loff_t len) +{ + loff_t endbyte; + + /* + * Careful about overflows. Len == 0 means "as much as possible". Use + * unsigned math because signed overflows are undefined and UBSan + * complains. + */ + endbyte = (u64)offset + (u64)len; + if (!len || endbyte < len) + endbyte = -1; + else + endbyte--; /* inclusive */ + + return endbyte; +} + +/* * Return the mem_map entry representing the 'offset' subpage within * the maximally aligned gigantic page 'base'. Handle any discontiguity * in the mem_map at MAX_ORDER_NR_PAGES boundaries. From patchwork Fri Mar 11 10:43:52 2022 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Charan Teja Kalla X-Patchwork-Id: 12777818 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 0E1B5C433EF for ; Fri, 11 Mar 2022 10:45:13 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id A943D8D0006; Fri, 11 Mar 2022 05:45:12 -0500 (EST) Received: by kanga.kvack.org (Postfix, from userid 40) id A1CF18D0001; Fri, 11 Mar 2022 05:45:12 -0500 (EST) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 8BEEF8D0006; Fri, 11 Mar 2022 05:45:12 -0500 (EST) X-Delivered-To: linux-mm@kvack.org Received: from relay.hostedemail.com (relay.hostedemail.com [64.99.140.26]) by kanga.kvack.org (Postfix) with ESMTP id 7BCC58D0001 for ; Fri, 11 Mar 2022 05:45:12 -0500 (EST) Received: from smtpin15.hostedemail.com (a10.router.float.18 [10.200.18.1]) by unirelay07.hostedemail.com (Postfix) with ESMTP id 5066E21475 for ; Fri, 11 Mar 2022 10:45:12 +0000 (UTC) X-FDA: 79231773264.15.6D6624A Received: from alexa-out.qualcomm.com (alexa-out.qualcomm.com [129.46.98.28]) by imf14.hostedemail.com (Postfix) with ESMTP id 89D96100020 for ; Fri, 11 Mar 2022 10:45:11 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=quicinc.com; i=@quicinc.com; q=dns/txt; s=qcdkim; t=1646995511; x=1678531511; h=from:to:cc:subject:date:message-id:in-reply-to: references:mime-version; bh=C12/qIJCuMb8jP6JyjtJ1oqtbsaCGfsZS+dgXzGtAdU=; b=mTHmrzDuhsw2kAB9x8HJZGQaBPXA5Ldhiid13Fp4SpcxH+KS6pDHEMOx QyfZIbbFNcbCwET2edZToKhM94dqVW/3Yz41+vIL0iQ9jM82TUW07GPMT lW/0ehxM318OjzAmyl0HhcJxwa8O4TQMRcJ7hXEIMy1XOAOwK/vULlprd Y=; Received: from ironmsg07-lv.qualcomm.com ([10.47.202.151]) by alexa-out.qualcomm.com with ESMTP; 11 Mar 2022 02:45:10 -0800 X-QCInternal: smtphost Received: from nasanex01c.na.qualcomm.com ([10.47.97.222]) by ironmsg07-lv.qualcomm.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 11 Mar 2022 02:45:10 -0800 Received: from nalasex01a.na.qualcomm.com (10.47.209.196) by nasanex01c.na.qualcomm.com (10.47.97.222) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id 15.2.986.15; Fri, 11 Mar 2022 02:45:09 -0800 Received: from hu-charante-hyd.qualcomm.com (10.80.80.8) by nalasex01a.na.qualcomm.com (10.47.209.196) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id 15.2.986.15; Fri, 11 Mar 2022 02:45:05 -0800 From: Charan Teja Kalla To: , , , , , , , , , CC: , , Charan Teja Kalla Subject: [PATCH V5,2/2] mm: shmem: implement POSIX_FADV_[WILL|DONT]NEED for shmem Date: Fri, 11 Mar 2022 16:13:52 +0530 Message-ID: <94fce97600df1402fad9f109ea34467d612be448.1646987674.git.quic_charante@quicinc.com> X-Mailer: git-send-email 2.7.4 In-Reply-To: References: MIME-Version: 1.0 X-Originating-IP: [10.80.80.8] X-ClientProxiedBy: nasanex01b.na.qualcomm.com (10.46.141.250) To nalasex01a.na.qualcomm.com (10.47.209.196) X-Rspamd-Server: rspam10 X-Rspamd-Queue-Id: 89D96100020 X-Stat-Signature: 5q9i6fhxiqm6ki9i3jhy1sjzaircstet X-Rspam-User: Authentication-Results: imf14.hostedemail.com; dkim=pass header.d=quicinc.com header.s=qcdkim header.b=mTHmrzDu; spf=pass (imf14.hostedemail.com: domain of quic_charante@quicinc.com designates 129.46.98.28 as permitted sender) smtp.mailfrom=quic_charante@quicinc.com; dmarc=pass (policy=none) header.from=quicinc.com X-HE-Tag: 1646995511-524615 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: 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 objects which are currently 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. Some questions asked while reviewing this patch: Q) Can the same thing be achieved with FD mapped to user and use madvise? A) All drivers are not mapping all the shmem fd's to user space and want to manage them with in the kernel. Ex: shmem memory can be mapped to the other subsystems and they fill in the data and then give it to other subsystem for further processing, where, the user mapping is not at all required. A simple example, memory that is given for gpu subsystem which can be filled directly and give to display subsystem. And the respective drivers know well about when to keep that memory in ram or swap based on may be a user activity. Q) Should we add the documentation section in Manual pages? A) The man[1] pages for the fadvise() whatever says is also applicable for shmem files. so couldn't feel it correct to add specific to shmem files separately. [1] https://linux.die.net/man/2/fadvise Q) The proposed semantics of POSIX_FADV_DONTNEED is actually similar to MADV_PAGEOUT and different from MADV_DONTNEED. This is a user facing API and this difference will cause confusion? A) man pages [1] says that "POSIX_FADV_DONTNEED attempts to free cached pages associated with the specified region." This means on issuing this FADV, it is expected to free the file cache pages. And it is implementation defined If the dirty pages may be attempted to writeback. And the unwritten dirty pages will not be freed. So, FADV_DONTNEED also covers the semantics of MADV_PAGEOUT for file pages and there is no purpose of PAGEOUT for file pages. [1] https://man7.org/linux/man-pages/man2/posix_fadvise.2.html Signed-off-by: Charan Teja Kalla --- Changes in V5: -- Moved the 'endbyte' calculations to a helper function which is also needed for shmem_fadvise. -- Addressed comments from Suren. Changes in V4: -- Changed the code to use reclaim_pages() to writeout the shmem pages to swap and then reclaim. -- Addressed comments from Mark Hemment and Matthew. -- fadvise() on shmem file may even unmap a page. -- https://patchwork.kernel.org/project/linux-mm/patch/1644572051-24091-1-git-send-email-quic_charante@quicinc.com/ Changes in V3: -- Considered THP pages while doing FADVISE_[DONT|WILL]NEED, identified by Matthew. -- xarray used properly, as identified by Matthew. -- Excluded mapped pages as it requires unmapping and the man pages of fadvise don't talk about them. -- RESEND: Fixed the compilation issue when CONFIG_TMPFS is not defined. -- https://patchwork.kernel.org/project/linux-mm/patch/1641488717-13865-1-git-send-email-quic_charante@quicinc.com/ Changes in V2: -- Rearranged the code to not to sleep with rcu_lock while using xas_() functionality. -- Addressed the comments from Suren. -- https://patchwork.kernel.org/project/linux-mm/patch/1638442253-1591-1-git-send-email-quic_charante@quicinc.com/ 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 | 123 +++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 123 insertions(+) diff --git a/mm/shmem.c b/mm/shmem.c index a09b29e..5fc2600 100644 --- a/mm/shmem.c +++ b/mm/shmem.c @@ -38,6 +38,9 @@ #include #include #include +#include +#include +#include static struct vfsmount *shm_mnt; @@ -2241,6 +2244,125 @@ static int shmem_mmap(struct file *file, struct vm_area_struct *vma) return 0; } +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)) { + put_page(page); + continue; + } + put_page(page); + + if (PageUnevictable(page) || page_mapcount(page) > 1) { + putback_lru_page(page); + continue; + } + + /* + * Prepare the page to be passed to the reclaim_pages(). + * VM couldn't reclaim the page unless we clear PG_young. + * Also, to ensure that the pages are written before + * reclaiming, page is set to dirty. + * Since we are not clearing the pte_young in the mapped + * page pte's, its reclaim may not be attempted. + */ + ClearPageReferenced(page); + test_and_clear_page_young(page); + list_add(&page->lru, list); + 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) +{ + 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); + reclaim_pages(&list); + + return 0; +} + +static int shmem_fadvise_willneed(struct address_space *mapping, + pgoff_t start, pgoff_t long end) +{ + struct page *page; + pgoff_t index; + + xa_for_each_range(&mapping->i_pages, index, page, start, end) { + if (!xa_is_value(page)) + continue; + page = shmem_read_mapping_page(mapping, index); + if (!IS_ERR(page)) + put_page(page); + } + + 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 = fadvise_calc_endbyte(offset, len); + + 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 struct inode *shmem_get_inode(struct super_block *sb, const struct inode *dir, umode_t mode, dev_t dev, unsigned long flags) { @@ -3777,6 +3899,7 @@ 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 = {