Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752693AbdHBInY (ORCPT ); Wed, 2 Aug 2017 04:43:24 -0400 Received: from szxga02-in.huawei.com ([45.249.212.188]:10820 "EHLO szxga02-in.huawei.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752227AbdHBInV (ORCPT ); Wed, 2 Aug 2017 04:43:21 -0400 Subject: Re: [PATCH] f2fs: provide f2fs_balance_fs to __write_data_page for dentry pages To: Jaegeuk Kim CC: Yunlong Song , chao , yuchao0 , miaoxie , "bintian.wang" , linux-fsdevel , linux-f2fs-devel , linux-kernel References: <1501334365-123333-1-git-send-email-yunlong.song@huawei.com> <20170730073154.GA13058@jaegeuk-macbookpro.roam.corp.google.com> <4916ac46.daf0.15d943f23b9.Coremail.sylinux@163.com> <20170801182254.GA52047@jaegeuk-macbookpro.roam.corp.google.com> From: Yunlong Song Message-ID: <4568e3fb-272c-1d67-ac9f-2f0e194bcdd5@huawei.com> Date: Wed, 2 Aug 2017 16:42:34 +0800 User-Agent: Mozilla/5.0 (Windows NT 6.1; WOW64; rv:52.0) Gecko/20100101 Thunderbird/52.2.1 MIME-Version: 1.0 In-Reply-To: <20170801182254.GA52047@jaegeuk-macbookpro.roam.corp.google.com> Content-Type: text/plain; charset="utf-8"; format=flowed Content-Transfer-Encoding: 8bit Content-Language: en-US X-Originating-IP: [10.111.220.140] X-CFilter-Loop: Reflected X-Mirapoint-Virus-RAPID-Raw: score=unknown(0), refid=str=0001.0A020202.59819094.0118,ss=1,re=0.000,recu=0.000,reip=0.000,cl=1,cld=1,fgs=0, ip=0.0.0.0, so=2014-11-16 11:51:01, dmn=2013-03-21 17:37:32 X-Mirapoint-Loop-Id: d1b0f988c3251c1940932c89627b5b53 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 10624 Lines: 265 Hi Jay, The case is like this: write_checkpoint: normal dentry page writeback of inodeB： -block_operations -f2fs_write_data_pages -SBI_BLOCK_OPS is set -f2fs_write_cache_pages -sync_dirty_inodes -__write_data_page -retry: -test SBI_BLOCK_OPS is set and skip f2fs_balance_fs inodeA <- list_first_entry(dirty_list) filemap_fdatawrite(inodeA) goto retry -SBI_BLOCK_OPS is clear write_checkpoint flow call sync_dirty_inodes to traversal the dirty inode list and filemap_fdatawrite each inode, during this period, if normal dentry_page writeback is processing inodeB, and syc_dirty_inodes is processing inodeA, then inodeB writeback flow will skip f2fs_balance_fs and may write the dentry page to reserved segments. On 2017/8/2 2:22, Jaegeuk Kim wrote: > On 08/01, Yunlong Song wrote: >> Hi Jay, >> The SBI_BLOCK_OPS can not cover all the case, once SBI_BLOCK_OPS is set, >> all the normal writeback >> (before the SBI_BLOCK_OPS is clear) of dentry pages which do not come from >> write_checkpoint flow will >> totally miss all the f2fs_balance_fs check. > Why not? There must be no dirty dentry pages after sync_dirty_inodes() in that > period which we grabbed the globla lock. > > Thanks, > >> On 2017/7/31 0:05, Yunlong Song wrote: >>> Hi Jay, >>> Chao has pointed out one reason, besides, I have another reason: we >>> should take care of writeback for f2fs_balance_fs carefully, because if >>> some bugs cause reserved segments unlikely used, which means >>> f2fs_balance_fs does not work or is skipped in some corner case that we >>> have not noticed or found out yet, then the reserved segments may be >>> continually used and even used up in the writeback process of dentry >>> page, since current design believe in the f2fs_balance_fs in system >>> call and has no check in denty page writeback. To avoid this, we can put >>> a f2fs_balance_fs in the dentry page writeback process to give f2fs more >>> robust in free segments reserved. This is worth, because free segments >>> reserved are so important, if they are used up, f2fs will enter a >>> totally wrong status and make a wrong image. >>> >>> On 07/30/2017 15:31, Jaegeuk Kim wrote: >>> >>> On 07/29, Yunlong Song wrote: >>> > f2fs_balance_fs of dentry pages is skipped in __write_data_page >>> due to deadlock >>> > of gc_mutex in write_checkpoint flow. This patch enables >>> f2fs_balance_fs for >>> > normal dentry page writeback to ensure there are always enough >>> free segments. >>> >>> Sorry, by the way, why do we need to do this? I subtly thought >>> that dirty node >>> pages can be produce by redirtied inodes from what we've not >>> covered through >>> filesystem calls. But, in dentry pages, we're controlling the >>> number of dirty >>> pages, and calling f2fs_balance_fs in each directory operations. >>> >>> Chao? >>> >>> Thanks, >>> >>> > >>> > Reported-by: Chao Yu >>> > Signed-off-by: Yunlong Song >>> > --- >>> > fs/f2fs/checkpoint.c | 2 +- >>> > fs/f2fs/data.c | 67 >>> +++++++++++++++++++++++++++++++++++++++++++++------- >>> > fs/f2fs/f2fs.h | 1 + >>> > 3 files changed, 61 insertions(+), 9 deletions(-) >>> > >>> > diff --git a/fs/f2fs/checkpoint.c b/fs/f2fs/checkpoint.c >>> > index 3c84a25..2882878 100644 >>> > --- a/fs/f2fs/checkpoint.c >>> > +++ b/fs/f2fs/checkpoint.c >>> > @@ -904,7 +904,7 @@ int sync_dirty_inodes(struct f2fs_sb_info >>> *sbi, enum inode_type type) >>> > if (inode) { >>> > unsigned long cur_ino = inode->i_ino; >>> > >>> > - filemap_fdatawrite(inode->i_mapping); >>> > + f2fs_filemap_fdatawrite(inode->i_mapping, is_dir); >>> > iput(inode); >>> > /* We need to give cpu to another writers. */ >>> > if (ino == cur_ino) { >>> > diff --git a/fs/f2fs/data.c b/fs/f2fs/data.c >>> > index aefc2a5..ed7efa5 100644 >>> > --- a/fs/f2fs/data.c >>> > +++ b/fs/f2fs/data.c >>> > @@ -1475,7 +1475,7 @@ int do_write_data_page(struct f2fs_io_info >>> *fio) >>> > } >>> > >>> > static int __write_data_page(struct page *page, bool *submitted, >>> > - struct writeback_control *wbc) >>> > + struct writeback_control *wbc, bool do_balance) >>> > { >>> > struct inode *inode = page->mapping->host; >>> > struct f2fs_sb_info *sbi = F2FS_I_SB(inode); >>> > @@ -1578,7 +1578,7 @@ static int __write_data_page(struct page >>> *page, bool *submitted, >>> > } >>> > >>> > unlock_page(page); >>> > - if (!S_ISDIR(inode->i_mode)) >>> > + if (do_balance) >>> > f2fs_balance_fs(sbi, need_balance_fs); >>> > >>> > if (unlikely(f2fs_cp_error(sbi))) { >>> > @@ -1602,7 +1602,7 @@ static int __write_data_page(struct page >>> *page, bool *submitted, >>> > static int f2fs_write_data_page(struct page *page, >>> > struct writeback_control *wbc) >>> > { >>> > - return __write_data_page(page, NULL, wbc); >>> > + return __write_data_page(page, NULL, wbc, true); >>> > } >>> > >>> > /* >>> > @@ -1611,7 +1611,7 @@ static int f2fs_write_data_page(struct >>> page *page, >>> > * warm/hot data page. >>> > */ >>> > static int f2fs_write_cache_pages(struct address_space *mapping, >>> > - struct writeback_control *wbc) >>> > + struct writeback_control *wbc, bool >>> do_balance) >>> > { >>> > int ret = 0; >>> > int done = 0; >>> > @@ -1701,7 +1701,7 @@ static int f2fs_write_cache_pages(struct >>> address_space *mapping, >>> > if (!clear_page_dirty_for_io(page)) >>> > goto continue_unlock; >>> > >>> > - ret = __write_data_page(page, &submitted, wbc); >>> > + ret = __write_data_page(page, &submitted, wbc, >>> do_balance); >>> > if (unlikely(ret)) { >>> > /* >>> > * keep nr_to_write, since vfs uses this to >>> > @@ -1756,8 +1756,8 @@ static int f2fs_write_cache_pages(struct >>> address_space *mapping, >>> > return ret; >>> > } >>> > >>> > -static int f2fs_write_data_pages(struct address_space *mapping, >>> > - struct writeback_control *wbc) >>> > +static int _f2fs_write_data_pages(struct address_space *mapping, >>> > + struct writeback_control *wbc, bool do_balance) >>> > { >>> > struct inode *inode = mapping->host; >>> > struct f2fs_sb_info *sbi = F2FS_I_SB(inode); >>> > @@ -1794,7 +1794,7 @@ static int f2fs_write_data_pages(struct >>> address_space *mapping, >>> > goto skip_write; >>> > >>> > blk_start_plug(&plug); >>> > - ret = f2fs_write_cache_pages(mapping, wbc); >>> > + ret = f2fs_write_cache_pages(mapping, wbc, do_balance); >>> > blk_finish_plug(&plug); >>> > >>> > if (wbc->sync_mode == WB_SYNC_ALL) >>> > @@ -1813,6 +1813,57 @@ static int f2fs_write_data_pages(struct >>> address_space *mapping, >>> > return 0; >>> > } >>> > >>> > +static int f2fs_write_data_pages(struct address_space *mapping, >>> > + struct writeback_control *wbc) >>> > +{ >>> > + return _f2fs_write_data_pages(mapping, wbc, true); >>> > +} >>> > + >>> > +/* >>> > + * This function was copied from do_writepages from >>> mm/page-writeback.c. >>> > + * The major change is changing writepages to >>> _f2fs_write_data_pages. >>> > + */ >>> > +static int f2fs_do_writepages(struct address_space *mapping, >>> > + struct writeback_control *wbc, bool is_dir) >>> > +{ >>> > + int ret; >>> > + >>> > + if (wbc->nr_to_write <= 0) >>> > + return 0; >>> > + while (1) { >>> > + ret = _f2fs_write_data_pages(mapping, wbc, !is_dir); >>> > + if ((ret != -ENOMEM) || (wbc->sync_mode != WB_SYNC_ALL)) >>> > + break; >>> > + cond_resched(); >>> > + congestion_wait(BLK_RW_ASYNC, HZ/50); >>> > + } >>> > + return ret; >>> > +} >>> > + >>> > +/* >>> > + * This function was copied from __filemap_fdatawrite_range from >>> > + * mm/filemap.c. The major change is changing do_writepages to >>> > + * f2fs_do_writepages. >>> > + */ >>> > +int f2fs_filemap_fdatawrite(struct address_space *mapping, bool >>> is_dir) >>> > +{ >>> > + int ret; >>> > + struct writeback_control wbc = { >>> > + .sync_mode = WB_SYNC_ALL, >>> > + .nr_to_write = LONG_MAX, >>> > + .range_start = 0, >>> > + .range_end = LLONG_MAX, >>> > + }; >>> > + >>> > + if (!mapping_cap_writeback_dirty(mapping)) >>> > + return 0; >>> > + >>> > + wbc_attach_fdatawrite_inode(&wbc, mapping->host); >>> > + ret = f2fs_do_writepages(mapping, &wbc, is_dir); >>> > + wbc_detach_inode(&wbc); >>> > + return ret; >>> > +} >>> > + >>> > static void f2fs_write_failed(struct address_space *mapping, >>> loff_t to) >>> > { >>> > struct inode *inode = mapping->host; >>> > diff --git a/fs/f2fs/f2fs.h b/fs/f2fs/f2fs.h >>> > index 9280283..ea9bebb 100644 >>> > --- a/fs/f2fs/f2fs.h >>> > +++ b/fs/f2fs/f2fs.h >>> > @@ -2572,6 +2572,7 @@ void f2fs_invalidate_page(struct page >>> *page, unsigned int offset, >>> > int f2fs_migrate_page(struct address_space *mapping, struct >>> page *newpage, >>> > struct page *page, enum migrate_mode mode); >>> > #endif >>> > +int f2fs_filemap_fdatawrite(struct address_space *mapping, bool >>> is_dir); >>> > >>> > /* >>> > * gc.c >>> > -- >>> > 1.8.5.2 >>> >> -- >> Thanks, >> Yunlong Song >> > . > -- Thanks, Yunlong Song