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[209.85.220.65]) by mx.google.com with SMTPS id s13sor3803400plr.24.2019.07.10.12.11.18 for (Google Transport Security); Wed, 10 Jul 2019 12:11:19 -0700 (PDT) Received-SPF: pass (google.com: domain of hannes@cmpxchg.org designates 209.85.220.65 as permitted sender) client-ip=209.85.220.65; Authentication-Results: mx.google.com; dkim=pass header.i=@cmpxchg-org.20150623.gappssmtp.com header.s=20150623 header.b=j9c62XFE; spf=pass (google.com: domain of hannes@cmpxchg.org designates 209.85.220.65 as permitted sender) smtp.mailfrom=hannes@cmpxchg.org; dmarc=pass (p=NONE sp=NONE dis=NONE) header.from=cmpxchg.org DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=cmpxchg-org.20150623.gappssmtp.com; s=20150623; h=date:from:to:cc:subject:message-id:references:mime-version :content-disposition:in-reply-to:user-agent; bh=3RBKExhVhuO8dUwdopkobYrfDp83fiSSvdj+BjPC70s=; b=j9c62XFEZ9kneeuEMtK85d/vkG2d0b3HHa2TZlXsQSuaSKSRug6eb1bl4cKUZZkmJK 6IS8RZlqzhzFjwNz+zV5QgphhyNsbooUbliEaAnL4/k7y78mowllauMGCE5dCXCUR5+L thZKWFHCr6OTl+X4yZ6gTpNHZ3qUDwhE+4uFb5Kl6OwMqJTXO/DGXzNq1TGMG1BZkTdw HGxldShXjkSPmX1j5S9pdclx8uY3JXY7bNK29ZFVh0twxvORyjed8MOPePpt96DK/DaI 5BDryfetRewi2JhNcZ3WsMMVy0mvAAX2JwEk1fsuD/9i0kMVR5sAqIqGyMl0WVWas+N/ NEiQ== X-Google-Smtp-Source: APXvYqzFRRFWfxpescU3C0myEwOeav3RIPv9v2eiOwcuRGi+UKzV4Z/k6Bf+F4vc1CD5unHTdPoy5A== X-Received: by 2002:a17:902:a50d:: with SMTP id s13mr40889083plq.12.1562785878616; Wed, 10 Jul 2019 12:11:18 -0700 (PDT) Received: from localhost ([2620:10d:c091:500::2:5b9d]) by smtp.gmail.com with ESMTPSA id t11sm3066474pgb.33.2019.07.10.12.11.17 (version=TLS1_3 cipher=AEAD-AES256-GCM-SHA384 bits=256/256); Wed, 10 Jul 2019 12:11:17 -0700 (PDT) Date: Wed, 10 Jul 2019 15:11:16 -0400 From: Johannes Weiner To: Song Liu Cc: linux-mm@kvack.org, linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org, matthew.wilcox@oracle.com, kirill.shutemov@linux.intel.com, kernel-team@fb.com, william.kucharski@oracle.com, akpm@linux-foundation.org, hdanton@sina.com Subject: Re: [PATCH v9 6/6] mm,thp: avoid writes to file with THP in pagecache Message-ID: <20190710191116.GG11197@cmpxchg.org> References: <20190625001246.685563-1-songliubraving@fb.com> <20190625001246.685563-7-songliubraving@fb.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20190625001246.685563-7-songliubraving@fb.com> User-Agent: Mutt/1.12.0 (2019-05-25) 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: On Mon, Jun 24, 2019 at 05:12:46PM -0700, Song Liu wrote: > In previous patch, an application could put part of its text section in > THP via madvise(). These THPs will be protected from writes when the > application is still running (TXTBSY). However, after the application > exits, the file is available for writes. > > This patch avoids writes to file THP by dropping page cache for the file > when the file is open for write. A new counter nr_thps is added to struct > address_space. In do_last(), if the file is open for write and nr_thps > is non-zero, we drop page cache for the whole file. > > Reported-by: kbuild test robot > Signed-off-by: Song Liu > --- > fs/inode.c | 3 +++ > fs/namei.c | 23 ++++++++++++++++++++++- > include/linux/fs.h | 32 ++++++++++++++++++++++++++++++++ > mm/filemap.c | 1 + > mm/khugepaged.c | 4 +++- > 5 files changed, 61 insertions(+), 2 deletions(-) > > diff --git a/fs/inode.c b/fs/inode.c > index df6542ec3b88..518113a4e219 100644 > --- a/fs/inode.c > +++ b/fs/inode.c > @@ -181,6 +181,9 @@ int inode_init_always(struct super_block *sb, struct inode *inode) > mapping->flags = 0; > mapping->wb_err = 0; > atomic_set(&mapping->i_mmap_writable, 0); > +#ifdef CONFIG_READ_ONLY_THP_FOR_FS > + atomic_set(&mapping->nr_thps, 0); > +#endif > mapping_set_gfp_mask(mapping, GFP_HIGHUSER_MOVABLE); > mapping->private_data = NULL; > mapping->writeback_index = 0; > diff --git a/fs/namei.c b/fs/namei.c > index 20831c2fbb34..3d95e94029cc 100644 > --- a/fs/namei.c > +++ b/fs/namei.c > @@ -3249,6 +3249,23 @@ static int lookup_open(struct nameidata *nd, struct path *path, > return error; > } > > +/* > + * The file is open for write, so it is not mmapped with VM_DENYWRITE. If > + * it still has THP in page cache, drop the whole file from pagecache > + * before processing writes. This helps us avoid handling write back of > + * THP for now. > + */ > +static inline void release_file_thp(struct file *file) > +{ > + if (IS_ENABLED(CONFIG_READ_ONLY_THP_FOR_FS)) { > + struct inode *inode = file_inode(file); > + > + if (inode_is_open_for_write(inode) && > + filemap_nr_thps(inode->i_mapping)) > + truncate_pagecache(inode, 0); > + } > +} > + > /* > * Handle the last step of open() > */ > @@ -3418,7 +3435,11 @@ static int do_last(struct nameidata *nd, > goto out; > opened: > error = ima_file_check(file, op->acc_mode); > - if (!error && will_truncate) > + if (error) > + goto out; > + > + release_file_thp(file); > + if (will_truncate) > error = handle_truncate(file); This would seem better placed in do_dentry_open(), where we're done with the namespace operation and actually work against the inode. Something roughly like this? diff --git a/fs/open.c b/fs/open.c index b5b80469b93d..cae893edbab6 100644 --- a/fs/open.c +++ b/fs/open.c @@ -799,6 +799,11 @@ static int do_dentry_open(struct file *f, if (!f->f_mapping->a_ops || !f->f_mapping->a_ops->direct_IO) return -EINVAL; } + + /* XXX: Huge page cache doesn't support writing yet */ + if ((f->f_mode & FMODE_WRITE) && filemap_nr_thps(inode->i_mapping)) + truncate_pagecache(inode, 0); + return 0; cleanup_all: