From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 3C8746FAF; Tue, 5 Dec 2023 03:28:30 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b="npa7/jiW" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 92EA2C433C8; Tue, 5 Dec 2023 03:28:29 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1701746910; bh=L6nsT5Wy/896KbcP4TrgQtT0Fr8NtWbQNW1DHDCsdNc=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=npa7/jiWeg1DUpVVdFWtOPggv5II6OfTV6X+c8YyDf2eh1pAQqik43tMVSXhctlKW 9eORWLJ9C9LhRDFw/HL4lCdG5G3ZyPf9w+weUNfMrx81epD4IPID69GHURRifCu25a xWE9U4eYCwwKxNi7QwE0T1PS612w/aNUqG6/3GMs= From: Greg Kroah-Hartman To: stable@vger.kernel.org Cc: Greg Kroah-Hartman , patches@lists.linux.dev, Dmitry Monakhov , Konstantin Khlebnikov , Amir Goldstein , Miklos Szeredi , Sasha Levin Subject: [PATCH 4.19 63/71] ovl: skip overlayfs superblocks at global sync Date: Tue, 5 Dec 2023 12:17:01 +0900 Message-ID: <20231205031521.539334896@linuxfoundation.org> X-Mailer: git-send-email 2.43.0 In-Reply-To: <20231205031517.859409664@linuxfoundation.org> References: <20231205031517.859409664@linuxfoundation.org> User-Agent: quilt/0.67 X-stable: review X-Patchwork-Hint: ignore Precedence: bulk X-Mailing-List: stable@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit 4.19-stable review patch. If anyone has any objections, please let me know. ------------------ From: Konstantin Khlebnikov [ Upstream commit 32b1924b210a70dcacdf65abd687c5ef86a67541 ] Stacked filesystems like overlayfs has no own writeback, but they have to forward syncfs() requests to backend for keeping data integrity. During global sync() each overlayfs instance calls method ->sync_fs() for backend although it itself is in global list of superblocks too. As a result one syscall sync() could write one superblock several times and send multiple disk barriers. This patch adds flag SB_I_SKIP_SYNC into sb->sb_iflags to avoid that. Reported-by: Dmitry Monakhov Signed-off-by: Konstantin Khlebnikov Reviewed-by: Amir Goldstein Signed-off-by: Miklos Szeredi Stable-dep-of: b836c4d29f27 ("ima: detect changes to the backing overlay file") Signed-off-by: Sasha Levin --- fs/overlayfs/super.c | 5 +++-- fs/sync.c | 3 ++- include/linux/fs.h | 2 ++ 3 files changed, 7 insertions(+), 3 deletions(-) diff --git a/fs/overlayfs/super.c b/fs/overlayfs/super.c index 1a7a1e2988855..1c1eb873e6ecc 100644 --- a/fs/overlayfs/super.c +++ b/fs/overlayfs/super.c @@ -268,8 +268,8 @@ static int ovl_sync_fs(struct super_block *sb, int wait) return 0; /* - * If this is a sync(2) call or an emergency sync, all the super blocks - * will be iterated, including upper_sb, so no need to do anything. + * Not called for sync(2) call or an emergency sync (SB_I_SKIP_SYNC). + * All the super blocks will be iterated, including upper_sb. * * If this is a syncfs(2) call, then we do need to call * sync_filesystem() on upper_sb, but enough if we do it when being @@ -1664,6 +1664,7 @@ static int ovl_fill_super(struct super_block *sb, void *data, int silent) sb->s_xattr = ovl_xattr_handlers; sb->s_fs_info = ofs; sb->s_flags |= SB_POSIXACL; + sb->s_iflags |= SB_I_SKIP_SYNC; err = -ENOMEM; root_dentry = d_make_root(ovl_new_inode(sb, S_IFDIR, 0)); diff --git a/fs/sync.c b/fs/sync.c index b54e0541ad899..917ebd12c2515 100644 --- a/fs/sync.c +++ b/fs/sync.c @@ -76,7 +76,8 @@ static void sync_inodes_one_sb(struct super_block *sb, void *arg) static void sync_fs_one_sb(struct super_block *sb, void *arg) { - if (!sb_rdonly(sb) && sb->s_op->sync_fs) + if (!sb_rdonly(sb) && !(sb->s_iflags & SB_I_SKIP_SYNC) && + sb->s_op->sync_fs) sb->s_op->sync_fs(sb, *(int *)arg); } diff --git a/include/linux/fs.h b/include/linux/fs.h index 95b8ef09b76cf..f89748aac8c32 100644 --- a/include/linux/fs.h +++ b/include/linux/fs.h @@ -1351,6 +1351,8 @@ extern int send_sigurg(struct fown_struct *fown); #define SB_I_IMA_UNVERIFIABLE_SIGNATURE 0x00000020 #define SB_I_UNTRUSTED_MOUNTER 0x00000040 +#define SB_I_SKIP_SYNC 0x00000100 /* Skip superblock at global sync */ + /* Possible states of 'frozen' field */ enum { SB_UNFROZEN = 0, /* FS is unfrozen */ -- 2.42.0