From mboxrd@z Thu Jan 1 00:00:00 1970 From: "Darrick J. Wong" Subject: [PATCH] ext4: support read-only images Date: Mon, 26 Jan 2015 23:45:51 -0800 Message-ID: <20150127074551.GD9976@birch.djwong.org> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Cc: linux-ext4@vger.kernel.org To: tytso@mit.edu Return-path: Received: from aserp1040.oracle.com ([141.146.126.69]:38462 "EHLO aserp1040.oracle.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753368AbbA0Hp4 (ORCPT ); Tue, 27 Jan 2015 02:45:56 -0500 Content-Disposition: inline Sender: linux-ext4-owner@vger.kernel.org List-ID: Add a rocompat feature, "readonly" to mark a FS image as read-only. The feature prevents the kernel and e2fsprogs from changing the image; the flag can be toggled by tune2fs. Signed-off-by: Darrick J. Wong --- fs/ext4/ext4.h | 1 + fs/ext4/super.c | 10 +++++++++- 2 files changed, 10 insertions(+), 1 deletion(-) diff --git a/fs/ext4/ext4.h b/fs/ext4/ext4.h index 3950a2f..5cf937d 100644 --- a/fs/ext4/ext4.h +++ b/fs/ext4/ext4.h @@ -1557,6 +1557,7 @@ static inline void ext4_clear_state_flags(struct ext4_inode_info *ei) * GDT_CSUM bits are mutually exclusive. */ #define EXT4_FEATURE_RO_COMPAT_METADATA_CSUM 0x0400 +#define EXT4_FEATURE_RO_COMPAT_READONLY 0x1000 #define EXT4_FEATURE_INCOMPAT_COMPRESSION 0x0001 #define EXT4_FEATURE_INCOMPAT_FILETYPE 0x0002 diff --git a/fs/ext4/super.c b/fs/ext4/super.c index 74c5f53..c65dede 100644 --- a/fs/ext4/super.c +++ b/fs/ext4/super.c @@ -2776,6 +2776,12 @@ static int ext4_feature_set_ok(struct super_block *sb, int readonly) if (readonly) return 1; + if (EXT4_HAS_RO_COMPAT_FEATURE(sb, EXT4_FEATURE_RO_COMPAT_READONLY)) { + ext4_msg(sb, KERN_INFO, "filesystem is read-only"); + sb->s_flags |= MS_RDONLY; + return 1; + } + /* Check that feature set is OK for a read-write mount */ if (EXT4_HAS_RO_COMPAT_FEATURE(sb, ~EXT4_FEATURE_RO_COMPAT_SUPP)) { ext4_msg(sb, KERN_ERR, "couldn't mount RDWR because of " @@ -4930,7 +4936,9 @@ static int ext4_remount(struct super_block *sb, int *flags, char *data) ext4_mark_recovery_complete(sb, es); } else { /* Make sure we can mount this feature set readwrite */ - if (!ext4_feature_set_ok(sb, 0)) { + if (EXT4_HAS_RO_COMPAT_FEATURE(sb, + EXT4_FEATURE_RO_COMPAT_READONLY) || + !ext4_feature_set_ok(sb, 0)) { err = -EROFS; goto restore_opts; }