Re: [PATCH 4/4] ext3: Warn if mounting rw on a disk requiring stable page writes
From: Dave Chinner <david@fromorbit.com>
Date: 2012-11-22 23:15:19
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On Wed, Nov 21, 2012 at 05:47:55PM -0800, Darrick J. Wong wrote:
On Thu, Nov 22, 2012 at 08:47:13AM +1100, NeilBrown wrote:quoted
On Wed, 21 Nov 2012 22:33:33 +0100 Jan Kara [off-list ref] wrote:quoted
On Wed 21-11-12 13:13:19, Darrick J. Wong wrote:quoted
On Wed, Nov 21, 2012 at 03:15:43AM +0100, Jan Kara wrote:quoted
On Tue 20-11-12 18:00:56, Darrick J. Wong wrote:quoted
ext3 doesn't properly isolate pages from changes during writeback. Since the recommended fix is to use ext4, for now we'll just print a warning if the user tries to mount in write mode. Signed-off-by: Darrick J. Wong <redacted> --- fs/ext3/super.c | 8 ++++++++ 1 file changed, 8 insertions(+)diff --git a/fs/ext3/super.c b/fs/ext3/super.c index 5366393..5b3725d 100644 --- a/fs/ext3/super.c +++ b/fs/ext3/super.c@@ -1325,6 +1325,14 @@ static int ext3_setup_super(struct super_block *sb, struct ext3_super_block *es, "forcing read-only mode"); res = MS_RDONLY; } + if (!read_only && + queue_requires_stable_pages(bdev_get_queue(sb->s_bdev))) { + ext3_msg(sb, KERN_ERR, + "error: ext3 cannot safely write data to a disk " + "requiring stable pages writes; forcing read-only " + "mode. Upgrading to ext4 is recommended."); + res = MS_RDONLY; + } if (read_only) return res; if (!(sbi->s_mount_state & EXT3_VALID_FS))Why this? ext3 should be fixed by your change to filemap_page_mkwrite()... Or does testing show otherwise?Yes, it's still broken even with this new set of changes. Now that I think about it a little more, I recall that writeback mode was actually fine, so this is a little harsh. Hm... looking at the ordered code a little more, it looks like ext3_ordered_write_end is calling journal_dirty_data_fn, which (I guess?) tries to write mapped buffers back through the journal? Taking it out seems to fix ordered mode, though I have a suspicion that it might very well break ordered mode too.Oh, right. kjournald writing buffers directly (without setting PageWriteback) will break things. So please, change warning to:Maybe we should just fix this anyway? I still have the patch that adds PG_stable (and changes the
Page flags are in short supply. If you need a page flag to fix a bug in a single filesytem, there's a couple of reserved private page flags that can be used. i.e PG_owner_priv_1. I don't think using a glbal page flag for just this purpose will fly, though... Cheers, Dave. -- Dave Chinner david@fromorbit.com