On Mon 11-09-17 23:05:23, Ross Zwisler wrote: > The current code has the potential for data corruption when changing an > inode's journaling mode, as that can result in a subsequent unsafe change > in S_DAX. > > I've captured an instance of this data corruption in the following fstest: > > https://patchwork.kernel.org/patch/9948377/ > > Prevent this data corruption from happening by disallowing changes to the > journaling mode if the '-o dax' mount option was used. This means that for > a given filesystem we could have a mix of inodes using either DAX or > data journaling, but whatever state the inodes are in will be held for the > duration of the mount. > > Signed-off-by: Ross Zwisler <ross.zwisler@xxxxxxxxxxxxxxx> > Suggested-by: Jan Kara <jack@xxxxxxx> I guess this is fine for now to stop corrupting data so: Reviewed-by: Jan Kara <jack@xxxxxxx> But I think we should work on more user friendly (i.e., permissive) version. Honza > --- > fs/ext4/inode.c | 5 ----- > fs/ext4/ioctl.c | 16 +++++++++++++--- > 2 files changed, 13 insertions(+), 8 deletions(-) > > diff --git a/fs/ext4/inode.c b/fs/ext4/inode.c > index e963508..3207333 100644 > --- a/fs/ext4/inode.c > +++ b/fs/ext4/inode.c > @@ -5971,11 +5971,6 @@ int ext4_change_inode_journal_flag(struct inode *inode, int val) > ext4_clear_inode_flag(inode, EXT4_INODE_JOURNAL_DATA); > } > ext4_set_aops(inode); > - /* > - * Update inode->i_flags after EXT4_INODE_JOURNAL_DATA was updated. > - * E.g. S_DAX may get cleared / set. > - */ > - ext4_set_inode_flags(inode); > > jbd2_journal_unlock_updates(journal); > percpu_up_write(&sbi->s_journal_flag_rwsem); > diff --git a/fs/ext4/ioctl.c b/fs/ext4/ioctl.c > index afb66d4..b0b754b 100644 > --- a/fs/ext4/ioctl.c > +++ b/fs/ext4/ioctl.c > @@ -290,10 +290,20 @@ static int ext4_ioctl_setflags(struct inode *inode, > if (err) > goto flags_out; > > - if ((jflag ^ oldflags) & (EXT4_JOURNAL_DATA_FL)) > + if ((jflag ^ oldflags) & (EXT4_JOURNAL_DATA_FL)) { > + /* > + * Changes to the journaling mode can cause unsafe changes to > + * S_DAX if we are using the DAX mount option. > + */ > + if (test_opt(inode->i_sb, DAX)) { > + err = -EBUSY; > + goto flags_out; > + } > + > err = ext4_change_inode_journal_flag(inode, jflag); > - if (err) > - goto flags_out; > + if (err) > + goto flags_out; > + } > if (migrate) { > if (flags & EXT4_EXTENTS_FL) > err = ext4_ext_migrate(inode); > -- > 2.9.5 > -- Jan Kara <jack@xxxxxxxx> SUSE Labs, CR
