On Mon 11-09-17 23:05:22, Ross Zwisler wrote: > If an inode has inline data it is currently prevented from using DAX by a > check in ext4_set_inode_flags(). When the inode grows inline data via > ext4_create_inline_data() or removes its inline data via > ext4_destroy_inline_data_nolock(), the value of S_DAX can change. > > Currently these changes are unsafe because we don't hold off page faults > and I/O, write back dirty radix tree entries and invalidate all mappings. > There are also issues with mm-level races when changing the value of S_DAX, > as well as issues with the VM_MIXEDMAP flag: > > https://www.spinics.net/lists/linux-xfs/msg09859.html > > The unsafe transition of S_DAX can reliably cause data corruption, as shown > by the following fstest: > > https://patchwork.kernel.org/patch/9948381/ > > Fix this issue by preventing the DAX mount option from being used on > filesystems that were created to support inline data. Inline data is an > option given to mkfs.ext4. > > Signed-off-by: Ross Zwisler <ross.zwisler@xxxxxxxxxxxxxxx> > CC: stable@xxxxxxxxxxxxxxx Looks good. You can add: Reviewed-by: Jan Kara <jack@xxxxxxx> Honza > --- > fs/ext4/inline.c | 10 ---------- > fs/ext4/super.c | 5 +++++ > 2 files changed, 5 insertions(+), 10 deletions(-) > > diff --git a/fs/ext4/inline.c b/fs/ext4/inline.c > index 28c5c3a..fd95019 100644 > --- a/fs/ext4/inline.c > +++ b/fs/ext4/inline.c > @@ -302,11 +302,6 @@ static int ext4_create_inline_data(handle_t *handle, > EXT4_I(inode)->i_inline_size = len + EXT4_MIN_INLINE_DATA_SIZE; > ext4_clear_inode_flag(inode, EXT4_INODE_EXTENTS); > ext4_set_inode_flag(inode, EXT4_INODE_INLINE_DATA); > - /* > - * Propagate changes to inode->i_flags as well - e.g. S_DAX may > - * get cleared > - */ > - ext4_set_inode_flags(inode); > get_bh(is.iloc.bh); > error = ext4_mark_iloc_dirty(handle, inode, &is.iloc); > > @@ -451,11 +446,6 @@ static int ext4_destroy_inline_data_nolock(handle_t *handle, > } > } > ext4_clear_inode_flag(inode, EXT4_INODE_INLINE_DATA); > - /* > - * Propagate changes to inode->i_flags as well - e.g. S_DAX may > - * get set. > - */ > - ext4_set_inode_flags(inode); > > get_bh(is.iloc.bh); > error = ext4_mark_iloc_dirty(handle, inode, &is.iloc); > diff --git a/fs/ext4/super.c b/fs/ext4/super.c > index c9e7be5..4251e50 100644 > --- a/fs/ext4/super.c > +++ b/fs/ext4/super.c > @@ -3707,6 +3707,11 @@ static int ext4_fill_super(struct super_block *sb, void *data, int silent) > } > > if (sbi->s_mount_opt & EXT4_MOUNT_DAX) { > + if (ext4_has_feature_inline_data(sb)) { > + ext4_msg(sb, KERN_ERR, "Cannot use DAX on a filesystem" > + " that may contain inline data"); > + goto failed_mount; > + } > err = bdev_dax_supported(sb, blocksize); > if (err) > goto failed_mount; > -- > 2.9.5 > -- Jan Kara <jack@xxxxxxxx> SUSE Labs, CR
