On Mon 25-02-13 20:07:39, Dmitry Monakhov wrote: > When ext4_split_extent_at() ends up doing zeroout & conversion to > initialized instead of split & conversion, ext4_split_extent() gets > confused and can wrongly mark the extent back as uninitialized resulting in > end IO code getting confused from large unwritten extents and may result in > data loss. > > The example of problematic behavior is: > lblk len lblk len > ext4_split_extent() (ex=[1000,30,uninit], map=[1010,10]) > ext4_split_extent_at() (split [1000,30,uninit] at 1020) > ext4_ext_insert_extent() -> ENOSPC > ext4_ext_zeroout() > -> extent [1000,30] is now initialized > ext4_split_extent_at() (split [1000,30,init] at 1010, > MARK_UNINIT1 | MARK_UNINIT2) > -> extent is split and parts marked as uninitialized > > Fix the problem by rechecking extent type after the first > ext4_split_extent_at() returns. None of split_flags can not be applied to > initialized extent so this patch also add BUG_ON to prevent similar issues > in future. > > TESTCASE: https://github.com/dmonakhov/xfstests/commit/b8a55eb5ce28c6ff29e620ab090902fcd5833597 > > Changes since V2: Patch no longer depends on Jan's "disable-uninit-ext-mergring" patch. Looks good. You can add: Reviewed-by: Jan Kara <jack@xxxxxxx> Honza > > Signed-off-by: Dmitry Monakhov <dmonakhov@xxxxxxxxxx> > --- > fs/ext4/extents.c | 22 ++++++++++++++++------ > 1 files changed, 16 insertions(+), 6 deletions(-) > > diff --git a/fs/ext4/extents.c b/fs/ext4/extents.c > index 372b2cb..3bd3ca5 100644 > --- a/fs/ext4/extents.c > +++ b/fs/ext4/extents.c > @@ -2943,6 +2943,10 @@ static int ext4_split_extent_at(handle_t *handle, > newblock = split - ee_block + ext4_ext_pblock(ex); > > BUG_ON(split < ee_block || split >= (ee_block + ee_len)); > + BUG_ON(!ext4_ext_is_uninitialized(ex) && > + split_flag & (EXT4_EXT_MAY_ZEROOUT | > + EXT4_EXT_MARK_UNINIT1 | > + EXT4_EXT_MARK_UNINIT2)); > > err = ext4_ext_get_access(handle, inode, path + depth); > if (err) > @@ -3061,19 +3065,25 @@ static int ext4_split_extent(handle_t *handle, > if (err) > goto out; > } > - > + /* > + * Update path is required because previous ext4_split_extent_at() may > + * result in split of original leaf or extent zeroout. > + */ > ext4_ext_drop_refs(path); > path = ext4_ext_find_extent(inode, map->m_lblk, path); > if (IS_ERR(path)) > return PTR_ERR(path); > + depth = ext_depth(inode); > + ex = path[depth].p_ext; > + uninitialized = ext4_ext_is_uninitialized(ex); > + split_flag1 = 0; > > if (map->m_lblk >= ee_block) { > - split_flag1 = split_flag & (EXT4_EXT_MAY_ZEROOUT | > - EXT4_EXT_DATA_VALID2); > - if (uninitialized) > + split_flag1 = split_flag & EXT4_EXT_DATA_VALID2; > + if (uninitialized) { > split_flag1 |= EXT4_EXT_MARK_UNINIT1; > - if (split_flag & EXT4_EXT_MARK_UNINIT2) > - split_flag1 |= EXT4_EXT_MARK_UNINIT2; > + split_flag1 |= split_flag & (EXT4_EXT_MAY_ZEROOUT | EXT4_EXT_MARK_UNINIT2); > + } > err = ext4_split_extent_at(handle, inode, path, > map->m_lblk, split_flag1, flags); > if (err) > -- > 1.7.1 > -- Jan Kara <jack@xxxxxxx> SUSE Labs, CR -- To unsubscribe from this list: send the line "unsubscribe linux-ext4" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
