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: b8a55eb5ce
Signed-off-by: Dmitry Monakhov <dmonakhov@openvz.org>
Signed-off-by: "Theodore Ts'o" <tytso@mit.edu>
Reviewed-by: Jan Kara <jack@suse.cz>
357b66fdc8