ext4: race-condition protection for ext4_convert_unwritten_extents_endio
We assumed that at the time we call ext4_convert_unwritten_extents_endio() extent in question is fully inside [map.m_lblk, map->m_len] because it was already split during submission. But this may not be true due to a race between writeback vs fallocate. If extent in question is larger than requested we will split it again. Special precautions should being done if zeroout required because [map.m_lblk, map->m_len] already contains valid data. Signed-off-by: NDmitry Monakhov <dmonakhov@openvz.org> Signed-off-by: N"Theodore Ts'o" <tytso@mit.edu> Cc: stable@vger.kernel.org
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