ext4: fix xfstest generic/299 block validity failures
Commit a115f749 (ext4: remove wait for unwritten extent conversion from ext4_truncate) exposed a bug in ext4_ext_handle_uninitialized_extents(). It can be triggered by xfstest generic/299 when run on a test file system created without a journal. This test continuously fallocates and truncates files to which random dio/aio writes are simultaneously performed by a separate process. The test completes successfully, but if the test filesystem is mounted with the block_validity option, a warning message stating that a logical block has been mapped to an illegal physical block is posted in the kernel log. The bug occurs when an extent is being converted to the written state by ext4_end_io_dio() and ext4_ext_handle_uninitialized_extents() discovers a mapping for an existing uninitialized extent. Although it sets EXT4_MAP_MAPPED in map->m_flags, it fails to set map->m_pblk to the discovered physical block number. Because map->m_pblk is not otherwise initialized or set by this function or its callers, its uninitialized value is returned to ext4_map_blocks(), where it is stored as a bogus mapping in the extent status tree. Since map->m_pblk can accidentally contain illegal values that are larger than the physical size of the file system, calls to check_block_validity() in ext4_map_blocks() that are enabled if the block_validity mount option is used can fail, resulting in the logged warning message. Signed-off-by:Eric Whitney <enwlinux@gmail.com> Signed-off-by:
"Theodore Ts'o" <tytso@mit.edu> Cc: stable@vger.kernel.org # 3.11+
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