Jan Kara have spotted interesting issue:
There are potential data corruption issue with direct IO overwrites
racing with truncate:
Like:
dio write truncate_task
->ext4_ext_direct_IO
->overwrite == 1
->down_read(&EXT4_I(inode)->i_data_sem);
->mutex_unlock(&inode->i_mutex);
->ext4_setattr()
->inode_dio_wait()
->truncate_setsize()
->ext4_truncate()
->down_write(&EXT4_I(inode)->i_data_sem);
->__blockdev_direct_IO
->ext4_get_block
->submit_io()
->up_read(&EXT4_I(inode)->i_data_sem);
# truncate data blocks, allocate them to
# other inode - bad stuff happens because
# dio is still in flight.
In order to serialize with truncate dio worker should grab extra i_dio_count
reference before drop i_mutex.
Reviewed-by: Jan Kara <jack@suse.cz>
Signed-off-by: Dmitry Monakhov <dmonakhov@openvz.org>
Signed-off-by: "Theodore Ts'o" <tytso@mit.edu>
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