When ext4_da_writepages increases the nr_to_write in writeback_control
then it must always re-base the return value. Originally there was a
(misguided) attempt prevent wbc.nr_to_write from going negative. In
fact, it's necessary to allow nr_to_write to be negative so that
wb_writeback() can correctly calculate how many pages were actually
written.
Signed-off-by: Richard Kennedy <richard@rsk.demon.co.uk>
Signed-off-by: "Theodore Ts'o" <tytso@mit.edu>
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