For filesystems with block size < page size, we need to set all the
per-block uptodate bits if the page was already uptodate at the time
we create the per-block metadata. This can happen if the page is
invalidated (eg by a write to drop_caches) but ultimately not removed
from the page cache.
This is a data corruption issue as page writeback skips blocks which
are marked !uptodate.
Fixes: b53f27525678 ("iomap: add support for sub-pagesize buffered I/O without buffer heads") Signed-off-by: Matthew Wilcox (Oracle) <willy@infradead.org> Reported-by: Qian Cai <cai@redhat.com> Cc: Brian Foster <bfoster@redhat.com> Reviewed-by: Gao Xiang <hsiangkao@redhat.com> Reviewed-by: Darrick J. Wong <darrick.wong@oracle.com> Signed-off-by: Darrick J. Wong <darrick.wong@oracle.com> Reviewed-by: Christoph Hellwig <hch@lst.de>