The problem appears to be here:
if (folio_mapping(folio) != mapping ||
!folio_test_dirty(folio)) {
folio_unlock(folio);
goto skip_write;
}
in my version it's:
if (folio->mapping != mapping ||
!folio_test_dirty(folio)) {
start += folio_size(folio);
folio_unlock(folio);
continue;
}
In your version, skip_write doesn't advance start if it too many skips occur.
Changing your version to match fixes the problem - or, at least, the
symptoms. I'm not sure exactly why it's occurring, but the -EBADF (-9) is
coming from cifs_get_writable_file() not finding an open file. I think this
is a Steve question.
With Vishal's change to use filemap_get_folios_tag() instead of
find_get_pages_range_tag(), the most common file write case (open, write,
write, ..., write, close) in which all the data is added to the pagecache in
one contiguous lump without seeking, hits this a lot.
Unfortunately, unlike find_get_pages_range_tag(), filemap_get_folios_tag()
doesn't allow you to set a limit on the number of pages it will return.
David
