On Tue, Dec 03, 2019 at 07:50:39AM -0500, Jan Stancek wrote:
My theory is that there's a race in iomap. There appear to be interleaved calls to iomap_set_range_uptodate() for same page with varying offset and length. Each call sees bitmap as _not_ entirely "uptodate" and hence doesn't call SetPageUptodate(). Even though each bit in bitmap ends up uptodate by the time all calls finish.
Weird. That should be prevented by the page lock that all callers of iomap_set_range_uptodate. But in case I miss something, does the patch below trigger? If not it is not jut a race, but might be some weird ordering problem with the bitops, especially if it only triggers on ppc, which is very weakly ordered.
diff --git a/fs/iomap/buffered-io.c b/fs/iomap/buffered-io.c index d33c7bc5ee92..25e942c71590 100644 --- a/fs/iomap/buffered-io.c +++ b/fs/iomap/buffered-io.c @@ -148,6 +148,8 @@ iomap_set_range_uptodate(struct page *page, unsigned off, unsigned len) unsigned int i; bool uptodate = true;
+ WARN_ON_ONCE(!PageLocked(page)); + if (iop) { for (i = 0; i < PAGE_SIZE / i_blocksize(inode); i++) { if (i >= first && i <= last)