On Tue, Sep 22, 2020 at 12:23:45PM -0400, Qian Cai wrote: > On Fri, 2020-09-11 at 00:47 +0100, Matthew Wilcox (Oracle) wrote: > > Size the uptodate array dynamically to support larger pages in the > > page cache. With a 64kB page, we're only saving 8 bytes per page today, > > but with a 2MB maximum page size, we'd have to allocate more than 4kB > > per page. Add a few debugging assertions. > > > > Signed-off-by: Matthew Wilcox (Oracle) <willy@xxxxxxxxxxxxx> > > Reviewed-by: Dave Chinner <dchinner@xxxxxxxxxx> > > Some syscall fuzzing will trigger this on powerpc: > > .config: https://gitlab.com/cailca/linux-mm/-/blob/master/powerpc.config > > [ 8805.895344][T445431] WARNING: CPU: 61 PID: 445431 at fs/iomap/buffered-io.c:78 iomap_page_release+0x250/0x270 Well, I'm glad it triggered. That warning is: WARN_ON_ONCE(bitmap_full(iop->uptodate, nr_blocks) != PageUptodate(page)); so there was definitely a problem of some kind. truncate_cleanup_page() calls do_invalidatepage() calls iomap_invalidatepage() calls iomap_page_release() Is this the first warning? I'm wondering if maybe there was an I/O error earlier which caused PageUptodate to get cleared again. If it's easy to reproduce, perhaps you could try something like this? +void dump_iomap_page(struct page *page, const char *reason) +{ + struct iomap_page *iop = to_iomap_page(page); + unsigned int nr_blocks = i_blocks_per_page(page->mapping->host, page); + + dump_page(page, reason); + if (iop) + printk("iop:reads %d writes %d uptodate %*pb\n", + atomic_read(&iop->read_bytes_pending), + atomic_read(&iop->write_bytes_pending), + nr_blocks, iop->uptodate); + else + printk("iop:none\n"); +} and then do something like: if (bitmap_full(iop->uptodate, nr_blocks) != PageUptodate(page)) dump_iomap_page(page, NULL);
