On Mon, May 16, 2022 at 8:55 PM Matthew Wilcox <willy@xxxxxxxxxxxxx> wrote: > > On Mon, May 16, 2022 at 08:47:52PM +0800, Hsin-Yi Wang wrote: > > On Mon, May 16, 2022 at 8:36 PM Matthew Wilcox <willy@xxxxxxxxxxxxx> wrote: > > > > > > On Mon, May 16, 2022 at 07:04:08PM +0800, Hsin-Yi Wang wrote: > > > > > + loff_t req_end = readahead_pos(ractl) + readahead_length(ractl); > > > > > + loff_t start = readahead_pos(ractl) &~ mask; > > > > > + size_t len = readahead_length(ractl) + readahead_pos(ractl) - start; > > > > > + struct squashfs_page_actor *actor; > > > > > + unsigned int nr_pages = 0; > > > > > + struct page **pages; > > > > > + u64 block = 0; > > > > > + int bsize, res, i, index; > > > > > + int file_end = i_size_read(inode) >> msblk->block_log; > > > > > + unsigned int max_pages = 1UL << shift; > > > > > + > > > > > + readahead_expand(ractl, start, (len | mask) + 1); > > > > > + > > > > > + if (readahead_pos(ractl) + readahead_length(ractl) < req_end || > > > > > + file_end == 0) > > > > > + return; > > > > > > What's the first half of this condition supposed to be checking for? > > > It seems to be checking whether readahead_expand() shrunk the range > > > covered by the ractl, but readahead_expand() never does that, so I'm > > > confused why you're checking for it. > > > > hi Matthew, > > > > This is to check if readahead_expand() expands as much as it's requested. > > I didn't encounter the mismatch so far in my testing. If this check is > > not necessary, it can be removed. > > Then I think req_end is miscalculated? It should surely be: > > req_end = start + (len | mask) + 1; > > But I'm not sure that we should be failing under such circumstances. > For example, we may have been asked to read 1.5MB, attempt to round up > to 2MB, and fail. But we can still submit a readahead for the first 1MB, > before leaving the second 512kB for readpage to handle. > > So maybe we should just remove this check entirely. I'll remove this in the next version.
