On Tue, May 14, 2024 at 05:22:08PM +0200, Johannes Thumshirn wrote: > From: Johannes Thumshirn <johannes.thumshirn@xxxxxxx> > > Move reading of the on-disk superblock from page to kmalloc()ed memory. No, this is wrong. > + super = kzalloc(ZONEFS_SUPER_SIZE, GFP_KERNEL); > + if (!super) > return -ENOMEM; > > + folio = virt_to_folio(super); This will stop working at some point. It'll return NULL once we get to the memdesc future (because the memdesc will be a slab, not a folio). > bio_init(&bio, sb->s_bdev, &bio_vec, 1, REQ_OP_READ); > bio.bi_iter.bi_sector = 0; > - __bio_add_page(&bio, page, PAGE_SIZE, 0); > + bio_add_folio_nofail(&bio, folio, ZONEFS_SUPER_SIZE, > + offset_in_folio(folio, super)); It also doesn't solve the problem of trying to read 4KiB from a device with 16KiB sectors. We'll have to fail the bio because there isn't enough memory in the bio to store one block. I think the right way to handle this is to call read_mapping_folio(). That will allocate a folio in the page cache for you (obeying the minimum folio size). Then you can examine the contents. It should actually remove code from zonefs. Don't forget to call folio_put() when you're done with it (either at unmount or at the end of mount if you copy what you need elsewhere).
