[bug report] libnvdimm: fix mishandled nvdimm_clear_poison() return value

[Dan Carpenter <error27@gmail.com>]

Hello Dan Williams,

The patch 868f036fee4b: "libnvdimm: fix mishandled
nvdimm_clear_poison() return value" from Dec 16, 2016, leads to the
following Smatch static checker warnings:

    drivers/nvdimm/claim.c:287 nsio_rw_bytes() warn:
    replace divide condition 'cleared / 512' with 'cleared >= 512'

    drivers/nvdimm/bus.c:210 nvdimm_account_cleared_poison() warn:
    replace divide condition 'cleared / 512' with 'cleared >= 512'

drivers/nvdimm/claim.c
    252 static int nsio_rw_bytes(struct nd_namespace_common *ndns,
    253                 resource_size_t offset, void *buf, size_t size, int rw,
    254                 unsigned long flags)
    255 {
    256         struct nd_namespace_io *nsio = to_nd_namespace_io(&ndns->dev);
    257         unsigned int sz_align = ALIGN(size + (offset & (512 - 1)), 512);
    258         sector_t sector = offset >> 9;
    259         int rc = 0, ret = 0;
    260 
    261         if (unlikely(!size))
    262                 return 0;
    263 
    264         if (unlikely(offset + size > nsio->size)) {
    265                 dev_WARN_ONCE(&ndns->dev, 1, "request out of range\n");
    266                 return -EFAULT;
    267         }
    268 
    269         if (rw == READ) {
    270                 if (unlikely(is_bad_pmem(&nsio->bb, sector, sz_align)))
    271                         return -EIO;
    272                 if (copy_mc_to_kernel(buf, nsio->addr + offset, size) != 0)
    273                         return -EIO;
    274                 return 0;
    275         }
    276 
    277         if (unlikely(is_bad_pmem(&nsio->bb, sector, sz_align))) {
    278                 if (IS_ALIGNED(offset, 512) && IS_ALIGNED(size, 512)
    279                                 && !(flags & NVDIMM_IO_ATOMIC)) {
    280                         long cleared;
    281 
    282                         might_sleep();
    283                         cleared = nvdimm_clear_poison(&ndns->dev,
    284                                         nsio->res.start + offset, size);
    285                         if (cleared < size)
    286                                 rc = -EIO;
--> 287                         if (cleared > 0 && cleared / 512) {
                                                   ^^^^^^^^^^^^^
Smatch suggests changing this to "&& cleared >= 512" but it doesn't make
sense to say if (cleared > 0 && cleared >= 512) {.  Probably what was
instead intended was "if (cleared > 0 && (cleared % 512) == 0) {"?

    288                                 cleared /= 512;
    289                                 badblocks_clear(&nsio->bb, sector, cleared);
    290                         }
    291                         arch_invalidate_pmem(nsio->addr + offset, size);
    292                 } else
    293                         rc = -EIO;
    294         }
    295 
    296         memcpy_flushcache(nsio->addr + offset, buf, size);
    297         ret = nvdimm_flush(to_nd_region(ndns->dev.parent), NULL);
    298         if (ret)
    299                 rc = ret;
    300 
    301         return rc;
    302 }

regards,
dan carpenter