[bug report] fsdax: output address in dax_iomap_pfn() and rename it

[Dan Carpenter <dan.carpenter@oracle.com>]

Hello Shiyang Ruan,

The patch 1447ac26a964: "fsdax: output address in dax_iomap_pfn() and
rename it" from Jun 3, 2022, leads to the following Smatch static
checker warning:

	fs/dax.c:1085 dax_iomap_direct_access()
	error: uninitialized symbol 'rc'.

fs/dax.c
    1052 static int dax_iomap_direct_access(const struct iomap *iomap, loff_t pos,
    1053                 size_t size, void **kaddr, pfn_t *pfnp)
    1054 {
    1055         pgoff_t pgoff = dax_iomap_pgoff(iomap, pos);
    1056         int id, rc;
    1057         long length;
    1058 
    1059         id = dax_read_lock();
    1060         length = dax_direct_access(iomap->dax_dev, pgoff, PHYS_PFN(size),
    1061                                    DAX_ACCESS, kaddr, pfnp);
    1062         if (length < 0) {
    1063                 rc = length;
    1064                 goto out;
    1065         }
    1066         if (!pfnp)
    1067                 goto out_check_addr;

Is this an error path?

    1068         rc = -EINVAL;
    1069         if (PFN_PHYS(length) < size)
    1070                 goto out;
    1071         if (pfn_t_to_pfn(*pfnp) & (PHYS_PFN(size)-1))
    1072                 goto out;
    1073         /* For larger pages we need devmap */
    1074         if (length > 1 && !pfn_t_devmap(*pfnp))
    1075                 goto out;
    1076         rc = 0;
    1077 
    1078 out_check_addr:
    1079         if (!kaddr)
    1080                 goto out;

How is it supposed to be handled if both "pfnp" and "kaddr" are NULL?

Smatch says that "kaddr" can never be NULL so this code is just future
proofing but I didn't look at it carefully.

    1081         if (!*kaddr)
    1082                 rc = -EFAULT;
    1083 out:
    1084         dax_read_unlock(id);
--> 1085         return rc;
    1086 }

regards,
dan carpenter