ceph: fix inode number handling on arches with 32-bit ino_t
Tuan and Ulrich mentioned that they were hitting a problem on s390x, which has a 32-bit ino_t value, even though it's a 64-bit arch (for historical reasons). I think the current handling of inode numbers in the ceph driver is wrong. It tries to use 32-bit inode numbers on 32-bit arches, but that's actually not a problem. 32-bit arches can deal with 64-bit inode numbers just fine when userland code is compiled with LFS support (the common case these days). What we really want to do is just use 64-bit numbers everywhere, unless someone has mounted with the ino32 mount option. In that case, we want to ensure that we hash the inode number down to something that will fit in 32 bits before presenting the value to userland. Add new helper functions that do this, and only do the conversion before presenting these values to userland in getattr and readdir. The inode table hashvalue is changed to just cast the inode number to unsigned long, as low-order bits are the most likely to vary anyway. While it's not strictly required, we do want to put something in inode->i_ino. Instead of basing it on BITS_PER_LONG, however, base it on the size of the ino_t type. NOTE: This is a user-visible change on 32-bit arches: 1/ inode numbers will be seen to have changed between kernel versions. 32-bit arches will see large inode numbers now instead of the hashed ones they saw before. 2/ any really old software not built with LFS support may start failing stat() calls with -EOVERFLOW on inode numbers >2^32. Nothing much we can do about these, but hopefully the intersection of people running such code on ceph will be very small. The workaround for both problems is to mount with "-o ino32". [ idryomov: changelog tweak ] URL: https://tracker.ceph.com/issues/46828 Reported-by:Ulrich Weigand <Ulrich.Weigand@de.ibm.com> Reported-and-Tested-by:
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