Created attachment 219540 [details]
convert 32 bit zfs_iocparm_t to 64 bit

When 32 bit applications use libzfs to access ZFS data, they always fail in zfs_open(), with 32 bit "zfs list" and "zpool list" crashing.

This is because /usr/src/sys/cddl/contrib/opensolaris/uts/common/fs/zfs/zfs_ioctl.c function zfsdev_ioctl() checks for:

---snip---
if (len != sizeof(zfs_iocparm_t)) {
---snip---

On amd64, sizeof(zfs_iocparm_t) is 24, as in /usr/src/sys/cddl/contrib/opensolaris/common/zfs/zfs_ioctl_compat.h we have:

---snip---
typedef struct zfs_iocparm {
        uint32_t        zfs_ioctl_version;
        uint64_t        zfs_cmd;
        uint64_t        zfs_cmd_size;
} zfs_iocparm_t;
---snip---

which has its fields aligned to 8 byte boundaries. On i386, they are aligned to 4 byte boundaries, sizeof(zfs_iocparm_t) is only 20, and every ioctl fails with EINVAL.

This affects Wine as it runs many 32 bit apps. Since Windows is case-insensitive, Wine has to slowly scan the entire directory when doing file I/O on a case-sensitive filesystem, to match filenames case-insensitively. ZFS can create filesystems with casesensitivity=insensitive, allowing Wine to skip the slow scan and speeding up file I/O considerably for some apps. When developing a patch to Wine to check that casesensitivity property and use it when insensitive (https://source.winehq.org/patches/data/195726) I noticed zfs_open() always fails, which led me to this bug.

The attached patch correctly converts the 32 bit zfs_iocparm_t to 64 bit, and allows at least Wine to work correctly. I haven't yet had a chance to test whether it fixes 32 bit versions of the "zpool" and "zfs" tools (which probably use more elaborate ioctls).