loader: update symlink support in zfs reader

[tsoome]

Summary

As the current zfs file system is providing symlink via system attributes, need to update the code accordingly.

Test Plan

Tested by browsing and reading different symlinks and by using names like /usr/bin/../lib, bin/.., etc/., etc/./inet, ./bin

[avg]

LGTM

[smh]

sys/boot/zfs/zfsimpl.c

2273 ↗

(On Diff #25494)

All of the above are only used in == DMU_OT_SA case so could be moved into that block with char *p;

2294 ↗

(On Diff #25494)

Does the boot code make use of SET_ERROR, I'm guessing not?

2382 ↗

(On Diff #25494)

Missing space

[tsoome]

sys/boot/zfs/zfsimpl.c

2294 ↗

(On Diff #25494)

no, it does not.

[tsoome]

Fixes suggested by smh.

[smh]

sys/boot/zfs/zfsimpl.c

2282 ↗

(On Diff #25520)

Just spotted that if you invert the condition you get an arguably cleaner flow e.g.

 else {
    if ((dn->dn_flags & DNODE_FLAG_SPILL_BLKPTR) == 0)
        return (EIO);

    blkptr_t *bp = &dn->dn_spill;

    size = BP_GET_LSIZE(bp);
    ...
}

[tsoome]

svn update; and clean up the inverted if statement.

[smh]

LGTM

[allanjude]

Approved By: allanjude