xfs: indirect health reporting

This series enables the XFS health reporting infrastructure to remember
indirect health concerns when resources are scarce.  For example, if a
scrub notices that there's something wrong with an inode's metadata but
memory reclaim needs to kill the incore inode, we ought to be able to
report that indirect observation in the AGI health report.

The first two patches in this series set that up, and the third one
provides a means for xfs_scrub to tell the kernel that it can forget the
indirect problem report.
-----BEGIN PGP SIGNATURE-----

iQIzBAABCgAdFiEEUzaAxoMeQq6m2jMV+H93GTRKtOsFAmFzTQ0ACgkQ+H93GTRK
tOudpw//VdN563yWjgqqRCzOuu30PaSG2xmL7L5xN8I+H2/j848AnWbuOqhw8Mdn
Vt+4NC0TX8Nk3Ib5B3jXkjwExJwQB3E4VsGlgxZSBgymKTp4kBE3ql4MuxOr7B2s
9a4ScM00/fUh1/qraLbrb1mYD0GZtmGw7joGDtQcTxq52nrAc61ek3oKp/I3UW4I
ufby/L1Tx46MeJzTVnZW9HV7RmpqzAGqrSmp56Onlw9zhfkpTlDUKNvbukNLSBgQ
bkpaSW6Avd/LaPhxCGjMQx/TaVcMRNmN+dVWB6b8Xixn4Yf3VSXw28u1PqBBXU6M
T9hBljb4STTvWYKEmPxba/T28chAWoqgRvGGvEljVLntd9k9ozEAuPfkJF/xIUHC
Nc3G1QjSrll4aSbh2uhlTNJ2D0TVTd06jRTqJLLE0S9Qphlmhvxeh8V7bH9Zrvln
PGtDQOgQKZ93gnJxehmYr2orNRjJsLFtcQVSnbmDgwYEyjY8KEYc9EE1lrFO9AsJ
uKzLY/7JKPWu69QcRNhsRyhzunZad9fOJ6X9hcFRLOUtoA311WD7kHKlfuGnl9nn
sxkqzajLp6pYu1CE9Ti9G1zL13n1YubxHW0oaLDuAEpI/0itYHPO6JI/xVdm/cta
hgyvBkTvXuL4jfX/0dm8VhFbPz37/0UCblYA1qj0U4bdpKSoba4=
=LIZv
-----END PGP SIGNATURE-----