NFSv4/flexfiles: report cancelled I/O as a layout error

When a layout is recalled or revoked the client cancels its in-flight I/O
so the layout can be returned.  The metadata server needs to learn that
this I/O to the storage device did not complete, so that it can reconcile
the affected mirror instance (or, if none remains, take other action).

The cancellation completed with -EAGAIN, which ff_layout_io_track_ds_error()
does not recognise: it fell through the switch and recorded nothing, so no
error was reported to the server.

-EAGAIN is overloaded in the RPC layer, so rather than key the reporting on
it, cancel the I/O with -ECANCELED and map that to NFS4ERR_NXIO in
ff_layout_io_track_ds_error() -- the status the client already reports for
the transport errors that leave an in-flight write incomplete.  The
cancelled I/O is then reported to the server via LAYOUTERROR / LAYOUTRETURN.

Unlike a genuine transport error, though, we aborted the I/O ourselves and
have no evidence the device is at fault, so once the error is recorded we
skip marking the device unreachable and forcing a further layout return.

The retry disposition is unchanged from the original -EAGAIN cancellation:
both NFS4ERR_NXIO and -ECANCELED are no-ops in ff_layout_async_handle_error(),
which still resets the I/O to pNFS (or the MDS), so it is re-driven as before.

Signed-off-by: Benjamin Coddington <bcodding@hammerspace.com>
Signed-off-by: Trond Myklebust <trond.myklebust@hammerspace.com>

0 files changed, 0 insertions, 0 deletions