RFC CRASHFIX: pnfs-obj: NONE-RPC LD must not call rpc_restart_call_prepare()

NONE-RPC layout-Drivers call nfs_writeback_done() as part of their completion of IO. (through pnfs_ld_write_done())

Inside nfs_writeback_done() there is code that does:

	else if (resp->count < argp->count) {
		...

		/* This a short write! */
		nfs_inc_stats(inode, NFSIOS_SHORTWRITE);

		... /* Prepare the remainder */

		rpc_restart_call_prepare(task);
	}

But for none-rpc LDs (objects, blocks) there is no task->tk_ops and this code will crash.

The same code exists in read.c::nfs_readpage_result_common() with same crash.

Therefor: NONE-RPC LDs *must not* call pnfs_ld_read/write_done with partial/short IO. Either complete everything or fail everything and IO will be resubmitted through MDS.

Below are a set of patches that fix this problem for objects layout, blocks maintainer should check that code does not allow a short IO as well.

The Fix is much easier at the LD level then at NFS-Core. Though it could be fixed there, I do not think it is worth it. I will submit a comment that warns for this. Certainly NFS-Core changes could not be so simple as below to be candidates for @Stable

These where lightly tested and are submitted for review. I will conduct heavy testing and will put them in linux-next only next week.

Here are the list of patches:

[PATCH 1/6] ore: Fix NFS crash by supporting any unaligned RAID IO [PATCH 2/6] ore: Remove support of partial IO request (NFS crash) [PATCH 3/6] pnfs-obj: Fix __r4w_get_page in the case of offset beyond i_size

These 3 completely plug the crash above, and are destined for Stable@

Trond please ACK the 3rd patch since I want to push this through my tree, as these are for ore mostly. (Please also review all of them, watch my back)

[PATCH 4/6] pnfs-obj: don't leak objio_state if ore_write/read fails.

A memory leak found on the way, in the error case. Should it be for Stable@ ?

[PATCH 4/5] NFS41: add pg_layout_private to nfs_pageio_descriptor

This is the patch by Peng Tao <[email protected]> which is needed for below fix. Minus the has_moreio flag.

[PATCH 5/5] pnfs-obj: Better IO pattern in case of unaligned offset

Though this patch is an optimization it fixes a very bad IO pattern. Please consider for the 3.5-rcX Kernel and don't postpone to 3.6 Merge window. If possible

Thanks for any review
Boaz