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 <bergwolf@xxxxxxxxx> 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
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