Currently when falling back to doing I/O through the MDS (via
pnfs_{read|write}_through_mds), the client frees the nfs_pgio_header
without releasing the reference taken on the dreq
via pnfs_generic_pg_{read|write}pages -> nfs_pgheader_init ->
nfs_direct_pgio_init. It then takes another reference on the dreq via
nfs_generic_pg_pgios -> nfs_pgheader_init -> nfs_direct_pgio_init and
as a result the requester will become stuck in inode_dio_wait. Once
that happens, other processes accessing the inode will become stuck as
well.
Moving the init_hdr call down to nfs_initiate_pgio ensures we take the
reference on the dreq only once.
This can be reproduced (sometimes) by performing "storage failover
takeover" commands on NetApp filer while doing direct I/O from a client.
This can also be reproduced using SystemTap to simulate a failure while
doing direct I/O from a client (from Dave Wysochanski
<dwysocha@xxxxxxxxxx>):
stap -v -g -e 'probe module("nfs_layout_nfsv41_files").function("nfs4_fl_prepare_ds").return { $return=NULL; exit(); }'
Suggested-by: Benjamin Coddington <bcodding@xxxxxxxxxx>
Signed-off-by: Scott Mayhew <smayhew@xxxxxxxxxx>
---
fs/nfs/pagelist.c | 6 +++---
1 file changed, 3 insertions(+), 3 deletions(-)
diff --git a/fs/nfs/pagelist.c b/fs/nfs/pagelist.c
index d0543e1..d478c19 100644
--- a/fs/nfs/pagelist.c
+++ b/fs/nfs/pagelist.c
@@ -54,9 +54,6 @@ void nfs_pgheader_init(struct nfs_pageio_descriptor *desc,
hdr->dreq = desc->pg_dreq;
hdr->release = release;
hdr->completion_ops = desc->pg_completion_ops;
- if (hdr->completion_ops->init_hdr)
- hdr->completion_ops->init_hdr(hdr);
-
hdr->pgio_mirror_idx = desc->pg_mirror_idx;
}
EXPORT_SYMBOL_GPL(nfs_pgheader_init);
@@ -607,6 +604,9 @@ int nfs_initiate_pgio(struct rpc_clnt *clnt, struct nfs_pgio_header *hdr,
};
int ret = 0;
+ if (hdr->completion_ops->init_hdr)
+ hdr->completion_ops->init_hdr(hdr);
+
hdr->rw_ops->rw_initiate(hdr, &msg, rpc_ops, &task_setup_data, how);
dprintk("NFS: initiated pgio call "
--
2.9.5
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