This is a note to let you know that I've just added the patch titled

nfs/pnfs: fix nfs_direct_req ref leak when i/o falls back to the mds

to the 4.9-stable tree which can be found at: http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git%3Ba=su...

The filename of the patch is: nfs-pnfs-fix-nfs_direct_req-ref-leak-when-i-o-falls-back-to-the-mds.patch and it can be found in the queue-4.9 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree, please let stable@vger.kernel.org know about it.

From ba4a76f703ab7eb72941fdaac848502073d6e9ee Mon Sep 17 00:00:00 2001

From: Scott Mayhew smayhew@redhat.com Date: Fri, 15 Dec 2017 16:12:32 -0500 Subject: nfs/pnfs: fix nfs_direct_req ref leak when i/o falls back to the mds

From: Scott Mayhew smayhew@redhat.com

commit ba4a76f703ab7eb72941fdaac848502073d6e9ee upstream.

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.

Ensure that pnfs_read_through_mds() and pnfs_write_through_mds() clean up correctly by calling hdr->completion_ops->completion() instead of calling hdr->release() directly.

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@redhat.com):

stap -v -g -e 'probe module("nfs_layout_nfsv41_files").function("nfs4_fl_prepare_ds").return { $return=NULL; exit(); }'

Suggested-by: Trond Myklebust trond.myklebust@primarydata.com Signed-off-by: Scott Mayhew smayhew@redhat.com Fixes: 1ca018d28d ("pNFS: Fix a memory leak when attempted pnfs fails") Signed-off-by: Trond Myklebust trond.myklebust@primarydata.com Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org

--- fs/nfs/pnfs.c | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-)

--- a/fs/nfs/pnfs.c +++ b/fs/nfs/pnfs.c @@ -2145,7 +2145,7 @@ pnfs_write_through_mds(struct nfs_pageio nfs_pageio_reset_write_mds(desc); mirror->pg_recoalesce = 1; } - hdr->release(hdr); + hdr->completion_ops->completion(hdr); }

static enum pnfs_try_status @@ -2256,7 +2256,7 @@ pnfs_read_through_mds(struct nfs_pageio_ nfs_pageio_reset_read_mds(desc); mirror->pg_recoalesce = 1; } - hdr->release(hdr); + hdr->completion_ops->completion(hdr); }

/*

Patches currently in stable-queue which might be from smayhew@redhat.com are

queue-4.9/nfs-pnfs-fix-nfs_direct_req-ref-leak-when-i-o-falls-back-to-the-mds.patch