Patch "pNFS: Fix a deadlock between read resends and layoutreturn" has been added to the 4.9-stable tree

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

pNFS: Fix a deadlock between read resends and layoutreturn

to the 4.9-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

The filename of the patch is:
pnfs-fix-a-deadlock-between-read-resends-and-layoutreturn.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 <[email protected]> know about it.

From: Trond Myklebust <[email protected]>
Date: Sun, 27 Nov 2016 15:12:39 -0500
Subject: pNFS: Fix a deadlock between read resends and layoutreturn

From: Trond Myklebust <[email protected]>

commit 54e4a0dfa25d9365c4e80a639e80d9213eb6edbe upstream.

We must not call nfs_pageio_init_read() on a new nfs_pageio_descriptor while holding a reference to a layout segment, as that can deadlock pnfs_update_layout().

---
 fs/nfs/flexfilelayout/flexfilelayout.c |    4 ++++
 fs/nfs/pnfs.c                          |    4 ++++
 2 files changed, 8 insertions(+)

@@ -28,6 +28,9 @@
 
 static struct group_info	*ff_zero_group;
 
+static void ff_layout_read_record_layoutstats_done(struct rpc_task *task,
+		struct nfs_pgio_header *hdr);
+
 static struct pnfs_layout_hdr *
 ff_layout_alloc_layout_hdr(struct inode *inode, gfp_t gfp_flags)
 {

@@ -1293,6 +1296,7 @@ static int ff_layout_read_done_cb(struct
 					hdr->pgio_mirror_idx + 1,
 					&hdr->pgio_mirror_idx))
 			goto out_eagain;
+		ff_layout_read_record_layoutstats_done(task, hdr);
 		pnfs_read_resend_pnfs(hdr);
 		return task->tk_status;
 	case -NFS4ERR_RESET_TO_MDS:

@@ -2293,6 +2293,10 @@ void pnfs_read_resend_pnfs(struct nfs_pg
 	struct nfs_pageio_descriptor pgio;
 
 	if (!test_and_set_bit(NFS_IOHDR_REDO, &hdr->flags)) {
+		/* Prevent deadlocks with layoutreturn! */
+		pnfs_put_lseg(hdr->lseg);
+		hdr->lseg = NULL;
+
 		nfs_pageio_init_read(&pgio, hdr->inode, false,
 					hdr->completion_ops);
 		hdr->task.tk_status = nfs_pageio_resend(&pgio, hdr);

Patches currently in stable-queue which might be from [email protected] are

queue-4.9/pnfs-fix-a-deadlock-between-read-resends-and-layoutreturn.patch queue-4.9/pnfs-don-t-clear-the-layout-stateid-if-a-layout-return-is-outstanding.patch queue-4.9/sunrpc-fix-refcounting-problems-with-auth_gss-messages.patch queue-4.9/pnfs-on-error-do-not-send-layoutget-until-the-layoutreturn-has-completed.patch queue-4.9/pnfs-clear-nfs_layout_return_requested-when-invalidating-the-layout-stateid.patch