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Commit f49f9baa authored by Fred Isaman's avatar Fred Isaman Committed by Trond Myklebust
Browse files

pnfs: fix pnfs lock inversion of i_lock and cl_lock 



The pnfs code was using throughout the lock order i_lock, cl_lock.
This conflicts with the nfs delegation code.  Rework the pnfs code
to avoid taking both locks simultaneously.

Currently the code takes the double lock to add/remove the layout to a
nfs_client list, while atomically checking that the list of lsegs is
empty.  To avoid this, we rely on existing serializations.  When a
layout is initialized with lseg count equal zero, LAYOUTGET's
openstateid serialization is in effect, making it safe to assume it
stays zero unless we change it.  And once a layout's lseg count drops
to zero, it is set as DESTROYED and so will stay at zero.

Signed-off-by: default avatarFred Isaman <iisaman@netapp.com>
Signed-off-by: default avatarTrond Myklebust <Trond.Myklebust@netapp.com>
parent 9f52c252

fs/nfs/callback_proc.c

+1 −1
Original line number Diff line number Diff line
@@ -188,10 +188,10 @@ static u32 initiate_bulk_draining(struct nfs_client *clp, 
			rv = NFS4ERR_DELAY;

		list_del_init(&lo->plh_bulk_recall);

		spin_unlock(&ino->i_lock);

		pnfs_free_lseg_list(&free_me_list);

		put_layout_hdr(lo);

		iput(ino);

	}

	pnfs_free_lseg_list(&free_me_list);

	return rv;

}

fs/nfs/pnfs.c

+25 −17
Original line number Diff line number Diff line
@@ -247,13 +247,6 @@ put_lseg_locked(struct pnfs_layout_segment *lseg, 
		BUG_ON(test_bit(NFS_LSEG_VALID, &lseg->pls_flags));

		list_del(&lseg->pls_list);

		if (list_empty(&lseg->pls_layout->plh_segs)) {

			struct nfs_client *clp;



			clp = NFS_SERVER(ino)->nfs_client;

			spin_lock(&clp->cl_lock);

			/* List does not take a reference, so no need for put here */

			list_del_init(&lseg->pls_layout->plh_layouts);

			spin_unlock(&clp->cl_lock);

			set_bit(NFS_LAYOUT_DESTROYED, &lseg->pls_layout->plh_flags);

			/* Matched by initial refcount set in alloc_init_layout_hdr */

			put_layout_hdr_locked(lseg->pls_layout);
@@ -319,11 +312,27 @@ mark_matching_lsegs_invalid(struct pnfs_layout_hdr *lo, 
	return invalid - removed;

}



/* note free_me must contain lsegs from a single layout_hdr */

void

pnfs_free_lseg_list(struct list_head *free_me)

{

	struct pnfs_layout_segment *lseg, *tmp;

	struct pnfs_layout_hdr *lo;



	if (list_empty(free_me))

		return;



	lo = list_first_entry(free_me, struct pnfs_layout_segment,

			      pls_list)->pls_layout;



	if (test_bit(NFS_LAYOUT_DESTROYED, &lo->plh_flags)) {

		struct nfs_client *clp;



		clp = NFS_SERVER(lo->plh_inode)->nfs_client;

		spin_lock(&clp->cl_lock);

		list_del_init(&lo->plh_layouts);

		spin_unlock(&clp->cl_lock);

	}

	list_for_each_entry_safe(lseg, tmp, free_me, pls_list) {

		list_del(&lseg->pls_list);

		free_lseg(lseg);
@@ -705,6 +714,7 @@ pnfs_update_layout(struct inode *ino, 
	struct nfs_client *clp = NFS_SERVER(ino)->nfs_client;

	struct pnfs_layout_hdr *lo;

	struct pnfs_layout_segment *lseg = NULL;

	bool first = false;



	if (!pnfs_enabled_sb(NFS_SERVER(ino)))

		return NULL;
@@ -735,7 +745,10 @@ pnfs_update_layout(struct inode *ino, 
	atomic_inc(&lo->plh_outstanding);



	get_layout_hdr(lo);

	if (list_empty(&lo->plh_segs)) {

	if (list_empty(&lo->plh_segs))

		first = true;

	spin_unlock(&ino->i_lock);

	if (first) {

		/* The lo must be on the clp list if there is any

		 * chance of a CB_LAYOUTRECALL(FILE) coming in.

		 */
@@ -744,18 +757,13 @@ pnfs_update_layout(struct inode *ino, 
		list_add_tail(&lo->plh_layouts, &clp->cl_layouts);

		spin_unlock(&clp->cl_lock);

	}

	spin_unlock(&ino->i_lock);



	lseg = send_layoutget(lo, ctx, iomode);

	if (!lseg) {

		spin_lock(&ino->i_lock);

		if (list_empty(&lo->plh_segs)) {

	if (!lseg && first) {

		spin_lock(&clp->cl_lock);

		list_del_init(&lo->plh_layouts);

		spin_unlock(&clp->cl_lock);

	}

		spin_unlock(&ino->i_lock);

	}

	atomic_dec(&lo->plh_outstanding);

	put_layout_hdr(lo);

out: