[PATCH 3/3] pnfs-submit: remove list_empty check from put_layout

[Fred Isaman <iisaman@xxxxxxxxxx>]

The check on list empty before destroying a layout has always bothered me.
Get rid of it by having lsegs take a reference on their backpointer.

Signed-off-by: Fred Isaman <iisaman@xxxxxxxxxx>
---
 fs/nfs/pnfs.c |   51 +++++++++++++++++++++++++++++----------------------
 1 files changed, 29 insertions(+), 22 deletions(-)

diff --git a/fs/nfs/pnfs.c b/fs/nfs/pnfs.c
index 49093a0..9a295cf 100644
--- a/fs/nfs/pnfs.c
+++ b/fs/nfs/pnfs.c
@@ -60,6 +60,7 @@ static int pnfs_initialized;
 static void pnfs_free_layout(struct pnfs_layout_type *lo,
 			     struct nfs4_pnfs_layout_segment *range);
 static enum pnfs_try_status pnfs_commit(struct nfs_write_data *data, int sync);
+static inline void get_layout(struct pnfs_layout_type *lo);
 
 /* Locking:
  *
@@ -335,25 +336,18 @@ grab_current_layout(struct nfs_inode *nfsi)
 static inline void
 put_layout(struct pnfs_layout_type *lo)
 {
-	struct inode *inode = PNFS_INODE(lo);
-	struct nfs_client *clp;
-
 	BUG_ON_UNLOCKED_LO(lo);
 	BUG_ON(lo->refcount <= 0);
 
-	if (--lo->refcount == 0 && list_empty(&lo->segs)) {
+	lo->refcount--;
+	if (!lo->refcount) {
 		struct layoutdriver_io_operations *io_ops =
 			PNFS_LD_IO_OPS(lo);
 
 		dprintk("%s: freeing layout %p\n", __func__, lo->ld_data);
+		WARN_ON(!list_empty(&lo->lo_layouts));
 		io_ops->free_layout(lo->ld_data);
 		lo->ld_data = NULL;
-
-		/* Unlist the layout. */
-		clp = NFS_SERVER(inode)->nfs_client;
-		spin_lock(&clp->cl_lock);
-		list_del_init(&lo->lo_layouts);
-		spin_unlock(&clp->cl_lock);
 	}
 }
 
@@ -397,6 +391,7 @@ init_lseg(struct pnfs_layout_type *lo, struct pnfs_layout_segment *lseg)
 	kref_init(&lseg->kref);
 	lseg->valid = true;
 	lseg->layout = lo;
+	get_layout(lo);
 }
 
 static void
@@ -406,6 +401,7 @@ destroy_lseg(struct kref *kref)
 		container_of(kref, struct pnfs_layout_segment, kref);
 
 	dprintk("--> %s\n", __func__);
+	put_layout(lseg->layout);
 	PNFS_LD_IO_OPS(lseg->layout)->free_lseg(lseg);
 }
 
@@ -670,6 +666,15 @@ pnfs_free_layout(struct pnfs_layout_type *lo,
 		list_del(&lseg->fi_list);
 		put_lseg_locked(lseg);
 	}
+	if (list_empty(&lo->segs)) {
+		struct nfs_client *clp;
+
+		clp = PNFS_NFS_SERVER(lo)->nfs_client;
+		spin_lock(&clp->cl_lock);
+		list_del_init(&lo->lo_layouts);
+		spin_unlock(&clp->cl_lock);
+		put_layout(lo);
+	}
 
 	dprintk("%s:Return\n", __func__);
 }
@@ -854,6 +859,15 @@ pnfs_insert_layout(struct pnfs_layout_type *lo,
 	dprintk("%s:Begin\n", __func__);
 
 	BUG_ON_UNLOCKED_LO(lo);
+	if (list_empty(&lo->segs)) {
+		struct nfs_client *clp = PNFS_NFS_SERVER(lo)->nfs_client;
+
+		spin_lock(&clp->cl_lock);
+		BUG_ON(!list_empty(&lo->lo_layouts));
+		list_add_tail(&lo->lo_layouts, &clp->cl_layouts);
+		spin_unlock(&clp->cl_lock);
+		get_layout(lo);
+	}
 	list_for_each_entry (lp, &lo->segs, fi_list) {
 		if (cmp_layout(&lp->range, &lseg->range) > 0)
 			continue;
@@ -896,11 +910,13 @@ alloc_init_layout(struct inode *ino)
 		return NULL;
 	}
 
+	spin_lock(&ino->i_lock);
 	BUG_ON(lo->ld_data != NULL);
 	lo->ld_data = ld_data;
 	memset(&lo->stateid, 0, NFS4_STATEID_SIZE);
 	lo->refcount = 1;
 	lo->roc_iomode = 0;
+	spin_unlock(&ino->i_lock);
 	return lo;
 }
 
@@ -951,17 +967,9 @@ get_lock_alloc_layout(struct inode *ino)
 		}
 
 		lo = alloc_init_layout(ino);
-		if (lo) {
-			struct nfs_client *clp = NFS_SERVER(ino)->nfs_client;
-
-			/* must grab the layout lock before the client lock */
+		if (lo)
 			spin_lock(&ino->i_lock);
-
-			spin_lock(&clp->cl_lock);
-			if (list_empty(&lo->lo_layouts))
-				list_add_tail(&lo->lo_layouts, &clp->cl_layouts);
-			spin_unlock(&clp->cl_lock);
-		} else
+		else
 			lo = ERR_PTR(-ENOMEM);
 
 		/* release the NFS_INO_LAYOUT_ALLOC bit and wake up waiters */
@@ -1247,14 +1255,13 @@ pnfs_layout_process(struct nfs4_pnfs_layoutget *lgp)
 		goto out;
 	}
 
+	spin_lock(&ino->i_lock);
 	init_lseg(lo, lseg);
 	lseg->range = res->lseg;
 	if (lgp->lsegpp) {
 		get_lseg(lseg);
 		*lgp->lsegpp = lseg;
 	}
-
-	spin_lock(&ino->i_lock);
 	pnfs_insert_layout(lo, lseg);
 
 	if (res->return_on_close) {
-- 
1.6.6.1

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