linux-kernel - [PATCH 1/4 v2] NFS: slight optimization for walking list for delegations

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Message-ID: <871sdsv1o5.fsf@notabene.neil.brown.name>
Date:   Thu, 31 May 2018 15:23:22 +1000
From:   NeilBrown <neilb@...e.com>
To:     Trond Myklebust <trond.myklebust@...marydata.com>,
        Anna Schumaker <anna.schumaker@...app.com>,
        linux-nfs@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: [PATCH 1/4 v2] NFS: slight optimization for walking list for delegations


There are 3 places where we walk the list of delegations
for an nfs_client.
In each case there are two nested loops, one for nfs_servers
and one for nfs_delegations.

When we find an interesting delegation we try to get an active
reference to the server.  If that fails, it is pointless to
continue to look at the other delegation for the server as
we will never be able to get an active reference.
So instead of continuing in the inner loop, break out
and continue in the outer loop.

Signed-off-by: NeilBrown <neilb@...e.com>
---

This time with a Signed-off-by - sorry.
I took the opportunity to follow Steven's suggestion
of adding a comment to the new 'break' statements.

Thanks,
NeilBrown

 fs/nfs/delegation.c | 6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

diff --git a/fs/nfs/delegation.c b/fs/nfs/delegation.c
index 1819d0d0ba4b..b9cd3864335b 100644
--- a/fs/nfs/delegation.c
+++ b/fs/nfs/delegation.c
@@ -495,7 +495,7 @@ int nfs_client_return_marked_delegations(struct nfs_client *clp)
 			if (!nfs_delegation_need_return(delegation))
 				continue;
 			if (!nfs_sb_active(server->super))
-				continue;
+				break; /* continue in outer loop */
 			inode = nfs_delegation_grab_inode(delegation);
 			if (inode == NULL) {
 				rcu_read_unlock();
@@ -887,7 +887,7 @@ void nfs_delegation_reap_unclaimed(struct nfs_client *clp)
 						&delegation->flags) == 0)
 				continue;
 			if (!nfs_sb_active(server->super))
-				continue;
+				break; /* continue in outer loop */
 			inode = nfs_delegation_grab_inode(delegation);
 			if (inode == NULL) {
 				rcu_read_unlock();
@@ -995,7 +995,7 @@ void nfs_reap_expired_delegations(struct nfs_client *clp)
 						&delegation->flags) == 0)
 				continue;
 			if (!nfs_sb_active(server->super))
-				continue;
+				break; /* continue in outer loop */
 			inode = nfs_delegation_grab_inode(delegation);
 			if (inode == NULL) {
 				rcu_read_unlock();
-- 
2.14.0.rc0.dirty


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