[for-6.13 PATCH 19/19] nfs: probe for LOCALIO when v3 client reconnects to server

Mike Snitzer
2024-11-08T23:40:29Z

Re-enabling NFSv3 LOCALIO is made more complex (than NFSv4) because v3
is stateless. As such, the hueristic used to identify a LOCALIO probe
point is more adhoc by nature: if/when NFSv3 client IO begins to
complete again in terms of normal RPC-based NFSv3 server IO, attempt
nfs_local_probe_async().

Care is taken to throttle the frequency of nfs_local_probe_async(),
otherwise there could be a flood of repeat calls to
nfs_local_probe_async().

Signed-off-by: Mike Snitzer <snitzer@kernel.org>
---
fs/nfs/internal.h | 5 +++++
fs/nfs/localio.c | 11 +++++++++++
fs/nfs/nfs3proc.c | 34 +++++++++++++++++++++++++++++++---
fs/nfs_common/nfslocalio.c | 4 ++++
include/linux/nfs_fs_sb.h | 1 +
include/linux/nfslocalio.h | 4 +++-
6 files changed, 55 insertions(+), 4 deletions(-)

diff --git a/fs/nfs/internal.h b/fs/nfs/internal.h
index efd42efd9405..fb1ab7cee6b9 100644
--- a/fs/nfs/internal.h
+++ b/fs/nfs/internal.h
@@ -470,6 +470,7 @@ extern int nfs_local_commit(struct nfsd_file *,
struct nfs_commit_data *,
const struct rpc_call_ops *, int);
extern bool nfs_server_is_local(const struct nfs_client *clp);
+extern bool nfs_server_was_local(const struct nfs_client *clp);

#else /* CONFIG_NFS_LOCALIO */
static inline void nfs_local_disable(struct nfs_client *clp) {}
@@ -499,6 +500,10 @@ static inline bool nfs_server_is_local(const struct nfs_client *clp)
{
return false;
}
+static inline bool nfs_server_was_local(const struct nfs_client *clp)
+{
+ return false;
+}
#endif /* CONFIG_NFS_LOCALIO */

/* super.c */
diff --git a/fs/nfs/localio.c b/fs/nfs/localio.c
index 710e537b3402..1559dc2f1850 100644
--- a/fs/nfs/localio.c
+++ b/fs/nfs/localio.c
@@ -64,6 +64,17 @@ bool nfs_server_is_local(const struct nfs_client *clp)
}
EXPORT_SYMBOL_GPL(nfs_server_is_local);

+static inline bool nfs_client_was_local(const struct nfs_client *clp)
+{
+ return !!test_bit(NFS_CS_LOCAL_IO_CAPABLE, &clp->cl_flags);
+}
+
+bool nfs_server_was_local(const struct nfs_client *clp)
+{
+ return nfs_client_was_local(clp) && localio_enabled;
+}
+EXPORT_SYMBOL_GPL(nfs_server_was_local);
+
/*
* UUID_IS_LOCAL XDR functions
*/
diff --git a/fs/nfs/nfs3proc.c b/fs/nfs/nfs3proc.c
index 1566163c6d85..4d2018760e9b 100644
--- a/fs/nfs/nfs3proc.c
+++ b/fs/nfs/nfs3proc.c
@@ -844,6 +844,29 @@ nfs3_proc_pathconf(struct nfs_server *server, struct nfs_fh *fhandle,
return status;
}

+static void nfs3_local_probe(struct nfs_server *server)
+{
+#if IS_ENABLED(CONFIG_NFS_LOCALIO)
+ struct nfs_client *clp = server->nfs_client;
+ nfs_uuid_t *nfs_uuid = &clp->cl_uuid;
+
+ if (likely(!nfs_server_was_local(clp)))
+ return;
+ /*
+ * Try re-enabling LOCALIO if it was previously enabled, but
+ * was disabled due to server restart, and IO has successfully
+ * completed in terms of normal RPC.
+ */
+ mutex_lock(&nfs_uuid->local_probe_mutex);
+ /* Arbitrary throttle to reduce nfs_local_probe_async() frequency */
+ if ((nfs_uuid->local_probe_count++ & 255) == 0) {
+ if (unlikely(!nfs_server_is_local(clp) && nfs_server_was_local(clp)))
+ nfs_local_probe_async(clp);
+ }
+ mutex_unlock(&nfs_uuid->local_probe_mutex);
+#endif
+}
+
static int nfs3_read_done(struct rpc_task *task, struct nfs_pgio_header *hdr)
{
struct inode *inode = hdr->inode;
@@ -855,8 +878,11 @@ static int nfs3_read_done(struct rpc_task *task, struct nfs_pgio_header *hdr)
if (nfs3_async_handle_jukebox(task, inode))
return -EAGAIN;

- if (task->tk_status >= 0 && !server->read_hdrsize)
- cmpxchg(&server->read_hdrsize, 0, hdr->res.replen);
+ if (task->tk_status >= 0) {
+ if (!server->read_hdrsize)
+ cmpxchg(&server->read_hdrsize, 0, hdr->res.replen);
+ nfs3_local_probe(server);
+ }

nfs_invalidate_atime(inode);
nfs_refresh_inode(inode, &hdr->fattr);
@@ -886,8 +912,10 @@ static int nfs3_write_done(struct rpc_task *task, struct nfs_pgio_header *hdr)

if (nfs3_async_handle_jukebox(task, inode))
return -EAGAIN;
- if (task->tk_status >= 0)
+ if (task->tk_status >= 0) {
nfs_writeback_update_inode(hdr);
+ nfs3_local_probe(NFS_SERVER(inode));
+ }
return 0;
}

diff --git a/fs/nfs_common/nfslocalio.c b/fs/nfs_common/nfslocalio.c
index fb376d38ac9a..852ba8fd73f3 100644
--- a/fs/nfs_common/nfslocalio.c
+++ b/fs/nfs_common/nfslocalio.c
@@ -43,6 +43,8 @@ void nfs_uuid_init(nfs_uuid_t *nfs_uuid)
INIT_LIST_HEAD(&nfs_uuid->list);
INIT_LIST_HEAD(&nfs_uuid->files);
spin_lock_init(&nfs_uuid->lock);
+ mutex_init(&nfs_uuid->local_probe_mutex);
+ nfs_uuid->local_probe_count = 0;
}
EXPORT_SYMBOL_GPL(nfs_uuid_init);

@@ -143,6 +145,8 @@ void nfs_localio_enable_client(struct nfs_client *clp)

spin_lock(&nfs_uuid->lock);
set_bit(NFS_CS_LOCAL_IO, &clp->cl_flags);
+ /* Also set hint that client and server are LOCALIO capable */
+ set_bit(NFS_CS_LOCAL_IO_CAPABLE, &clp->cl_flags);
trace_nfs_localio_enable_client(clp);
spin_unlock(&nfs_uuid->lock);
}
diff --git a/include/linux/nfs_fs_sb.h b/include/linux/nfs_fs_sb.h
index 63d7e0f478d8..45906c402c98 100644
--- a/include/linux/nfs_fs_sb.h
+++ b/include/linux/nfs_fs_sb.h
@@ -51,6 +51,7 @@ struct nfs_client {
#define NFS_CS_REUSEPORT 8 /* - reuse src port on reconnect */
#define NFS_CS_PNFS 9 /* - Server used for pnfs */
#define NFS_CS_LOCAL_IO 10 /* - client is local */
+#define NFS_CS_LOCAL_IO_CAPABLE 11 /* - client was previously local */
struct sockaddr_storage cl_addr; /* server identifier */
size_t cl_addrlen;
char * cl_hostname; /* hostname of server */
diff --git a/include/linux/nfslocalio.h b/include/linux/nfslocalio.h
index c68a529230c1..3dfef0bb18fe 100644
--- a/include/linux/nfslocalio.h
+++ b/include/linux/nfslocalio.h
@@ -27,7 +27,9 @@ struct nfs_file_localio;
*/
typedef struct {
uuid_t uuid;
- /* sadly this struct is just over a cacheline, avoid bouncing */
+ struct mutex local_probe_mutex;
+ unsigned local_probe_count;
+ /* sadly this struct is over a cacheline, avoid bouncing */
spinlock_t ____cacheline_aligned lock;
struct list_head list;
spinlock_t *list_lock; /* nn->local_clients_lock */
--
2.44.0