[PATCH v4 7/7] smb: client: allow nolease option to be reconfigured on remount

[rajasimandalos]

From: Rajasi Mandal <rajasimandal@xxxxxxxxxxxxx>

Changing nolease via remount is silently accepted but has no effect:
the value is not propagated to the live tcons, and stale lease-bearing
state from before the switch keeps using the old behavior.

Make nolease take effect on remount:

 - Add smb3_sync_tcon_opts() which walks the tlink_tree under
   tlink_tree_lock and propagates ctx->no_lease to tcon->no_lease for
   every tcon under this superblock so future opens honor the new
   setting.  Call it from smb3_reconfigure() after the context has
   been updated.

 - On switch to nolease, drop deferred file handles via
   cifs_close_all_deferred_files_sb() (each holds an active lease).

 - On switch to nolease, evict cached directory fids via the new
   invalidate_all_cached_dirs_sb() helper (each holds a directory
   lease).

invalidate_all_cached_dirs_sb() mirrors cifs_close_all_deferred_files_sb():
take tc_count refs on every tcon under tlink_tree_lock, drop the lock,
then call invalidate_all_cached_dirs() per tcon (it can sleep).  Two
new tcon_ref trace tags are added for the audit trail.

Move tcon->no_lease out of the bitfield word into a plain bool.  As a
runtime writer it now shares storage with need_reconnect/need_reopen_files,
which the reconnect/reopen paths update locklessly; a bitfield write is a
read-modify-write of the whole word and could clobber a concurrent
need_reconnect update.  Its own memory location removes that race.

Existing open handles keep their leases until the server breaks them
or userspace closes the file -- nolease only governs new opens.

Signed-off-by: Rajasi Mandal <rajasimandal@xxxxxxxxxxxxx>
Reviewed-by: Bharath SM <bharathsm@xxxxxxxxxxxxx>
---
 fs/smb/client/cached_dir.c | 44 ++++++++++++++++++++++++++++++++++++++
 fs/smb/client/cached_dir.h |  1 +
 fs/smb/client/cifsglob.h   |  2 +-
 fs/smb/client/fs_context.c | 40 ++++++++++++++++++++++++++++++++++
 fs/smb/client/trace.h      |  2 ++
 5 files changed, 88 insertions(+), 1 deletion(-)

diff --git a/fs/smb/client/cached_dir.c b/fs/smb/client/cached_dir.c
index 88d5e9a32f28..58d68a8f4d41 100644
--- a/fs/smb/client/cached_dir.c
+++ b/fs/smb/client/cached_dir.c
@@ -637,6 +637,50 @@ void invalidate_all_cached_dirs(struct cifs_tcon *tcon, bool sync)
 		flush_delayed_work(&cfids->laundromat_work);
 }
 
+/*
+ * Invalidate cached directory entries across all tcons under a
+ * superblock.  Collect references on each tcon under tlink_tree_lock,
+ * then call invalidate_all_cached_dirs() outside the spinlock since it
+ * can sleep.  Holding a tc_count reference prevents the tcon from being
+ * freed by tlink_expire_delayed() between dropping the spinlock and
+ * the call.
+ */
+void invalidate_all_cached_dirs_sb(struct cifs_sb_info *cifs_sb)
+{
+	struct rb_root *root = &cifs_sb->tlink_tree;
+	struct rb_node *node;
+	struct cifs_tcon *tcon;
+	struct tcon_link *tlink;
+	struct tcon_list *tmp_list, *q;
+	LIST_HEAD(tcon_head);
+
+	spin_lock(&cifs_sb->tlink_tree_lock);
+	for (node = rb_first(root); node; node = rb_next(node)) {
+		tlink = rb_entry(node, struct tcon_link, tl_rbnode);
+		tcon = tlink_tcon(tlink);
+		if (IS_ERR(tcon))
+			continue;
+		tmp_list = kmalloc_obj(struct tcon_list, GFP_ATOMIC);
+		if (!tmp_list)
+			break;
+		tmp_list->tcon = tcon;
+		spin_lock(&tcon->tc_lock);
+		++tcon->tc_count;
+		trace_smb3_tcon_ref(tcon->debug_id, tcon->tc_count,
+				    netfs_trace_tcon_ref_get_cached_inval_sb);
+		spin_unlock(&tcon->tc_lock);
+		list_add_tail(&tmp_list->entry, &tcon_head);
+	}
+	spin_unlock(&cifs_sb->tlink_tree_lock);
+
+	list_for_each_entry_safe(tmp_list, q, &tcon_head, entry) {
+		invalidate_all_cached_dirs(tmp_list->tcon, true);
+		list_del(&tmp_list->entry);
+		cifs_put_tcon(tmp_list->tcon, netfs_trace_tcon_ref_put_cached_inval_sb);
+		kfree(tmp_list);
+	}
+}
+
 static void
 cached_dir_offload_close(struct work_struct *work)
 {
diff --git a/fs/smb/client/cached_dir.h b/fs/smb/client/cached_dir.h
index fc756836da95..606ba2a0b64f 100644
--- a/fs/smb/client/cached_dir.h
+++ b/fs/smb/client/cached_dir.h
@@ -90,6 +90,7 @@ void close_cached_dir(struct cached_fid *cfid);
 void drop_cached_dir_by_name(const unsigned int xid, struct cifs_tcon *tcon,
 			     const char *name, struct cifs_sb_info *cifs_sb);
 void close_all_cached_dirs(struct cifs_sb_info *cifs_sb);
+void invalidate_all_cached_dirs_sb(struct cifs_sb_info *cifs_sb);
 void invalidate_all_cached_dirs(struct cifs_tcon *tcon, bool sync);
 bool cached_dir_lease_break(struct cifs_tcon *tcon, __u8 lease_key[16]);
 
diff --git a/fs/smb/client/cifsglob.h b/fs/smb/client/cifsglob.h
index 38e27ba6d8f6..713ca152b0ea 100644
--- a/fs/smb/client/cifsglob.h
+++ b/fs/smb/client/cifsglob.h
@@ -1262,9 +1262,9 @@ struct cifs_tcon {
 	bool need_reopen_files:1; /* need to reopen tcon file handles */
 	bool use_resilient:1; /* use resilient instead of durable handles */
 	bool use_persistent:1; /* use persistent instead of durable handles */
-	bool no_lease:1;    /* Do not request leases on files or directories */
 	bool use_witness:1; /* use witness protocol */
 	bool dummy:1; /* dummy tcon used for reconnecting channels */
+	bool no_lease;    /* Do not request leases on files or directories */
 	__le32 capabilities;
 	__u32 share_flags;
 	__u32 maximal_access;
diff --git a/fs/smb/client/fs_context.c b/fs/smb/client/fs_context.c
index 0a72e1089ff7..53f986d8e9e0 100644
--- a/fs/smb/client/fs_context.c
+++ b/fs/smb/client/fs_context.c
@@ -35,6 +35,7 @@
 #include "nterr.h"
 #include "rfc1002pdu.h"
 #include "fs_context.h"
+#include "cached_dir.h"
 
 DEFINE_MUTEX(cifs_mount_mutex);
 
@@ -1287,6 +1288,43 @@ static void smb3_sync_ses_chan_max(struct cifs_ses *ses, size_t max_channels)
 	spin_unlock(&ses->chan_lock);
 }
 
+/*
+ * Propagate ctx->no_lease to every tcon under this superblock so future
+ * opens honor the new setting after a remount.  When switching to nolease,
+ * also drop deferred file handles and invalidate cached directory fids,
+ * since each holds an active lease from before the switch.
+ *
+ * Existing open handles keep their leases until the server breaks them
+ * or userspace closes the file -- nolease only governs new opens.
+ */
+static void smb3_sync_tcon_opts(struct cifs_sb_info *cifs_sb,
+				struct smb3_fs_context *ctx)
+{
+	struct tcon_link *tlink;
+	struct cifs_tcon *tcon;
+	struct rb_node *node;
+
+	spin_lock(&cifs_sb->tlink_tree_lock);
+	for (node = rb_first(&cifs_sb->tlink_tree); node; node = rb_next(node)) {
+		tlink = rb_entry(node, struct tcon_link, tl_rbnode);
+		tcon = tlink_tcon(tlink);
+		if (IS_ERR(tcon))
+			continue;
+		tcon->no_lease = ctx->no_lease;
+	}
+	spin_unlock(&cifs_sb->tlink_tree_lock);
+
+	/*
+	 * Both _sb() helpers iterate all tcons internally and handle
+	 * their own locking.  They can sleep, so they must be called
+	 * outside tlink_tree_lock.
+	 */
+	if (ctx->no_lease) {
+		cifs_close_all_deferred_files_sb(cifs_sb);
+		invalidate_all_cached_dirs_sb(cifs_sb);
+	}
+}
+
 /*
  * Synchronize server-level options that are stored on TCP_Server_Info
  * at mount time.  These fields are consulted at runtime (retry logic)
@@ -1483,6 +1521,8 @@ static int smb3_reconfigure(struct fs_context *fc)
 #endif
 	if (!rc)
 		smb3_sync_server_opts(cifs_sb);
+	if (!rc)
+		smb3_sync_tcon_opts(cifs_sb, cifs_sb->ctx);
 
 	return rc;
 
diff --git a/fs/smb/client/trace.h b/fs/smb/client/trace.h
index 5b21ad3c15fb..1e61a36759ed 100644
--- a/fs/smb/client/trace.h
+++ b/fs/smb/client/trace.h
@@ -173,6 +173,7 @@
 	EM(netfs_trace_tcon_ref_free_ipc,		"FRE Ipc   ") \
 	EM(netfs_trace_tcon_ref_free_ipc_fail,		"FRE Ipc-F ") \
 	EM(netfs_trace_tcon_ref_free_reconnect_server,	"FRE Reconn") \
+	EM(netfs_trace_tcon_ref_get_cached_inval_sb,	"GET Ch-IvS") \
 	EM(netfs_trace_tcon_ref_get_cached_laundromat,	"GET Ch-Lau") \
 	EM(netfs_trace_tcon_ref_get_cached_lease_break,	"GET Ch-Lea") \
 	EM(netfs_trace_tcon_ref_get_cancelled_close,	"GET Cn-Cls") \
@@ -186,6 +187,7 @@
 	EM(netfs_trace_tcon_ref_new_ipc,		"NEW Ipc   ") \
 	EM(netfs_trace_tcon_ref_new_reconnect_server,	"NEW Reconn") \
 	EM(netfs_trace_tcon_ref_put_cached_close,	"PUT Ch-Cls") \
+	EM(netfs_trace_tcon_ref_put_cached_inval_sb,	"PUT Ch-IvS") \
 	EM(netfs_trace_tcon_ref_put_cancelled_close,	"PUT Cn-Cls") \
 	EM(netfs_trace_tcon_ref_put_cancelled_close_fid, "PUT Cn-Fid") \
 	EM(netfs_trace_tcon_ref_put_cancelled_mid,	"PUT Cn-Mid") \
-- 
2.43.0