smb: client: Update IO sizes after reconnection

When a SMB connection is reset and reconnected, the negotiated IO
parameters (rsize/wsize) can become out of sync with the server's
current capabilities. This can lead to suboptimal performance or
even IO failures if the server's limits have changed.

This patch implements automatic IO size renegotiation:
1. Adds cifs_renegotiate_iosize() function to update all superblocks
   associated with a tree connection
2. Updates each mount's rsize/wsize based on current server capabilities
3. Calls this function after successful tree connection reconnection

With this change, all mount points will automatically maintain optimal
and reliable IO parameters after network disruptions, using the
bidirectional mapping added in previous patches.

This completes the series improving connection resilience by keeping
mount parameters synchronized with server capabilities.

Signed-off-by: Wang Zhaolong <wangzhaolong1@huawei.com>
Signed-off-by: Steve French <stfrench@microsoft.com>

Author: Wang Zhaolong

fs/smb/client/smb2pdu.c

@@ -43,6 +43,7 @@
 #endif
 #include "cached_dir.h"
 #include "compress.h"
+#include "fs_context.h"
 
 /*
  *  The following table defines the expected "StructureSize" of SMB2 requests
@@ -4089,6 +4090,24 @@ smb2_echo_callback(struct mid_q_entry *mid)
 	add_credits(server, &credits, CIFS_ECHO_OP);
 }
 
+static void cifs_renegotiate_iosize(struct TCP_Server_Info *server,
+				    struct cifs_tcon *tcon)
+{
+	struct cifs_sb_info *cifs_sb;
+
+	if (server == NULL || tcon == NULL)
+		return;
+
+	spin_lock(&tcon->sb_list_lock);
+	list_for_each_entry(cifs_sb, &tcon->cifs_sb_list, tcon_sb_link) {
+		cifs_sb->ctx->rsize =
+			server->ops->negotiate_rsize(tcon, cifs_sb->ctx);
+		cifs_sb->ctx->wsize =
+			server->ops->negotiate_wsize(tcon, cifs_sb->ctx);
+	}
+	spin_unlock(&tcon->sb_list_lock);
+}
+
 void smb2_reconnect_server(struct work_struct *work)
 {
 	struct TCP_Server_Info *server = container_of(work,
@@ -4174,9 +4193,10 @@ void smb2_reconnect_server(struct work_struct *work)
 
 	list_for_each_entry_safe(tcon, tcon2, &tmp_list, rlist) {
 		rc = smb2_reconnect(SMB2_INTERNAL_CMD, tcon, server, true);
-		if (!rc)
+		if (!rc) {
+			cifs_renegotiate_iosize(server, tcon);
 			cifs_reopen_persistent_handles(tcon);
-		else
+		} else
 			resched = true;
 		list_del_init(&tcon->rlist);
 		if (tcon->ipc)