[PATCH 5/9] smb/client: retry change notify after invalid cached handle

[ChenXiaoSong <chenxiaosong@chenxiaosong.com>]

From: ChenXiaoSong <chenxiaosong@kylinos.cn>

The notify ioctl caches a separate FID in cifsFileInfo. That
handle is not reopened by cifs_reopen_file(), so it can become
stale across reconnects. If the server returns STATUS_INVALID_HANDLE
for the cached FID, SMB2_change_notify() maps it to -EBADF, but
smb3_notify() kept reusing the bad handle.

Invalidate the cached notify FID on -EBADF and retry once so the
next attempt opens a fresh handle. Clear only if the cached FID
still matches the failed one to avoid racing with another thread
that reopened it.

Signed-off-by: ChenXiaoSong <chenxiaosong@kylinos.cn>
---
 fs/smb/client/smb2ops.c | 36 ++++++++++++++++++++++++++++++++++--
 1 file changed, 34 insertions(+), 2 deletions(-)

diff --git a/fs/smb/client/smb2ops.c b/fs/smb/client/smb2ops.c
index d6a33acc62ff..9c2455b5fb03 100644
--- a/fs/smb/client/smb2ops.c
+++ b/fs/smb/client/smb2ops.c
@@ -2365,7 +2365,21 @@ smb3_enum_snapshots(const unsigned int xid, struct cifs_tcon *tcon,
 	return rc;
 }
 
-
+static void
+smb3_notify_invalidate_fid(struct cifsFileInfo *cfile,
+			   const struct cifs_fid *fid)
+{
+	mutex_lock(&cfile->notify_fid_mutex);
+	if (cfile->has_notify_fid &&
+	    cfile->notify_fid.persistent_fid == fid->persistent_fid &&
+	    cfile->notify_fid.volatile_fid == fid->volatile_fid) {
+		cfile->has_notify_fid = false;
+		memset(&cfile->notify_fid, 0, sizeof(cfile->notify_fid));
+		cifs_put_tlink(cfile->notify_tlink);
+		cfile->notify_tlink = NULL;
+	}
+	mutex_unlock(&cfile->notify_fid_mutex);
+}
 
 static int
 smb3_notify(const unsigned int xid, struct file *pfile,
@@ -2388,6 +2402,7 @@ smb3_notify(const unsigned int xid, struct file *pfile,
 	u8 oplock = SMB2_OPLOCK_LEVEL_NONE;
 	int rc = 0;
 	__u32 ret_len = 0;
+	bool retry = false;
 
 	if (return_changes) {
 		if (copy_from_user(&notify, ioc_buf, sizeof(struct smb3_notify_info))) {
@@ -2418,6 +2433,7 @@ smb3_notify(const unsigned int xid, struct file *pfile,
 		cfile = pfile->private_data;
 	}
 
+retry_notify:
 	mutex_lock(&cfile->notify_fid_mutex);
 	if (!cfile->has_notify_fid) {
 		page = alloc_dentry_path();
@@ -2468,7 +2484,23 @@ smb3_notify(const unsigned int xid, struct file *pfile,
 	rc = SMB2_change_notify(xid, tcon, fid.persistent_fid, fid.volatile_fid,
 				notify.watch_tree, notify.completion_filter,
 				notify.data_len, &returned_ioctl_info, &ret_len);
-
+	if (rc == -EBADF) {
+		smb3_notify_invalidate_fid(cfile, &fid);
+		if (retry)
+			goto notify_done;
+
+		kfree(returned_ioctl_info);
+		returned_ioctl_info = NULL;
+		free_dentry_path(page);
+		page = NULL;
+		kfree(utf16_path);
+		utf16_path = NULL;
+		ret_len = 0;
+		retry = true;
+		goto retry_notify;
+	}
+
+notify_done:
 	cifs_dbg(FYI, "change notify for %pd rc %d\n", dentry, rc);
 	if (return_changes && (ret_len > 0) && (notify.data_len > 0)) {
 		if (ret_len > notify.data_len)
-- 
2.54.0