smb: client: fix data loss due to broken rename(2)

Rename of open files in SMB2+ has been broken for a very long time,
resulting in data loss as the CIFS client would fail the rename(2)
call with -ENOENT and then removing the target file.

Fix this by implementing ->rename_pending_delete() for SMB2+, which
will rename busy files to random filenames (e.g. silly rename) during
unlink(2) or rename(2), and then marking them to delete-on-close.

Besides, introduce a FIND_WR_NO_PENDING_DELETE flag to prevent open(2)
from reusing open handles that had been marked as delete pending.
Handle it in cifs_get_readable_path() as well.

Reported-by: Jean-Baptiste Denis <[email protected]>
Closes: https://marc.info/[email protected]
Reviewed-by: David Howells <[email protected]>
Cc: [email protected]
Signed-off-by: Paulo Alcantara (Red Hat) <[email protected]>
Cc: Frank Sorenson <[email protected]>
Cc: Olga Kornievskaia <[email protected]>
Cc: Benjamin Coddington <[email protected]>
Cc: Scott Mayhew <[email protected]>
Cc: [email protected]
Signed-off-by: Steve French <[email protected]>

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