xfs: add writable tracepoint for xfs file buffer read

hulk inclusion
category: feature
bugzilla: https://gitee.com/openeuler/kernel/issues/I3UHF8


CVE: NA

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This patch adds a new struct xfs_writable_file into file
uapi/include/linux/xfs.h and adds a tracepoint that can modify
struct xfs_writable_file. Then we can set file->f_mode in ebpf
program to control the file.

Signed-off-by: Yufen Yu <yuyufen@huawei.com>
Reviewed-by: Hou Tao <houtao1@huawei.com>
Signed-off-by: Yang Yingliang <yangyingliang@huawei.com>