On 2013/2/19 20:59, Jan Kara wrote: > On Tue 19-02-13 19:47:30, Li Zefan wrote: >> On 2013/2/19 17:19, Jan Kara wrote: >>> On Tue 19-02-13 09:22:40, Li Zefan wrote: >>>> There's a long long-standing bug...As long as I don't know when it dates >>>> from. >>>> >>>> I've written and attached a simple program to reproduce this bug, and it can >>>> immediately trigger the bug in my box. It uses two threads, one keeps calling >>>> read(), and the other calling readdir(), both on the same directory fd. >>> So the fact that read() or even write() to fd opened O_RDONLY has *any* >>> effect on f_pos looks really unexpected to me. I think we really should >>> have there: >>> if (ret >= 0) >>> file_pos_write(...); >> >> I thought about this. The problem is then we have to check every fop->write() >> to see if any of them can return -errno with file->f_pos changed and fix them, >> though it's do-able. > But returning error and advancing f_pos would be a bug - specification > says write() returns the number of bytes written or -1 and f_pos should be > advanced by the number of bytes written. > Oh, I had an illusion that vfs saves f_pos and calls write() and restore f_pos if write() fails. -- To unsubscribe from this list: send the line "unsubscribe linux-ext4" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
