Messages in this thread | | | Date | Thu, 22 Feb 2007 15:50:03 -0500 | From | Peter Staubach <> | Subject | Re: [PATCH] update ctime and mtime for mmaped write |
| |
Miklos Szeredi wrote: >>> Take this example: >>> >>> fd = open() >>> addr = mmap(.., fd) >>> write(fd, ...) >>> close(fd) >>> sleep(100) >>> msync(addr,...) >>> munmap(addr) >>> >>> The file times will be updated in write(), but with your patch, the >>> bit in the mapping will also be set. >>> >>> Then in msync() the file times will be updated again, which is wrong, >>> since the memory was _not_ modified through the mapping. >>> >> This is correct. I have updated my proposed patch to include the clearing >> of AS_MCTIME in the routine which updates the mtime field. >> > > That doesn't really help. Look at __generic_file_aio_write_nolock(). > file_update_time() is called before the data is written, so after the > last write, there will be nothing to clear the flag. > > And even if fixed this case by moving the file_update_time() call to > the end of the function, there's no guarantee, that some filesystem > won't do something exotic and call set_page_dirty() indenpendently of > write(). Good luck auditing all the set_page_dirty() calls ;)
Interesting.
No, I wouldn't want to get into worrying about set_page_dirty() calls. Life is short and people have too much imagination... :-)
Thanx...
ps
- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
| |