On Wed, Dec 05, 2012 at 12:16:50AM +0800, qixuan wu wrote:

    Is there the possibility: one thread(A) is read_dir(directly read
from buffer head), and another thread(B) is creating item, and fill
this buffer header at the same time. During create item, first modify
the last item's rec_len(let it point to next item which initially is
zero), then fill this added new item.

This should be handled by the VFS, which uses i_mutex to protect
directories before calling the filesystem-specific lookup, rename,
readdir, etc functions.

So absent some bug where we are missing taking i_mutex (a quick check
didn't show any obvious missing paths, although I didn't do an
exhaustive code audit), we should be OK.... if we had a bug here, I
would have expected that one of the fs stress tests that we run would
have shown them up pretty quickly.

Regards,

						- Ted