Re: FTS not ready for a remount during traversal

[Jim Meyering]

Kamil Dudka wrote:
> On Thu October 22 2009 16:42:48 Jim Meyering wrote:
>> Have you measured the performance penalty it incurs?
>> I hope it is possible to do the same thing, but with less of a penalty.
>>
>> I'm afraid we'll have to do something like that one way or
>> another.  At best, the impact will be so small that we won't
>> even have to provide a new "flag" to enable it.
...
> There is no measurable performance penalty, assuming you have more files than
> directories in the tree (which is IMO the common use case). I am attaching
> also a filtered strace output showing the cost of the second stat call:
>
> # strace -rve trace=openat,newfstatat -o trace.raw du -sh /var
> # grep -A1 -B1 openat trace.raw | lzma -c > trace.lzma

Hi Kamil,

Sorry about the delay.
I'm trying to reconcile this file system's behavior with
fundamental assumptions about unchanging device/inode,
and as a result am having second thoughts.

What event causes the directory's stat.st_dev to change?
Opening the directory?  Calling readdir?  Accessing one
of its entries?

Can you describe how to reproduce the problem on rawhide or Fedora 12?

Jim