I don't think it is so unusual to have a directory listing become out of
date.
This must happen frequently while one process is navigating the directory,
another can change entries in it.
The first process won't know anything about changes to the structure once
it has traversed that particular node. Why would this example be any
different ?
|---------+------------------------------------------->
| | Christian Magnusson |
| | <[EMAIL PROTECTED]|
| | m> |
| | Sent by: |
| | [EMAIL PROTECTED]|
| | ceforge.net |
| | |
| | |
| | 19/04/2005 12:50 |
| | Please respond to |
| | owfs-developers |
| | |
|---------+------------------------------------------->
>-------------------------------------------------------------------------------------------------------------|
|
|
| To: owfs-developers <owfs-developers@lists.sourceforge.net>
|
| cc:
|
| Subject: RE: [Owfs-developers] OWFS and FUSE Debugging with UML
(UserMode Linux) |
>-------------------------------------------------------------------------------------------------------------|
On Tue, 2005-04-19 at 09:31 +0100, [EMAIL PROTECTED] wrote:
> What is the expected value of st_nlink - should it include the number of
> dirs in sub-dirs as well.
> That doesn't sound right to me.
>
yes... It should be like that. Temp-sensor 10.xxxxxxxxxx/. should have
st_nlink=2 since there are no directories in that sensor.
DS1991 02.xxxxxxxxxxx/. should have st_nlink=4 since there are two
directories. (/settings and /pages)
> Once a directory is enumerated, the number of sub-dirs is known and
> contained in a linked list.
> Iterating that list to count the sub-dirs should be trivial.
>
The problem is the root directories on each server like /bus.0/bus.0/.
It could contain:
/bus.0/bus.0/. st_nlink = 7 + xxxx
/bus.0/bus.0/..
/bus.0/bus.0/settings/
/bus.0/bus.0/statistics/
/bus.0/bus.0/structure/
/bus.0/bus.0/system/
/bus.0/bus.0/uncached/
+ some devices
/bus.0/bus.0/10.0000000000/
+ eventually some more directories
/bus.0/bus.0/bus.0/
/bus.0/bus.0/bus.1/
/bus.0/bus.0/bus.2/
/bus.0/bus.0/alarm/
/bus.0/bus.0/simultaneous/
This means that fstat("/bus.0/bus.0/.") have to make a complete
list of the remote server before returning the correct st_nlink,
or perhaps return the number of directories saved in the cache.
If you run 'ls /bus.0/bus.0' it's usually implemented as
while ((entry = readdir(dir)) != NULL) {
if(!(cur = my_fstat(fullname, strrchr(fullname, '/') + 1))) continue;
add_file_to_list(cur);
}
closedir(dir);
print_all_files_in_list();
It makes a fstat() after each entry, and it's hard to know the result
of fstat('/bus.0/bus.0/.') before the whole directory is read once
at least.
I'm sure it will be fixed soon, but I haven't come up to a fool-proof
solution for it that works for many simultaneous readdir() calls. I
think fstat() might return wrong value if new devices (or alarm)
are detected on the second call to readdir().
/Christian
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