On Wed, 2007-04-11 at 08:33 +1000, Neil Brown wrote: > A READDIR (aka getdents2) should take a directory handle, a cookie, > and a filename, and should return filenames and cookies. The > cookies may all be identical or may not. The filename might be used > by the filesystem, or it might not. > > Filesystems that require a cursor in the 'struct file' to support > (local) getdents cannot be used with NFS. > > While it doesn't make it possible to support all conceivable > filesystems, it should make it easier for some filesystems to support > the demands of NFS.
In order to be useful, I think you need to add a demand that the READDIR call cannot loop back on itself for the case of a series of sequential reads. IOW: if a client attempts to step sequentially through the directory, and is supplying valid filenames+cookies from the preceding READDIR call, then the next READDIR call should be guaranteed never to loop back to an earlier entry. Alternatively, if there is a danger that it might due to some sudden and radical change in the directory layout, then it should notify the client by returning something like a BAD_COOKIE error. Otherwise, the client would have to cache _all_ previous READDIR results since the last opendir()/rewinddir() in order to be able to do its own loop detection and that will obviously never scale for large directories or for directories that change frequently... Cheers Trond - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [EMAIL PROTECTED] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
