On 02/12/2013 09:28 PM, J. Bruce Fields wrote: > 06effdbb49af5f6c "nfsd: vfs_llseek() with 32 or 64 bit offsets (hashes)" > and previous patches solved problems with hash collisions in large > directories by using 64- instead of 32- bit directory hashes in some > cases. But it caused problems for users who assume directory offsets > are "small". Two cases we've run across: > > - older NFS clients: 64-bit cookies cause applications on many > older clients to fail. > - gluster: gluster assumed that it could take the top bits of > the offset for its own use. > > In both cases we could argue we're in the right: the nfs protocol > defines cookies to be 64 bits, so clients should be prepared to handle > them (remapping to smaller integers if necessary to placate applications > using older system interfaces). And gluster was incorrect to assume > that the "offset" was really an "offset" as opposed to just an opaque > value. > > But in practice things that worked fine for a long time break on a > kernel upgrade. > > So at a minimum I think we owe people a workaround, and turning off > dir_index may not be practical for everyone. > > A "no_64bit_cookies" export option would provide a workaround for NFS > servers with older NFS clients, but not for applications like gluster. > > For that reason I'd rather have a way to turn this off on a given ext4 > filesystem. Is that practical? I think Ted needs to answer if he would accept another mount option. But before we are going this way, what is gluster doing if there are hash collions? Thanks, Bernd -- To unsubscribe from this list: send the line "unsubscribe linux-ext4" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
