On Friday 26 January 2007 15:42, Jeff Layton wrote: > Kirill Korotaev wrote: > > Jeff, > > > > is 100% uniqeness is so much required for pipe inode numbers? > > AFAIU, it is not that critical for pipefs (unlike smb, nfs etc.) > > > > Thanks, > > Kirill > > There is no in-kernel reason why i_ino uniqueness is important for > pipefs. Where it might matter is userspace. The i_ino value is used for: > > 1) the st_ino value returned in stat calls > > 2) the dentry name (generated as "[inode_number]") > > So while it's certainly not "correct" to have multiple inodes with the same > number on any filesystem, it is probably more important in some places is > others. For pipefs, maybe it isn't, especially given a potential 6% > performance impact to fix it. Anyone else have thoughts? For dentry name, we certainly could use "[address of inode]" instead of "[inode number]" to get unicity, but do we care ? For st_ino values on pipefs and sockets, I doubt any user application would care. I never had to fstat() a socket fd. Of course it's a file descriptor, but all we really want to do with this kind of file descriptor is to call socket API. And for some heavy loaded internet servers , the additional cost of insert/delete a node in a machine shared tree could be a problem. Some weeks ago I suggested to not hash pipe/socket dentries in order to save some locked ops (see commits 304e61e6fbadec586dfe002b535f169a04248e49 & b3423415fbc2e5461605826317da1c8dbbf21f97 ), so obviously I prefer not adding another tree ops. However, pipe/sockets creation/destroy are probably not that frequent, so the 6% perf impact is not that big :) Eric - To unsubscribe from this list: send the line "unsubscribe linux-fsdevel" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
