On Fri, Dec 13, 2013 at 08:32:56PM +0100, Sander Klein wrote: > On , J. Bruce Fields wrote: > >>>I think what happens is that exportfs flushes the kernel's export cache > >>>at which point every use of an uncached export triggers an upcall to > >>>mountd. That upcall is probably visible in the strace as a read of a > >>>file descriptor associated with /proc/net/sunrpc/nfsd.fh/content. > >>> > >>>That upcall is handled by nfs-utils/utils/mountd/cache.c:nfsd_fh(), > >>>which is given a filehandle fragment identifying the filesystem in > >>>question and has to match it to an export. > >>> > >>>That's done by match_fsid(). Which does do a stat of the export path, > >>>but not of all the devices.... That's probably happening in one of the > >>>libblkid calls in uuid_by_path()? I wonder if there's something wrong > >>>with libblkid configuration or with the way we're using it? > >> > >>Is there any way I can help getting this fixed? My coding skills are > >>limited but I am very willing to help in any way I can. > > > >I wonder if ltrace could help determine if libblkid is where most of > >those stat's are coming from (and if so, which calls)? > > > >May also be worth reading up on libblkid (man libblkid, etc.) and > >checking your configuration to make sure there's nothing obvious broken > >there. (If so, maybe the libblkid commandline tools would exhibit the > >same problem?) > > I didn't have any config in /etc/blkid.conf and the manpage says it > will use EVALUATE=udev,scan which in fact scans through all the > /dev/disk/by-* dirs and parses the /proc/partitions. I put > 'EVALUATE=scan' in /etc/blkid.conf but that doesn't help. I > restarted anything NFS related... > > I also attached ltrace to the rpc.mountd process. The output of the > trace is at http://pastebin.com/ika1Vetq . I'm not sure what I'm > looking for. The ltrace is done on a server with only 10 harddisks > but the strace showed the same behavour of newfstatat-ing every disk > in a lot of ways. Hm. I *think* that those SYS_262's are the newfstatat's. And it looks like they happen as part of the implementation of blkid_devno_to_devname (just because you see that call start above the SYS_262's and return only after). That is indeed called from utils/mountd/cache.c:get_uuid_blkdev(). So libblkid is mapping device numbers to paths by stat'ing lots of stuff under /dev. I'm not sure what to do about that.... Cc'ing util-linux in case they can help. --b. -- To unsubscribe from this list: send the line "unsubscribe linux-nfs" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
