On Wed, Jun 26, 2024 at 10:49:44AM -0400, Benjamin Coddington wrote:
> On 25 Jun 2024, at 16:02, cel@xxxxxxxxxx wrote:
>
> > From: Chuck Lever <chuck.lever@xxxxxxxxxx>
> >
> > During generic/069 runs with pNFS SCSI layouts, the NFS client emits
> > the following in the system journal:
> >
> > kernel: pNFS: failed to open device /dev/disk/by-id/dm-uuid-mpath-0x6001405e3366f045b7949eb8e4540b51 (-2)
> > kernel: pNFS: using block device sdb (reservation key 0x666b60901e7b26b3)
> > kernel: pNFS: failed to open device /dev/disk/by-id/dm-uuid-mpath-0x6001405e3366f045b7949eb8e4540b51 (-2)
> > kernel: pNFS: using block device sdb (reservation key 0x666b60901e7b26b3)
> > kernel: sd 6:0:0:1: reservation conflict
> > kernel: sd 6:0:0:1: [sdb] tag#16 FAILED Result: hostbyte=DID_OK driverbyte=DRIVER_OK cmd_age=0s
> > kernel: sd 6:0:0:1: [sdb] tag#16 CDB: Write(10) 2a 00 00 00 00 50 00 00 08 00
> > kernel: reservation conflict error, dev sdb, sector 80 op 0x1:(WRITE) flags 0x0 phys_seg 1 prio class 2
> > kernel: sd 6:0:0:1: reservation conflict
> > kernel: sd 6:0:0:1: reservation conflict
> > kernel: sd 6:0:0:1: [sdb] tag#18 FAILED Result: hostbyte=DID_OK driverbyte=DRIVER_OK cmd_age=0s
> > kernel: sd 6:0:0:1: [sdb] tag#17 FAILED Result: hostbyte=DID_OK driverbyte=DRIVER_OK cmd_age=0s
> > kernel: sd 6:0:0:1: [sdb] tag#18 CDB: Write(10) 2a 00 00 00 00 60 00 00 08 00
> > kernel: sd 6:0:0:1: [sdb] tag#17 CDB: Write(10) 2a 00 00 00 00 58 00 00 08 00
> > kernel: reservation conflict error, dev sdb, sector 96 op 0x1:(WRITE) flags 0x0 phys_seg 1 prio class 0
> > kernel: reservation conflict error, dev sdb, sector 88 op 0x1:(WRITE) flags 0x0 phys_seg 1 prio class 0
> > systemd[1]: fstests-generic-069.scope: Deactivated successfully.
> > systemd[1]: fstests-generic-069.scope: Consumed 5.092s CPU time.
> > systemd[1]: media-test.mount: Deactivated successfully.
> > systemd[1]: media-scratch.mount: Deactivated successfully.
> > kernel: sd 6:0:0:1: reservation conflict
> > kernel: failed to unregister PR key.
> >
> > This appears to be due to a race. bl_alloc_lseg() calls this:
> >
> > 561 static struct nfs4_deviceid_node *
> > 562 bl_find_get_deviceid(struct nfs_server *server,
> > 563 const struct nfs4_deviceid *id, const struct cred *cred,
> > 564 gfp_t gfp_mask)
> > 565 {
> > 566 struct nfs4_deviceid_node *node;
> > 567 unsigned long start, end;
> > 568
> > 569 retry:
> > 570 node = nfs4_find_get_deviceid(server, id, cred, gfp_mask);
> > 571 if (!node)
> > 572 return ERR_PTR(-ENODEV);
> >
> > nfs4_find_get_deviceid() does a lookup without the spin lock first.
> > If it can't find a matching deviceid, it creates a new device_info
> > (which calls bl_alloc_deviceid_node, and that registers the device's
> > PR key).
> >
> > Then it takes the nfs4_deviceid_lock and looks up the deviceid again.
> > If it finds it this time, bl_find_get_deviceid() frees the spare
> > (new) device_info, which unregisters the PR key for the same device.
> >
> > Any subsequent I/O from this client on that device gets EBADE.
> >
> > The umount later unregisters the device's PR key again.
> >
> > To prevent this problem, register the PR key after the deviceid_node
> > lookup.
> >
> > Signed-off-by: Christoph Hellwig <hch@xxxxxx>
> > Signed-off-by: Chuck Lever <chuck.lever@xxxxxxxxxx>
> > ---
> > fs/nfs/blocklayout/blocklayout.c | 25 +++++----
> > fs/nfs/blocklayout/blocklayout.h | 9 +++-
> > fs/nfs/blocklayout/dev.c | 91 ++++++++++++++++++++++++--------
> > 3 files changed, 94 insertions(+), 31 deletions(-)
> >
> > diff --git a/fs/nfs/blocklayout/blocklayout.c b/fs/nfs/blocklayout/blocklayout.c
> > index 6be13e0ec170..0becdec12970 100644
> > --- a/fs/nfs/blocklayout/blocklayout.c
> > +++ b/fs/nfs/blocklayout/blocklayout.c
> > @@ -564,25 +564,32 @@ bl_find_get_deviceid(struct nfs_server *server,
> > gfp_t gfp_mask)
> > {
> > struct nfs4_deviceid_node *node;
> > - unsigned long start, end;
> > + int err = -ENODEV;
>
> Just a nit - this err var seems unnecessary.. especially as still we do..
>
> > retry:
> > node = nfs4_find_get_deviceid(server, id, cred, gfp_mask);
> > if (!node)
> > return ERR_PTR(-ENODEV);
>
> .. this, which seems clearer. Looking at the return at the bottom makes me
> think 'err' could be something else, but it can't. Looks good to me
> otherwise.
@err used to carry the return from bl_register_dev(); in Christoph's
stand-alone patch, that was an int. I'll get rid of it.
> Reviewed-by: Benjamin Coddington <bcodding@xxxxxxxxxx>
Thanks for rechecking our work!
--
Chuck Lever
