nfs/blocklayout: Fix premature PR key unregistration

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@lst.de>
Signed-off-by: Chuck Lever <chuck.lever@oracle.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Benjamin Coddington <bcodding@redhat.com>
Signed-off-by: Anna Schumaker <Anna.Schumaker@Netapp.com>

1 files changed, 8 insertions, 1 deletions

diff --git a/fs/nfs/blocklayout/blocklayout.h b/fs/nfs/blocklayout/blocklayout.h
index f1eeb4914199..6da40ca19570 100644
--- a/fs/nfs/blocklayout/blocklayout.h
+++ b/fs/nfs/blocklayout/blocklayout.h
@@ -104,20 +104,26 @@ struct pnfs_block_dev {
 	u64				start;
 	u64				len;
 
+	enum pnfs_block_volume_type	type;
 	u32				nr_children;
 	struct pnfs_block_dev		*children;
 	u64				chunk_size;
 
 	struct file			*bdev_file;
 	u64				disk_offset;
+	unsigned long			flags;
 
 	u64				pr_key;
-	bool				pr_registered;
 
 	bool (*map)(struct pnfs_block_dev *dev, u64 offset,
 			struct pnfs_block_dev_map *map);
 };
 
+/* pnfs_block_dev flag bits */
+enum {
+	PNFS_BDEV_REGISTERED = 0,
+};
+
 /* sector_t fields are all in 512-byte sectors */
 struct pnfs_block_extent {
 	union {
@@ -172,6 +178,7 @@ struct bl_msg_hdr {
 #define BL_DEVICE_REQUEST_ERR          0x2 /* User level process fails */
 
 /* dev.c */
+bool bl_register_dev(struct pnfs_block_dev *d);
 struct nfs4_deviceid_node *bl_alloc_deviceid_node(struct nfs_server *server,
 		struct pnfs_device *pdev, gfp_t gfp_mask);
 void bl_free_deviceid_node(struct nfs4_deviceid_node *d);