Transparent State Migration copies a client's lease state from the server where a filesystem used to reside to the server where it now resides. When an NFSv4.1 client first contacts that destination server, it uses EXCHANGE_ID to detect trunking relationships. The lease that was copied there is returned to that client, but the destination server sets EXCHGID4_FLAG_CONFIRMED_R when replying to the client. This is because the lease was confirmed on the source server (before it was copied). Normally, when CONFIRMED_R is set, a client purges the lease and creates a new one. However, that throws away the entire benefit of Transparent State Migration. Therefore, the client must not purge that lease when it is possible that Transparent State Migration has occurred.
Showing the changes to include/linux (1 of 3 files). Show all
Unified · Split
| @@ -42,6 +42,7 @@ struct nfs_client { · 41 unmodified lines | ||
| 42 | 42 | #define NFS_CS_MIGRATION 2 /* - transparent state migr */ |
| 43 | 43 | #define NFS_CS_INFINITE_SLOTS 3 /* - don't limit TCP slots */ |
| 44 | 44 | #define NFS_CS_NO_RETRANS_TIMEOUT 4 /* - Disable retransmit timeouts */ |
| 45 | +#define NFS_CS_TSM_POSSIBLE 5 /* - Maybe state migration */ | |
| 45 | 46 | struct sockaddr_storage cl_addr; /* server identifier */ |
| 46 | 47 | size_t cl_addrlen; |
| 47 | 48 | char * cl_hostname; /* hostname of server */ |
| @@ -210,6 +211,7 @@ struct nfs_server { · 162 unmodified lines | ||
| 210 | 211 | unsigned long mig_status; |
| 211 | 212 | #define NFS_MIG_IN_TRANSITION (1) |
| 212 | 213 | #define NFS_MIG_FAILED (2) |
| 214 | +#define NFS_MIG_TSM_POSSIBLE (3) | |
| 213 | 215 | |
| 214 | 216 | void (*destroy)(struct nfs_server *); |
| 215 | 217 | |