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authorChuck Lever <chuck.lever@oracle.com>2011-12-05 15:40:30 -0500
committerTrond Myklebust <Trond.Myklebust@netapp.com>2012-01-05 10:42:39 -0500
commit43717c7daebf10b43f12e68512484b3095bb1ba5 (patch)
tree0c3465ca158dc0d582a8645edfb6d16377afdf5f /init/do_mounts.c
parent68c97153fb7f2877f98aa6c29546381d9cad2fed (diff)
downloadlinux-aarch64-43717c7daebf10b43f12e68512484b3095bb1ba5.tar.gz
NFS: Retry mounting NFSROOT
Lukas Razik <linux@razik.name> reports that on his SPARC system, booting with an NFS root file system stopped working after commit 56463e50 "NFS: Use super.c for NFSROOT mount option parsing." We found that the network switch to which Lukas' client was attached was delaying access to the LAN after the client's NIC driver reported that its link was up. The delay was longer than the timeouts used in the NFS client during mounting. NFSROOT worked for Lukas before commit 56463e50 because in those kernels, the client's first operation was an rpcbind request to determine which port the NFS server was listening on. When that request failed after a long timeout, the client simply selected the default NFS port (2049). By that time the switch was allowing access to the LAN, and the mount succeeded. Neither of these client behaviors is desirable, so reverting 56463e50 is really not a choice. Instead, introduce a mechanism that retries the NFSROOT mount request several times. This is the same tactic that normal user space NFS mounts employ to overcome server and network delays. Signed-off-by: Lukas Razik <linux@razik.name> [ cel: match kernel coding style, add proper patch description ] [ cel: add exponential back-off ] Signed-off-by: Chuck Lever <chuck.lever@oracle.com> Tested-by: Lukas Razik <linux@razik.name> Cc: stable@kernel.org # > 2.6.38 Signed-off-by: Trond Myklebust <Trond.Myklebust@netapp.com>
Diffstat (limited to 'init/do_mounts.c')
-rw-r--r--init/do_mounts.c35
1 files changed, 31 insertions, 4 deletions
diff --git a/init/do_mounts.c b/init/do_mounts.c
index 0f6e1d985a3b..db6e5ee0e1db 100644
--- a/init/do_mounts.c
+++ b/init/do_mounts.c
@@ -398,15 +398,42 @@ out:
}
#ifdef CONFIG_ROOT_NFS
+
+#define NFSROOT_TIMEOUT_MIN 5
+#define NFSROOT_TIMEOUT_MAX 30
+#define NFSROOT_RETRY_MAX 5
+
static int __init mount_nfs_root(void)
{
char *root_dev, *root_data;
+ unsigned int timeout;
+ int try, err;
- if (nfs_root_data(&root_dev, &root_data) != 0)
- return 0;
- if (do_mount_root(root_dev, "nfs", root_mountflags, root_data) != 0)
+ err = nfs_root_data(&root_dev, &root_data);
+ if (err != 0)
return 0;
- return 1;
+
+ /*
+ * The server or network may not be ready, so try several
+ * times. Stop after a few tries in case the client wants
+ * to fall back to other boot methods.
+ */
+ timeout = NFSROOT_TIMEOUT_MIN;
+ for (try = 1; ; try++) {
+ err = do_mount_root(root_dev, "nfs",
+ root_mountflags, root_data);
+ if (err == 0)
+ return 1;
+ if (try > NFSROOT_RETRY_MAX)
+ break;
+
+ /* Wait, in case the server refused us immediately */
+ ssleep(timeout);
+ timeout <<= 1;
+ if (timeout > NFSROOT_TIMEOUT_MAX)
+ timeout = NFSROOT_TIMEOUT_MAX;
+ }
+ return 0;
}
#endif