Regression caused by commit 4bdc33ed("NFSDv4.2: Add NFS v4.2 support to the NFS server")

[Jongman Heo]

Hi all,

My embedded development box fails to NFS-boot with NFS server which uses recent kernel.

Using git bisect, I found it is caused by commit 4bdc33ed ("NFSDv4.2: Add NFS v4.2 support to the NFS server").


1. dmesg (NFS boot failure case)

...
[    2.040893] ADDRCONF(NETDEV_UP): eth0: link is not ready
[    2.046207] e1000: eth0 NIC Link is Up 1000 Mbps Full Duplex, Flow Control: RX
[    2.053570] ADDRCONF(NETDEV_CHANGE): eth0: link becomes ready
[    3.055023] IP-Config: Guessing netmask 255.255.0.0
[    3.059979] IP-Config: Gateway not on directly connected network.
[    3.066330] Looking up port of RPC 100003/2 on 165.213.88.249
[    3.074001] Looking up port of RPC 100005/1 on 165.213.88.249
[    3.122878] VFS: Unable to mount root fs via NFS, trying floppy.
[    3.129134] VFS: Cannot open root device "nfs" or unknown-block(2,0)
[    3.135478] Please append a correct "root=" boot option; here are the available partitions:
[    3.143831] 1f00            3072 mtdblock0 (driver?)
[    3.148798] 1f01              64 mtdblock1 (driver?)
[    3.153758] 1f02              64 mtdblock2 (driver?)
[    3.158719] 1f03              64 mtdblock3 (driver?)
[    3.163682] 1f04              64 mtdblock4 (driver?)
[    3.168644] 1f05              64 mtdblock5 (driver?)
[    3.173607] 1f06              64 mtdblock6 (driver?)
[    3.178568] 0800       488386584 sda driver: sd
[    3.183099]   0801          506016 sda1
[    3.186927]   0802         4008217 sda2
[    3.190755]   0803       483869767 sda3
[    3.194584] b300         1880064 mmcblk0 driver: mmcblk
[    3.199802]   b301            4096 mmcblk0p1
[    3.204063]   b302          102400 mmcblk0p2
[    3.208330]   b303            4096 mmcblk0p3
[    3.212594]   b304               1 mmcblk0p4
[    3.216855]   b305            2048 mmcblk0p5
[    3.221116]   b306            2048 mmcblk0p6
[    3.225382]   b307            2048 mmcblk0p7
[    3.229644]   b308            4096 mmcblk0p8
[    3.233906]   b309           12288 mmcblk0p9
[    3.238176]   b30a           16384 mmcblk0p10
[    3.242524]   b30b          142336 mmcblk0p11
[    3.246869]   b30c         1572864 mmcblk0p12
[    3.251219] b320           12288 mmcblk0gp1 (driver?)
[    3.256272] b310           12288 mmcblk0gp0 (driver?)
[    3.261320] Kernel panic - not syncing: VFS: Unable to mount root fs on unknown-block(2,0)
[    3.269566] Pid: 1, comm: swapper Not tainted 2.6.35 #1
[    3.274776] Call Trace:
[    3.277232]  [<80d0db5b>] ? printk+0x1e/0x20
[    3.281492]  [<80d0dad1>] panic+0x65/0xd1
[    3.285495]  [<80eb9ce3>] mount_block_root+0x125/0x1be
[    3.290631]  [<809d1f6d>] ? sys_mknod+0x2d/0x30
[    3.295156]  [<80eb9f6d>] mount_root+0xd0/0xf2
[    3.299591]  [<80eba0d9>] prepare_namespace+0x14a/0x184
[    3.304803]  [<809c44f6>] ? sys_access+0x26/0x30
[    3.309411]  [<80eb9a4e>] kernel_init+0x25e/0x26e
[    3.314105]  [<80eb97f0>] ? kernel_init+0x0/0x26e
[    3.318800]  [<80903242>] kernel_thread_helper+0x6/0x10


2. Client (my embedded box) configuration
  It's kernel 2.6.35 based, and has following NFS kernel configs.

# grep NFS .config
CONFIG_NFS_FS=y
CONFIG_NFS_V3=y
CONFIG_NFS_V3_ACL=y
CONFIG_NFS_V4=y
# CONFIG_NFS_V4_1 is not set
CONFIG_ROOT_NFS=y
# CONFIG_NFSD is not set
CONFIG_NFS_ACL_SUPPORT=y
CONFIG_NFS_COMMON=y


3. Server (NFSD) configuration
   Fedora 19 + latest linus git kernel 3.12.0-rc2+ (commit 22356f44, mm: Place preemption point in do_mlockall() loop)


4. workaround

Reverting the commit 4bdc33ed resolves my issue, NFS boot is working then.
I've done git bisect, but lost the resulting bisect log due to sudden power loss :(.

Best regards,
Jongman Heo
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