PHP fails to start sessions – disk corrupted

In my Linux server, I can't login to my PHP application having an issue related to PHP sessions:

PHP Error Logs:

[Sat May 21 21:27:50 2011] [error] [client ] PHP Warning:  Unknown: open(/tmp/sess_8lh0d15nu33p5r659ge35spn13, O_RDWR) failed: Invalid argument (22) in Unknown on line 0
[Sat May 21 21:27:50 2011] [error] [client ] PHP Warning:  Unknown: Failed to write session data (files). Please verify that the current setting of session.save_path is correct () in Unknown on line 0

Kernel Logs:

May 21 03:55:35 server1 kernel: EXT4-fs error (device dm-0): ext4_mb_generate_buddy: EXT4-fs: group 32: 6059 blocks in bitmap, 6057 in gd
May 21 03:55:40 server1 kernel: JBD: Spotted dirty metadata buffer (dev = dm-0, blocknr = 0). There's a risk of filesystem corruption in case of system crash.
May 21 03:55:40 server1 kernel: JBD: Spotted dirty metadata buffer (dev = dm-0, blocknr = 0). There's a risk of filesystem corruption in case of system crash.
May 21 04:15:01 server1 pcscd: winscard.c:309:SCardConnect() Reader E-Gate 0 0 Not Found
May 21 04:15:01 server1 pcscd: winscard.c:309:SCardConnect() Reader E-Gate 0 0 Not Found
May 21 04:15:01 server1 pcscd: winscard.c:309:SCardConnect() Reader E-Gate 0 0 Not Found
May 21 04:15:01 server1 pcscd: winscard.c:309:SCardConnect() Reader E-Gate 0 0 Not Found
May 21 05:15:02 server1 pcscd: winscard.c:309:SCardConnect() Reader E-Gate 0 0 Not Found
May 21 05:15:02 server1 pcscd: winscard.c:309:SCardConnect() Reader E-Gate 0 0 Not Found
May 21 05:15:02 server1 pcscd: winscard.c:309:SCardConnect() Reader E-Gate 0 0 Not Found
May 21 05:15:02 server1 pcscd: winscard.c:309:SCardConnect() Reader E-Gate 0 0 Not Found
May 21 08:56:14 server1 auditd[1114]: Audit daemon rotating log files
May 21 09:00:30 server1 kernel: EXT4-fs error (device dm-0): ext4_mb_generate_buddy: EXT4-fs: group 420: 7487 blocks in bitmap, 3391 in gd
May 21 09:00:30 server1 kernel: JBD: Spotted dirty metadata buffer (dev = dm-0, blocknr = 0). There's a risk of filesystem corruption in case of system crash.
May 21 09:01:50 server1 kernel: pa dbc9d240: logic 16384, phys. 19312640, len 2048

May 21 09:01:58 server1 kernel: EXT4-fs error (device dm-0): mb_free_blocks: double-free of inode 0's block 19313904(bit 13552 in group 589)
May 21 20:28:02 server1 kernel: EXT4-fs error (device dm-0): ext4_mb_generate_buddy: EXT4-fs: group 390: 5661 blocks in bitmap, 3613 in gd
May 21 20:28:02 server1 kernel: EXT4-fs error (device dm-0): ext4_mb_generate_buddy: EXT4-fs: group 586: 3179 blocks in bitmap, 1131 in gd
May 21 20:37:30 server1 kernel: EXT4-fs error (device dm-0): ext4_mb_generate_buddy: EXT4-fs: group 345: 10181 blocks in bitmap, 7621 in gd

Everything was fine, no changes done in the server or application lately. I thought the tmp folder is corrupted and tried to change php session.save_path to other writable dir, but it did not help.

Thanks in advance for any help or direction.