[LU-2370] ldiskfs / ext4 panic with accessing to mb_groups procfs file

• Type: Bug
• Resolution: Fixed
• Priority: Minor
• Fix Version/s: Lustre 2.4.0
• Labels: patch
• Environment: any ext4 based ldiskfs (may be ext3 based also)
• Severity: 3
• Assignee: WC Triage
• Reporter: Alexey Lyashkov

Description

fixed in valina kernel as
commit 95599968d19db175829fb580baa6b68939b320fb
Author: Salman Qazi <[e-mail]>
Date: Thu May 31 23:52:14 2012 -0400
ext4: remove mb_groups before tearing down the buddy_cache
We can't have references held on pages in the s_buddy_cache while we are
trying to truncate its pages and put the inode. All the pages must be
gone before we reach clear_inode. This can only be gauranteed if we
can prevent new users from grabbing references to s_buddy_cache's pages.
The original bug can be reproduced and the bug fix can be verified by:
while true; do mount -t ext4 /dev/ram0 /export/hda3/ram0; \
umount /export/hda3/ram0; done &
while true; do cat /proc/fs/ext4/ram0/mb_groups; done
Signed-off-by: Salman Qazi <[e-mail]>
Signed-off-by: "Theodore Ts'o" <[e-mail]>
Cc: [e-mail]