From: Salman Qazi Date: Fri, 1 Jun 2012 03:52:14 +0000 (-0400) Subject: ext4: remove mb_groups before tearing down the buddy_cache X-Git-Tag: v3.0.34~5 X-Git-Url: http://git.ipfire.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=32e090b1f4bdfe9756e1b8f0b5280acb036d1c61;p=people%2Fms%2Flinux.git ext4: remove mb_groups before tearing down the buddy_cache commit 95599968d19db175829fb580baa6b68939b320fb upstream. 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 Signed-off-by: "Theodore Ts'o" Signed-off-by: Greg Kroah-Hartman --- diff --git a/fs/ext4/mballoc.c b/fs/ext4/mballoc.c index e3d557569970..b6adf68a5c02 100644 --- a/fs/ext4/mballoc.c +++ b/fs/ext4/mballoc.c @@ -2528,6 +2528,9 @@ int ext4_mb_release(struct super_block *sb) struct ext4_sb_info *sbi = EXT4_SB(sb); struct kmem_cache *cachep = get_groupinfo_cache(sb->s_blocksize_bits); + if (sbi->s_proc) + remove_proc_entry("mb_groups", sbi->s_proc); + if (sbi->s_group_info) { for (i = 0; i < ngroups; i++) { grinfo = ext4_get_group_info(sb, i); @@ -2575,8 +2578,6 @@ int ext4_mb_release(struct super_block *sb) } free_percpu(sbi->s_locality_groups); - if (sbi->s_proc) - remove_proc_entry("mb_groups", sbi->s_proc); return 0; }