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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 <sqazi@google.com>
Signed-off-by: "Theodore Ts'o" <tytso@mit.edu>
Cc: stable@kernel.org
This commit is contained in:
Salman Qazi 2012-05-31 23:52:14 -04:00 committed by Theodore Ts'o
parent 02b7831019
commit 95599968d1
1 changed files with 3 additions and 2 deletions
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5
fs/ext4/mballoc.c
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@ -2517,6 +2517,9 @@ 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);
@ -2564,8 +2567,6 @@ 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;
}