Commit 95599968 authored May 31, 2012 by Salman Qazi Committed by Theodore Ts'o May 31, 2012

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

parent 02b78310

fs/ext4/mballoc.c

+3 −2

Original line number	Diff line number	Diff line
		@@ -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;
		}

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