From: Eric Sandeen Subject: [PATCH] fix ext4_free_inode vs. ext4_claim_inode race Date: Tue, 03 Mar 2009 22:38:41 -0600 Message-ID: <49AE05D1.9050607@redhat.com> Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit Cc: "Aneesh Kumar K.V" To: ext4 development Return-path: Received: from mx2.redhat.com ([66.187.237.31]:37459 "EHLO mx2.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752185AbZCDEis (ORCPT ); Tue, 3 Mar 2009 23:38:48 -0500 Sender: linux-ext4-owner@vger.kernel.org List-ID: I was seeing fsck errors on inode bitmaps after a 4 thread dbench run on a 4 cpu machine: Inode bitmap differences: -50736 -(50752--50753) etc... I believe that this is because ext4_free_inode() uses atomic bitops, and although ext4_new_inode() *used* to also use atomic bitops for synchronization, commit 393418676a7602e1d7d3f6e560159c65c8cbd50e changed this to use the sb_bgl_lock, so that we could also synchronize against read_inode_bitmap and initialization of uninit inode tables. However, that change left ext4_free_inode using atomic bitops, which I think leaves no synchronization between setting & unsetting bits in the inode table. The below patch fixes it for me, although I wonder if we're getting at all heavy-handed with this spinlock... Signed-off-by: Eric Sandeen --- Index: linux-2.6/fs/ext4/ialloc.c =================================================================== --- linux-2.6.orig/fs/ext4/ialloc.c +++ linux-2.6/fs/ext4/ialloc.c @@ -188,7 +188,7 @@ void ext4_free_inode(handle_t *handle, s struct ext4_group_desc *gdp; struct ext4_super_block *es; struct ext4_sb_info *sbi; - int fatal = 0, err, count; + int fatal = 0, err, count, cleared; ext4_group_t flex_group; if (atomic_read(&inode->i_count) > 1) { @@ -248,8 +248,10 @@ void ext4_free_inode(handle_t *handle, s goto error_return; /* Ok, now we can actually update the inode bitmaps.. */ - if (!ext4_clear_bit_atomic(sb_bgl_lock(sbi, block_group), - bit, bitmap_bh->b_data)) + spin_lock(sb_bgl_lock(sbi, block_group)); + cleared = ext4_clear_bit(bit, bitmap_bh->b_data); + spin_unlock(sb_bgl_lock(sbi, block_group)); + if (!cleared) ext4_error(sb, "ext4_free_inode", "bit already cleared for inode %lu", ino); else {