From: Mingming Cao <cmm@us.ibm.com>
Subject: ext3_forget() and ext3_free_blocks()
Date: Thu, 01 Feb 2007 12:56:13 -0800
Message-ID: <1170363373.4271.44.camel@localhost.localdomain>
References: <20070201010836.31a63ef2.akpm@osdl.org>
Reply-To: cmm@us.ibm.com
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Cc: "linux-ext4@vger.kernel.org" <linux-ext4@vger.kernel.org>,
	Andreas Gruenbacher <agruen@suse.de>
To: Andrew Morton <akpm@osdl.org>
In-Reply-To: <20070201010836.31a63ef2.akpm@osdl.org>
Sender: linux-ext4-owner@vger.kernel.org

I am chasing a ext3 bug which double free the same xattr block from two
different inode. While I am looking at the code ext3_xattr_release_block
() I found ext3_free_block() is called before ext3_forget():

ext3_xattr_release_block(handle_t *handle, struct inode *inode,
                         struct buffer_head *bh)
{
        struct mb_cache_entry *ce = NULL;

        ce = mb_cache_entry_get(ext3_xattr_cache, bh->b_bdev, bh->b_blocknr);
        if (BHDR(bh)->h_refcount == cpu_to_le32(1)) {
                ea_bdebug(bh, "refcount now=0; freeing");
                if (ce)
                        mb_cache_entry_free(ce);
                ext3_free_blocks(handle, inode, bh->b_blocknr, 1);
                get_bh(bh);
                ext3_forget(handle, 1, inode, bh, bh->b_blocknr);
        } else {

Is this a potential problem? Looks like other places calling
ext3_free_block() it all has ext3_forget() called before that.

Though this seems not related to the double-free bug I see, as I
reversed the order and rerun the test, the bug still reproduced. But
just curious..


Thanks,
Mingming