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From: Matthew Wilcox <willy@infradead.org>
To: Hugh Dickins <hughd@google.com>
Cc: Andrew Morton <akpm@linux-foundation.org>,
	linux-mm@kvack.org, linux-fsdevel@vger.kernel.org,
	linux-nvdimm@lists.01.org, linux-kernel@vger.kernel.org
Subject: Re: BUG_ON(!mapping_empty(&inode->i_data))
Date: Fri, 2 Apr 2021 14:27:08 +0100	[thread overview]
Message-ID: <20210402132708.GM351017@casper.infradead.org> (raw)
In-Reply-To: <20210402031305.GK351017@casper.infradead.org>

On Fri, Apr 02, 2021 at 04:13:05AM +0100, Matthew Wilcox wrote:
> +	for (;;) {
> +		xas_load(xas);
> +		if (!xas_is_node(xas))
> +			break;
> +		xas_delete_node(xas);
> +		xas->xa_index -= XA_CHUNK_SIZE;
> +		if (xas->xa_index < index)
> +			break;

That's a bug.  index can be 0, so the condition would never be true.
It should be:

		if (xas->xa_index <= (index | XA_CHUNK_MASK))
			break;
		xas->xa_index -= XA_CHUNK_SIZE;

The test doesn't notice this bug because the tree is otherwise empty,
and the !xas_is_node(xas) condition is hit first.  The next test will
notice this.
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  reply	other threads:[~2021-04-02 13:27 UTC|newest]

Thread overview: 11+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-03-31  1:30 BUG_ON(!mapping_empty(&inode->i_data)) Hugh Dickins
2021-03-31  2:49 ` BUG_ON(!mapping_empty(&inode->i_data)) Matthew Wilcox
2021-03-31 21:58   ` BUG_ON(!mapping_empty(&inode->i_data)) Hugh Dickins
2021-04-01 17:06     ` BUG_ON(!mapping_empty(&inode->i_data)) Matthew Wilcox
2021-04-02  3:13       ` BUG_ON(!mapping_empty(&inode->i_data)) Matthew Wilcox
2021-04-02 13:27         ` Matthew Wilcox [this message]
2021-04-02 17:04           ` BUG_ON(!mapping_empty(&inode->i_data)) Matthew Wilcox
2021-04-02 20:24             ` BUG_ON(!mapping_empty(&inode->i_data)) Hugh Dickins
2021-04-02 21:16               ` BUG_ON(!mapping_empty(&inode->i_data)) Hugh Dickins
2021-04-30  4:16                 ` BUG_ON(!mapping_empty(&inode->i_data)) Andrew Morton
2021-04-30  5:41                   ` BUG_ON(!mapping_empty(&inode->i_data)) Hugh Dickins

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