linux-ext4 - Re: [PATCH] ext4: Fix delalloc sync hang with journal lock inversion

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Date:	Thu, 22 May 2008 15:55:48 +0530
From:	"Aneesh Kumar K.V" <aneesh.kumar@...ux.vnet.ibm.com>
To:	cmm@...ibm.com
Cc:	linux-ext4@...r.kernel.org, tytso@....edu, sandeen@...hat.com
Subject: Re: [PATCH] ext4: Fix delalloc sync hang with journal lock
	inversion

On Wed, May 21, 2008 at 11:14:17PM +0530, Aneesh Kumar K.V wrote:
> Signed-off-by: Aneesh Kumar K.V <aneesh.kumar@...ux.vnet.ibm.com>
> ---
>  fs/ext4/inode.c |   10 +++++++---
>  1 files changed, 7 insertions(+), 3 deletions(-)
> 
> diff --git a/fs/ext4/inode.c b/fs/ext4/inode.c
> index 46cc610..076d00f 100644
> --- a/fs/ext4/inode.c
> +++ b/fs/ext4/inode.c
> @@ -1571,13 +1571,17 @@ static int ext4_da_writepages(struct address_space *mapping,
>  		 */
>  		if (wbc->nr_to_write > EXT4_MAX_WRITEBACK_PAGES)
>  			wbc->nr_to_write = EXT4_MAX_WRITEBACK_PAGES;
> -		to_write -= wbc->nr_to_write;
> 
> +		to_write -= wbc->nr_to_write;
>  		ret = mpage_da_writepages(mapping, wbc, ext4_da_get_block_write);
>  		ext4_journal_stop(handle);
> -		to_write +=wbc->nr_to_write;
> +		if (wbc->nr_to_write) {
> +			/* We failed to write what we requested for */
> +			to_write += wbc->nr_to_write;
> +			break;
> +		}
> +		wbc->nr_to_write = to_write;
>  	}
> -
>  out_writepages:
>  	wbc->nr_to_write = to_write;
>  	wbc->range_cyclic = range_cyclic;

We need related fix for ext4_da_writepage. We need to allocate blocks in
ext4_da_writepage and we are called with page_lock. The handle
will be NULL in the below case and that would result in
ext4_get_block starting a new transaction when allocating blocks.


static int __ext4_da_writepage(struct page *page,
				struct writeback_control *wbc)
{
	struct inode *inode = page->mapping->host;
	handle_t *handle = NULL;
	int ret = 0;

	handle = ext4_journal_current_handle();

	if (test_opt(inode->i_sb, NOBH) && ext4_should_writeback_data(inode))
		ret = nobh_writepage(page, ext4_get_block, wbc);
	else
		ret = block_write_full_page(page, ext4_get_block, wbc);

	if (!ret && inode->i_size > EXT4_I(inode)->i_disksize) {
		EXT4_I(inode)->i_disksize = inode->i_size;
		ext4_mark_inode_dirty(handle, inode);
	}

	return ret;
}

-aneesh
--
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