[Cluster-devel] [PATCH] GFS2: fix block allocation check for fallocate

[Steven Whitehouse]

Hi,

On Fri, 2011-03-11 at 00:49 -0600, Benjamin Marzinski wrote:
> GFS2 fallocate wasn't properly checking if a blocks were already allocated.
> In write_empty_blocks(), if a page didn't have buffer_heads attached, GFS2
> was always treating it as if there were no blocks allocated for that page.
> GFS2 now calls gfs2_block_map() to check if the blocks are allocated before
> writing them out.
> 
> Signed-off-by: Benjamin Marzinski <bmarzins at redhat.com>
> ---
>  fs/gfs2/file.c |   56 +++++++++++++++++++++++++++++++-------------------------
>  1 file changed, 31 insertions(+), 25 deletions(-)
> 
Thanks for the patch. Now in the -nmw git tree,

Steve.

> Index: gfs2-2.6-nmw/fs/gfs2/file.c
> ===================================================================
> --- gfs2-2.6-nmw.orig/fs/gfs2/file.c
> +++ gfs2-2.6-nmw/fs/gfs2/file.c
> @@ -622,8 +622,7 @@ static void empty_write_end(struct page 
>  {
>  	struct gfs2_inode *ip = GFS2_I(page->mapping->host);
>  
> -	page_zero_new_buffers(page, from, to);
> -	flush_dcache_page(page);
> +	zero_user(page, from, to-from);
>  	mark_page_accessed(page);
>  
>  	if (!gfs2_is_writeback(ip))
> @@ -632,36 +631,43 @@ static void empty_write_end(struct page 
>  	block_commit_write(page, from, to);
>  }
>  
> -static int write_empty_blocks(struct page *page, unsigned from, unsigned to)
> +static int needs_empty_write(sector_t block, struct inode *inode)
>  {
> -	unsigned start, end, next;
> -	struct buffer_head *bh, *head;
>  	int error;
> +	struct buffer_head bh_map = { .b_state = 0, .b_blocknr = 0 };
>  
> -	if (!page_has_buffers(page)) {
> -		error = __block_write_begin(page, from, to - from, gfs2_block_map);
> -		if (unlikely(error))
> -			return error;
> +	bh_map.b_size = 1 << inode->i_blkbits;
> +	error = gfs2_block_map(inode, block, &bh_map, 0);
> +	if (unlikely(error))
> +		return error;
> +	return !buffer_mapped(&bh_map);
> +}
>  
> -		empty_write_end(page, from, to);
> -		return 0;
> -	}
> +static int write_empty_blocks(struct page *page, unsigned from, unsigned to)
> +{
> +	struct inode *inode = page->mapping->host;
> +	unsigned start, end, next, blksize;
> +	sector_t block = page->index << (PAGE_CACHE_SHIFT - inode->i_blkbits);
> +	int ret;
>  
> -	bh = head = page_buffers(page);
> +	blksize = 1 << inode->i_blkbits;
>  	next = end = 0;
>  	while (next < from) {
> -		next += bh->b_size;
> -		bh = bh->b_this_page;
> +		next += blksize;
> +		block++;
>  	}
>  	start = next;
>  	do {
> -		next += bh->b_size;
> -		if (buffer_mapped(bh)) {
> +		next += blksize;
> +		ret = needs_empty_write(block, inode);
> +		if (unlikely(ret < 0))
> +			return ret;
> +		if (ret == 0) {
>  			if (end) {
> -				error = __block_write_begin(page, start, end - start,
> -							    gfs2_block_map);
> -				if (unlikely(error))
> -					return error;
> +				ret = __block_write_begin(page, start, end - start,
> +							  gfs2_block_map);
> +				if (unlikely(ret))
> +					return ret;
>  				empty_write_end(page, start, end);
>  				end = 0;
>  			}
> @@ -669,13 +675,13 @@ static int write_empty_blocks(struct pag
>  		}
>  		else
>  			end = next;
> -		bh = bh->b_this_page;
> +		block++;
>  	} while (next < to);
>  
>  	if (end) {
> -		error = __block_write_begin(page, start, end - start, gfs2_block_map);
> -		if (unlikely(error))
> -			return error;
> +		ret = __block_write_begin(page, start, end - start, gfs2_block_map);
> +		if (unlikely(ret))
> +			return ret;
>  		empty_write_end(page, start, end);
>  	}
>  
>