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Commit 4e9563fd authored by Mark Fasheh's avatar Mark Fasheh
Browse files

ocfs2: fix write() performance regression 



On file systems which don't support sparse files, Ocfs2_map_page_blocks()
was reading blocks on appending writes. This caused write performance to
suffer dramatically. Fix this by detecting an appending write on a nonsparse
fs and skipping the read.

Signed-off-by: default avatarMark Fasheh <mark.fasheh@oracle.com>
parent 9ea2d32f

fs/ocfs2/aops.c

+22 −0
Original line number Diff line number Diff line
@@ -728,6 +728,27 @@ static void ocfs2_clear_page_regions(struct page *page, 
	kunmap_atomic(kaddr, KM_USER0);

}



/*

 * Nonsparse file systems fully allocate before we get to the write

 * code. This prevents ocfs2_write() from tagging the write as an

 * allocating one, which means ocfs2_map_page_blocks() might try to

 * read-in the blocks at the tail of our file. Avoid reading them by

 * testing i_size against each block offset.

 */

static int ocfs2_should_read_blk(struct inode *inode, struct page *page,

				 unsigned int block_start)

{

	u64 offset = page_offset(page) + block_start;



	if (ocfs2_sparse_alloc(OCFS2_SB(inode->i_sb)))

		return 1;



	if (i_size_read(inode) > offset)

		return 1;



	return 0;

}



/*

 * Some of this taken from block_prepare_write(). We already have our

 * mapping by now though, and the entire write will be allocating or
@@ -781,6 +802,7 @@ int ocfs2_map_page_blocks(struct page *page, u64 *p_blkno, 
				set_buffer_uptodate(bh);

		} else if (!buffer_uptodate(bh) && !buffer_delay(bh) &&

			   !buffer_new(bh) &&

			   ocfs2_should_read_blk(inode, page, block_start) &&

			   (block_start < from || block_end > to)) {

			ll_rw_block(READ, 1, &bh);

			*wait_bh++=bh;