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Commit efc91ed0 authored by Trond Myklebust's avatar Trond Myklebust
Browse files

NFS: Optimise append writes with holes 



If a file is being extended, and we're creating a hole, we might as well
declare the entire page to be up to date.

This patch significantly improves the write performance for sparse files
in the case where lseek(SEEK_END) is used to append several non-contiguous
writes at intervals of < PAGE_SIZE.

Signed-off-by: default avatarTrond Myklebust <Trond.Myklebust@netapp.com>
parent b390c2b5

fs/nfs/file.c

+20 −0
Original line number Diff line number Diff line
@@ -344,6 +344,26 @@ static int nfs_write_end(struct file *file, struct address_space *mapping, 
	unsigned offset = pos & (PAGE_CACHE_SIZE - 1);

	int status;



	/*

	 * Zero any uninitialised parts of the page, and then mark the page

	 * as up to date if it turns out that we're extending the file.

	 */

	if (!PageUptodate(page)) {

		unsigned pglen = nfs_page_length(page);

		unsigned end = offset + len;



		if (pglen == 0) {

			zero_user_segments(page, 0, offset,

					end, PAGE_CACHE_SIZE);

			SetPageUptodate(page);

		} else if (end >= pglen) {

			zero_user_segment(page, end, PAGE_CACHE_SIZE);

			if (offset == 0)

				SetPageUptodate(page);

		} else

			zero_user_segment(page, pglen, PAGE_CACHE_SIZE);

	}



	lock_kernel();

	status = nfs_updatepage(file, page, offset, copied);

	unlock_kernel();

fs/nfs/write.c

+3 −9
Original line number Diff line number Diff line
@@ -616,7 +616,7 @@ static struct nfs_page * nfs_update_request(struct nfs_open_context* ctx, 
			spin_unlock(&inode->i_lock);

			radix_tree_preload_end();

			req = new;

			goto zero_page;

			goto out;

		}

		spin_unlock(&inode->i_lock);
@@ -649,19 +649,13 @@ static struct nfs_page * nfs_update_request(struct nfs_open_context* ctx, 
		req->wb_offset = offset;

		req->wb_pgbase = offset;

		req->wb_bytes = max(end, rqend) - req->wb_offset;

		goto zero_page;

		goto out;

	}



	if (end > rqend)

		req->wb_bytes = end - req->wb_offset;



	return req;

zero_page:

	/* If this page might potentially be marked as up to date,

	 * then we need to zero any uninitalised data. */

	if (req->wb_pgbase == 0 && req->wb_bytes != PAGE_CACHE_SIZE

			&& !PageUptodate(req->wb_page))

		zero_user_segment(req->wb_page, req->wb_bytes, PAGE_CACHE_SIZE);

out:

	return req;

}