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Commit 6d17d653 authored by Trond Myklebust's avatar Trond Myklebust
Browse files

NFS: Simplify page writeback 



We don't expect the page header lock to ever be held across I/O, so
it should always be safe to wait for it, even if we're doing nonblocking
writebacks.

Signed-off-by: default avatarTrond Myklebust <trond.myklebust@primarydata.com>
parent ef954844

fs/nfs/write.c

+10 −20
Original line number Diff line number Diff line
@@ -366,7 +366,6 @@ nfs_page_group_clear_bits(struct nfs_page *req) 
 * @inode - inode associated with request page group, must be holding inode lock

 * @head  - head request of page group, must be holding head lock

 * @req   - request that couldn't lock and needs to wait on the req bit lock

 * @nonblock - if true, don't actually wait

 *

 * NOTE: this must be called holding page_group bit lock and inode spin lock

 *       and BOTH will be released before returning.
@@ -375,7 +374,7 @@ nfs_page_group_clear_bits(struct nfs_page *req) 
 */

static int

nfs_unroll_locks_and_wait(struct inode *inode, struct nfs_page *head,

			  struct nfs_page *req, bool nonblock)

			  struct nfs_page *req)

	__releases(&inode->i_lock)

{

	struct nfs_page *tmp;
@@ -396,10 +395,7 @@ nfs_unroll_locks_and_wait(struct inode *inode, struct nfs_page *head, 
	/* release ref from nfs_page_find_head_request_locked */

	nfs_release_request(head);



	if (!nonblock)

	ret = nfs_wait_on_request(req);

	else

		ret = -EAGAIN;

	nfs_release_request(req);



	return ret;
@@ -464,7 +460,6 @@ nfs_destroy_unlinked_subrequests(struct nfs_page *destroy_list, 
 *                              operations for this page.

 *

 * @page - the page used to lookup the "page group" of nfs_page structures

 * @nonblock - if true, don't block waiting for request locks

 *

 * This function joins all sub requests to the head request by first

 * locking all requests in the group, cancelling any pending operations
@@ -478,7 +473,7 @@ nfs_destroy_unlinked_subrequests(struct nfs_page *destroy_list, 
 * error was encountered.

 */

static struct nfs_page *

nfs_lock_and_join_requests(struct page *page, bool nonblock)

nfs_lock_and_join_requests(struct page *page)

{

	struct inode *inode = page_file_mapping(page)->host;

	struct nfs_page *head, *subreq;
@@ -511,16 +506,11 @@ nfs_lock_and_join_requests(struct page *page, bool nonblock) 
	if (ret < 0) {

		spin_unlock(&inode->i_lock);



		if (!nonblock && ret == -EAGAIN) {

		nfs_page_group_lock_wait(head);

		nfs_release_request(head);

		goto try_again;

	}



		nfs_release_request(head);

		return ERR_PTR(ret);

	}



	/* lock each request in the page group */

	subreq = head;

	do {
@@ -543,7 +533,7 @@ nfs_lock_and_join_requests(struct page *page, bool nonblock) 
			/* releases page group bit lock and

			 * inode spin lock and all references */

			ret = nfs_unroll_locks_and_wait(inode, head,

				subreq, nonblock);

				subreq);



			if (ret == 0)

				goto try_again;
@@ -624,12 +614,12 @@ nfs_error_is_fatal_on_server(int err) 
 * May return an error if the user signalled nfs_wait_on_request().

 */

static int nfs_page_async_flush(struct nfs_pageio_descriptor *pgio,

				struct page *page, bool nonblock)

				struct page *page)

{

	struct nfs_page *req;

	int ret = 0;



	req = nfs_lock_and_join_requests(page, nonblock);

	req = nfs_lock_and_join_requests(page);

	if (!req)

		goto out;

	ret = PTR_ERR(req);
@@ -672,7 +662,7 @@ static int nfs_do_writepage(struct page *page, struct writeback_control *wbc, 
	int ret;



	nfs_pageio_cond_complete(pgio, page_index(page));

	ret = nfs_page_async_flush(pgio, page, wbc->sync_mode == WB_SYNC_NONE);

	ret = nfs_page_async_flush(pgio, page);

	if (ret == -EAGAIN) {

		redirty_page_for_writepage(wbc, page);

		ret = 0;
@@ -2015,7 +2005,7 @@ int nfs_wb_page_cancel(struct inode *inode, struct page *page) 


	/* blocking call to cancel all requests and join to a single (head)

	 * request */

	req = nfs_lock_and_join_requests(page, false);

	req = nfs_lock_and_join_requests(page);



	if (IS_ERR(req)) {

		ret = PTR_ERR(req);