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Commit e468bae9 authored by Trond Myklebust's avatar Trond Myklebust
Browse files

NFS: Allow redirtying of a completed unstable write. 



Currently, if an unstable write completes, we cannot redirty the page in
order to reflect a new change in the page data until after we've sent a
COMMIT request.

This patch allows a page rewrite to proceed without the unnecessary COMMIT
step, putting it immediately back onto the dirty page list, undoing the
VM unstable write accounting, and removing the NFS_PAGE_TAG_COMMIT tag from
the NFS radix tree.

Signed-off-by: default avatarTrond Myklebust <Trond.Myklebust@netapp.com>
parent e7d39069

fs/nfs/write.c

+32 −33
Original line number Diff line number Diff line
@@ -242,12 +242,9 @@ static int nfs_page_async_flush(struct nfs_pageio_descriptor *pgio, 
			return ret;

		spin_lock(&inode->i_lock);

	}

	if (test_bit(PG_NEED_COMMIT, &req->wb_flags)) {

		/* This request is marked for commit */

	if (test_bit(PG_CLEAN, &req->wb_flags)) {

		spin_unlock(&inode->i_lock);

		nfs_clear_page_tag_locked(req);

		nfs_pageio_complete(pgio);

		return 0;

		BUG();

	}

	if (nfs_set_page_writeback(page) != 0) {

		spin_unlock(&inode->i_lock);
@@ -391,19 +388,6 @@ nfs_mark_request_dirty(struct nfs_page *req) 
	__set_page_dirty_nobuffers(req->wb_page);

}



/*

 * Check if a request is dirty

 */

static inline int

nfs_dirty_request(struct nfs_page *req)

{

	struct page *page = req->wb_page;



	if (page == NULL || test_bit(PG_NEED_COMMIT, &req->wb_flags))

		return 0;

	return !PageWriteback(page);

}



#if defined(CONFIG_NFS_V3) || defined(CONFIG_NFS_V4)

/*

 * Add a request to the inode's commit list.
@@ -416,7 +400,7 @@ nfs_mark_request_commit(struct nfs_page *req) 


	spin_lock(&inode->i_lock);

	nfsi->ncommit++;

	set_bit(PG_NEED_COMMIT, &(req)->wb_flags);

	set_bit(PG_CLEAN, &(req)->wb_flags);

	radix_tree_tag_set(&nfsi->nfs_page_tree,

			req->wb_index,

			NFS_PAGE_TAG_COMMIT);
@@ -426,6 +410,19 @@ nfs_mark_request_commit(struct nfs_page *req) 
	__mark_inode_dirty(inode, I_DIRTY_DATASYNC);

}



static int

nfs_clear_request_commit(struct nfs_page *req)

{

	struct page *page = req->wb_page;



	if (test_and_clear_bit(PG_CLEAN, &(req)->wb_flags)) {

		dec_zone_page_state(page, NR_UNSTABLE_NFS);

		dec_bdi_stat(page->mapping->backing_dev_info, BDI_RECLAIMABLE);

		return 1;

	}

	return 0;

}



static inline

int nfs_write_need_commit(struct nfs_write_data *data)

{
@@ -435,7 +432,7 @@ int nfs_write_need_commit(struct nfs_write_data *data) 
static inline

int nfs_reschedule_unstable_write(struct nfs_page *req)

{

	if (test_bit(PG_NEED_COMMIT, &req->wb_flags)) {

	if (test_and_clear_bit(PG_NEED_COMMIT, &req->wb_flags)) {

		nfs_mark_request_commit(req);

		return 1;

	}
@@ -451,6 +448,12 @@ nfs_mark_request_commit(struct nfs_page *req) 
{

}



static inline int

nfs_clear_request_commit(struct nfs_page *req)

{

	return 0;

}



static inline

int nfs_write_need_commit(struct nfs_write_data *data)

{
@@ -508,11 +511,8 @@ static void nfs_cancel_commit_list(struct list_head *head) 


	while(!list_empty(head)) {

		req = nfs_list_entry(head->next);

		dec_zone_page_state(req->wb_page, NR_UNSTABLE_NFS);

		dec_bdi_stat(req->wb_page->mapping->backing_dev_info,

				BDI_RECLAIMABLE);

		nfs_list_remove_request(req);

		clear_bit(PG_NEED_COMMIT, &(req)->wb_flags);

		nfs_clear_request_commit(req);

		nfs_inode_remove_request(req);

		nfs_unlock_request(req);

	}
@@ -584,8 +584,7 @@ static struct nfs_page *nfs_try_to_update_request(struct inode *inode, 
		 * Note: nfs_flush_incompatible() will already

		 * have flushed out requests having wrong owners.

		 */

		if (!nfs_dirty_request(req)

		    || offset > rqend

		if (offset > rqend

		    || end < req->wb_offset)

			goto out_flushme;
@@ -601,6 +600,10 @@ static struct nfs_page *nfs_try_to_update_request(struct inode *inode, 
		spin_lock(&inode->i_lock);

	}



	if (nfs_clear_request_commit(req))

		radix_tree_tag_clear(&NFS_I(inode)->nfs_page_tree,

				req->wb_index, NFS_PAGE_TAG_COMMIT);



	/* Okay, the request matches. Update the region */

	if (offset < req->wb_offset) {

		req->wb_offset = offset;
@@ -682,8 +685,7 @@ int nfs_flush_incompatible(struct file *file, struct page *page) 
		req = nfs_page_find_request(page);

		if (req == NULL)

			return 0;

		do_flush = req->wb_page != page || req->wb_context != ctx

			|| !nfs_dirty_request(req);

		do_flush = req->wb_page != page || req->wb_context != ctx;

		nfs_release_request(req);

		if (!do_flush)

			return 0;
@@ -1288,10 +1290,7 @@ static void nfs_commit_release(void *calldata) 
	while (!list_empty(&data->pages)) {

		req = nfs_list_entry(data->pages.next);

		nfs_list_remove_request(req);

		clear_bit(PG_NEED_COMMIT, &(req)->wb_flags);

		dec_zone_page_state(req->wb_page, NR_UNSTABLE_NFS);

		dec_bdi_stat(req->wb_page->mapping->backing_dev_info,

				BDI_RECLAIMABLE);

		nfs_clear_request_commit(req);



		dprintk("NFS:       commit (%s/%lld %d@%lld)",

			req->wb_context->path.dentry->d_inode->i_sb->s_id,
@@ -1467,7 +1466,7 @@ int nfs_wb_page_cancel(struct inode *inode, struct page *page) 
		req = nfs_page_find_request(page);

		if (req == NULL)

			goto out;

		if (test_bit(PG_NEED_COMMIT, &req->wb_flags)) {

		if (test_bit(PG_CLEAN, &req->wb_flags)) {

			nfs_release_request(req);

			break;

		}

include/linux/nfs_page.h

+6 −3
Original line number Diff line number Diff line
@@ -27,9 +27,12 @@ 
/*

 * Valid flags for a dirty buffer

 */

#define PG_BUSY			0

#define PG_NEED_COMMIT		1

#define PG_NEED_RESCHED		2

enum {

	PG_BUSY = 0,

	PG_CLEAN,

	PG_NEED_COMMIT,

	PG_NEED_RESCHED,

};



struct nfs_inode;

struct nfs_page {