NFSv4.1: add generic layer hooks for pnfs COMMIT

We create three major hooks for the pnfs code.

pnfs_mark_request_commit() is called during writeback_done from
nfs_mark_request_commit, which gives the driver an opportunity to
claim it wants control over commiting a particular req.

pnfs_choose_commit_list() is called from nfs_scan_list
to choose which list a given req should be added to, based on
where we intend to send it for COMMIT.  It is up to the driver
to have preallocated list headers for each destination it may need.

pnfs_commit_list() is how the driver actually takes control, it is
used instead of nfs_commit_list().

In order to pass information between the above functions, we create
a union in nfs_page to hold a lseg (which is possible because the req is
not on any list while in transition), and add some flags to indicate
if we need to use the pnfs code.
Signed-off-by: Fred Isaman <iisaman@netapp.com>
Signed-off-by: Trond Myklebust <Trond.Myklebust@netapp.com>

fs/nfs/pagelist.c

@@ -398,6 +398,7 @@ int nfs_scan_list(struct nfs_inode *nfsi,
 	pgoff_t idx_end;
 	int found, i;
 	int res;
+	struct list_head *list;
 
 	res = 0;
 	if (npages == 0)
@@ -418,10 +419,10 @@ int nfs_scan_list(struct nfs_inode *nfsi,
 			idx_start = req->wb_index + 1;
 			if (nfs_set_page_tag_locked(req)) {
 				kref_get(&req->wb_kref);
-				nfs_list_remove_request(req);
 				radix_tree_tag_clear(&nfsi->nfs_page_tree,
 						req->wb_index, tag);
-				nfs_list_add_request(req, dst);
+				list = pnfs_choose_commit_list(req, dst);
+				nfs_list_add_request(req, list);
 				res++;
 				if (res == INT_MAX)
 					goto out;

fs/nfs/pnfs.h

@@ -74,6 +74,13 @@ struct pnfs_layoutdriver_type {
 	/* test for nfs page cache coalescing */
 	int (*pg_test)(struct nfs_pageio_descriptor *, struct nfs_page *, struct nfs_page *);
 
+	/* Returns true if layoutdriver wants to divert this request to
+	 * driver's commit routine.
+	 */
+	bool (*mark_pnfs_commit)(struct pnfs_layout_segment *lseg);
+	struct list_head * (*choose_commit_list) (struct nfs_page *req);
+	int (*commit_pagelist)(struct inode *inode, struct list_head *mds_pages, int how);
+
 	/*
 	 * Return PNFS_ATTEMPTED to indicate the layout code has attempted
 	 * I/O, else return PNFS_NOT_ATTEMPTED to fall back to normal NFS
@@ -169,6 +176,51 @@ static inline int pnfs_enabled_sb(struct nfs_server *nfss)
 	return nfss->pnfs_curr_ld != NULL;
 }
 
+static inline void
+pnfs_mark_request_commit(struct nfs_page *req, struct pnfs_layout_segment *lseg)
+{
+	if (lseg) {
+		struct pnfs_layoutdriver_type *ld;
+
+		ld = NFS_SERVER(req->wb_page->mapping->host)->pnfs_curr_ld;
+		if (ld->mark_pnfs_commit && ld->mark_pnfs_commit(lseg)) {
+			set_bit(PG_PNFS_COMMIT, &req->wb_flags);
+			req->wb_commit_lseg = get_lseg(lseg);
+		}
+	}
+}
+
+static inline int
+pnfs_commit_list(struct inode *inode, struct list_head *mds_pages, int how)
+{
+	if (!test_and_clear_bit(NFS_INO_PNFS_COMMIT, &NFS_I(inode)->flags))
+		return PNFS_NOT_ATTEMPTED;
+	return NFS_SERVER(inode)->pnfs_curr_ld->commit_pagelist(inode, mds_pages, how);
+}
+
+static inline struct list_head *
+pnfs_choose_commit_list(struct nfs_page *req, struct list_head *mds)
+{
+	struct list_head *rv;
+
+	if (test_and_clear_bit(PG_PNFS_COMMIT, &req->wb_flags)) {
+		struct inode *inode = req->wb_commit_lseg->pls_layout->plh_inode;
+
+		set_bit(NFS_INO_PNFS_COMMIT, &NFS_I(inode)->flags);
+		rv = NFS_SERVER(inode)->pnfs_curr_ld->choose_commit_list(req);
+		/* matched by ref taken when PG_PNFS_COMMIT is set */
+		put_lseg(req->wb_commit_lseg);
+	} else
+		rv = mds;
+	return rv;
+}
+
+static inline void pnfs_clear_request_commit(struct nfs_page *req)
+{
+	if (test_and_clear_bit(PG_PNFS_COMMIT, &req->wb_flags))
+		put_lseg(req->wb_commit_lseg);
+}
+
 #else  /* CONFIG_NFS_V4_1 */
 
 static inline void pnfs_destroy_all_layouts(struct nfs_client *clp)
@@ -252,6 +304,27 @@ pnfs_pageio_init_write(struct nfs_pageio_descriptor *pgio, struct inode *ino)
 	pgio->pg_test = NULL;
 }
 
+static inline void
+pnfs_mark_request_commit(struct nfs_page *req, struct pnfs_layout_segment *lseg)
+{
+}
+
+static inline int
+pnfs_commit_list(struct inode *inode, struct list_head *mds_pages, int how)
+{
+	return PNFS_NOT_ATTEMPTED;
+}
+
+static inline struct list_head *
+pnfs_choose_commit_list(struct nfs_page *req, struct list_head *mds)
+{
+	return mds;
+}
+
+static inline void pnfs_clear_request_commit(struct nfs_page *req)
+{
+}
+
 #endif /* CONFIG_NFS_V4_1 */
 
 #endif /* FS_NFS_PNFS_H */

fs/nfs/write.c

@@ -441,7 +441,7 @@ nfs_mark_request_dirty(struct nfs_page *req)
  * Add a request to the inode's commit list.
  */
 static void
-nfs_mark_request_commit(struct nfs_page *req)
+nfs_mark_request_commit(struct nfs_page *req, struct pnfs_layout_segment *lseg)
 {
 	struct inode *inode = req->wb_context->path.dentry->d_inode;
 	struct nfs_inode *nfsi = NFS_I(inode);
@@ -453,6 +453,7 @@ nfs_mark_request_commit(struct nfs_page *req)
 			NFS_PAGE_TAG_COMMIT);
 	nfsi->ncommit++;
 	spin_unlock(&inode->i_lock);
+	pnfs_mark_request_commit(req, lseg);
 	inc_zone_page_state(req->wb_page, NR_UNSTABLE_NFS);
 	inc_bdi_stat(req->wb_page->mapping->backing_dev_info, BDI_RECLAIMABLE);
 	__mark_inode_dirty(inode, I_DIRTY_DATASYNC);
@@ -481,10 +482,11 @@ int nfs_write_need_commit(struct nfs_write_data *data)
 }
 
 static inline
-int nfs_reschedule_unstable_write(struct nfs_page *req)
+int nfs_reschedule_unstable_write(struct nfs_page *req,
+				  struct nfs_write_data *data)
 {
 	if (test_and_clear_bit(PG_NEED_COMMIT, &req->wb_flags)) {
-		nfs_mark_request_commit(req);
+		nfs_mark_request_commit(req, data->lseg);
 		return 1;
 	}
 	if (test_and_clear_bit(PG_NEED_RESCHED, &req->wb_flags)) {
@@ -495,7 +497,7 @@ int nfs_reschedule_unstable_write(struct nfs_page *req)
 }
 #else
 static inline void
-nfs_mark_request_commit(struct nfs_page *req)
+nfs_mark_request_commit(struct nfs_page *req, struct pnfs_layout_segment *lseg)
 {
 }
 
@@ -512,7 +514,8 @@ int nfs_write_need_commit(struct nfs_write_data *data)
 }
 
 static inline
-int nfs_reschedule_unstable_write(struct nfs_page *req)
+int nfs_reschedule_unstable_write(struct nfs_page *req,
+				  struct nfs_write_data *data)
 {
 	return 0;
 }
@@ -615,9 +618,11 @@ static struct nfs_page *nfs_try_to_update_request(struct inode *inode,
 	}
 
 	if (nfs_clear_request_commit(req) &&
-			radix_tree_tag_clear(&NFS_I(inode)->nfs_page_tree,
-				req->wb_index, NFS_PAGE_TAG_COMMIT) != NULL)
+	    radix_tree_tag_clear(&NFS_I(inode)->nfs_page_tree,
+				 req->wb_index, NFS_PAGE_TAG_COMMIT) != NULL) {
 		NFS_I(inode)->ncommit--;
+		pnfs_clear_request_commit(req);
+	}
 
 	/* Okay, the request matches. Update the region */
 	if (offset < req->wb_offset) {
@@ -765,11 +770,12 @@ int nfs_updatepage(struct file *file, struct page *page,
 	return status;
 }
 
-static void nfs_writepage_release(struct nfs_page *req)
+static void nfs_writepage_release(struct nfs_page *req,
+				  struct nfs_write_data *data)
 {
 	struct page *page = req->wb_page;
 
-	if (PageError(req->wb_page) || !nfs_reschedule_unstable_write(req))
+	if (PageError(req->wb_page) || !nfs_reschedule_unstable_write(req, data))
 		nfs_inode_remove_request(req);
 	nfs_clear_page_tag_locked(req);
 	nfs_end_page_writeback(page);
@@ -1087,7 +1093,7 @@ static void nfs_writeback_release_partial(void *calldata)
 
 out:
 	if (atomic_dec_and_test(&req->wb_complete))
-		nfs_writepage_release(req);
+		nfs_writepage_release(req, data);
 	nfs_writedata_release(calldata);
 }
 
@@ -1154,7 +1160,7 @@ static void nfs_writeback_release_full(void *calldata)
 
 		if (nfs_write_need_commit(data)) {
 			memcpy(&req->wb_verf, &data->verf, sizeof(req->wb_verf));
-			nfs_mark_request_commit(req);
+			nfs_mark_request_commit(req, data->lseg);
 			dprintk(" marked for commit\n");
 			goto next;
 		}
@@ -1357,14 +1363,15 @@ static void nfs_init_commit(struct nfs_write_data *data,
 	nfs_fattr_init(&data->fattr);
 }
 
-static void nfs_retry_commit(struct list_head *page_list)
+static void nfs_retry_commit(struct list_head *page_list,
+		      struct pnfs_layout_segment *lseg)
 {
 	struct nfs_page *req;
 
 	while (!list_empty(page_list)) {
 		req = nfs_list_entry(page_list->next);
 		nfs_list_remove_request(req);
-		nfs_mark_request_commit(req);
+		nfs_mark_request_commit(req, lseg);
 		dec_zone_page_state(req->wb_page, NR_UNSTABLE_NFS);
 		dec_bdi_stat(req->wb_page->mapping->backing_dev_info,
 			     BDI_RECLAIMABLE);
@@ -1389,7 +1396,7 @@ nfs_commit_list(struct inode *inode, struct list_head *head, int how)
 	nfs_init_commit(data, head);
 	return nfs_initiate_commit(data, NFS_CLIENT(inode), data->mds_ops, how);
  out_bad:
-	nfs_retry_commit(head);
+	nfs_retry_commit(head, NULL);
 	nfs_commit_clear_lock(NFS_I(inode));
 	return -ENOMEM;
 }
@@ -1477,7 +1484,11 @@ int nfs_commit_inode(struct inode *inode, int how)
 	res = nfs_scan_commit(inode, &head, 0, 0);
 	spin_unlock(&inode->i_lock);
 	if (res) {
-		int error = nfs_commit_list(inode, &head, how);
+		int error;
+
+		error = pnfs_commit_list(inode, &head, how);
+		if (error == PNFS_NOT_ATTEMPTED)
+			error = nfs_commit_list(inode, &head, how);
 		if (error < 0)
 			return error;
 		if (!may_wait)

include/linux/nfs_fs.h

@@ -226,6 +226,7 @@ struct nfs_inode {
 #define NFS_INO_FSCACHE		(5)		/* inode can be cached by FS-Cache */
 #define NFS_INO_FSCACHE_LOCK	(6)		/* FS-Cache cookie management lock */
 #define NFS_INO_COMMIT		(7)		/* inode is committing unstable writes */
+#define NFS_INO_PNFS_COMMIT	(8)		/* use pnfs code for commit */
 
 static inline struct nfs_inode *NFS_I(const struct inode *inode)
 {

include/linux/nfs_page.h

@@ -33,11 +33,15 @@ enum {
 	PG_CLEAN,
 	PG_NEED_COMMIT,
 	PG_NEED_RESCHED,
+	PG_PNFS_COMMIT,
 };
 
 struct nfs_inode;
 struct nfs_page {
-	struct list_head	wb_list;	/* Defines state of page: */
+	union {
+		struct list_head	wb_list;	/* Defines state of page: */
+		struct pnfs_layout_segment *wb_commit_lseg; /* Used when PG_PNFS_COMMIT set */
+	};
 	struct page		*wb_page;	/* page to read in/write out */
 	struct nfs_open_context	*wb_context;	/* File state context info */
 	struct nfs_lock_context	*wb_lock_context;	/* lock context info */