queue-3.16/nfs-use-kmap-kunmap-directly.patch

From: Fabian Frederick <fabf@skynet.be>
Date: Wed, 3 May 2017 20:52:21 +0200
Subject: nfs: use kmap/kunmap directly

commit 0795bf8357c1887e2a95e6e4f5b89d0896a0d929 upstream.

This patch removes useless nfs_readdir_get_array() and
nfs_readdir_release_array() as suggested by Trond Myklebust

nfs_readdir() calls nfs_revalidate_mapping() before
readdir_search_pagecache() , nfs_do_filldir(), uncached_readdir()
so mapping should be correct.

While kmap() can't fail, all subsequent error checks were removed
as well as unused labels.

Signed-off-by: Fabian Frederick <fabf@skynet.be>
Signed-off-by: Trond Myklebust <trond.myklebust@primarydata.com>
Signed-off-by: Ben Hutchings <ben@decadent.org.uk>
---
 fs/nfs/dir.c | 67 ++++++++++------------------------------------------
 1 file changed, 12 insertions(+), 55 deletions(-)

--- a/fs/nfs/dir.c
+++ b/fs/nfs/dir.c
@@ -170,27 +170,6 @@ typedef struct {
 } nfs_readdir_descriptor_t;
 
 /*
- * The caller is responsible for calling nfs_readdir_release_array(page)
- */
-static
-struct nfs_cache_array *nfs_readdir_get_array(struct page *page)
-{
-	void *ptr;
-	if (page == NULL)
-		return ERR_PTR(-EIO);
-	ptr = kmap(page);
-	if (ptr == NULL)
-		return ERR_PTR(-ENOMEM);
-	return ptr;
-}
-
-static
-void nfs_readdir_release_array(struct page *page)
-{
-	kunmap(page);
-}
-
-/*
  * we are freeing strings created by nfs_add_to_readdir_array()
  */
 static
@@ -229,13 +208,10 @@ int nfs_readdir_make_qstr(struct qstr *s
 static
 int nfs_readdir_add_to_array(struct nfs_entry *entry, struct page *page)
 {
-	struct nfs_cache_array *array = nfs_readdir_get_array(page);
+	struct nfs_cache_array *array = kmap(page);
 	struct nfs_cache_array_entry *cache_entry;
 	int ret;
 
-	if (IS_ERR(array))
-		return PTR_ERR(array);
-
 	cache_entry = &array->array[array->size];
 
 	/* Check that this entry lies within the page bounds */
@@ -254,7 +230,7 @@ int nfs_readdir_add_to_array(struct nfs_
 	if (entry->eof != 0)
 		array->eof_index = array->size;
 out:
-	nfs_readdir_release_array(page);
+	kunmap(page);
 	return ret;
 }
 
@@ -343,11 +319,7 @@ int nfs_readdir_search_array(nfs_readdir
 	struct nfs_cache_array *array;
 	int status;
 
-	array = nfs_readdir_get_array(desc->page);
-	if (IS_ERR(array)) {
-		status = PTR_ERR(array);
-		goto out;
-	}
+	array = kmap(desc->page);
 
 	if (*desc->dir_cookie == 0)
 		status = nfs_readdir_search_for_pos(array, desc);
@@ -359,8 +331,7 @@ int nfs_readdir_search_array(nfs_readdir
 		desc->current_index += array->size;
 		desc->page_index++;
 	}
-	nfs_readdir_release_array(desc->page);
-out:
+	kunmap(desc->page);
 	return status;
 }
 
@@ -551,13 +522,10 @@ int nfs_readdir_page_filler(nfs_readdir_
 	} while (!entry->eof);
 
 	if (count == 0 || (status == -EBADCOOKIE && entry->eof != 0)) {
-		array = nfs_readdir_get_array(page);
-		if (!IS_ERR(array)) {
-			array->eof_index = array->size;
-			status = 0;
-			nfs_readdir_release_array(page);
-		} else
-			status = PTR_ERR(array);
+		array = kmap(page);
+		array->eof_index = array->size;
+		status = 0;
+		kunmap(page);
 	}
 
 	put_page(scratch);
@@ -627,11 +595,7 @@ int nfs_readdir_xdr_to_array(nfs_readdir
 		goto out;
 	}
 
-	array = nfs_readdir_get_array(page);
-	if (IS_ERR(array)) {
-		status = PTR_ERR(array);
-		goto out_label_free;
-	}
+	array = kmap(page);
 	memset(array, 0, sizeof(struct nfs_cache_array));
 	array->eof_index = -1;
 
@@ -655,8 +619,7 @@ int nfs_readdir_xdr_to_array(nfs_readdir
 
 	nfs_readdir_free_large_page(pages_ptr, pages, array_size);
 out_release_array:
-	nfs_readdir_release_array(page);
-out_label_free:
+	kunmap(page);
 	nfs4_label_free(entry.label);
 out:
 	nfs_free_fattr(entry.fattr);
@@ -754,12 +717,7 @@ int nfs_do_filldir(nfs_readdir_descripto
 	struct nfs_cache_array *array = NULL;
 	struct nfs_open_dir_context *ctx = file->private_data;
 
-	array = nfs_readdir_get_array(desc->page);
-	if (IS_ERR(array)) {
-		res = PTR_ERR(array);
-		goto out;
-	}
-
+	array = kmap(desc->page);
 	for (i = desc->cache_entry_index; i < array->size; i++) {
 		struct nfs_cache_array_entry *ent;
 
@@ -780,8 +738,7 @@ int nfs_do_filldir(nfs_readdir_descripto
 	if (array->eof_index >= 0)
 		desc->eof = 1;
 
-	nfs_readdir_release_array(desc->page);
-out:
+	kunmap(desc->page);
 	cache_page_release(desc);
 	dfprintk(DIRCACHE, "NFS: nfs_do_filldir() filling ended @ cookie %Lu; returning = %d\n",
 			(unsigned long long)*desc->dir_cookie, res);