clean up write_begin usage for directories in pagecache

For filesystem that implement directories in pagecache we call
block_write_begin with an already allocated page for this code, while the
normal regular file write path uses the default block_write_begin behaviour.

Get rid of the __foofs_write_begin helper and opencode the normal write_begin
call in foofs_write_begin, while adding a new foofs_prepare_chunk helper for
the directory code.  The added benefit is that foofs_prepare_chunk has
a much saner calling convention.

Note that the interruptible flag passed into block_write_begin is always
ignored if we already pass in a page (see next patch for details), and
we never were doing truncations of exessive blocks for this case either so we
can switch directly to block_write_begin_newtrunc.

Signed-off-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>

3 files changed, 13 insertions, 23 deletions

diff --git a/fs/minix/dir.c b/fs/minix/dir.c
index 1dbf921ca44b..085a9262c692 100644
--- a/fs/minix/dir.c
+++ b/fs/minix/dir.c
@@ -271,8 +271,7 @@ int minix_add_link(struct dentry *dentry, struct inode *inode)
 
 got_it:
 	pos = page_offset(page) + p - (char *)page_address(page);
-	err = __minix_write_begin(NULL, page->mapping, pos, sbi->s_dirsize,
-					AOP_FLAG_UNINTERRUPTIBLE, &page, NULL);
+	err = minix_prepare_chunk(page, pos, sbi->s_dirsize);
 	if (err)
 		goto out_unlock;
 	memcpy (namx, name, namelen);
@@ -297,8 +296,7 @@ out_unlock:
 
 int minix_delete_entry(struct minix_dir_entry *de, struct page *page)
 {
-	struct address_space *mapping = page->mapping;
-	struct inode *inode = (struct inode*)mapping->host;
+	struct inode *inode = page->mapping->host;
 	char *kaddr = page_address(page);
 	loff_t pos = page_offset(page) + (char*)de - kaddr;
 	struct minix_sb_info *sbi = minix_sb(inode->i_sb);
@@ -306,8 +304,7 @@ int minix_delete_entry(struct minix_dir_entry *de, struct page *page)
 	int err;
 
 	lock_page(page);
-	err = __minix_write_begin(NULL, mapping, pos, len,
-					AOP_FLAG_UNINTERRUPTIBLE, &page, NULL);
+	err = minix_prepare_chunk(page, pos, len);
 	if (err == 0) {
 		if (sbi->s_version == MINIX_V3)
 			((minix3_dirent *) de)->inode = 0;
@@ -325,16 +322,14 @@ int minix_delete_entry(struct minix_dir_entry *de, struct page *page)
 
 int minix_make_empty(struct inode *inode, struct inode *dir)
 {
-	struct address_space *mapping = inode->i_mapping;
-	struct page *page = grab_cache_page(mapping, 0);
+	struct page *page = grab_cache_page(inode->i_mapping, 0);
 	struct minix_sb_info *sbi = minix_sb(inode->i_sb);
 	char *kaddr;
 	int err;
 
 	if (!page)
 		return -ENOMEM;
-	err = __minix_write_begin(NULL, mapping, 0, 2 * sbi->s_dirsize,
-					AOP_FLAG_UNINTERRUPTIBLE, &page, NULL);
+	err = minix_prepare_chunk(page, 0, 2 * sbi->s_dirsize);
 	if (err) {
 		unlock_page(page);
 		goto fail;
@@ -425,8 +420,7 @@ not_empty:
 void minix_set_link(struct minix_dir_entry *de, struct page *page,
 	struct inode *inode)
 {
-	struct address_space *mapping = page->mapping;
-	struct inode *dir = mapping->host;
+	struct inode *dir = page->mapping->host;
 	struct minix_sb_info *sbi = minix_sb(dir->i_sb);
 	loff_t pos = page_offset(page) +
 			(char *)de-(char*)page_address(page);
@@ -434,8 +428,7 @@ void minix_set_link(struct minix_dir_entry *de, struct page *page,
 
 	lock_page(page);
 
-	err = __minix_write_begin(NULL, mapping, pos, sbi->s_dirsize,
-					AOP_FLAG_UNINTERRUPTIBLE, &page, NULL);
+	err = minix_prepare_chunk(page, pos, sbi->s_dirsize);
 	if (err == 0) {
 		if (sbi->s_version == MINIX_V3)
 			((minix3_dirent *) de)->inode = inode->i_ino;
diff --git a/fs/minix/inode.c b/fs/minix/inode.c
index 756f8c93780c..f4abe45229bb 100644
--- a/fs/minix/inode.c
+++ b/fs/minix/inode.c
@@ -357,12 +357,10 @@ static int minix_readpage(struct file *file, struct page *page)
 	return block_read_full_page(page,minix_get_block);
 }
 
-int __minix_write_begin(struct file *file, struct address_space *mapping,
-			loff_t pos, unsigned len, unsigned flags,
-			struct page **pagep, void **fsdata)
+int minix_prepare_chunk(struct page *page, loff_t pos, unsigned len)
 {
-	return block_write_begin(file, mapping, pos, len, flags, pagep, fsdata,
-				minix_get_block);
+	return block_write_begin_newtrunc(NULL, page->mapping, pos, len, 0,
+					  &page, NULL, minix_get_block);
 }
 
 static int minix_write_begin(struct file *file, struct address_space *mapping,
@@ -370,7 +368,8 @@ static int minix_write_begin(struct file *file, struct address_space *mapping,
 			struct page **pagep, void **fsdata)
 {
 	*pagep = NULL;
-	return __minix_write_begin(file, mapping, pos, len, flags, pagep, fsdata);
+	return block_write_begin(file, mapping, pos, len, flags, pagep, fsdata,
+				minix_get_block);
 }
 
 static sector_t minix_bmap(struct address_space *mapping, sector_t block)
diff --git a/fs/minix/minix.h b/fs/minix/minix.h
index 111f34ee9e3b..407b1c84911e 100644
--- a/fs/minix/minix.h
+++ b/fs/minix/minix.h
@@ -53,9 +53,7 @@ extern int minix_new_block(struct inode * inode);
 extern void minix_free_block(struct inode *inode, unsigned long block);
 extern unsigned long minix_count_free_blocks(struct minix_sb_info *sbi);
 extern int minix_getattr(struct vfsmount *, struct dentry *, struct kstat *);
-extern int __minix_write_begin(struct file *file, struct address_space *mapping,
-			loff_t pos, unsigned len, unsigned flags,
-			struct page **pagep, void **fsdata);
+extern int minix_prepare_chunk(struct page *page, loff_t pos, unsigned len);
 
 extern void V1_minix_truncate(struct inode *);
 extern void V2_minix_truncate(struct inode *);