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 <[e-mail]>
Signed-off-by: Al Viro <[e-mail]>

fs/ext2/dir.c

···
 	return res;
 }
 
+static int ext2_prepare_chunk(struct page *page, loff_t pos, unsigned len)
+{
+	return block_write_begin_newtrunc(NULL, page->mapping, pos, len, 0,
+					  &page, NULL, ext2_get_block);
+}
+
 /* Releases the page */
 void ext2_set_link(struct inode *dir, struct ext2_dir_entry_2 *de,
 		   struct page *page, struct inode *inode, int update_times)
···
 	int err;
 
 	lock_page(page);
-	err = __ext2_write_begin(NULL, page->mapping, pos, len,
-				AOP_FLAG_UNINTERRUPTIBLE, &page, NULL);
+	err = ext2_prepare_chunk(page, pos, len);
 	BUG_ON(err);
 	de->inode = cpu_to_le32(inode->i_ino);
 	ext2_set_de_type(de, inode);
···
 got_it:
 	pos = page_offset(page) +
 		(char*)de - (char*)page_address(page);
-	err = __ext2_write_begin(NULL, page->mapping, pos, rec_len, 0,
-							&page, NULL);
+	err = ext2_prepare_chunk(page, pos, rec_len);
 	if (err)
 		goto out_unlock;
 	if (de->inode) {
···
  */
 int ext2_delete_entry (struct ext2_dir_entry_2 * dir, struct page * page )
 {
-	struct address_space *mapping = page->mapping;
-	struct inode *inode = mapping->host;
+	struct inode *inode = page->mapping->host;
 	char *kaddr = page_address(page);
 	unsigned from = ((char*)dir - kaddr) & ~(ext2_chunk_size(inode)-1);
 	unsigned to = ((char *)dir - kaddr) +
···
 		from = (char*)pde - (char*)page_address(page);
 	pos = page_offset(page) + from;
 	lock_page(page);
-	err = __ext2_write_begin(NULL, page->mapping, pos, to - from, 0,
-							&page, NULL);
+	err = ext2_prepare_chunk(page, pos, to - from);
 	BUG_ON(err);
 	if (pde)
 		pde->rec_len = ext2_rec_len_to_disk(to - from);
···
  */
 int ext2_make_empty(struct inode *inode, struct inode *parent)
 {
-	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);
 	unsigned chunk_size = ext2_chunk_size(inode);
 	struct ext2_dir_entry_2 * de;
 	int err;
···
 	if (!page)
 		return -ENOMEM;
 
-	err = __ext2_write_begin(NULL, page->mapping, 0, chunk_size, 0,
-							&page, NULL);
+	err = ext2_prepare_chunk(page, 0, chunk_size);
 	if (err) {
 		unlock_page(page);
 		goto fail;

fs/ext2/ext2.h

···
 extern void ext2_get_inode_flags(struct ext2_inode_info *);
 extern int ext2_fiemap(struct inode *inode, struct fiemap_extent_info *fieinfo,
 		       u64 start, u64 len);
-int __ext2_write_begin(struct file *file, struct address_space *mapping,
-		loff_t pos, unsigned len, unsigned flags,
-		struct page **pagep, void **fsdata);
 
 /* ioctl.c */
 extern long ext2_ioctl(struct file *, unsigned int, unsigned long);

fs/ext2/inode.c

···
 	return mpage_readpages(mapping, pages, nr_pages, ext2_get_block);
 }
 
-int __ext2_write_begin(struct file *file, struct address_space *mapping,
-		loff_t pos, unsigned len, unsigned flags,
-		struct page **pagep, void **fsdata)
-{
-	return block_write_begin_newtrunc(file, mapping, pos, len, flags,
-					pagep, fsdata, ext2_get_block);
-}
-
 static int
 ext2_write_begin(struct file *file, struct address_space *mapping,
 		loff_t pos, unsigned len, unsigned flags,
···
 	int ret;
 
 	*pagep = NULL;
-	ret = __ext2_write_begin(file, mapping, pos, len, flags, pagep, fsdata);
+	ret = block_write_begin_newtrunc(file, mapping, pos, len, flags,
+					 pagep, fsdata, ext2_get_block);
 	if (ret < 0)
 		ext2_write_failed(mapping, pos + len);
 	return ret;

fs/minix/dir.c

···
 
 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);
···
 
 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);
···
 	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;
···
 
 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;
···
 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);
···
 
 	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;

fs/minix/inode.c

···
 	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,
···
 			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)

fs/minix/minix.h

···
 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 *);

fs/nilfs2/dir.c

···
 	return last_byte;
 }
 
-static int nilfs_prepare_chunk_uninterruptible(struct page *page,
-					       struct address_space *mapping,
-					       unsigned from, unsigned to)
+static int nilfs_prepare_chunk(struct page *page, unsigned from, unsigned to)
 {
 	loff_t pos = page_offset(page) + from;
-	return block_write_begin(NULL, mapping, pos, to - from,
-				 AOP_FLAG_UNINTERRUPTIBLE, &page,
-				 NULL, nilfs_get_block);
-}
-
-static int nilfs_prepare_chunk(struct page *page,
-			       struct address_space *mapping,
-			       unsigned from, unsigned to)
-{
-	loff_t pos = page_offset(page) + from;
-	return block_write_begin(NULL, mapping, pos, to - from, 0, &page,
-				 NULL, nilfs_get_block);
+	return block_write_begin_newtrunc(NULL, page->mapping, pos, to - from,
+					  0, &page, NULL, nilfs_get_block);
 }
 
 static void nilfs_commit_chunk(struct page *page,
···
 	int err;
 
 	lock_page(page);
-	err = nilfs_prepare_chunk_uninterruptible(page, mapping, from, to);
+	err = nilfs_prepare_chunk(page, from, to);
 	BUG_ON(err);
 	de->inode = cpu_to_le64(inode->i_ino);
 	nilfs_set_de_type(de, inode);
···
 got_it:
 	from = (char *)de - (char *)page_address(page);
 	to = from + rec_len;
-	err = nilfs_prepare_chunk(page, page->mapping, from, to);
+	err = nilfs_prepare_chunk(page, from, to);
 	if (err)
 		goto out_unlock;
 	if (de->inode) {
···
 	if (pde)
 		from = (char *)pde - (char *)page_address(page);
 	lock_page(page);
-	err = nilfs_prepare_chunk(page, mapping, from, to);
+	err = nilfs_prepare_chunk(page, from, to);
 	BUG_ON(err);
 	if (pde)
 		pde->rec_len = cpu_to_le16(to - from);
···
 	if (!page)
 		return -ENOMEM;
 
-	err = nilfs_prepare_chunk(page, mapping, 0, chunk_size);
+	err = nilfs_prepare_chunk(page, 0, chunk_size);
 	if (unlikely(err)) {
 		unlock_page(page);
 		goto fail;

fs/sysv/dir.c

···
 	pos = page_offset(page) +
 			(char*)de - (char*)page_address(page);
 	lock_page(page);
-	err = __sysv_write_begin(NULL, page->mapping, pos, SYSV_DIRSIZE,
-				AOP_FLAG_UNINTERRUPTIBLE, &page, NULL);
+	err = sysv_prepare_chunk(page, pos, SYSV_DIRSIZE);
 	if (err)
 		goto out_unlock;
 	memcpy (de->name, name, namelen);
···
 
 int sysv_delete_entry(struct sysv_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 = (char*)page_address(page);
 	loff_t pos = page_offset(page) + (char *)de - kaddr;
 	int err;
 
 	lock_page(page);
-	err = __sysv_write_begin(NULL, mapping, pos, SYSV_DIRSIZE,
-				AOP_FLAG_UNINTERRUPTIBLE, &page, NULL);
+	err = sysv_prepare_chunk(page, pos, SYSV_DIRSIZE);
 	BUG_ON(err);
 	de->inode = 0;
 	err = dir_commit_chunk(page, pos, SYSV_DIRSIZE);
···
 
 int sysv_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 sysv_dir_entry * de;
 	char *base;
 	int err;
 
 	if (!page)
 		return -ENOMEM;
-	err = __sysv_write_begin(NULL, mapping, 0, 2 * SYSV_DIRSIZE,
-				AOP_FLAG_UNINTERRUPTIBLE, &page, NULL);
+	err = sysv_prepare_chunk(page, 0, 2 * SYSV_DIRSIZE);
 	if (err) {
 		unlock_page(page);
 		goto fail;
···
 void sysv_set_link(struct sysv_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;
 	loff_t pos = page_offset(page) +
 			(char *)de-(char*)page_address(page);
 	int err;
 
 	lock_page(page);
-	err = __sysv_write_begin(NULL, mapping, pos, SYSV_DIRSIZE,
-				AOP_FLAG_UNINTERRUPTIBLE, &page, NULL);
+	err = sysv_prepare_chunk(page, pos, SYSV_DIRSIZE);
 	BUG_ON(err);
 	de->inode = cpu_to_fs16(SYSV_SB(inode->i_sb), inode->i_ino);
 	err = dir_commit_chunk(page, pos, SYSV_DIRSIZE);

fs/sysv/itree.c

···
 	return block_read_full_page(page,get_block);
 }
 
-int __sysv_write_begin(struct file *file, struct address_space *mapping,
-			loff_t pos, unsigned len, unsigned flags,
-			struct page **pagep, void **fsdata)
+int sysv_prepare_chunk(struct page *page, loff_t pos, unsigned len)
 {
-	return block_write_begin(file, mapping, pos, len, flags, pagep, fsdata,
-				get_block);
+	return block_write_begin_newtrunc(NULL, page->mapping, pos, len, 0,
+					  &page, NULL, get_block);
 }
 
 static int sysv_write_begin(struct file *file, struct address_space *mapping,
···
 			struct page **pagep, void **fsdata)
 {
 	*pagep = NULL;
-	return __sysv_write_begin(file, mapping, pos, len, flags, pagep, fsdata);
+	return block_write_begin(file, mapping, pos, len, flags, pagep, fsdata,
+				get_block);
 }
 
 static sector_t sysv_bmap(struct address_space *mapping, sector_t block)

fs/sysv/sysv.h

···
 
 /* itree.c */
 extern void sysv_truncate(struct inode *);
-extern int __sysv_write_begin(struct file *file, struct address_space *mapping,
-			loff_t pos, unsigned len, unsigned flags,
-			struct page **pagep, void **fsdata);
+extern int sysv_prepare_chunk(struct page *page, loff_t pos, unsigned len);
 
 /* inode.c */
 extern struct inode *sysv_iget(struct super_block *, unsigned int);

fs/ufs/dir.c

···
 	int err;
 
 	lock_page(page);
-	err = __ufs_write_begin(NULL, page->mapping, pos, len,
-				AOP_FLAG_UNINTERRUPTIBLE, &page, NULL);
+	err = ufs_prepare_chunk(page, pos, len);
 	BUG_ON(err);
 
 	de->d_ino = cpu_to_fs32(dir->i_sb, inode->i_ino);
···
 got_it:
 	pos = page_offset(page) +
 			(char*)de - (char*)page_address(page);
-	err = __ufs_write_begin(NULL, page->mapping, pos, rec_len,
-				AOP_FLAG_UNINTERRUPTIBLE, &page, NULL);
+	err = ufs_prepare_chunk(page, pos, rec_len);
 	if (err)
 		goto out_unlock;
 	if (de->d_ino) {
···
 		     struct page * page)
 {
 	struct super_block *sb = inode->i_sb;
-	struct address_space *mapping = page->mapping;
 	char *kaddr = page_address(page);
 	unsigned from = ((char*)dir - kaddr) & ~(UFS_SB(sb)->s_uspi->s_dirblksize - 1);
 	unsigned to = ((char*)dir - kaddr) + fs16_to_cpu(sb, dir->d_reclen);
···
 
 	pos = page_offset(page) + from;
 	lock_page(page);
-	err = __ufs_write_begin(NULL, mapping, pos, to - from,
-				AOP_FLAG_UNINTERRUPTIBLE, &page, NULL);
+	err = ufs_prepare_chunk(page, pos, to - from);
 	BUG_ON(err);
 	if (pde)
 		pde->d_reclen = cpu_to_fs16(sb, to - from);
···
 	if (!page)
 		return -ENOMEM;
 
-	err = __ufs_write_begin(NULL, mapping, 0, chunk_size,
-				AOP_FLAG_UNINTERRUPTIBLE, &page, NULL);
+	err = ufs_prepare_chunk(page, 0, chunk_size);
 	if (err) {
 		unlock_page(page);
 		goto fail;

fs/ufs/inode.c

···
 	return block_read_full_page(page,ufs_getfrag_block);
 }
 
-int __ufs_write_begin(struct file *file, struct address_space *mapping,
-			loff_t pos, unsigned len, unsigned flags,
-			struct page **pagep, void **fsdata)
+int ufs_prepare_chunk(struct page *page, loff_t pos, unsigned len)
 {
-	return block_write_begin(file, mapping, pos, len, flags, pagep, fsdata,
-				ufs_getfrag_block);
+	return block_write_begin_newtrunc(NULL, page->mapping, pos, len, 0,
+					  &page, NULL, ufs_getfrag_block);
 }
 
 static int ufs_write_begin(struct file *file, struct address_space *mapping,
···
 			struct page **pagep, void **fsdata)
 {
 	*pagep = NULL;
-	return __ufs_write_begin(file, mapping, pos, len, flags, pagep, fsdata);
+	return block_write_begin(file, mapping, pos, len, flags, pagep, fsdata,
+				ufs_getfrag_block);
 }
 
 static sector_t ufs_bmap(struct address_space *mapping, sector_t block)

fs/ufs/util.h

···
 
 extern dev_t ufs_get_inode_dev(struct super_block *, struct ufs_inode_info *);
 extern void ufs_set_inode_dev(struct super_block *, struct ufs_inode_info *, dev_t);
-extern int __ufs_write_begin(struct file *file, struct address_space *mapping,
-		loff_t pos, unsigned len, unsigned flags,
-		struct page **pagep, void **fsdata);
+extern int ufs_prepare_chunk(struct page *page, loff_t pos, unsigned len);
 
 /*
  * These functions manipulate ufs buffers