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/sysv/dir.c b/fs/sysv/dir.c
index 79941e4..a77c421 100644
--- a/fs/sysv/dir.c
+++ b/fs/sysv/dir.c
@@ -218,8 +218,7 @@ got_it:
 	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);
@@ -239,15 +238,13 @@ out_unlock:
 
 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);
@@ -259,16 +256,14 @@ int sysv_delete_entry(struct sysv_dir_entry *de, struct page *page)
 
 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;
@@ -341,15 +336,13 @@ not_empty:
 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);
diff --git a/fs/sysv/itree.c b/fs/sysv/itree.c
index f042eec..4068f48 100644
--- a/fs/sysv/itree.c
+++ b/fs/sysv/itree.c
@@ -459,12 +459,10 @@ static int sysv_readpage(struct file *file, struct page *page)
 	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,
@@ -472,7 +470,8 @@ 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)
diff --git a/fs/sysv/sysv.h b/fs/sysv/sysv.h
index 94cb9b4..bb55cdb 100644
--- a/fs/sysv/sysv.h
+++ b/fs/sysv/sysv.h
@@ -136,9 +136,7 @@ extern unsigned long sysv_count_free_blocks(struct super_block *);
 
 /* 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);