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, 14 insertions, 24 deletions

diff --git a/fs/ext2/dir.c b/fs/ext2/dir.c
index 7516957273ed..6b946bae11cf 100644
--- a/fs/ext2/dir.c
+++ b/fs/ext2/dir.c
@@ -448,6 +448,12 @@ ino_t ext2_inode_by_name(struct inode *dir, struct qstr *child)
         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)
@@ -458,8 +464,7 @@ void ext2_set_link(struct inode *dir, struct ext2_dir_entry_2 *de,
         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);
@@ -542,8 +547,7 @@ int ext2_add_link (struct dentry *dentry, struct inode *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) {
@@ -576,8 +580,7 @@ out_unlock:
  */
 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) +
@@ -601,8 +604,7 @@ int ext2_delete_entry (struct ext2_dir_entry_2 * dir, struct page * page )
                 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);
@@ -621,8 +623,7 @@ out:
  */
 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;
@@ -631,8 +632,7 @@ int ext2_make_empty(struct inode *inode, struct inode *parent)
         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;
diff --git a/fs/ext2/ext2.h b/fs/ext2/ext2.h
index 52b34f1d2738..8f53d11bf957 100644
--- a/fs/ext2/ext2.h
+++ b/fs/ext2/ext2.h
@@ -127,9 +127,6 @@ extern void ext2_set_inode_flags(struct inode *inode);
 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);
diff --git a/fs/ext2/inode.c b/fs/ext2/inode.c
index 348805cd4109..2f4dfbcd7696 100644
--- a/fs/ext2/inode.c
+++ b/fs/ext2/inode.c
@@ -765,14 +765,6 @@ ext2_readpages(struct file *file, struct address_space *mapping,
         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,
@@ -781,7 +773,8 @@ ext2_write_begin(struct file *file, struct address_space *mapping,
         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;