vfs: Create __block_page_mkwrite() helper passing error values back

Create __block_page_mkwrite() helper which does all what block_page_mkwrite()
does except that it passes back errors from __block_write_begin /
block_commit_write calls.

Reviewed-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Jan Kara <jack@suse.cz>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>

diff --git a/fs/buffer.c b/fs/buffer.c
index a08bb8e..f6ad8f9 100644 (file)
--- a/fs/buffer.c
+++ b/fs/buffer.c
@@ -2332,23 +2332,22 @@ EXPORT_SYMBOL(block_commit_write);
  * beyond EOF, then the page is guaranteed safe against truncation until we
  * unlock the page.
  */
-int
-block_page_mkwrite(struct vm_area_struct *vma, struct vm_fault *vmf,
-                  get_block_t get_block)
+int __block_page_mkwrite(struct vm_area_struct *vma, struct vm_fault *vmf,
+                        get_block_t get_block)
 {
        struct page *page = vmf->page;
        struct inode *inode = vma->vm_file->f_path.dentry->d_inode;
        unsigned long end;
        loff_t size;
-       int ret = VM_FAULT_NOPAGE; /* make the VM retry the fault */
+       int ret;
 
        lock_page(page);
        size = i_size_read(inode);
        if ((page->mapping != inode->i_mapping) ||
            (page_offset(page) > size)) {
-               /* page got truncated out from underneath us */
-               unlock_page(page);
-               goto out;
+               /* We overload EFAULT to mean page got truncated */
+               ret = -EFAULT;
+               goto out_unlock;
        }
 
        /* page is wholly or partially inside EOF */
@@ -2361,18 +2360,22 @@ block_page_mkwrite(struct vm_area_struct *vma, struct vm_fault *vmf,
        if (!ret)
                ret = block_commit_write(page, 0, end);
 
-       if (unlikely(ret)) {
-               unlock_page(page);
-               if (ret == -ENOMEM)
-                       ret = VM_FAULT_OOM;
-               else /* -ENOSPC, -EIO, etc */
-                       ret = VM_FAULT_SIGBUS;
-       } else
-               ret = VM_FAULT_LOCKED;
-
-out:
+       if (unlikely(ret < 0))
+               goto out_unlock;
+       return 0;
+out_unlock:
+       unlock_page(page);
        return ret;
 }
+EXPORT_SYMBOL(__block_page_mkwrite);
+
+int block_page_mkwrite(struct vm_area_struct *vma, struct vm_fault *vmf,
+                  get_block_t get_block)
+{
+       int ret = __block_page_mkwrite(vma, vmf, get_block);
+
+       return block_page_mkwrite_return(ret);
+}
 EXPORT_SYMBOL(block_page_mkwrite);
 
 /*

diff --git a/include/linux/buffer_head.h b/include/linux/buffer_head.h
index f5df235..2bf6a91 100644 (file)
--- a/include/linux/buffer_head.h
+++ b/include/linux/buffer_head.h
@@ -217,8 +217,22 @@ int cont_write_begin(struct file *, struct address_space *, loff_t,
                        get_block_t *, loff_t *);
 int generic_cont_expand_simple(struct inode *inode, loff_t size);
 int block_commit_write(struct page *page, unsigned from, unsigned to);
+int __block_page_mkwrite(struct vm_area_struct *vma, struct vm_fault *vmf,
+                               get_block_t get_block);
 int block_page_mkwrite(struct vm_area_struct *vma, struct vm_fault *vmf,
                                get_block_t get_block);
+/* Convert errno to return value from ->page_mkwrite() call */
+static inline int block_page_mkwrite_return(int err)
+{
+       if (err == 0)
+               return VM_FAULT_LOCKED;
+       if (err == -EFAULT)
+               return VM_FAULT_NOPAGE;
+       if (err == -ENOMEM)
+               return VM_FAULT_OOM;
+       /* -ENOSPC, -EDQUOT, -EIO ... */
+       return VM_FAULT_SIGBUS;
+}
 sector_t generic_block_bmap(struct address_space *, sector_t, get_block_t *);
 int block_truncate_page(struct address_space *, loff_t, get_block_t *);
 int nobh_write_begin(struct address_space *, loff_t, unsigned, unsigned,