X-Git-Url: http://pilppa.org/gitweb/?a=blobdiff_plain;f=fs%2Fbuffer.c;h=75b51dfa5e0396dd2fa17756819bd678fda00208;hb=fa7744dbb69c06b69c7449063c440d8a53df9e6c;hp=0f9006714230073ea656aa909de6cd18ed05e903;hpb=f3d9071667752e5d419e59f76912ed3fb4a6bb9c;p=linux-2.6-omap-h63xx.git

diff --git a/fs/buffer.c b/fs/buffer.c
index 0f900671423..75b51dfa5e0 100644
--- a/fs/buffer.c
+++ b/fs/buffer.c
@@ -2194,6 +2194,52 @@ int generic_commit_write(struct file *file, struct page *page,
 	return 0;
 }
 
+/*
+ * block_page_mkwrite() is not allowed to change the file size as it gets
+ * called from a page fault handler when a page is first dirtied. Hence we must
+ * be careful to check for EOF conditions here. We set the page up correctly
+ * for a written page which means we get ENOSPC checking when writing into
+ * holes and correct delalloc and unwritten extent mapping on filesystems that
+ * support these features.
+ *
+ * We are not allowed to take the i_mutex here so we have to play games to
+ * protect against truncate races as the page could now be beyond EOF.  Because
+ * vmtruncate() writes the inode size before removing pages, once we have the
+ * page lock we can determine safely if the page is beyond EOF. If it is not
+ * 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 page *page,
+		   get_block_t get_block)
+{
+	struct inode *inode = vma->vm_file->f_path.dentry->d_inode;
+	unsigned long end;
+	loff_t size;
+	int ret = -EINVAL;
+
+	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 */
+		goto out_unlock;
+	}
+
+	/* page is wholly or partially inside EOF */
+	if (((page->index + 1) << PAGE_CACHE_SHIFT) > size)
+		end = size & ~PAGE_CACHE_MASK;
+	else
+		end = PAGE_CACHE_SIZE;
+
+	ret = block_prepare_write(page, 0, end, get_block);
+	if (!ret)
+		ret = block_commit_write(page, 0, end);
+
+out_unlock:
+	unlock_page(page);
+	return ret;
+}
 
 /*
  * nobh_prepare_write()'s prereads are special: the buffer_heads are freed
@@ -2588,13 +2634,10 @@ sector_t generic_block_bmap(struct address_space *mapping, sector_t block,
 	return tmp.b_blocknr;
 }
 
-static int end_bio_bh_io_sync(struct bio *bio, unsigned int bytes_done, int err)
+static void end_bio_bh_io_sync(struct bio *bio, int err)
 {
 	struct buffer_head *bh = bio->bi_private;
 
-	if (bio->bi_size)
-		return 1;
-
 	if (err == -EOPNOTSUPP) {
 		set_bit(BIO_EOPNOTSUPP, &bio->bi_flags);
 		set_bit(BH_Eopnotsupp, &bh->b_state);
@@ -2602,7 +2645,6 @@ static int end_bio_bh_io_sync(struct bio *bio, unsigned int bytes_done, int err)
 
 	bh->b_end_io(bh, test_bit(BIO_UPTODATE, &bio->bi_flags));
 	bio_put(bio);
-	return 0;
 }
 
 int submit_bh(int rw, struct buffer_head * bh)
@@ -2977,6 +3019,7 @@ EXPORT_SYMBOL(__brelse);
 EXPORT_SYMBOL(__wait_on_buffer);
 EXPORT_SYMBOL(block_commit_write);
 EXPORT_SYMBOL(block_prepare_write);
+EXPORT_SYMBOL(block_page_mkwrite);
 EXPORT_SYMBOL(block_read_full_page);
 EXPORT_SYMBOL(block_sync_page);
 EXPORT_SYMBOL(block_truncate_page);