Fixed MTP to work with TWRP

fs/udf/symlink.c

@@ -0,0 +1,160 @@
+/*
+ * symlink.c
+ *
+ * PURPOSE
+ *	Symlink handling routines for the OSTA-UDF(tm) filesystem.
+ *
+ * COPYRIGHT
+ *	This file is distributed under the terms of the GNU General Public
+ *	License (GPL). Copies of the GPL can be obtained from:
+ *		ftp://prep.ai.mit.edu/pub/gnu/GPL
+ *	Each contributing author retains all rights to their own work.
+ *
+ *  (C) 1998-2001 Ben Fennema
+ *  (C) 1999 Stelias Computing Inc
+ *
+ * HISTORY
+ *
+ *  04/16/99 blf  Created.
+ *
+ */
+
+#include "udfdecl.h"
+#include <linux/uaccess.h>
+#include <linux/errno.h>
+#include <linux/fs.h>
+#include <linux/time.h>
+#include <linux/mm.h>
+#include <linux/stat.h>
+#include <linux/pagemap.h>
+#include <linux/buffer_head.h>
+#include "udf_i.h"
+
+static int udf_pc_to_char(struct super_block *sb, unsigned char *from,
+			  int fromlen, unsigned char *to, int tolen)
+{
+	struct pathComponent *pc;
+	int elen = 0;
+	int comp_len;
+	unsigned char *p = to;
+
+	/* Reserve one byte for terminating \0 */
+	tolen--;
+	while (elen < fromlen) {
+		pc = (struct pathComponent *)(from + elen);
+		elen += sizeof(struct pathComponent);
+		switch (pc->componentType) {
+		case 1:
+			/*
+			 * Symlink points to some place which should be agreed
+ 			 * upon between originator and receiver of the media. Ignore.
+			 */
+			if (pc->lengthComponentIdent > 0) {
+				elen += pc->lengthComponentIdent;
+				break;
+			}
+			/* Fall through */
+		case 2:
+			if (tolen == 0)
+				return -ENAMETOOLONG;
+			p = to;
+			*p++ = '/';
+			tolen--;
+			break;
+		case 3:
+			if (tolen < 3)
+				return -ENAMETOOLONG;
+			memcpy(p, "../", 3);
+			p += 3;
+			tolen -= 3;
+			break;
+		case 4:
+			if (tolen < 2)
+				return -ENAMETOOLONG;
+			memcpy(p, "./", 2);
+			p += 2;
+			tolen -= 2;
+			/* that would be . - just ignore */
+			break;
+		case 5:
+			elen += pc->lengthComponentIdent;
+			if (elen > fromlen)
+				return -EIO;
+			comp_len = udf_get_filename(sb, pc->componentIdent,
+						    pc->lengthComponentIdent,
+						    p, tolen);
+			p += comp_len;
+			tolen -= comp_len;
+			if (tolen == 0)
+				return -ENAMETOOLONG;
+			*p++ = '/';
+			tolen--;
+			break;
+		}
+	}
+	if (p > to + 1)
+		p[-1] = '\0';
+	else
+		p[0] = '\0';
+	return 0;
+}
+
+static int udf_symlink_filler(struct file *file, struct page *page)
+{
+	struct inode *inode = page->mapping->host;
+	struct buffer_head *bh = NULL;
+	unsigned char *symlink;
+	int err;
+	unsigned char *p = kmap(page);
+	struct udf_inode_info *iinfo;
+	uint32_t pos;
+
+	/* We don't support symlinks longer than one block */
+	if (inode->i_size > inode->i_sb->s_blocksize) {
+		err = -ENAMETOOLONG;
+		goto out_unmap;
+	}
+
+	iinfo = UDF_I(inode);
+	pos = udf_block_map(inode, 0);
+
+	down_read(&iinfo->i_data_sem);
+	if (iinfo->i_alloc_type == ICBTAG_FLAG_AD_IN_ICB) {
+		symlink = iinfo->i_ext.i_data + iinfo->i_lenEAttr;
+	} else {
+		bh = sb_bread(inode->i_sb, pos);
+
+		if (!bh) {
+			err = -EIO;
+			goto out_unlock_inode;
+		}
+
+		symlink = bh->b_data;
+	}
+
+	err = udf_pc_to_char(inode->i_sb, symlink, inode->i_size, p, PAGE_SIZE);
+	brelse(bh);
+	if (err)
+		goto out_unlock_inode;
+
+	up_read(&iinfo->i_data_sem);
+	SetPageUptodate(page);
+	kunmap(page);
+	unlock_page(page);
+	return 0;
+
+out_unlock_inode:
+	up_read(&iinfo->i_data_sem);
+	SetPageError(page);
+out_unmap:
+	kunmap(page);
+	unlock_page(page);
+	return err;
+}
+
+/*
+ * symlinks can't do much...
+ */
+const struct address_space_operations udf_symlink_aops = {
+	.readpage		= udf_symlink_filler,
+};