ext3: Improve truncate error handling

New truncate calling convention allows us to handle errors from
ext3_block_truncate_page(). So reorganize the code so that
ext3_block_truncate_page() is called before we change inode size.

This also removes unnecessary block zeroing from error recovery after failed
buffered writes (zeroing isn't needed because we could have never written
non-zero data to disk). We have to be careful and keep zeroing in direct IO
write error recovery because there we might have already overwritten end of the
last file block.

Signed-off-by: Jan Kara <[e-mail]>

fs/ext3/inode.c

···
 #include "acl.h"
 
 static int ext3_writepage_trans_blocks(struct inode *inode);
+static int ext3_block_truncate_page(struct inode *inode, loff_t from);
 
 /*
  * Test whether an inode is a fast symlink.
···
 	ext3_truncate(inode);
 }
 
+/*
+ * Truncate blocks that were not used by direct IO write. We have to zero out
+ * the last file block as well because direct IO might have written to it.
+ */
+static void ext3_truncate_failed_direct_write(struct inode *inode)
+{
+	ext3_block_truncate_page(inode, inode->i_size);
+	ext3_truncate(inode);
+}
+
 static int ext3_write_begin(struct file *file, struct address_space *mapping,
 				loff_t pos, unsigned len, unsigned flags,
 				struct page **pagep, void **fsdata)
···
 		loff_t end = offset + iov_length(iov, nr_segs);
 
 		if (end > isize)
-			ext3_truncate_failed_write(inode);
+			ext3_truncate_failed_direct_write(inode);
 	}
 	if (ret == -ENOSPC && ext3_should_retry_alloc(inode->i_sb, &retries))
 		goto retry;
···
 			/* This is really bad luck. We've written the data
 			 * but cannot extend i_size. Truncate allocated blocks
 			 * and pretend the write failed... */
-			ext3_truncate_failed_write(inode);
+			ext3_truncate_failed_direct_write(inode);
 			ret = PTR_ERR(handle);
 			goto out;
 		}
···
  * This required during truncate. We need to physically zero the tail end
  * of that block so it doesn't yield old data if the file is later grown.
  */
-static int ext3_block_truncate_page(handle_t *handle, struct page *page,
-		struct address_space *mapping, loff_t from)
+static int ext3_block_truncate_page(struct inode *inode, loff_t from)
 {
 	ext3_fsblk_t index = from >> PAGE_CACHE_SHIFT;
-	unsigned offset = from & (PAGE_CACHE_SIZE-1);
+	unsigned offset = from & (PAGE_CACHE_SIZE - 1);
 	unsigned blocksize, iblock, length, pos;
-	struct inode *inode = mapping->host;
+	struct page *page;
+	handle_t *handle = NULL;
 	struct buffer_head *bh;
 	int err = 0;
 
+	/* Truncated on block boundary - nothing to do */
 	blocksize = inode->i_sb->s_blocksize;
+	if ((from & (blocksize - 1)) == 0)
+		return 0;
+
+	page = grab_cache_page(inode->i_mapping, index);
+	if (!page)
+		return -ENOMEM;
 	length = blocksize - (offset & (blocksize - 1));
 	iblock = index << (PAGE_CACHE_SHIFT - inode->i_sb->s_blocksize_bits);
 
···
 			goto unlock;
 	}
 
+	/* data=writeback mode doesn't need transaction to zero-out data */
+	if (!ext3_should_writeback_data(inode)) {
+		/* We journal at most one block */
+		handle = ext3_journal_start(inode, 1);
+		if (IS_ERR(handle)) {
+			clear_highpage(page);
+			flush_dcache_page(page);
+			err = PTR_ERR(handle);
+			goto unlock;
+		}
+	}
+
 	if (ext3_should_journal_data(inode)) {
 		BUFFER_TRACE(bh, "get write access");
 		err = ext3_journal_get_write_access(handle, bh);
 		if (err)
-			goto unlock;
+			goto stop;
 	}
 
 	zero_user(page, offset, length);
···
 			err = ext3_journal_dirty_data(handle, bh);
 		mark_buffer_dirty(bh);
 	}
+stop:
+	if (handle)
+		ext3_journal_stop(handle);
 
 unlock:
 	unlock_page(page);
···
 	struct ext3_inode_info *ei = EXT3_I(inode);
 	__le32 *i_data = ei->i_data;
 	int addr_per_block = EXT3_ADDR_PER_BLOCK(inode->i_sb);
-	struct address_space *mapping = inode->i_mapping;
 	int offsets[4];
 	Indirect chain[4];
 	Indirect *partial;
···
 	int n;
 	long last_block;
 	unsigned blocksize = inode->i_sb->s_blocksize;
-	struct page *page;
 
 	trace_ext3_truncate_enter(inode);
 
···
 	if (inode->i_size == 0 && ext3_should_writeback_data(inode))
 		ext3_set_inode_state(inode, EXT3_STATE_FLUSH_ON_CLOSE);
 
-	/*
-	 * We have to lock the EOF page here, because lock_page() nests
-	 * outside journal_start().
-	 */
-	if ((inode->i_size & (blocksize - 1)) == 0) {
-		/* Block boundary? Nothing to do */
-		page = NULL;
-	} else {
-		page = grab_cache_page(mapping,
-				inode->i_size >> PAGE_CACHE_SHIFT);
-		if (!page)
-			goto out_notrans;
-	}
-
 	handle = start_transaction(inode);
-	if (IS_ERR(handle)) {
-		if (page) {
-			clear_highpage(page);
-			flush_dcache_page(page);
-			unlock_page(page);
-			page_cache_release(page);
-		}
+	if (IS_ERR(handle))
 		goto out_notrans;
-	}
 
 	last_block = (inode->i_size + blocksize-1)
 					>> EXT3_BLOCK_SIZE_BITS(inode->i_sb);
-
-	if (page)
-		ext3_block_truncate_page(handle, page, mapping, inode->i_size);
-
 	n = ext3_block_to_path(inode, last_block, offsets, NULL);
 	if (n == 0)
 		goto out_stop;	/* error */
···
 		}
 
 		error = ext3_orphan_add(handle, inode);
+		if (error) {
+			ext3_journal_stop(handle);
+			goto err_out;
+		}
 		EXT3_I(inode)->i_disksize = attr->ia_size;
-		rc = ext3_mark_inode_dirty(handle, inode);
-		if (!error)
-			error = rc;
+		error = ext3_mark_inode_dirty(handle, inode);
 		ext3_journal_stop(handle);
+		if (error) {
+			/* Some hard fs error must have happened. Bail out. */
+			ext3_orphan_del(NULL, inode);
+			goto err_out;
+		}
+		rc = ext3_block_truncate_page(inode, attr->ia_size);
+		if (rc) {
+			/* Cleanup orphan list and exit */
+			handle = ext3_journal_start(inode, 3);
+			if (IS_ERR(handle)) {
+				ext3_orphan_del(NULL, inode);
+				goto err_out;
+			}
+			ext3_orphan_del(handle, inode);
+			ext3_journal_stop(handle);
+			goto err_out;
+		}
 	}
 
 	if ((attr->ia_valid & ATTR_SIZE) &&