ext4: rename and extend ext4_block_truncate_page()

Rename ext4_block_truncate_page() to ext4_block_zero_eof() and extend
its signature to accept an explicit 'end' offset instead of calculating
the block boundary. This helper function now can replace all cases
requiring zeroing of the partial EOF block, including the append
buffered write paths in ext4_*_write_end().

Signed-off-by: Zhang Yi <yi.zhang@huawei.com>
Reviewed-by: Jan Kara <jack@suse.cz>
Link: https://patch.msgid.link/20260327102939.1095257-3-yi.zhang@huaweicloud.com
Signed-off-by: Theodore Ts'o <tytso@mit.edu>

Author: zhangyi089

fs/ext4/ext4.h

@@ -3097,6 +3097,8 @@ extern int ext4_chunk_trans_blocks(struct inode *, int nrblocks);
 extern int ext4_chunk_trans_extent(struct inode *inode, int nrblocks);
 extern int ext4_meta_trans_blocks(struct inode *inode, int lblocks,
 				  int pextents);
+extern int ext4_block_zero_eof(handle_t *handle, struct inode *inode,
+			       loff_t from, loff_t end);
 extern int ext4_zero_partial_blocks(handle_t *handle, struct inode *inode,
 			     loff_t lstart, loff_t lend);
 extern vm_fault_t ext4_page_mkwrite(struct vm_fault *vmf);

fs/ext4/extents.c

@@ -4654,8 +4654,8 @@ static int ext4_alloc_file_blocks(struct file *file, ext4_lblk_t offset,
 						      inode_get_ctime(inode));
 			if (epos > old_size) {
 				pagecache_isize_extended(inode, old_size, epos);
-				ext4_zero_partial_blocks(handle, inode,
-						     old_size, epos - old_size);
+				ext4_block_zero_eof(handle, inode, old_size,
+						    epos);
 			}
 		}
 		ret2 = ext4_mark_inode_dirty(handle, inode);

fs/ext4/inode.c

@@ -1468,7 +1468,7 @@ static int ext4_write_end(const struct kiocb *iocb,
 
 	if (old_size < pos && !verity) {
 		pagecache_isize_extended(inode, old_size, pos);
-		ext4_zero_partial_blocks(handle, inode, old_size, pos - old_size);
+		ext4_block_zero_eof(handle, inode, old_size, pos);
 	}
 	/*
 	 * Don't mark the inode dirty under folio lock. First, it unnecessarily
@@ -1586,7 +1586,7 @@ static int ext4_journalled_write_end(const struct kiocb *iocb,
 
 	if (old_size < pos && !verity) {
 		pagecache_isize_extended(inode, old_size, pos);
-		ext4_zero_partial_blocks(handle, inode, old_size, pos - old_size);
+		ext4_block_zero_eof(handle, inode, old_size, pos);
 	}
 
 	if (size_changed) {
@@ -3282,7 +3282,7 @@ static int ext4_da_do_write_end(struct address_space *mapping,
 	if (IS_ERR(handle))
 		return PTR_ERR(handle);
 	if (zero_len)
-		ext4_zero_partial_blocks(handle, inode, old_size, zero_len);
+		ext4_block_zero_eof(handle, inode, old_size, pos);
 	ext4_mark_inode_dirty(handle, inode);
 	ext4_journal_stop(handle);
 
@@ -4162,26 +4162,31 @@ static int ext4_block_zero_page_range(handle_t *handle,
 }
 
 /*
- * ext4_block_truncate_page() zeroes out a mapping from file offset `from'
- * up to the end of the block which corresponds to `from'.
- * 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.
+ * Zero out a mapping from file offset 'from' up to the end of the block
+ * which corresponds to 'from' or to the given 'end' inside this block.
+ * This required during truncate up and performing append writes. We need
+ * to physically zero the tail end of that block so it doesn't yield old
+ * data if the file is grown.
  */
-static int ext4_block_truncate_page(handle_t *handle,
-		struct address_space *mapping, loff_t from)
+int ext4_block_zero_eof(handle_t *handle, struct inode *inode,
+			loff_t from, loff_t end)
 {
-	unsigned length;
-	unsigned blocksize;
-	struct inode *inode = mapping->host;
+	unsigned int blocksize = i_blocksize(inode);
+	unsigned int offset;
+	loff_t length = end - from;
 
+	offset = from & (blocksize - 1);
+	if (!offset || from >= end)
+		return 0;
 	/* If we are processing an encrypted inode during orphan list handling */
 	if (IS_ENCRYPTED(inode) && !fscrypt_has_encryption_key(inode))
 		return 0;
 
-	blocksize = i_blocksize(inode);
-	length = blocksize - (from & (blocksize - 1));
+	if (length > blocksize - offset)
+		length = blocksize - offset;
 
-	return ext4_block_zero_page_range(handle, mapping, from, length, NULL);
+	return ext4_block_zero_page_range(handle, inode->i_mapping, from,
+					  length, NULL);
 }
 
 int ext4_zero_partial_blocks(handle_t *handle, struct inode *inode,
@@ -4535,7 +4540,6 @@ int ext4_truncate(struct inode *inode)
 	unsigned int credits;
 	int err = 0, err2;
 	handle_t *handle;
-	struct address_space *mapping = inode->i_mapping;
 
 	/*
 	 * There is a possibility that we're either freeing the inode
@@ -4578,8 +4582,9 @@ int ext4_truncate(struct inode *inode)
 		goto out_trace;
 	}
 
+	/* Zero to the end of the block containing i_size */
 	if (inode->i_size & (inode->i_sb->s_blocksize - 1))
-		ext4_block_truncate_page(handle, mapping, inode->i_size);
+		ext4_block_zero_eof(handle, inode, inode->i_size, LLONG_MAX);
 
 	/*
 	 * We add the inode to the orphan list, so that if this
@@ -5968,8 +5973,8 @@ int ext4_setattr(struct mnt_idmap *idmap, struct dentry *dentry,
 				inode_set_mtime_to_ts(inode,
 						      inode_set_ctime_current(inode));
 				if (oldsize & (inode->i_sb->s_blocksize - 1))
-					ext4_block_truncate_page(handle,
-							inode->i_mapping, oldsize);
+					ext4_block_zero_eof(handle, inode,
+							    oldsize, LLONG_MAX);
 			}
 
 			if (shrink)