ext4: refactor ext4_zero_range()

[ Upstream commit 53471e0 ]

The current implementation of ext4_zero_range() contains complex
position calculations and stale error tags. To improve the code's
clarity and maintainability, it is essential to clean up the code and
improve its readability, this can be achieved by: a) simplifying and
renaming variables, making the style the same as ext4_punch_hole(); b)
eliminating unnecessary position calculations, writing back all data in
data=journal mode, and drop page cache from the original offset to the
end, rather than using aligned blocks; c) renaming the stale out_mutex
tags.

Signed-off-by: Zhang Yi <[email protected]>
Reviewed-by: Jan Kara <[email protected]>
Reviewed-by: Ojaswin Mujoo <[email protected]>
Link: https://patch.msgid.link/[email protected]
Signed-off-by: Theodore Ts'o <[email protected]>
Stable-dep-of: 29ec9be ("ext4: fix incorrect punch max_end")
Signed-off-by: Sasha Levin <[email protected]>
Signed-off-by: Greg Kroah-Hartman <[email protected]>

Author: zhangyi089

fs/ext4/extents.c

@@ -4571,118 +4571,86 @@ static long ext4_zero_range(struct file *file, loff_t offset,
 	struct inode *inode = file_inode(file);
 	struct address_space *mapping = file->f_mapping;
 	handle_t *handle = NULL;
-	unsigned int max_blocks;
 	loff_t new_size = 0;
-	int ret = 0;
-	int flags;
-	int credits;
-	int partial_begin, partial_end;
-	loff_t start, end;
-	ext4_lblk_t lblk;
+	loff_t end = offset + len;
+	ext4_lblk_t start_lblk, end_lblk;
+	unsigned int blocksize = i_blocksize(inode);
 	unsigned int blkbits = inode->i_blkbits;
+	int ret, flags, credits;
 
 	trace_ext4_zero_range(inode, offset, len, mode);
 
-	/*
-	 * Round up offset. This is not fallocate, we need to zero out
-	 * blocks, so convert interior block aligned part of the range to
-	 * unwritten and possibly manually zero out unaligned parts of the
-	 * range. Here, start and partial_begin are inclusive, end and
-	 * partial_end are exclusive.
-	 */
-	start = round_up(offset, 1 << blkbits);
-	end = round_down((offset + len), 1 << blkbits);
-
-	if (start < offset || end > offset + len)
-		return -EINVAL;
-	partial_begin = offset & ((1 << blkbits) - 1);
-	partial_end = (offset + len) & ((1 << blkbits) - 1);
-
-	lblk = start >> blkbits;
-	max_blocks = (end >> blkbits);
-	if (max_blocks < lblk)
-		max_blocks = 0;
-	else
-		max_blocks -= lblk;
-
 	inode_lock(inode);
 
 	/*
 	 * Indirect files do not support unwritten extents
 	 */
 	if (!(ext4_test_inode_flag(inode, EXT4_INODE_EXTENTS))) {
 		ret = -EOPNOTSUPP;
-		goto out_mutex;
+		goto out;
 	}
 
 	if (!(mode & FALLOC_FL_KEEP_SIZE) &&
-	    (offset + len > inode->i_size ||
-	     offset + len > EXT4_I(inode)->i_disksize)) {
-		new_size = offset + len;
+	    (end > inode->i_size || end > EXT4_I(inode)->i_disksize)) {
+		new_size = end;
 		ret = inode_newsize_ok(inode, new_size);
 		if (ret)
-			goto out_mutex;
+			goto out;
 	}
 
-	flags = EXT4_GET_BLOCKS_CREATE_UNWRIT_EXT;
-
 	/* Wait all existing dio workers, newcomers will block on i_rwsem */
 	inode_dio_wait(inode);
 
 	ret = file_modified(file);
 	if (ret)
-		goto out_mutex;
-
-	/* Preallocate the range including the unaligned edges */
-	if (partial_begin || partial_end) {
-		ret = ext4_alloc_file_blocks(file,
-				round_down(offset, 1 << blkbits) >> blkbits,
-				(round_up((offset + len), 1 << blkbits) -
-				 round_down(offset, 1 << blkbits)) >> blkbits,
-				new_size, flags);
-		if (ret)
-			goto out_mutex;
+		goto out;
 
-	}
+	/*
+	 * Prevent page faults from reinstantiating pages we have released
+	 * from page cache.
+	 */
+	filemap_invalidate_lock(mapping);
 
-	/* Zero range excluding the unaligned edges */
-	if (max_blocks > 0) {
-		flags |= (EXT4_GET_BLOCKS_CONVERT_UNWRITTEN |
-			  EXT4_EX_NOCACHE);
+	ret = ext4_break_layouts(inode);
+	if (ret)
+		goto out_invalidate_lock;
 
-		/*
-		 * Prevent page faults from reinstantiating pages we have
-		 * released from page cache.
-		 */
-		filemap_invalidate_lock(mapping);
+	flags = EXT4_GET_BLOCKS_CREATE_UNWRIT_EXT;
+	/* Preallocate the range including the unaligned edges */
+	if (!IS_ALIGNED(offset | end, blocksize)) {
+		ext4_lblk_t alloc_lblk = offset >> blkbits;
+		ext4_lblk_t len_lblk = EXT4_MAX_BLOCKS(len, offset, blkbits);
 
-		ret = ext4_break_layouts(inode);
-		if (ret) {
-			filemap_invalidate_unlock(mapping);
-			goto out_mutex;
-		}
+		ret = ext4_alloc_file_blocks(file, alloc_lblk, len_lblk,
+					     new_size, flags);
+		if (ret)
+			goto out_invalidate_lock;
+	}
 
-		ret = ext4_update_disksize_before_punch(inode, offset, len);
-		if (ret) {
-			filemap_invalidate_unlock(mapping);
-			goto out_mutex;
-		}
+	ret = ext4_update_disksize_before_punch(inode, offset, len);
+	if (ret)
+		goto out_invalidate_lock;
 
-		/* Now release the pages and zero block aligned part of pages */
-		ret = ext4_truncate_page_cache_block_range(inode, start, end);
-		if (ret) {
-			filemap_invalidate_unlock(mapping);
-			goto out_mutex;
-		}
+	/* Now release the pages and zero block aligned part of pages */
+	ret = ext4_truncate_page_cache_block_range(inode, offset, end);
+	if (ret)
+		goto out_invalidate_lock;
 
-		ret = ext4_alloc_file_blocks(file, lblk, max_blocks, new_size,
-					     flags);
-		filemap_invalidate_unlock(mapping);
+	/* Zero range excluding the unaligned edges */
+	start_lblk = EXT4_B_TO_LBLK(inode, offset);
+	end_lblk = end >> blkbits;
+	if (end_lblk > start_lblk) {
+		ext4_lblk_t zero_blks = end_lblk - start_lblk;
+
+		flags |= (EXT4_GET_BLOCKS_CONVERT_UNWRITTEN | EXT4_EX_NOCACHE);
+		ret = ext4_alloc_file_blocks(file, start_lblk, zero_blks,
+					     new_size, flags);
 		if (ret)
-			goto out_mutex;
+			goto out_invalidate_lock;
 	}
-	if (!partial_begin && !partial_end)
-		goto out_mutex;
+	/* Finish zeroing out if it doesn't contain partial block */
+	if (IS_ALIGNED(offset | end, blocksize))
+		goto out_invalidate_lock;
 
 	/*
 	 * In worst case we have to writeout two nonadjacent unwritten
@@ -4695,25 +4663,29 @@ static long ext4_zero_range(struct file *file, loff_t offset,
 	if (IS_ERR(handle)) {
 		ret = PTR_ERR(handle);
 		ext4_std_error(inode->i_sb, ret);
-		goto out_mutex;
+		goto out_invalidate_lock;
 	}
 
+	/* Zero out partial block at the edges of the range */
+	ret = ext4_zero_partial_blocks(handle, inode, offset, len);
+	if (ret)
+		goto out_handle;
+
 	if (new_size)
 		ext4_update_inode_size(inode, new_size);
 	ret = ext4_mark_inode_dirty(handle, inode);
 	if (unlikely(ret))
 		goto out_handle;
-	/* Zero out partial block at the edges of the range */
-	ret = ext4_zero_partial_blocks(handle, inode, offset, len);
-	if (ret >= 0)
-		ext4_update_inode_fsync_trans(handle, inode, 1);
 
+	ext4_update_inode_fsync_trans(handle, inode, 1);
 	if (file->f_flags & O_SYNC)
 		ext4_handle_sync(handle);
 
 out_handle:
 	ext4_journal_stop(handle);
-out_mutex:
+out_invalidate_lock:
+	filemap_invalidate_unlock(mapping);
+out:
 	inode_unlock(inode);
 	return ret;
 }