Simplify ext4_collapse_range() and align its code style with that of
ext4_zero_range() and ext4_punch_hole(). Refactor it by: a) renaming
variables, b) removing redundant input parameter checks and moving
the remaining checks under i_rwsem in preparation for future
refactoring, and c) renaming the three stale error tags.

Signed-off-by: Zhang Yi <yi.zhang@huawei.com>
---
 fs/ext4/extents.c | 103 +++++++++++++++++++++-------------------------
 1 file changed, 48 insertions(+), 55 deletions(-)

diff --git a/fs/ext4/extents.c b/fs/ext4/extents.c
index f843342e5164..a4e95f3b5f09 100644
--- a/fs/ext4/extents.c
+++ b/fs/ext4/extents.c
@@ -5295,43 +5295,36 @@ static int ext4_collapse_range(struct file *file, loff_t offset, loff_t len)
 	struct inode *inode = file_inode(file);
 	struct super_block *sb = inode->i_sb;
 	struct address_space *mapping = inode->i_mapping;
-	ext4_lblk_t punch_start, punch_stop;
+	loff_t end = offset + len;
+	ext4_lblk_t start_lblk, end_lblk;
 	handle_t *handle;
 	unsigned int credits;
-	loff_t new_size, ioffset;
+	loff_t start, new_size;
 	int ret;
 
-	/*
-	 * We need to test this early because xfstests assumes that a
-	 * collapse range of (0, 1) will return EOPNOTSUPP if the file
-	 * system does not support collapse range.
-	 */
-	if (!ext4_test_inode_flag(inode, EXT4_INODE_EXTENTS))
-		return -EOPNOTSUPP;
+	trace_ext4_collapse_range(inode, offset, len);
 
-	/* Collapse range works only on fs cluster size aligned regions. */
-	if (!IS_ALIGNED(offset | len, EXT4_CLUSTER_SIZE(sb)))
-		return -EINVAL;
+	inode_lock(inode);
 
-	trace_ext4_collapse_range(inode, offset, len);
+	/* Currently just for extent based files */
+	if (!ext4_test_inode_flag(inode, EXT4_INODE_EXTENTS)) {
+		ret = -EOPNOTSUPP;
+		goto out;
+	}
 
-	punch_start = offset >> EXT4_BLOCK_SIZE_BITS(sb);
-	punch_stop = (offset + len) >> EXT4_BLOCK_SIZE_BITS(sb);
+	/* Collapse range works only on fs cluster size aligned regions. */
+	if (!IS_ALIGNED(offset | len, EXT4_CLUSTER_SIZE(sb))) {
+		ret = -EINVAL;
+		goto out;
+	}
 
-	inode_lock(inode);
 	/*
 	 * There is no need to overlap collapse range with EOF, in which case
 	 * it is effectively a truncate operation
 	 */
-	if (offset + len >= inode->i_size) {
+	if (end >= inode->i_size) {
 		ret = -EINVAL;
-		goto out_mutex;
-	}
-
-	/* Currently just for extent based files */
-	if (!ext4_test_inode_flag(inode, EXT4_INODE_EXTENTS)) {
-		ret = -EOPNOTSUPP;
-		goto out_mutex;
+		goto out;
 	}
 
 	/* Wait for existing dio to complete */
@@ -5339,7 +5332,7 @@ static int ext4_collapse_range(struct file *file, loff_t offset, loff_t len)
 
 	ret = file_modified(file);
 	if (ret)
-		goto out_mutex;
+		goto out;
 
 	/*
 	 * Prevent page faults from reinstantiating pages we have released from
@@ -5349,55 +5342,52 @@ static int ext4_collapse_range(struct file *file, loff_t offset, loff_t len)
 
 	ret = ext4_break_layouts(inode);
 	if (ret)
-		goto out_mmap;
+		goto out_invalidate_lock;
 
 	/*
+	 * Write tail of the last page before removed range and data that
+	 * will be shifted since they will get removed from the page cache
+	 * below. We are also protected from pages becoming dirty by
+	 * i_rwsem and invalidate_lock.
 	 * Need to round down offset to be aligned with page size boundary
 	 * for page size > block size.
 	 */
-	ioffset = round_down(offset, PAGE_SIZE);
-	/*
-	 * Write tail of the last page before removed range since it will get
-	 * removed from the page cache below.
-	 */
-	ret = filemap_write_and_wait_range(mapping, ioffset, offset);
-	if (ret)
-		goto out_mmap;
-	/*
-	 * Write data that will be shifted to preserve them when discarding
-	 * page cache below. We are also protected from pages becoming dirty
-	 * by i_rwsem and invalidate_lock.
-	 */
-	ret = filemap_write_and_wait_range(mapping, offset + len,
-					   LLONG_MAX);
+	start = round_down(offset, PAGE_SIZE);
+	ret = filemap_write_and_wait_range(mapping, start, offset);
+	if (!ret)
+		ret = filemap_write_and_wait_range(mapping, end, LLONG_MAX);
 	if (ret)
-		goto out_mmap;
-	truncate_pagecache(inode, ioffset);
+		goto out_invalidate_lock;
+
+	truncate_pagecache(inode, start);
 
 	credits = ext4_writepage_trans_blocks(inode);
 	handle = ext4_journal_start(inode, EXT4_HT_TRUNCATE, credits);
 	if (IS_ERR(handle)) {
 		ret = PTR_ERR(handle);
-		goto out_mmap;
+		goto out_invalidate_lock;
 	}
 	ext4_fc_mark_ineligible(sb, EXT4_FC_REASON_FALLOC_RANGE, handle);
 
+	start_lblk = offset >> inode->i_blkbits;
+	end_lblk = (offset + len) >> inode->i_blkbits;
+
 	down_write(&EXT4_I(inode)->i_data_sem);
 	ext4_discard_preallocations(inode);
-	ext4_es_remove_extent(inode, punch_start, EXT_MAX_BLOCKS - punch_start);
+	ext4_es_remove_extent(inode, start_lblk, EXT_MAX_BLOCKS - start_lblk);
 
-	ret = ext4_ext_remove_space(inode, punch_start, punch_stop - 1);
+	ret = ext4_ext_remove_space(inode, start_lblk, end_lblk - 1);
 	if (ret) {
 		up_write(&EXT4_I(inode)->i_data_sem);
-		goto out_stop;
+		goto out_handle;
 	}
 	ext4_discard_preallocations(inode);
 
-	ret = ext4_ext_shift_extents(inode, handle, punch_stop,
-				     punch_stop - punch_start, SHIFT_LEFT);
+	ret = ext4_ext_shift_extents(inode, handle, end_lblk,
+				     end_lblk - start_lblk, SHIFT_LEFT);
 	if (ret) {
 		up_write(&EXT4_I(inode)->i_data_sem);
-		goto out_stop;
+		goto out_handle;
 	}
 
 	new_size = inode->i_size - len;
@@ -5405,16 +5395,19 @@ static int ext4_collapse_range(struct file *file, loff_t offset, loff_t len)
 	EXT4_I(inode)->i_disksize = new_size;
 
 	up_write(&EXT4_I(inode)->i_data_sem);
-	if (IS_SYNC(inode))
-		ext4_handle_sync(handle);
 	ret = ext4_mark_inode_dirty(handle, inode);
+	if (ret)
+		goto out_handle;
+
 	ext4_update_inode_fsync_trans(handle, inode, 1);
+	if (IS_SYNC(inode))
+		ext4_handle_sync(handle);
 
-out_stop:
+out_handle:
 	ext4_journal_stop(handle);
-out_mmap:
+out_invalidate_lock:
 	filemap_invalidate_unlock(mapping);
-out_mutex:
+out:
 	inode_unlock(inode);
 	return ret;
 }
-- 
2.39.2