Re: [PATCH v4 06/10] ext4: refactor ext4_collapse_range()

[Ojaswin Mujoo <ojaswin@linux.ibm.com>]

On Mon, Dec 16, 2024 at 09:39:11AM +0800, Zhang Yi wrote:
> From: Zhang Yi <yi.zhang@huawei.com>
> 
> 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.

Looks good, feel free to add:

Reviewed-by: Ojaswin Mujoo <ojaswin@linux.ibm.com>

> 
> Signed-off-by: Zhang Yi <yi.zhang@huawei.com>
> Reviewed-by: Jan Kara <jack@suse.cz>
> ---
>  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 97ad6fea58d3..8a0a720803a8 100644
> --- a/fs/ext4/extents.c
> +++ b/fs/ext4/extents.c
> @@ -5292,43 +5292,36 @@ 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 */
> @@ -5336,7 +5329,7 @@ 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
> @@ -5346,55 +5339,52 @@ 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;
> @@ -5402,16 +5392,19 @@ 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;
>  }
> -- 
> 2.46.1
>