Re: [PATCH v2 3/8] ext4: make __ext4_block_zero_page_range() support large folio

Ojaswin Mujoo
2025-05-20T10:42:26Z

On Mon, May 12, 2025 at 02:33:14PM +0800, Zhang Yi wrote:
> From: Zhang Yi <yi.zhang@huawei.com>
>
> The partial block zero range helper __ext4_block_zero_page_range()
> currently only supports folios of PAGE_SIZE in size. The calculations
> for the start block and the offset within a folio for the given range
> are incorrect. Modify the implementation to use offset_in_folio()
> instead of directly masking PAGE_SIZE - 1, which will be able to support
> for large folios.

Looks good, feel free to add:

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

>
> Signed-off-by: Zhang Yi <yi.zhang@huawei.com>
> ---
> fs/ext4/inode.c | 7 +++----
> 1 file changed, 3 insertions(+), 4 deletions(-)
>
> diff --git a/fs/ext4/inode.c b/fs/ext4/inode.c
> index 4d8187f3814e..573ae0b3be1d 100644
> --- a/fs/ext4/inode.c
> +++ b/fs/ext4/inode.c
> @@ -3701,9 +3701,7 @@ void ext4_set_aops(struct inode *inode)
> static int __ext4_block_zero_page_range(handle_t *handle,
> struct address_space *mapping, loff_t from, loff_t length)
> {
> - ext4_fsblk_t index = from >> PAGE_SHIFT;
> - unsigned offset = from & (PAGE_SIZE-1);
> - unsigned blocksize, pos;
> + unsigned int offset, blocksize, pos;
> ext4_lblk_t iblock;
> struct inode *inode = mapping->host;
> struct buffer_head *bh;
> @@ -3718,13 +3716,14 @@ static int __ext4_block_zero_page_range(handle_t *handle,
>
> blocksize = inode->i_sb->s_blocksize;
>
> - iblock = index << (PAGE_SHIFT - inode->i_sb->s_blocksize_bits);
> + iblock = folio->index << (PAGE_SHIFT - inode->i_sb->s_blocksize_bits);
>
> bh = folio_buffers(folio);
> if (!bh)
> bh = create_empty_buffers(folio, blocksize, 0);
>
> /* Find the buffer that contains "offset" */
> + offset = offset_in_folio(folio, from);
> pos = blocksize;
> while (offset >= pos) {
> bh = bh->b_this_page;
> --
> 2.46.1
>