On Mon 16-12-24 09:39:08, Zhang Yi wrote:
> From: Zhang Yi <yi.zhang@xxxxxxxxxx>
>
> There is no need to write back all data before punching a hole in
> non-journaled mode since it will be dropped soon after removing space.
> Therefore, the call to filemap_write_and_wait_range() can be eliminated.
> Besides, similar to ext4_zero_range(), we must address the case of
> partially punched folios when block size < page size. It is essential to
> remove writable userspace mappings to ensure that the folio can be
> faulted again during subsequent mmap write access.
>
> In journaled mode, we need to write dirty pages out before discarding
> page cache in case of crash before committing the freeing data
> transaction, which could expose old, stale data, even if synchronization
> has been performed.
>
> Signed-off-by: Zhang Yi <yi.zhang@xxxxxxxxxx>
Looks good. Feel free to add:
Reviewed-by: Jan Kara <jack@xxxxxxx>
Honza
> ---
> fs/ext4/inode.c | 18 +++++-------------
> 1 file changed, 5 insertions(+), 13 deletions(-)
>
> diff --git a/fs/ext4/inode.c b/fs/ext4/inode.c
> index bf735d06b621..a5ba2b71d508 100644
> --- a/fs/ext4/inode.c
> +++ b/fs/ext4/inode.c
> @@ -4018,17 +4018,6 @@ int ext4_punch_hole(struct file *file, loff_t offset, loff_t length)
>
> trace_ext4_punch_hole(inode, offset, length, 0);
>
> - /*
> - * Write out all dirty pages to avoid race conditions
> - * Then release them.
> - */
> - if (mapping_tagged(mapping, PAGECACHE_TAG_DIRTY)) {
> - ret = filemap_write_and_wait_range(mapping, offset,
> - offset + length - 1);
> - if (ret)
> - return ret;
> - }
> -
> inode_lock(inode);
>
> /* No need to punch hole beyond i_size */
> @@ -4090,8 +4079,11 @@ int ext4_punch_hole(struct file *file, loff_t offset, loff_t length)
> ret = ext4_update_disksize_before_punch(inode, offset, length);
> if (ret)
> goto out_dio;
> - truncate_pagecache_range(inode, first_block_offset,
> - last_block_offset);
> +
> + ret = ext4_truncate_page_cache_block_range(inode,
> + first_block_offset, last_block_offset + 1);
> + if (ret)
> + goto out_dio;
> }
>
> if (ext4_test_inode_flag(inode, EXT4_INODE_EXTENTS))
> --
> 2.46.1
>
--
Jan Kara <jack@xxxxxxxx>
SUSE Labs, CR
