2016-08-15 19:09:13

by Ross Zwisler

Subject: [PATCH 2/7] ext4: tell DAX the size of allocation holes

When DAX calls _ext4_get_block() and the file offset points to a hole we
currently don't set bh->b_size. When we re-enable PMD faults DAX will
need bh->b_size to tell it the size of the hole so it can decide whether to
fault in a 4 KiB zero page or a 2 MiB zero page.

_ext4_get_block() has the hole size information from ext4_map_blocks(), so
populate bh->b_size.

Signed-off-by: Ross Zwisler <ross.zwisler-VuQAYsv1563Yd54FQh9/[email protected]>
---
fs/ext4/inode.c | 3 +++
1 file changed, 3 insertions(+)

diff --git a/fs/ext4/inode.c b/fs/ext4/inode.c
index 3131747..1808013 100644
--- a/fs/ext4/inode.c
+++ b/fs/ext4/inode.c
@@ -759,6 +759,9 @@ static int _ext4_get_block(struct inode *inode, sector_t iblock,
ext4_update_bh_state(bh, map.m_flags);
bh->b_size = inode->i_sb->s_blocksize * map.m_len;
ret = 0;
+ } else if (ret == 0) {
+ /* hole case, need to fill in bh->b_size */
+ bh->b_size = inode->i_sb->s_blocksize * map.m_len;
}
return ret;
}
--
2.9.0

2016-08-16 09:12:38

by Jan Kara

Subject: Re: [PATCH 2/7] ext4: tell DAX the size of allocation holes

On Mon 15-08-16 13:09:13, Ross Zwisler wrote:
> When DAX calls _ext4_get_block() and the file offset points to a hole we
> currently don't set bh->b_size. When we re-enable PMD faults DAX will
> need bh->b_size to tell it the size of the hole so it can decide whether to
> fault in a 4 KiB zero page or a 2 MiB zero page.
>
> _ext4_get_block() has the hole size information from ext4_map_blocks(), so
> populate bh->b_size.
>
> Signed-off-by: Ross Zwisler <[email protected]>

Looks good. You can add:

Reviewed-by: Jan Kara <[email protected]>

Honza

> ---
> fs/ext4/inode.c | 3 +++
> 1 file changed, 3 insertions(+)
>
> diff --git a/fs/ext4/inode.c b/fs/ext4/inode.c
> index 3131747..1808013 100644
> --- a/fs/ext4/inode.c
> +++ b/fs/ext4/inode.c
> @@ -759,6 +759,9 @@ static int _ext4_get_block(struct inode *inode, sector_t iblock,
> ext4_update_bh_state(bh, map.m_flags);
> bh->b_size = inode->i_sb->s_blocksize * map.m_len;
> ret = 0;
> + } else if (ret == 0) {
> + /* hole case, need to fill in bh->b_size */
> + bh->b_size = inode->i_sb->s_blocksize * map.m_len;
> }
> return ret;
> }
> --
> 2.9.0
>
>
--
Jan Kara <[email protected]>
SUSE Labs, CR

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