On Fri 03-07-15 11:15:11, Matthew Wilcox wrote:
> From: Matthew Wilcox <willy@xxxxxxxxxxxxxxx>
>
> Currently, if ext4's get_block encounters a hole, it does not modify the
> buffer_head. That's fine for many callers, but for DAX, it's useful to
> know how large the hole is. XFS already returns the length of the hole,
> so this improvement should not confuse any callers.
>
> Signed-off-by: Matthew Wilcox <willy@xxxxxxxxxxxxxxx>
So I'm somewhat wondering: What is the reason of BH_Uptodate flag being
set? I can see the XFS sets it in some cases as well but the use of the
flag isn't really clear to me...
Honza
> ---
> fs/ext4/ext4.h | 6 ++++--
> fs/ext4/inode.c | 6 +++++-
> 2 files changed, 9 insertions(+), 3 deletions(-)
>
> diff --git a/fs/ext4/ext4.h b/fs/ext4/ext4.h
> index 9a83f14..7b7c097 100644
> --- a/fs/ext4/ext4.h
> +++ b/fs/ext4/ext4.h
> @@ -154,12 +154,14 @@ struct ext4_allocation_request {
> * well as to store the information returned by ext4_map_blocks(). It
> * takes less room on the stack than a struct buffer_head.
> */
> +#define EXT4_MAP_UPTODATE (1 << BH_Uptodate)
> #define EXT4_MAP_NEW (1 << BH_New)
> #define EXT4_MAP_MAPPED (1 << BH_Mapped)
> #define EXT4_MAP_UNWRITTEN (1 << BH_Unwritten)
> #define EXT4_MAP_BOUNDARY (1 << BH_Boundary)
> -#define EXT4_MAP_FLAGS (EXT4_MAP_NEW | EXT4_MAP_MAPPED |\
> - EXT4_MAP_UNWRITTEN | EXT4_MAP_BOUNDARY)
> +#define EXT4_MAP_FLAGS (EXT4_MAP_UPTODATE | EXT4_MAP_NEW | \
> + EXT4_MAP_MAPPED | EXT4_MAP_UNWRITTEN | \
> + EXT4_MAP_BOUNDARY)
>
> struct ext4_map_blocks {
> ext4_fsblk_t m_pblk;
> diff --git a/fs/ext4/inode.c b/fs/ext4/inode.c
> index 9b46f6f..0fc49ac 100644
> --- a/fs/ext4/inode.c
> +++ b/fs/ext4/inode.c
> @@ -494,7 +494,11 @@ int ext4_map_blocks(handle_t *handle, struct inode *inode,
> retval = map->m_len;
> map->m_len = retval;
> } else if (ext4_es_is_delayed(&es) || ext4_es_is_hole(&es)) {
> - retval = 0;
> + map->m_flags |= EXT4_MAP_UPTODATE;
> + retval = es.es_len - (map->m_lblk - es.es_lblk);
> + if (retval > map->m_len)
> + retval = map->m_len;
> + map->m_len = retval;
> } else {
> BUG_ON(1);
> }
> --
> 2.1.4
>
> --
> To unsubscribe from this list: send the line "unsubscribe linux-ext4" in
> the body of a message to majordomo@xxxxxxxxxxxxxxx
> More majordomo info at http://vger.kernel.org/majordomo-info.html
--
Jan Kara <jack@xxxxxxx>
SUSE Labs, CR
--
To unsubscribe from this list: send the line "unsubscribe linux-ext4" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at http://vger.kernel.org/majordomo-info.html
