Re: [PATCH 1/2] ext4, dax: update dax check to skip journal inode

[Dan Williams <dan.j.williams@intel.com>]

On Tue, Sep 11, 2018 at 8:42 AM, Toshi Kani <toshi.kani@hpe.com> wrote:
> Ext4 mount path calls ext4_iget() to obtain the journal inode.  This
> inode does not support DAX, and 'ext4_da_aops' needs to be set.  It
> currently works for the DAX mount case because ext4_iget() always set
> 'ext4_da_aops' to any regular files.
>
>   ext4_fill_super
>     ext4_load_journal
>       ext4_get_journal_inode
>         ext4_iget
>
> In preparation to fix ext4_iget() to set 'ext4_dax_aops' for DAX files,
> update ext4_should_use_dax() to return false for the journal inode.
>
> Fixes: 5f0663bb4a64f588f0a2dd6d1be68d40f9af0086

Just a minor format recommendation:

Fixes: 5f0663bb4a64 ("ext4, dax: introduce ext4_dax_aops")
Cc: <stable@vger.kernel.org>

> Signed-off-by: Toshi Kani <toshi.kani@hpe.com>
> Cc: Jan Kara <jack@suse.cz>
> Cc: Dan Williams <dan.j.williams@intel.com>
> Cc: "Theodore Ts'o" <tytso@mit.edu>
> Cc: Andreas Dilger <adilger.kernel@dilger.ca>
> ---
>  fs/ext4/ext4_jbd2.h |    8 ++++++++
>  fs/ext4/inode.c     |    2 ++
>  2 files changed, 10 insertions(+)
>
> diff --git a/fs/ext4/ext4_jbd2.h b/fs/ext4/ext4_jbd2.h
> index 15b6dd733780..9847dc980a0d 100644
> --- a/fs/ext4/ext4_jbd2.h
> +++ b/fs/ext4/ext4_jbd2.h
> @@ -437,6 +437,14 @@ static inline int ext4_should_writeback_data(struct inode *inode)
>         return ext4_inode_journal_mode(inode) & EXT4_INODE_WRITEBACK_DATA_MODE;
>  }
>
> +static inline int ext4_is_journal_inode(struct inode *inode)
> +{
> +       struct ext4_sb_info *sbi = EXT4_SB(inode->i_sb);
> +       unsigned int journal_inum = le32_to_cpu(sbi->s_es->s_journal_inum);
> +
> +       return journal_inum && (journal_inum == inode->i_ino);
> +}
> +
>  /*
>   * This function controls whether or not we should try to go down the
>   * dioread_nolock code paths, which makes it safe to avoid taking
> diff --git a/fs/ext4/inode.c b/fs/ext4/inode.c
> index d0dd585add6a..775cd9b4af55 100644
> --- a/fs/ext4/inode.c
> +++ b/fs/ext4/inode.c
> @@ -4686,6 +4686,8 @@ static bool ext4_should_use_dax(struct inode *inode)
>                 return false;
>         if (ext4_should_journal_data(inode))
>                 return false;
> +       if (ext4_is_journal_inode(inode))
> +               return false;

This looks good to me.

Reviewed-by: Dan Williams <dan.j.williams@intel.com>
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