Re: [PATCH 01/10] btrfs: create a mount option for dax

[Nikolay Borisov <nborisov@suse.com>]

On 5.12.18 г. 14:28 ч., Goldwyn Rodrigues wrote:
> From: Goldwyn Rodrigues <rgoldwyn@suse.com>
> 
> Also, set the inode->i_flags to S_DAX
> 
> Signed-off-by: Goldwyn Rodrigues <rgoldwyn@suse.com>

Reviewed-by: Nikolay Borisov <nborisov@suse.com>

One question below though .

> ---
>  fs/btrfs/ctree.h |  1 +
>  fs/btrfs/ioctl.c |  5 ++++-
>  fs/btrfs/super.c | 15 +++++++++++++++
>  3 files changed, 20 insertions(+), 1 deletion(-)
> 
> diff --git a/fs/btrfs/ctree.h b/fs/btrfs/ctree.h
> index 68f322f600a0..5cc470fa6a40 100644
> --- a/fs/btrfs/ctree.h
> +++ b/fs/btrfs/ctree.h
> @@ -1353,6 +1353,7 @@ static inline u32 BTRFS_MAX_XATTR_SIZE(const struct btrfs_fs_info *info)
>  #define BTRFS_MOUNT_FREE_SPACE_TREE	(1 << 26)
>  #define BTRFS_MOUNT_NOLOGREPLAY		(1 << 27)
>  #define BTRFS_MOUNT_REF_VERIFY		(1 << 28)
> +#define BTRFS_MOUNT_DAX			(1 << 29)
>  
>  #define BTRFS_DEFAULT_COMMIT_INTERVAL	(30)
>  #define BTRFS_DEFAULT_MAX_INLINE	(2048)
> diff --git a/fs/btrfs/ioctl.c b/fs/btrfs/ioctl.c
> index 802a628e9f7d..e9146c157816 100644
> --- a/fs/btrfs/ioctl.c
> +++ b/fs/btrfs/ioctl.c
> @@ -149,8 +149,11 @@ void btrfs_sync_inode_flags_to_i_flags(struct inode *inode)
>  	if (binode->flags & BTRFS_INODE_DIRSYNC)
>  		new_fl |= S_DIRSYNC;
>  
> +	if ((btrfs_test_opt(btrfs_sb(inode->i_sb), DAX)) && S_ISREG(inode->i_mode))
> +		new_fl |= S_DAX;
> +
>  	set_mask_bits(&inode->i_flags,
> -		      S_SYNC | S_APPEND | S_IMMUTABLE | S_NOATIME | S_DIRSYNC,
> +		      S_SYNC | S_APPEND | S_IMMUTABLE | S_NOATIME | S_DIRSYNC | S_DAX,
>  		      new_fl);
>  }
>  
> diff --git a/fs/btrfs/super.c b/fs/btrfs/super.c
> index 645fc81e2a94..035263b61cf5 100644
> --- a/fs/btrfs/super.c
> +++ b/fs/btrfs/super.c
> @@ -326,6 +326,7 @@ enum {
>  	Opt_treelog, Opt_notreelog,
>  	Opt_usebackuproot,
>  	Opt_user_subvol_rm_allowed,
> +	Opt_dax,
>  
>  	/* Deprecated options */
>  	Opt_alloc_start,
> @@ -393,6 +394,7 @@ static const match_table_t tokens = {
>  	{Opt_notreelog, "notreelog"},
>  	{Opt_usebackuproot, "usebackuproot"},
>  	{Opt_user_subvol_rm_allowed, "user_subvol_rm_allowed"},
> +	{Opt_dax, "dax"},
>  
>  	/* Deprecated options */
>  	{Opt_alloc_start, "alloc_start=%s"},
> @@ -739,6 +741,17 @@ int btrfs_parse_options(struct btrfs_fs_info *info, char *options,
>  		case Opt_user_subvol_rm_allowed:
>  			btrfs_set_opt(info->mount_opt, USER_SUBVOL_RM_ALLOWED);
>  			break;
> +#ifdef CONFIG_FS_DAX
> +		case Opt_dax:
> +			if (btrfs_super_num_devices(info->super_copy) > 1) {
> +				btrfs_info(info,
> +					   "dax not supported for multi-device btrfs partition\n");

What prevents supporting dax for multiple devices so long as all devices
are dax?

<snip>

>