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Date:   Thu, 14 May 2020 13:06:16 +0200
From:   Jan Kara <jack@suse.cz>
To:     ira.weiny@intel.com
Cc:     linux-ext4@vger.kernel.org,
        Andreas Dilger <adilger.kernel@dilger.ca>,
        "Theodore Y. Ts'o" <tytso@mit.edu>, Jan Kara <jack@suse.cz>,
        Al Viro <viro@zeniv.linux.org.uk>,
        Dan Williams <dan.j.williams@intel.com>,
        Dave Chinner <david@fromorbit.com>,
        Christoph Hellwig <hch@lst.de>, Jeff Moyer <jmoyer@redhat.com>,
        "Darrick J. Wong" <darrick.wong@oracle.com>,
        linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org
Subject: Re: [PATCH V1 8/9] fs/ext4: Introduce DAX inode flag
Message-ID: <20200514110616.GF9569@quack2.suse.cz>
References: <20200514065316.2500078-1-ira.weiny@intel.com>
 <20200514065316.2500078-9-ira.weiny@intel.com>
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On Wed 13-05-20 23:53:14, ira.weiny@intel.com wrote:
> From: Ira Weiny <ira.weiny@intel.com>
> 
> Add a flag to preserve FS_XFLAG_DAX in the ext4 inode.
> 
> Set the flag to be user visible and changeable.  Set the flag to be
> inherited.  Allow applications to change the flag at any time.
> 
> Finally, on regular files, flag the inode to not be cached to facilitate
> changing S_DAX on the next creation of the inode.
> 
> Signed-off-by: Ira Weiny <ira.weiny@intel.com>

The patch looks good to me. You can add:

Reviewed-by: Jan Kara <jack@suse.cz>

								Honza

> 
> ---
> Change from V0:
> 	Add FS_DAX_FL to include/uapi/linux/fs.h
> 		to be consistent
> 	Move ext4_dax_dontcache() to ext4_ioctl_setflags()
> 		This ensures that it is only set when the flags are going to be
> 		set and not if there is an error
> 		Also this sets don't cache in the FS_IOC_SETFLAGS case
> 
> Change from RFC:
> 	use new d_mark_dontcache()
> 	Allow caching if ALWAYS/NEVER is set
> 	Rebased to latest Linus master
> 	Change flag to unused 0x01000000
> 	update ext4_should_enable_dax()
> ---
>  fs/ext4/ext4.h          | 13 +++++++++----
>  fs/ext4/inode.c         |  4 +++-
>  fs/ext4/ioctl.c         | 24 +++++++++++++++++++++++-
>  include/uapi/linux/fs.h |  1 +
>  4 files changed, 36 insertions(+), 6 deletions(-)
> 
> diff --git a/fs/ext4/ext4.h b/fs/ext4/ext4.h
> index 01d1de838896..715f8f2029b2 100644
> --- a/fs/ext4/ext4.h
> +++ b/fs/ext4/ext4.h
> @@ -415,13 +415,16 @@ struct flex_groups {
>  #define EXT4_VERITY_FL			0x00100000 /* Verity protected inode */
>  #define EXT4_EA_INODE_FL	        0x00200000 /* Inode used for large EA */
>  /* 0x00400000 was formerly EXT4_EOFBLOCKS_FL */
> +
> +#define EXT4_DAX_FL			0x01000000 /* Inode is DAX */
> +
>  #define EXT4_INLINE_DATA_FL		0x10000000 /* Inode has inline data. */
>  #define EXT4_PROJINHERIT_FL		0x20000000 /* Create with parents projid */
>  #define EXT4_CASEFOLD_FL		0x40000000 /* Casefolded file */
>  #define EXT4_RESERVED_FL		0x80000000 /* reserved for ext4 lib */
>  
> -#define EXT4_FL_USER_VISIBLE		0x705BDFFF /* User visible flags */
> -#define EXT4_FL_USER_MODIFIABLE		0x604BC0FF /* User modifiable flags */
> +#define EXT4_FL_USER_VISIBLE		0x715BDFFF /* User visible flags */
> +#define EXT4_FL_USER_MODIFIABLE		0x614BC0FF /* User modifiable flags */
>  
>  /* Flags we can manipulate with through EXT4_IOC_FSSETXATTR */
>  #define EXT4_FL_XFLAG_VISIBLE		(EXT4_SYNC_FL | \
> @@ -429,14 +432,16 @@ struct flex_groups {
>  					 EXT4_APPEND_FL | \
>  					 EXT4_NODUMP_FL | \
>  					 EXT4_NOATIME_FL | \
> -					 EXT4_PROJINHERIT_FL)
> +					 EXT4_PROJINHERIT_FL | \
> +					 EXT4_DAX_FL)
>  
>  /* Flags that should be inherited by new inodes from their parent. */
>  #define EXT4_FL_INHERITED (EXT4_SECRM_FL | EXT4_UNRM_FL | EXT4_COMPR_FL |\
>  			   EXT4_SYNC_FL | EXT4_NODUMP_FL | EXT4_NOATIME_FL |\
>  			   EXT4_NOCOMPR_FL | EXT4_JOURNAL_DATA_FL |\
>  			   EXT4_NOTAIL_FL | EXT4_DIRSYNC_FL |\
> -			   EXT4_PROJINHERIT_FL | EXT4_CASEFOLD_FL)
> +			   EXT4_PROJINHERIT_FL | EXT4_CASEFOLD_FL |\
> +			   EXT4_DAX_FL)
>  
>  /* Flags that are appropriate for regular files (all but dir-specific ones). */
>  #define EXT4_REG_FLMASK (~(EXT4_DIRSYNC_FL | EXT4_TOPDIR_FL | EXT4_CASEFOLD_FL |\
> diff --git a/fs/ext4/inode.c b/fs/ext4/inode.c
> index 140b1930e2f4..105cf04f7940 100644
> --- a/fs/ext4/inode.c
> +++ b/fs/ext4/inode.c
> @@ -4400,6 +4400,8 @@ int ext4_get_inode_loc(struct inode *inode, struct ext4_iloc *iloc)
>  
>  static bool ext4_should_enable_dax(struct inode *inode)
>  {
> +	unsigned int flags = EXT4_I(inode)->i_flags;
> +
>  	if (test_opt2(inode->i_sb, DAX_NEVER))
>  		return false;
>  	if (!S_ISREG(inode->i_mode))
> @@ -4418,7 +4420,7 @@ static bool ext4_should_enable_dax(struct inode *inode)
>  	if (test_opt(inode->i_sb, DAX_ALWAYS))
>  		return true;
>  
> -	return false;
> +	return flags & EXT4_DAX_FL;
>  }
>  
>  void ext4_set_inode_flags(struct inode *inode, bool init)
> diff --git a/fs/ext4/ioctl.c b/fs/ext4/ioctl.c
> index 145083e8cd1e..d6d018ea8e94 100644
> --- a/fs/ext4/ioctl.c
> +++ b/fs/ext4/ioctl.c
> @@ -292,6 +292,21 @@ static int ext4_ioctl_check_immutable(struct inode *inode, __u32 new_projid,
>  	return 0;
>  }
>  
> +static void ext4_dax_dontcache(struct inode *inode, unsigned int flags)
> +{
> +	struct ext4_inode_info *ei = EXT4_I(inode);
> +
> +	if (S_ISDIR(inode->i_mode))
> +		return;
> +
> +	if (test_opt2(inode->i_sb, DAX_NEVER) ||
> +	    test_opt(inode->i_sb, DAX_ALWAYS))
> +		return;
> +
> +	if ((ei->i_flags ^ flags) & EXT4_DAX_FL)
> +		d_mark_dontcache(inode);
> +}
> +
>  static int ext4_ioctl_setflags(struct inode *inode,
>  			       unsigned int flags)
>  {
> @@ -369,6 +384,8 @@ static int ext4_ioctl_setflags(struct inode *inode,
>  	if (err)
>  		goto flags_err;
>  
> +	ext4_dax_dontcache(inode, flags);
> +
>  	for (i = 0, mask = 1; i < 32; i++, mask <<= 1) {
>  		if (!(mask & EXT4_FL_USER_MODIFIABLE))
>  			continue;
> @@ -528,12 +545,15 @@ static inline __u32 ext4_iflags_to_xflags(unsigned long iflags)
>  		xflags |= FS_XFLAG_NOATIME;
>  	if (iflags & EXT4_PROJINHERIT_FL)
>  		xflags |= FS_XFLAG_PROJINHERIT;
> +	if (iflags & EXT4_DAX_FL)
> +		xflags |= FS_XFLAG_DAX;
>  	return xflags;
>  }
>  
>  #define EXT4_SUPPORTED_FS_XFLAGS (FS_XFLAG_SYNC | FS_XFLAG_IMMUTABLE | \
>  				  FS_XFLAG_APPEND | FS_XFLAG_NODUMP | \
> -				  FS_XFLAG_NOATIME | FS_XFLAG_PROJINHERIT)
> +				  FS_XFLAG_NOATIME | FS_XFLAG_PROJINHERIT | \
> +				  FS_XFLAG_DAX)
>  
>  /* Transfer xflags flags to internal */
>  static inline unsigned long ext4_xflags_to_iflags(__u32 xflags)
> @@ -552,6 +572,8 @@ static inline unsigned long ext4_xflags_to_iflags(__u32 xflags)
>  		iflags |= EXT4_NOATIME_FL;
>  	if (xflags & FS_XFLAG_PROJINHERIT)
>  		iflags |= EXT4_PROJINHERIT_FL;
> +	if (xflags & FS_XFLAG_DAX)
> +		iflags |= EXT4_DAX_FL;
>  
>  	return iflags;
>  }
> diff --git a/include/uapi/linux/fs.h b/include/uapi/linux/fs.h
> index 379a612f8f1d..7c5f6eb51e2d 100644
> --- a/include/uapi/linux/fs.h
> +++ b/include/uapi/linux/fs.h
> @@ -262,6 +262,7 @@ struct fsxattr {
>  #define FS_EA_INODE_FL			0x00200000 /* Inode used for large EA */
>  #define FS_EOFBLOCKS_FL			0x00400000 /* Reserved for ext4 */
>  #define FS_NOCOW_FL			0x00800000 /* Do not cow file */
> +#define FS_DAX_FL			0x01000000 /* Inode is DAX */
>  #define FS_INLINE_DATA_FL		0x10000000 /* Reserved for ext4 */
>  #define FS_PROJINHERIT_FL		0x20000000 /* Create with parents projid */
>  #define FS_CASEFOLD_FL			0x40000000 /* Folder is case insensitive */
> -- 
> 2.25.1
> 
-- 
Jan Kara <jack@suse.com>
SUSE Labs, CR