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Date:   Fri, 22 May 2020 23:13:41 -0600
From:   Andreas Dilger <adilger@...ger.ca>
To:     ira.weiny@...el.com
Cc:     Ext4 Developers List <linux-ext4@...r.kernel.org>,
        "Theodore Y. Ts'o" <tytso@....edu>, Jan Kara <jack@...e.cz>,
        Eric Biggers <ebiggers@...nel.org>,
        Al Viro <viro@...iv.linux.org.uk>,
        Dan Williams <dan.j.williams@...el.com>,
        Dave Chinner <david@...morbit.com>,
        Christoph Hellwig <hch@....de>, Jeff Moyer <jmoyer@...hat.com>,
        "Darrick J. Wong" <darrick.wong@...cle.com>,
        linux-fsdevel <linux-fsdevel@...r.kernel.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH V4 7/8] fs/ext4: Introduce DAX inode flag

On May 21, 2020, at 1:13 PM, ira.weiny@...el.com wrote:
> 
> From: Ira Weiny <ira.weiny@...el.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 with the
> exception of if VERITY or ENCRYPT is set.
> 
> Disallow setting VERITY or ENCRYPT if DAX is set.
> 
> 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@...el.com>

Reviewed-by: Andreas Dilger <adilger@...ger.ca>

> 
> ---
> Changes from V3:
> 	Move bit to bit25 per Andreas
> 
> Change from V2:
> 	Add in making verity and DAX exclusive.
> 	'Squash' in making encryption and DAX exclusive.
> 	Add in EXT4_INODE_DAX flag definition to be compatible with
> 		ext4_[set|test]_inode_flag() bit operations
> 	Use ext4_[set|test]_inode_flag() bit operations to be consistent
> 		with other code.
> 
> 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          | 14 ++++++++++----
> fs/ext4/inode.c         |  2 +-
> fs/ext4/ioctl.c         | 34 +++++++++++++++++++++++++++++++++-
> fs/ext4/super.c         |  3 +++
> fs/ext4/verity.c        |  2 +-
> include/uapi/linux/fs.h |  1 +
> 6 files changed, 49 insertions(+), 7 deletions(-)
> 
> diff --git a/fs/ext4/ext4.h b/fs/ext4/ext4.h
> index 65ffb831b2b9..09b8906568d2 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			0x02000000 /* 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		0x725BDFFF /* User visible flags */
> +#define EXT4_FL_USER_MODIFIABLE		0x624BC0FF /* 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 |\
> @@ -488,6 +493,7 @@ enum {
> 	EXT4_INODE_VERITY	= 20,	/* Verity protected inode */
> 	EXT4_INODE_EA_INODE	= 21,	/* Inode used for large EA */
> /* 22 was formerly EXT4_INODE_EOFBLOCKS */
> +	EXT4_INODE_DAX		= 25,	/* Inode is DAX */
> 	EXT4_INODE_INLINE_DATA	= 28,	/* Data in inode. */
> 	EXT4_INODE_PROJINHERIT	= 29,	/* Create with parents projid */
> 	EXT4_INODE_RESERVED	= 31,	/* reserved for ext4 lib */
> diff --git a/fs/ext4/inode.c b/fs/ext4/inode.c
> index 68fac9289109..778b0dbe3da6 100644
> --- a/fs/ext4/inode.c
> +++ b/fs/ext4/inode.c
> @@ -4419,7 +4419,7 @@ static bool ext4_should_enable_dax(struct inode *inode)
> 	if (test_opt(inode->i_sb, DAX_ALWAYS))
> 		return true;
> 
> -	return false;
> +	return ext4_test_inode_flag(inode, EXT4_INODE_DAX);
> }
> 
> void ext4_set_inode_flags(struct inode *inode, bool init)
> diff --git a/fs/ext4/ioctl.c b/fs/ext4/ioctl.c
> index 145083e8cd1e..668b8c17d6eb 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)
> {
> @@ -303,6 +318,16 @@ static int ext4_ioctl_setflags(struct inode *inode,
> 	unsigned int jflag;
> 	struct super_block *sb = inode->i_sb;
> 
> +	if (ext4_test_inode_flag(inode, EXT4_INODE_DAX)) {
> +		if (ext4_test_inode_flag(inode, EXT4_INODE_VERITY) ||
> +		    ext4_test_inode_flag(inode, EXT4_INODE_ENCRYPT) ||
> +		    ext4_test_inode_state(inode,
> +					  EXT4_STATE_VERITY_IN_PROGRESS)) {
> +			err = -EOPNOTSUPP;
> +			goto flags_out;
> +		}
> +	}
> +
> 	/* Is it quota file? Do not allow user to mess with it */
> 	if (ext4_is_quota_file(inode))
> 		goto flags_out;
> @@ -369,6 +394,8 @@ 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 +555,15 @@ 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 +582,8 @@ 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/fs/ext4/super.c b/fs/ext4/super.c
> index 5e056aa20ce9..3658e3016999 100644
> --- a/fs/ext4/super.c
> +++ b/fs/ext4/super.c
> @@ -1323,6 +1323,9 @@ static int ext4_set_context(struct inode *inode, const void *ctx, size_t len,
> 	if (WARN_ON_ONCE(IS_DAX(inode) && i_size_read(inode)))
> 		return -EINVAL;
> 
> +	if (ext4_test_inode_flag(inode, EXT4_INODE_DAX))
> +		return -EOPNOTSUPP;
> +
> 	res = ext4_convert_inline_data(inode);
> 	if (res)
> 		return res;
> diff --git a/fs/ext4/verity.c b/fs/ext4/verity.c
> index 89a155ece323..4fecb3e4e338 100644
> --- a/fs/ext4/verity.c
> +++ b/fs/ext4/verity.c
> @@ -113,7 +113,7 @@ static int ext4_begin_enable_verity(struct file *filp)
> 	handle_t *handle;
> 	int err;
> 
> -	if (IS_DAX(inode))
> +	if (IS_DAX(inode) || ext4_test_inode_flag(inode, EXT4_INODE_DAX))
> 		return -EINVAL;
> 
> 	if (ext4_verity_in_progress(inode))
> diff --git a/include/uapi/linux/fs.h b/include/uapi/linux/fs.h
> index 379a612f8f1d..f44eb0a04afd 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			0x02000000 /* 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
> 


Cheers, Andreas






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