Re: [PATCH V4 4/8] fs/ext4: Update ext4_should_use_dax()

Jan Kara
2020-05-22T10:41:17Z

On Thu 21-05-20 12:13:09, ira.weiny@intel.com wrote:
> From: Ira Weiny <ira.weiny@intel.com>
>
> S_DAX should only be enabled when the underlying block device supports
> dax.
>
> Cache the underlying support for DAX in the super block and modify
> ext4_should_use_dax() to check for device support prior to the over
> riding mount option.
>
> While we are at it change the function to ext4_should_enable_dax() as
> this better reflects the ask as well as matches xfs.
>
> 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

>
> ---
> Changes from V3:
> Add a sb DAX supported flag for performance
>
> Changes from RFC
> Change function name to 'should enable'
> Clean up bool conversion
> Reorder this for better bisect-ability
> ---
> fs/ext4/ext4.h | 1 +
> fs/ext4/inode.c | 15 ++++++++++-----
> fs/ext4/super.c | 5 ++++-
> 3 files changed, 15 insertions(+), 6 deletions(-)
>
> diff --git a/fs/ext4/ext4.h b/fs/ext4/ext4.h
> index 1a3daf2d18ef..0b4db9ce7756 100644
> --- a/fs/ext4/ext4.h
> +++ b/fs/ext4/ext4.h
> @@ -1979,6 +1979,7 @@ static inline bool ext4_has_incompat_features(struct super_block *sb)
> */
> #define EXT4_FLAGS_RESIZING 0
> #define EXT4_FLAGS_SHUTDOWN 1
> +#define EXT4_FLAGS_BDEV_IS_DAX 2
>
> static inline int ext4_forced_shutdown(struct ext4_sb_info *sbi)
> {
> diff --git a/fs/ext4/inode.c b/fs/ext4/inode.c
> index a10ff12194db..6532870f6a0b 100644
> --- a/fs/ext4/inode.c
> +++ b/fs/ext4/inode.c
> @@ -4398,10 +4398,10 @@ int ext4_get_inode_loc(struct inode *inode, struct ext4_iloc *iloc)
> !ext4_test_inode_state(inode, EXT4_STATE_XATTR));
> }
>
> -static bool ext4_should_use_dax(struct inode *inode)
> +static bool ext4_should_enable_dax(struct inode *inode)
> {
> - if (!test_opt(inode->i_sb, DAX_ALWAYS))
> - return false;
> + struct ext4_sb_info *sbi = EXT4_SB(inode->i_sb);
> +
> if (!S_ISREG(inode->i_mode))
> return false;
> if (ext4_should_journal_data(inode))
> @@ -4412,7 +4412,12 @@ static bool ext4_should_use_dax(struct inode *inode)
> return false;
> if (ext4_test_inode_flag(inode, EXT4_INODE_VERITY))
> return false;
> - return true;
> + if (!test_bit(EXT4_FLAGS_BDEV_IS_DAX, &sbi->s_ext4_flags))
> + return false;
> + if (test_opt(inode->i_sb, DAX_ALWAYS))
> + return true;
> +
> + return false;
> }
>
> void ext4_set_inode_flags(struct inode *inode)
> @@ -4430,7 +4435,7 @@ void ext4_set_inode_flags(struct inode *inode)
> new_fl |= S_NOATIME;
> if (flags & EXT4_DIRSYNC_FL)
> new_fl |= S_DIRSYNC;
> - if (ext4_should_use_dax(inode))
> + if (ext4_should_enable_dax(inode))
> new_fl |= S_DAX;
> if (flags & EXT4_ENCRYPT_FL)
> new_fl |= S_ENCRYPTED;
> diff --git a/fs/ext4/super.c b/fs/ext4/super.c
> index 7b99c44d0a91..f7d76dcaedfe 100644
> --- a/fs/ext4/super.c
> +++ b/fs/ext4/super.c
> @@ -4092,13 +4092,16 @@ static int ext4_fill_super(struct super_block *sb, void *data, int silent)
> goto failed_mount;
> }
>
> + if (bdev_dax_supported(sb->s_bdev, blocksize))
> + set_bit(EXT4_FLAGS_BDEV_IS_DAX, &sbi->s_ext4_flags);
> +
> if (sbi->s_mount_opt & EXT4_MOUNT_DAX_ALWAYS) {
> if (ext4_has_feature_inline_data(sb)) {
> ext4_msg(sb, KERN_ERR, "Cannot use DAX on a filesystem"
> " that may contain inline data");
> goto failed_mount;
> }
> - if (!bdev_dax_supported(sb->s_bdev, blocksize)) {
> + if (!test_bit(EXT4_FLAGS_BDEV_IS_DAX, &sbi->s_ext4_flags)) {
> ext4_msg(sb, KERN_ERR,
> "DAX unsupported by block device.");
> goto failed_mount;
> --
> 2.25.1
>
--
Jan Kara <jack@suse.com>
SUSE Labs, CR