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SubjectRe: [PATCH 1/3] fs: remove FS_COW_FL
Any comments? If this patch is acceptable, it should be queued for .39?
since fs.h is exported to userspace.

Li Zefan wrote:
> FS_COW_FL and FS_NOCOW_FL were newly introduced to control per file
> COW in btrfs, but FS_NOCOW_FL is sufficient.
>
> The fact is we don't have corresponding BTRFS_INODE_COW flag.
>
> COW is default, and FS_NOCOW_FL can be used to switch off COW for
> a single file.
>
> If we mount btrfs with nodatacow, a newly created file will be set with
> the FS_NOCOW_FL flag. So to turn on COW for it, we can just clear the
> FS_NOCOW_FL flag.
>
> Signed-off-by: Li Zefan <lizf@cn.fujitsu.com>
> ---
> fs/btrfs/ioctl.c | 15 ++++++---------
> include/linux/fs.h | 1 -
> 2 files changed, 6 insertions(+), 10 deletions(-)
>
> diff --git a/fs/btrfs/ioctl.c b/fs/btrfs/ioctl.c
> index f580a3a..3240dd9 100644
> --- a/fs/btrfs/ioctl.c
> +++ b/fs/btrfs/ioctl.c
> @@ -144,16 +144,13 @@ static int check_flags(unsigned int flags)
> if (flags & ~(FS_IMMUTABLE_FL | FS_APPEND_FL | \
> FS_NOATIME_FL | FS_NODUMP_FL | \
> FS_SYNC_FL | FS_DIRSYNC_FL | \
> - FS_NOCOMP_FL | FS_COMPR_FL | \
> - FS_NOCOW_FL | FS_COW_FL))
> + FS_NOCOMP_FL | FS_COMPR_FL |
> + FS_NOCOW_FL))
> return -EOPNOTSUPP;
>
> if ((flags & FS_NOCOMP_FL) && (flags & FS_COMPR_FL))
> return -EINVAL;
>
> - if ((flags & FS_NOCOW_FL) && (flags & FS_COW_FL))
> - return -EINVAL;
> -
> return 0;
> }
>
> @@ -218,6 +215,10 @@ static int btrfs_ioctl_setflags(struct file *file, void __user *arg)
> ip->flags |= BTRFS_INODE_DIRSYNC;
> else
> ip->flags &= ~BTRFS_INODE_DIRSYNC;
> + if (flags & FS_NOCOW_FL)
> + ip->flags |= BTRFS_INODE_NODATACOW;
> + else
> + ip->flags &= ~BTRFS_INODE_NODATACOW;
>
> /*
> * The COMPRESS flag can only be changed by users, while the NOCOMPRESS
> @@ -231,10 +232,6 @@ static int btrfs_ioctl_setflags(struct file *file, void __user *arg)
> ip->flags |= BTRFS_INODE_COMPRESS;
> ip->flags &= ~BTRFS_INODE_NOCOMPRESS;
> }
> - if (flags & FS_NOCOW_FL)
> - ip->flags |= BTRFS_INODE_NODATACOW;
> - else if (flags & FS_COW_FL)
> - ip->flags &= ~BTRFS_INODE_NODATACOW;
>
> trans = btrfs_join_transaction(root, 1);
> BUG_ON(IS_ERR(trans));
> diff --git a/include/linux/fs.h b/include/linux/fs.h
> index de9dd81..56a4141 100644
> --- a/include/linux/fs.h
> +++ b/include/linux/fs.h
> @@ -365,7 +365,6 @@ struct inodes_stat_t {
> #define FS_EXTENT_FL 0x00080000 /* Extents */
> #define FS_DIRECTIO_FL 0x00100000 /* Use direct i/o */
> #define FS_NOCOW_FL 0x00800000 /* Do not cow file */
> -#define FS_COW_FL 0x02000000 /* Cow file */
> #define FS_RESERVED_FL 0x80000000 /* reserved for ext2 lib */
>
> #define FS_FL_USER_VISIBLE 0x0003DFFF /* User visible flags */


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