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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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