[PATCH 3/3] btrfs: implement .splice_direct extent copying

Zach Brown
2013-09-11T17:16:47Z

This patch re-uses the existing btrfs file cloning ioctl code to
implement the .splice_direct copy offloading file operation.

The existing extent item copying btrfs_ioctl_clone() is renamed to a
shared btrfs_clone_extents(). The ioctl specific code (mostly simple
entry-point stuff that splice() already does elsewhere) is moved to a
new much smaller btrfs_ioctl_clone().

btrfs_splice_direct() thus inherits the conservative limitations of the
btrfs clone ioctl: it only allows block-aligned copies between files on
the same snapshot.

Signed-off-by: Zach Brown <zab@redhat.com>
---
fs/btrfs/ctree.h | 2 ++
fs/btrfs/file.c | 11 ++++++++++
fs/btrfs/ioctl.c | 64 +++++++++++++++++++++++++++++++-------------------------
3 files changed, 48 insertions(+), 29 deletions(-)

diff --git a/fs/btrfs/ctree.h b/fs/btrfs/ctree.h
index e795bf1..f73830e 100644
--- a/fs/btrfs/ctree.h
+++ b/fs/btrfs/ctree.h
@@ -3648,6 +3648,8 @@ int btrfs_defrag_file(struct inode *inode, struct file *file,
u64 newer_than, unsigned long max_pages);
void btrfs_get_block_group_info(struct list_head *groups_list,
struct btrfs_ioctl_space_info *space);
+long btrfs_clone_extents(struct file *file, struct file *src_file, u64 off,
+ u64 olen, u64 destoff);

/* file.c */
int btrfs_auto_defrag_init(void);
diff --git a/fs/btrfs/file.c b/fs/btrfs/file.c
index 4d2eb64..82aec93 100644
--- a/fs/btrfs/file.c
+++ b/fs/btrfs/file.c
@@ -2557,6 +2557,16 @@ out:
return offset;
}

+static long btrfs_splice_direct(struct file *in, loff_t in_pos,
+ struct file *out, loff_t out_pos, size_t len,
+ unsigned int flags)
+{
+ int ret = btrfs_clone_extents(out, in, in_pos, len, out_pos);
+ if (ret == 0)
+ ret = len;
+ return ret;
+}
+
const struct file_operations btrfs_file_operations = {
.llseek = btrfs_file_llseek,
.read = do_sync_read,
@@ -2573,6 +2583,7 @@ const struct file_operations btrfs_file_operations = {
#ifdef CONFIG_COMPAT
.compat_ioctl = btrfs_ioctl,
#endif
+ .splice_direct = btrfs_splice_direct,
};

void btrfs_auto_defrag_exit(void)
diff --git a/fs/btrfs/ioctl.c b/fs/btrfs/ioctl.c
index 238a055..cddf6ef 100644
--- a/fs/btrfs/ioctl.c
+++ b/fs/btrfs/ioctl.c
@@ -2469,13 +2469,12 @@ out:
return ret;
}

-static noinline long btrfs_ioctl_clone(struct file *file, unsigned long srcfd,
- u64 off, u64 olen, u64 destoff)
+long btrfs_clone_extents(struct file *file, struct file *src_file, u64 off,
+ u64 olen, u64 destoff)
{
struct inode *inode = file_inode(file);
+ struct inode *src = file_inode(src_file);
struct btrfs_root *root = BTRFS_I(inode)->root;
- struct fd src_file;
- struct inode *src;
struct btrfs_trans_handle *trans;
struct btrfs_path *path;
struct extent_buffer *leaf;
@@ -2498,10 +2497,6 @@ static noinline long btrfs_ioctl_clone(struct file *file, unsigned long srcfd,
* they don't overlap)?
*/

- /* the destination must be opened for writing */
- if (!(file->f_mode & FMODE_WRITE) || (file->f_flags & O_APPEND))
- return -EINVAL;
-
if (btrfs_root_readonly(root))
return -EROFS;

@@ -2509,48 +2504,36 @@ static noinline long btrfs_ioctl_clone(struct file *file, unsigned long srcfd,
if (ret)
return ret;

- src_file = fdget(srcfd);
- if (!src_file.file) {
- ret = -EBADF;
- goto out_drop_write;
- }
-
ret = -EXDEV;
- if (src_file.file->f_path.mnt != file->f_path.mnt)
- goto out_fput;
-
- src = file_inode(src_file.file);
+ if (src_file->f_path.mnt != file->f_path.mnt)
+ goto out_drop_write;

ret = -EINVAL;
if (src == inode)
same_inode = 1;

- /* the src must be open for reading */
- if (!(src_file.file->f_mode & FMODE_READ))
- goto out_fput;
-
/* don't make the dst file partly checksummed */
if ((BTRFS_I(src)->flags & BTRFS_INODE_NODATASUM) !=
(BTRFS_I(inode)->flags & BTRFS_INODE_NODATASUM))
- goto out_fput;
+ goto out_drop_write;

ret = -EISDIR;
if (S_ISDIR(src->i_mode) || S_ISDIR(inode->i_mode))
- goto out_fput;
+ goto out_drop_write;

ret = -EXDEV;
if (src->i_sb != inode->i_sb)
- goto out_fput;
+ goto out_drop_write;

ret = -ENOMEM;
buf = vmalloc(btrfs_level_size(root, 0));
if (!buf)
- goto out_fput;
+ goto out_drop_write;

path = btrfs_alloc_path();
if (!path) {
vfree(buf);
- goto out_fput;
+ goto out_drop_write;
}
path->reada = 2;

@@ -2867,13 +2850,36 @@ out_unlock:
mutex_unlock(&inode->i_mutex);
vfree(buf);
btrfs_free_path(path);
-out_fput:
- fdput(src_file);
out_drop_write:
mnt_drop_write_file(file);
return ret;
}

+static noinline long btrfs_ioctl_clone(struct file *file, unsigned long srcfd,
+ u64 off, u64 olen, u64 destoff)
+{
+ struct fd src_file;
+ int ret;
+
+ /* the destination must be opened for writing */
+ if (!(file->f_mode & FMODE_WRITE) || (file->f_flags & O_APPEND))
+ return -EINVAL;
+
+ src_file = fdget(srcfd);
+ if (!src_file.file)
+ return -EBADF;
+
+ /* the src must be open for reading */
+ if (!(src_file.file->f_mode & FMODE_READ))
+ ret = -EINVAL;
+ else
+ ret = btrfs_clone_extents(file, src_file.file, off, olen,
+ destoff);
+
+ fdput(src_file);
+ return ret;
+}
+
static long btrfs_ioctl_clone_range(struct file *file, void __user *argp)
{
struct btrfs_ioctl_clone_range_args args;
--
1.7.11.7