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vfs: pull btrfs clone API to vfs layer

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The btrfs clone ioctls are now adopted by other file systems, with NFS
and CIFS already having support for them, and XFS being under active
development.  To avoid growth of various slightly incompatible
implementations, add one to the VFS.  Note that clones are different from
file copies in several ways:

 - they are atomic vs other writers
 - they support whole file clones
 - they support 64-bit legth clones
 - they do not allow partial success (aka short writes)
 - clones are expected to be a fast metadata operation

Because of that it would be rather cumbersome to try to piggyback them on
top of the recent clone_file_range infrastructure.  The converse isn't
true and the clone_file_range system call could try clone file range as
a first attempt to copy, something that further patches will enable.

Based on earlier work from Peng Tao.

Signed-off-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
This commit is contained in:
Christoph Hellwig
2015-12-03 12:59:50 +01:00
committed by Al Viro
parent acc15575e7
commit 04b38d6012
11 changed files with 255 additions and 194 deletions
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9
include/uapi/linux/fs.h
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@@ -39,6 +39,13 @@
#define RENAME_EXCHANGE (1 << 1) /* Exchange source and dest */
#define RENAME_WHITEOUT (1 << 2) /* Whiteout source */
struct file_clone_range {
__s64 src_fd;
__u64 src_offset;
__u64 src_length;
__u64 dest_offset;
};
struct fstrim_range {
__u64 start;
__u64 len;
@@ -159,6 +166,8 @@ struct inodes_stat_t {
#define FIFREEZE _IOWR('X', 119, int) /* Freeze */
#define FITHAW _IOWR('X', 120, int) /* Thaw */
#define FITRIM _IOWR('X', 121, struct fstrim_range) /* Trim */
#define FICLONE _IOW(0x94, 9, int)
#define FICLONERANGE _IOW(0x94, 13, struct file_clone_range)
#define FS_IOC_GETFLAGS _IOR('f', 1, long)
#define FS_IOC_SETFLAGS _IOW('f', 2, long)