btrfs: offline dedupe

This patch adds an ioctl, BTRFS_IOC_FILE_EXTENT_SAME which will try to
de-duplicate a list of extents across a range of files.

Internally, the ioctl re-uses code from the clone ioctl. This avoids
rewriting a large chunk of extent handling code.

Userspace passes in an array of file, offset pairs along with a length
argument. The ioctl will then (for each dedupe) do a byte-by-byte comparison
of the user data before deduping the extent. Status and number of bytes
deduped are returned for each operation.

Signed-off-by: Mark Fasheh <mfasheh@suse.de>
Reviewed-by: Zach Brown <zab@redhat.com>
Signed-off-by: Josef Bacik <jbacik@fusionio.com>
Signed-off-by: Chris Mason <chris.mason@fusionio.com>

1 files changed, 28 insertions, 0 deletions

diff --git a/include/uapi/linux/btrfs.h b/include/uapi/linux/btrfs.h
index 05aed70627e2..90d7bd9d839c 100644
--- a/include/uapi/linux/btrfs.h
+++ b/include/uapi/linux/btrfs.h
@@ -305,6 +305,31 @@ struct btrfs_ioctl_clone_range_args {
 #define BTRFS_DEFRAG_RANGE_COMPRESS 1
 #define BTRFS_DEFRAG_RANGE_START_IO 2
 
+#define BTRFS_SAME_DATA_DIFFERS 1
+/* For extent-same ioctl */
+struct btrfs_ioctl_same_extent_info {
+        __s64 fd;               /* in - destination file */
+        __u64 logical_offset;   /* in - start of extent in destination */
+        __u64 bytes_deduped;    /* out - total # of bytes we were able
+                                 * to dedupe from this file */
+        /* status of this dedupe operation:
+         * 0 if dedup succeeds
+         * < 0 for error
+         * == BTRFS_SAME_DATA_DIFFERS if data differs
+         */
+        __s32 status;           /* out - see above description */
+        __u32 reserved;
+};
+
+struct btrfs_ioctl_same_args {
+        __u64 logical_offset;   /* in - start of extent in source */
+        __u64 length;           /* in - length of extent */
+        __u16 dest_count;       /* in - total elements in info array */
+        __u16 reserved1;
+        __u32 reserved2;
+        struct btrfs_ioctl_same_extent_info info[0];
+};
+
 struct btrfs_ioctl_space_info {
         __u64 flags;
         __u64 total_bytes;
@@ -579,4 +604,7 @@ static inline char *btrfs_err_str(enum btrfs_err_code err_code)
                                       struct btrfs_ioctl_get_dev_stats)
 #define BTRFS_IOC_DEV_REPLACE _IOWR(BTRFS_IOCTL_MAGIC, 53, \
                                     struct btrfs_ioctl_dev_replace_args)
+#define BTRFS_IOC_FILE_EXTENT_SAME _IOWR(BTRFS_IOCTL_MAGIC, 54, \
+                                         struct btrfs_ioctl_same_args)
+
 #endif /* _UAPI_LINUX_BTRFS_H */