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ioctl: add note regarding CLONE_RANGE(len=0) behaviour

Message ID 1391696958-4522-1-git-send-email-ddiss@suse.de (mailing list archive)
State Accepted, archived
Headers show

Commit Message

David Disseldorp Feb. 6, 2014, 2:29 p.m. UTC 
A BTRFS_IOC_CLONE_RANGE request with a src_length value of zero has the
effect of cloning all data from src_offset through to end-of-file.

Document this behaviour in the header file for those who (like me)
incorrectly assume that no data is cloned in such a case.

Signed-off-by: David Disseldorp <ddiss@suse.de>
---
 ioctl.h | 1 +
 1 file changed, 1 insertion(+)
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Patch

diff --git a/ioctl.h b/ioctl.h
index a589cd7..f7d435d 100644
--- a/ioctl.h
+++ b/ioctl.h
@@ -506,6 +506,7 @@  static inline char *btrfs_err_str(enum btrfs_err_code err_code)
 #define BTRFS_IOC_SCAN_DEV _IOW(BTRFS_IOCTL_MAGIC, 4, \
 				   struct btrfs_ioctl_vol_args)
 
+/* With a @src_length of zero, the range from @src_offset->EOF is cloned! */
 struct btrfs_ioctl_clone_range_args {
 	__s64 src_fd;
 	__u64 src_offset, src_length;