From: Olga Kornievskaia <kolga@xxxxxxxxxx> A proposed VFS change removes the check for the files to reside under the same file system. Instead, a file system driver implementation is allowed to perform a cross-device copy_file_range() and if the file system fails to support it instead fallback to doing a do_splice copy. Therefore, EXDEV error code only applies to kernel version prior to such support. Signed-off-by: Olga Kornievskaia <kolga@xxxxxxxxxx> --- man2/copy_file_range.2 | 6 ++++-- 1 file changed, 4 insertions(+), 2 deletions(-) diff --git a/man2/copy_file_range.2 b/man2/copy_file_range.2 index 20374ab..2cd9fae 100644 --- a/man2/copy_file_range.2 +++ b/man2/copy_file_range.2 @@ -39,7 +39,8 @@ The .BR copy_file_range () system call performs an in-kernel copy between two file descriptors without the additional cost of transferring data from the kernel to user space -and then back into the kernel. +and then back into the kernel. Since kernel version 4.21(???) passed in +file descriptors are not required to be under the same mounted file system. It copies up to .I len bytes of data from file descriptor @@ -131,7 +132,8 @@ There is not enough space on the target filesystem to complete the copy. .B EXDEV The files referred to by .IR file_in " and " file_out -are not on the same mounted filesystem. +are not on the same mounted filesystem when the kernel does not support +cross device file copy. .SH VERSIONS The .BR copy_file_range () -- 1.8.3.1
