Update with all the missing errors the syscall can return, the behaviour the syscall should have w.r.t. to copies within single files, etc. [Amir] Copying beyond EOF returns zero. Signed-off-by: Dave Chinner <dchinner@xxxxxxxxxx> Signed-off-by: Amir Goldstein <amir73il@xxxxxxxxx> --- man2/copy_file_range.2 | 93 ++++++++++++++++++++++++++++++++++-------- 1 file changed, 77 insertions(+), 16 deletions(-) diff --git a/man2/copy_file_range.2 b/man2/copy_file_range.2 index 2438b63c8..fab11f977 100644 --- a/man2/copy_file_range.2 +++ b/man2/copy_file_range.2 @@ -42,9 +42,9 @@ without the additional cost of transferring data from the kernel to user space and then back into the kernel. It copies up to .I len -bytes of data from file descriptor +bytes of data from the source file descriptor .I fd_in -to file descriptor +to target file descriptor .IR fd_out , overwriting any data that exists within the requested range of the target file. .PP @@ -74,6 +74,11 @@ is not changed, but .I off_in is adjusted appropriately. .PP +.I fd_in +and +.I fd_out +can refer to the same file. If they refer to the same file, then the source and +target ranges are not allowed to overlap. .PP The .I flags @@ -84,6 +89,11 @@ Upon successful completion, .BR copy_file_range () will return the number of bytes copied between files. This could be less than the length originally requested. +If the file offset of +.I fd_in +is at or past the end of file, no bytes are copied, and +.BR copy_file_range () +returns zero. .PP On error, .BR copy_file_range () @@ -93,12 +103,16 @@ is set to indicate the error. .SH ERRORS .TP .B EBADF -One or more file descriptors are not valid; or +One or more file descriptors are not valid. +.TP +.B EBADF .I fd_in is not open for reading; or .I fd_out -is not open for writing; or -the +is not open for writing. +.TP +.B EBADF +The .B O_APPEND flag is set for the open file description (see .BR open (2)) @@ -106,17 +120,36 @@ referred to by the file descriptor .IR fd_out . .TP .B EFBIG -An attempt was made to write a file that exceeds the implementation-defined -maximum file size or the process's file size limit, -or to write at a position past the maximum allowed offset. +An attempt was made to write at a position past the maximum file offset the +kernel supports. +.TP +.B EFBIG +An attempt was made to write a range that exceeds the allowed maximum file size. +The maximum file size differs between filesystem implemenations and can be +different to the maximum allowed file offset. +.TP +.B EFBIG +An attempt was made to write beyond the process's file size resource +limit. This may also result in the process receiving a +.I SIGXFSZ +signal. .TP .B EINVAL -Requested range extends beyond the end of the source file; or the +The .I flags argument is not 0. .TP -.B EIO -A low-level I/O error occurred while copying. +.B EINVAL +.I fd_in +and +.I fd_out +refer to the same file and the source and target ranges overlap. +.TP +.B EINVAL +.I fd_in +or +.I fd_out +is not a regular file. .TP .B EISDIR .I fd_in @@ -124,22 +157,50 @@ or .I fd_out refers to a directory. .TP +.B EOVERFLOW +The requested source or destination range is too large to represent in the +specified data types. +.TP +.B EIO +A low-level I/O error occurred while copying. +.TP .B ENOMEM Out of memory. .TP -.B ENOSPC -There is not enough space on the target filesystem to complete the copy. -.TP .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 (pre Linux 5.3). +.TP +.B ENOSPC +There is not enough space on the target filesystem to complete the copy. +.TP +.B TXTBSY +.I fd_in +or +.I fd_out +refers to an active swap file. +.TP +.B EPERM +.I fd_out +refers to an immutable file. +.TP +.B EACCES +The user does not have write permissions for the destination file. .SH VERSIONS The .BR copy_file_range () system call first appeared in Linux 4.5, but glibc 2.27 provides a user-space emulation when it is not available. .\" https://sourceware.org/git/?p=glibc.git;a=commit;f=posix/unistd.h;h=bad7a0c81f501fbbcc79af9eaa4b8254441c4a1f +.PP +A major rework of the kernel implementation occurred in 5.3. Areas of the API +that weren't clearly defined were clarified and the API bounds are much more +strictly checked than on earlier kernels. Applications should target the +behaviour and requirements of 5.3 kernels. +.PP +First support for cross-filesystem copies was introduced in Linux 5.3. Older +kernels will return -EXDEV when cross-filesystem copies are attempted. .SH CONFORMING TO The .BR copy_file_range () @@ -224,7 +285,7 @@ main(int argc, char **argv) } len \-= ret; - } while (len > 0); + } while (len > 0 && ret > 0); close(fd_in); close(fd_out); -- 2.17.1
