[was: man pages for undocumented system calls] Stephan, Thanks for this page. It is worth documenting the existence of this system call, but we need to do it differently: 1. It's best documented as an addition to the sync_file_rabge.2 page. 2. There needs to be an explanation of why the system call exists. I wrote the patch below for man-pages-3.29. Cheers, Michael --- a/man2/sync_file_range.2 +++ b/man2/sync_file_range.2 @@ -179,6 +180,40 @@ appeared on Linux in kernel 2.6.17. .SH "CONFORMING TO" This system call is Linux-specific, and should be avoided in portable programs. +.SH NOTES +Some architectures (e.g., PowerPC, ARM) +need 64-bit arguments to be aligned in a suitable pair of registers. +.\" See kernel commit edd5cd4a9424f22b0fa08bef5e299d41befd5622 +On such architectures, the call signature of +.BR sync_file_range () +is flawed, since it forces a register to be wasted as padding between the +.I fd +and +.I offset +arguments. +Therefore, these architectures define a different +system call that orders the arguments suitably: +.PP +.in +4n +.nf +.BI "int sync_file_range2(int " fd ", unsigned int " flags , +.BI " off64_t " offset ", off64_t " nbytes ); +.fi +.in +.PP +The behavior of this system call is otherwise exactly the same as +.BR sync_file_range(). + +A system call with this signature first appeared on the ARM architecture +in Linux 2.6.20, with the name +.BR arm_sync_file_range (). +It was renamed in Linux 2.6.22, +when the analogous system call was added for PowerPC. +On architectures where glibc support is provided, +glibc transparently wraps +.BR sync_file_range2 () +under the name +.BR sync_file_range (). .SH "SEE ALSO" .BR fdatasync (2), .BR fsync (2), -- Michael Kerrisk Linux man-pages maintainer; http://www.kernel.org/doc/man-pages/ Author of "The Linux Programming Interface"; http://man7.org/tlpi/ -- To unsubscribe from this list: send the line "unsubscribe linux-man" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
