On Sat, Jul 27, 2019 at 01:35:06AM +0000, Rick Macklem wrote: > Konstantin Belousov wrote: > >On Thu, Jul 25, 2019 at 05:46:17AM +0000, Rick Macklem wrote: > >> Author: rmacklem > >> Date: Thu Jul 25 05:46:16 2019 > >> New Revision: 350315 > >> URL: https://svnweb.freebsd.org/changeset/base/350315 > >> > >> Log: > >> Add kernel support for a Linux compatible copy_file_range(2) syscall. > > > >> Modified: head/sys/kern/syscalls.master > >> >=====================================================================>========= > >> --- head/sys/kern/syscalls.master Thu Jul 25 03:55:05 2019 > >> (r350314) > >> +++ head/sys/kern/syscalls.master Thu Jul 25 05:46:16 2019 > >> (r350315) > >> @@ -3175,6 +3175,16 @@ > >> int flag > >> ); > >> } > >> +569 AUE_NULL STD { > >> + ssize_t copy_file_range( > >> + int infd, > >> + _Inout_opt_ off_t *inoffp, > >> + int outfd, > >> + _Inout_opt_ off_t *outoffp, > >> + size_t len, > >> + unsigned int flags > >> + ); > >> + } > > > >I sat to write the compat32 shims, and only then noted that len has size_t > >type. Why is it size_t and not off_t ? > Well, that's what Linux did. > > Also, since it returns ssize_t, it can't do more than SSIZE_MAX > (generally 1/2 of SIZE_T_MAX). Returning ssize_t is also what Linux > does and is consistent with read(2)/write(2).
If changing the length argument type to off_t, it is reasonable to change the return type to off_t as well. We already have the lseek(2) syscall that requires two return registers on 32bit. Note that it is reasonable for read(2) to take length as size_t-typed parameter, because size_t is the type for object sizes. There is no object in user address space for copy_file_range(2) API, so potentially wider off_t is acceptable and is in fact useful there. It is useful on 32bit machines where FreeBSD size_t is 32bit, while off_t is 64bit. _______________________________________________ svn-src-all@freebsd.org mailing list https://lists.freebsd.org/mailman/listinfo/svn-src-all To unsubscribe, send any mail to "svn-src-all-unsubscr...@freebsd.org"
