On Thu, Mar 10, 2016 at 07:15:04PM +0100, Michael Kerrisk (man-pages) wrote: > Hi Christoph, > > On 03/03/2016 04:03 PM, Christoph Hellwig wrote: > > From: Milosz Tanski <milosz@xxxxxxxxx> > > > > New syscalls that take an flag argument. No flags are added yet in this > > patch. > > Are there some man pages patches for these proposed system calls? This is what I have: --- >From d33a02d56f447a6cb223b3964e1dd894f2921d5c Mon Sep 17 00:00:00 2001 From: Milosz Tanski <milosz@xxxxxxxxx> Date: Fri, 11 Mar 2016 10:52:31 +0100 Subject: add preadv2/pwritev2 documentation New syscalls that are a variation on the preadv/pwritev but support an extra flag argument. Signed-off-by: Milosz Tanski <milosz@xxxxxxxxx> [hch: added RWF_HIPRI documentation] Signed-off-by: Christoph Hellwig <hch@xxxxxx> --- man2/readv.2 | 63 +++++++++++++++++++++++++++++++++++++++++++++++++++--------- 1 file changed, 54 insertions(+), 9 deletions(-) diff --git a/man2/readv.2 b/man2/readv.2 index 93f2b6f..5cba5e2 100644 --- a/man2/readv.2 +++ b/man2/readv.2 @@ -45,6 +45,12 @@ readv, writev, preadv, pwritev \- read or write data into multiple buffers .sp .BI "ssize_t pwritev(int " fd ", const struct iovec *" iov ", int " iovcnt , .BI " off_t " offset ); +.sp +.BI "ssize_t preadv2(int " fd ", const struct iovec *" iov ", int " iovcnt , +.BI " off_t " offset ", int " flags ); +.sp +.BI "ssize_t pwritev2(int " fd ", const struct iovec *" iov ", int " iovcnt , +.BI " off_t " offset ", int " flags ); .fi .sp .in -4n @@ -166,9 +172,9 @@ The system call combines the functionality of .BR writev () and -.BR pwrite (2). +.BR pwrite (2) "." It performs the same task as -.BR writev (), +.BR writev () "," but adds a fourth argument, .IR offset , which specifies the file offset at which the output operation @@ -178,15 +184,43 @@ The file offset is not changed by these system calls. The file referred to by .I fd must be capable of seeking. +.SS preadv2() and pwritev2() + +This pair of system calls has similar functionality to the +.BR preadv () +and +.BR pwritev () +calls, but adds a fifth argument, \fIflags\fP, which modifies the behavior on a per call basis. + +Like the +.BR preadv () +and +.BR pwritev () +calls, they accept an \fIoffset\fP argument. Unlike those calls, if the \fIoffset\fP argument is set to -1 then the current file offset is used and updated. + +The \fIflags\fP arguments to +.BR preadv2 () +and +.BR pwritev2 () +contains a bitwise OR of one or more of the following flags: +.TP +.BR RWF_HIPRI " (since Linux 4.6)" +High priority read/write. Allows block based filesystems to use polling of the +device, which provides lower latency, but may use additional ressources. (Currently +only usable on a file descriptor opened using the +.BR O_DIRECT " flag)." + .SH RETURN VALUE On success, -.BR readv () -and +.BR readv () "," .BR preadv () -return the number of bytes read; -.BR writev () and +.BR preadv2 () +return the number of bytes read; +.BR writev () "," .BR pwritev () +and +.BR pwritev2 () return the number of bytes written. Note that is not an error for a successful call to transfer fewer bytes @@ -202,9 +236,11 @@ The errors are as given for and .BR write (2). Furthermore, -.BR preadv () -and +.BR preadv () "," +.BR preadv2 () "," .BR pwritev () +and +.BR pwritev2 () can also fail for the same reasons as .BR lseek (2). Additionally, the following error is defined: @@ -218,12 +254,17 @@ value. .TP .B EINVAL The vector count \fIiovcnt\fP is less than zero or greater than the -permitted maximum. +permitted maximum. Or, an unknown flag is specified in \fIflags\fP. .SH VERSIONS .BR preadv () and .BR pwritev () first appeared in Linux 2.6.30; library support was added in glibc 2.10. +.sp +.BR preadv2 () +and +.BR pwritev2 () +first appeared in Linux 4.6 .SH CONFORMING TO .BR readv (), .BR writev (): @@ -237,6 +278,10 @@ POSIX.1-2001, POSIX.1-2008, .BR preadv (), .BR pwritev (): nonstandard, but present also on the modern BSDs. +.sp +.BR preadv2 (), +.BR pwritev2 (): +nonstandard, Linux extension. .SH NOTES POSIX.1 allows an implementation to place a limit on the number of items that can be passed in -- 2.1.4 -- To unsubscribe from this list: send the line "unsubscribe linux-fsdevel" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
