linux-kernel - [patch] man-pages: add documentation about the memlock implications of io

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Date:	Mon, 09 Mar 2009 11:59:20 -0400
From:	Jeff Moyer <jmoyer@...hat.com>
To:	linux-aio <linux-aio@...ck.org>, michael.kerrisk@...il.com
Cc:	zach.brown@...cle.com, bcrl@...ck.org,
	Andrew Morton <akpm@...ux-foundation.org>,
	linux-kernel@...r.kernel.org
Subject: [patch] man-pages: add documentation about the memlock implications of io_setup

Hi,

This patch, against man-pages-3.19, adds verbiage surrounding the newly
proposed accounting of pinned aio completion ring pages against the
memlock rlimit.  It also fixes up a few references to aio_context_t
(which should be io_context_t).  Sorry for conflating the two, I can
break it apart if needed.

Cheers,
Jeff

diff -up man-pages-3.19/man2/io_cancel.2.orig man-pages-3.19/man2/io_cancel.2
--- man-pages-3.19/man2/io_cancel.2.orig	2009-03-08 11:57:50.000000000 -0400
+++ man-pages-3.19/man2/io_cancel.2	2009-03-08 11:58:01.000000000 -0400
@@ -32,7 +32,7 @@ io_cancel \- cancel an outstanding async
 .\"#include <linux/aio.h>
 .sp
 .\" .HP 16
-.BI "int io_cancel(aio_context_t " ctx_id ", struct iocb *" iocb ,
+.BI "int io_cancel(io_context_t " ctx_id ", struct iocb *" iocb ,
 .BI "              struct io_event *" result );
 .\" .ad
 .\" .hy
diff -up man-pages-3.19/man2/io_destroy.2.orig man-pages-3.19/man2/io_destroy.2
--- man-pages-3.19/man2/io_destroy.2.orig	2009-03-08 11:58:08.000000000 -0400
+++ man-pages-3.19/man2/io_destroy.2	2009-03-08 11:58:16.000000000 -0400
@@ -31,7 +31,7 @@ io_destroy \- destroy an asynchronous I/
 .\" #include <linux/aio.h>
 .sp
 .\" .HP 17
-.BI "int io_destroy(aio_context_t " ctx );
+.BI "int io_destroy(io_context_t " ctx );
 .\" .ad
 .\" .hy
 .sp
diff -up man-pages-3.19/man2/io_setup.2.orig man-pages-3.19/man2/io_setup.2
--- man-pages-3.19/man2/io_setup.2.orig	2009-03-08 11:53:39.000000000 -0400
+++ man-pages-3.19/man2/io_setup.2	2009-03-08 11:57:09.000000000 -0400
@@ -31,7 +31,7 @@ io_setup \- create an asynchronous I/O c
 .\" #include <linux/aio.h>
 .sp
 .\" .HP 15
-.BI "int io_setup(unsigned " nr_events ", aio_context_t *" ctxp );
+.BI "int io_setup(unsigned " nr_events ", io_context_t *" ctxp );
 .\" .ad
 .\" .hy
 .sp
@@ -45,7 +45,9 @@ at least \fInr_events\fP.
 \fIctxp\fP must not point to an AIO context that already exists, and must
 be initialized to 0 prior to the call.
 On successful creation of the AIO context, \fI*ctxp\fP is filled in
-with the resulting handle.
+with the resulting handle.  Memory is reserved by the kernel for the completion
+ring and, because this memory is pinned, it will be charged against the
+process's memlock rlimit.
 .SH "RETURN VALUE"
 On success,
 .BR io_setup ()
@@ -54,7 +56,8 @@ For the failure return, see NOTES.
 .SH "ERRORS"
 .TP
 .B EAGAIN
-The specified \fInr_events\fP exceeds the user's limit of available events.
+The specified \fInr_events\fP exceeds the process's limit of available events.
+Try increasing the memlock rlimit for the process.
 .TP
 .B EFAULT
 An invalid pointer is passed for \fIctxp\fP.
diff -up man-pages-3.19/man2/io_submit.2.orig man-pages-3.19/man2/io_submit.2
--- man-pages-3.19/man2/io_submit.2.orig	2009-03-08 11:58:26.000000000 -0400
+++ man-pages-3.19/man2/io_submit.2	2009-03-08 11:58:34.000000000 -0400
@@ -31,7 +31,7 @@ io_submit \- submit asynchronous I/O blo
 .\" #include <linux/aio.h>
 .sp
 .\" .HP 16
-.BI "int io_submit(aio_context_t " ctx_id ", long " nr \
+.BI "int io_submit(io_context_t " ctx_id ", long " nr \
 ", struct iocb **" iocbpp );
 .\" .ad
 .\" .hy
@@ -63,7 +63,7 @@ The file descriptor specified in the fir
 One of the data structures points to invalid data.
 .TP
 .B EINVAL
-The \fIaio_context\fP specified by \fIctx_id\fP is invalid.
+The \fIio_context\fP specified by \fIctx_id\fP is invalid.
 \fInr\fP is less than 0.
 The \fIiocb\fP at *iocbpp[0] is not properly initialized,
 or the operation specified is invalid for the file descriptor
diff -up man-pages-3.19/man7/capabilities.7.orig man-pages-3.19/man7/capabilities.7
--- man-pages-3.19/man7/capabilities.7.orig	2009-03-08 11:52:56.000000000 -0400
+++ man-pages-3.19/man7/capabilities.7	2009-03-08 11:53:14.000000000 -0400
@@ -129,7 +129,8 @@ Lock memory
 .RB ( mlock (2),
 .BR mlockall (2),
 .BR mmap (2),
-.BR shmctl (2)).
+.BR shmctl (2),
+.BR io_setup (2)).
 .TP
 .B CAP_IPC_OWNER
 Bypass permission checks for operations on System V IPC objects.
--
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