The patch titled
Subject: ipc/mqueue: switch back to using non-max values on create
has been removed from the -mm tree. Its filename was
ipc-mqueue-switch-back-to-using-non-max-values-on-create.patch
This patch was dropped because it was merged into mainline or a subsystem tree
The current -mm tree may be found at http://userweb.kernel.org/~akpm/mmotm/
------------------------------------------------------
From: Doug Ledford <dledford@xxxxxxxxxx>
Subject: ipc/mqueue: switch back to using non-max values on create
Commit b231cca4381 ("message queues: increase range limits") changed how
we create a queue that does not include an attr struct passed to open so
that it creates the queue with whatever the maximum values are. However,
if the admin has set the maximums to allow flexibility in creating a queue
(aka, both a large size and large queue are allowed, but combined they
create a queue too large for the RLIMIT_MSGQUEUE of the user), then
attempts to create a queue without an attr struct will fail. Switch back
to using acceptable defaults regardless of what the maximums are.
Note: so far, we only know of a few applications that rely on this
behavior (specifically, set the maximums in /proc, then run the
application which calls mq_open() without passing in an attr struct, and
the application expects the newly created message queue to have the
maximum sizes that were set in /proc used on the mq_open() call, and all
of those applications that we know of are actually part of regression test
suites that were coded to do something like this:
for size in 4096 65536 $((1024 * 1024)) $((16 * 1024 * 1024)); do
echo $size > /proc/sys/fs/mqueue/msgsize_max
mq_open || echo "Error opening mq with size $size"
done
These test suites that depend on any behavior like this are broken. The
concept that programs should rely upon the system wide maximum in order to
get their desired results instead of simply using a attr struct to specify
what they want is fundamentally unfriendly programming practice for any
multi-tasking OS.
Fixing this will break those few apps that we know of (and those app
authors recognize the brokenness of their code and the need to fix it).
However, the following patch "mqueue: separate mqueue default value"
allows a workaround in the form of new knobs for the default msg queue
creation parameters for any software out there that we don't already know
about that might rely on this behavior at the moment.
Signed-off-by: Doug Ledford <dledford@xxxxxxxxxx>
Cc: Serge E. Hallyn <serue@xxxxxxxxxx>
Cc: Amerigo Wang <amwang@xxxxxxxxxx>
Cc: Joe Korty <joe.korty@xxxxxxxx>
Cc: Jiri Slaby <jslaby@xxxxxxx>
Acked-by: KOSAKI Motohiro <kosaki.motohiro@xxxxxxxxxxxxxx>
Cc: Manfred Spraul <manfred@xxxxxxxxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
include/linux/ipc_namespace.h | 2 ++
ipc/mqueue.c | 5 +++--
2 files changed, 5 insertions(+), 2 deletions(-)
diff -puN include/linux/ipc_namespace.h~ipc-mqueue-switch-back-to-using-non-max-values-on-create include/linux/ipc_namespace.h
--- a/include/linux/ipc_namespace.h~ipc-mqueue-switch-back-to-using-non-max-values-on-create
+++ a/include/linux/ipc_namespace.h
@@ -95,9 +95,11 @@ extern int mq_init_ns(struct ipc_namespa
#define DFLT_QUEUESMAX 256 /* max number of message queues */
#define HARD_QUEUESMAX 1024
#define MIN_MSGMAX 1
+#define DFLT_MSG 10U
#define DFLT_MSGMAX 10 /* max number of messages in each queue */
#define HARD_MSGMAX (32768*sizeof(void *)/4)
#define MIN_MSGSIZEMAX 128
+#define DFLT_MSGSIZE 8192U
#define DFLT_MSGSIZEMAX 8192 /* max message size */
#define HARD_MSGSIZEMAX (8192*128)
#else
diff -puN ipc/mqueue.c~ipc-mqueue-switch-back-to-using-non-max-values-on-create ipc/mqueue.c
--- a/ipc/mqueue.c~ipc-mqueue-switch-back-to-using-non-max-values-on-create
+++ a/ipc/mqueue.c
@@ -144,8 +144,9 @@ static struct inode *mqueue_get_inode(st
info->qsize = 0;
info->user = NULL; /* set when all is ok */
memset(&info->attr, 0, sizeof(info->attr));
- info->attr.mq_maxmsg = ipc_ns->mq_msg_max;
- info->attr.mq_msgsize = ipc_ns->mq_msgsize_max;
+ info->attr.mq_maxmsg = min(ipc_ns->mq_msg_max, DFLT_MSG);
+ info->attr.mq_msgsize =
+ min(ipc_ns->mq_msgsize_max, DFLT_MSGSIZE);
if (attr) {
info->attr.mq_maxmsg = attr->mq_maxmsg;
info->attr.mq_msgsize = attr->mq_msgsize;
_
Patches currently in -mm which might be from dledford@xxxxxxxxxx are
origin.patch
ipc-mqueue-enforce-hard-limits.patch
ipc-mqueue-update-maximums-for-the-mqueue-subsystem.patch
mqueue-revert-bump-up-dflt_max.patch
mqueue-dont-use-kmalloc-with-kmalloc_max_size.patch
mqueue-separate-mqueue-default-value-from-maximum-value-v2.patch
selftests-add-mq_open_tests.patch
ipc-mqueue-improve-performance-of-send-recv.patch
ipc-mqueue-correct-mq_attr_ok-test.patch
ipc-mqueue-strengthen-checks-on-mqueue-creation.patch
tools-selftests-add-mq_perf_tests.patch
ipc-mqueue-add-rbtree-node-caching-support.patch
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