The patch titled
NOMMU: make SYSV SHM nattch work correctly
has been added to the -mm tree. Its filename is
nommu-make-sysv-shm-nattch-work-correctly.patch
*** Remember to use Documentation/SubmitChecklist when testing your code ***
See http://www.zip.com.au/~akpm/linux/patches/stuff/added-to-mm.txt to find
out what to do about this
------------------------------------------------------
Subject: NOMMU: make SYSV SHM nattch work correctly
From: David Howells <dhowells@xxxxxxxxxx>
Make the SYSV SHM nattch counter work correctly by forcing multiple VMAs to
be produced to represent MAP_SHARED segments, even if they overlap exactly.
Using this test program:
http://people.redhat.com/~dhowells/doshm.c
Run as:
doshm sysv
I can see nattch going from one before the patch:
# /doshm sysv
Command: sysv
shmid: 65536
memory: 0xc3700000
c0b00000-c0b04000 rw-p 00000000 00:00 0
c0bb0000-c0bba788 r-xs 00000000 00:0b 14582157 /lib/ld-uClibc-0.9.28.so
c3180000-c31dede4 r-xs 00000000 00:0b 14582179 /lib/libuClibc-0.9.28.so
c3520000-c352278c rw-p 00000000 00:0b 13763417 /doshm
c3584000-c35865e8 r-xs 00000000 00:0b 13763417 /doshm
c3588000-c358aa00 rw-p 00008000 00:0b 14582157 /lib/ld-uClibc-0.9.28.so
c3590000-c359b6c0 rw-p 00000000 00:00 0
c3620000-c3640000 rwxp 00000000 00:00 0
c3700000-c37fa000 rw-S 00000000 00:06 1411 /SYSV00000000 (deleted)
c3700000-c37fa000 rw-S 00000000 00:06 1411 /SYSV00000000 (deleted)
nattch 1
To two after the patch:
# /doshm sysv
Command: sysv
shmid: 0
memory: 0xc3700000
c0bb0000-c0bba788 r-xs 00000000 00:0b 14582157 /lib/ld-uClibc-0.9.28.so
c3180000-c31dede4 r-xs 00000000 00:0b 14582179 /lib/libuClibc-0.9.28.so
c3320000-c3340000 rwxp 00000000 00:00 0
c3530000-c35325e8 r-xs 00000000 00:0b 13763417 /doshm
c3534000-c353678c rw-p 00000000 00:0b 13763417 /doshm
c3538000-c353aa00 rw-p 00008000 00:0b 14582157 /lib/ld-uClibc-0.9.28.so
c3590000-c359b6c0 rw-p 00000000 00:00 0
c35a4000-c35a8000 rw-p 00000000 00:00 0
c3700000-c37fa000 rw-S 00000000 00:06 1369 /SYSV00000000 (deleted)
c3700000-c37fa000 rw-S 00000000 00:06 1369 /SYSV00000000 (deleted)
nattch 2
That's +1 to nattch for each shmat() made.
Signed-off-by: David Howells <dhowells@xxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
mm/nommu.c | 6 ++++++
1 files changed, 6 insertions(+)
diff -puN mm/nommu.c~nommu-make-sysv-shm-nattch-work-correctly mm/nommu.c
--- a/mm/nommu.c~nommu-make-sysv-shm-nattch-work-correctly
+++ a/mm/nommu.c
@@ -826,6 +826,11 @@ unsigned long do_mmap_pgoff(struct file
unsigned long pglen = (len + PAGE_SIZE - 1) >> PAGE_SHIFT;
unsigned long vmpglen;
+ /* suppress VMA sharing for shared regions */
+ if (vm_flags & VM_SHARED &&
+ capabilities & BDI_CAP_MAP_DIRECT)
+ goto dont_share_VMAs;
+
for (rb = rb_first(&nommu_vma_tree); rb; rb = rb_next(rb)) {
vma = rb_entry(rb, struct vm_area_struct, vm_rb);
@@ -859,6 +864,7 @@ unsigned long do_mmap_pgoff(struct file
goto shared;
}
+ dont_share_VMAs:
vma = NULL;
/* obtain the address at which to make a shared mapping
_
Patches currently in -mm which might be from dhowells@xxxxxxxxxx are
frv-fix-unannotated-variable-declarations.patch
nommu-supply-get_unmapped_area-to-fix-nommu-sysv-shm.patch
nommu-make-sysv-shm-nattch-work-correctly.patch
nommu-present-backing-device-capabilities-for-mtd.patch
nommu-add-support-for-direct-mapping-through-mtdconcat.patch
nommu-generalise-the-handling-of-mtd-specific-superblocks.patch
nommu-make-it-possible-for-romfs-to-use-mtd-devices.patch
romfs-printk-format-warnings.patch
nommu-hide-vm_mm-in-nommu-mode.patch
doc-atomic_add_unless-doesnt-imply-mb-on-failure.patch
kill-net-rxrpc-rxrpc_symsc.patch
use-symbolic-constants-in-generic-lseek-code.patch
use-use-seek_max-to-validate-user-lseek-arguments.patch
kconfig-centralize-the-selection-of-semaphore-debugging.patch
aio-use-flush_work.patch
kblockd-use-flush_work.patch
relayfs-use-flush_keventd_work.patch
tg3-use-flush_keventd_work.patch
e1000-use-flush_keventd_work.patch
libata-use-flush_work.patch
phy-use-flush_work.patch
workqueue-kill-noautorel-works.patch
mutex-subsystem-synchro-test-module.patch
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