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authorDavid Howells <dhowells@redhat.com>2007-03-22 00:11:24 -0800
committerLinus Torvalds <torvalds@woody.linux-foundation.org>2007-03-22 19:39:06 -0700
commit165b239270be610a1e3999cb0d2e4e2c1f2a8fd4 (patch)
tree3ae32cc616047b3960d1fe33b0583faa3094b82c
parentd56e03cd275486eb8141116a7af2df7457cb0115 (diff)
downloadlinux-linaro-stable-165b239270be610a1e3999cb0d2e4e2c1f2a8fd4.tar.gz
[PATCH] NOMMU: make SYSV SHM nattch work correctly
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@redhat.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
-rw-r--r--mm/nommu.c6
1 files changed, 6 insertions, 0 deletions
diff --git a/mm/nommu.c b/mm/nommu.c
index ba6df4d29979..cbbc13774819 100644
--- a/mm/nommu.c
+++ b/mm/nommu.c
@@ -826,6 +826,11 @@ unsigned long do_mmap_pgoff(struct file *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 *file,
goto shared;
}
+ dont_share_VMAs:
vma = NULL;
/* obtain the address at which to make a shared mapping