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ashmem for 2.6.27.

Forward port of ashmem to 2.6.27.

Signed-off-by: Robert Love <rlove@google.com>

ashmem: Don't install fault handler for private mmaps.

Ashmem is used to create named private heaps. If this heap is backed
by a tmpfs file it will allocate two pages for every page touched.
In 2.6.27, the extra page would later be freed, but 2.6.29 does not
scan anonymous pages when running without swap so the memory is not
freed while the file is referenced. This change changes the behavior
of private ashmem mmaps to match /dev/zero instead tmpfs.

Signed-off-by: Arve Hjønnevåg <arve@android.com>

ashmem: Add common prefix to name reported in /proc/pid/maps

Signed-off-by: Arve Hjønnevåg <arve@android.com>

ashmem: don't require a page aligned size

This makes ashmem more similar to shmem and mmap, by
not requiring the specified size to be page aligned,
instead rounding it internally as needed.

Signed-off-by: Marco Nelissen <marcone@android.com>
1 parent 96b7efe commit d457dac3b0b10d882a08ec7b8d85a8a351a6c89f Robert Love committed with Arve Hjønnevåg Oct 14, 2008
Showing with 738 additions and 5 deletions.
  1. +48 −0 include/linux/ashmem.h
  2. +1 −0 include/linux/mm.h
  3. +9 −0 init/Kconfig
  4. +1 −0 mm/Makefile
  5. +670 −0 mm/ashmem.c
  6. +9 −5 mm/shmem.c
View
@@ -0,0 +1,48 @@
+/*
+ * include/linux/ashmem.h
+ *
+ * Copyright 2008 Google Inc.
+ * Author: Robert Love
+ *
+ * This file is dual licensed. It may be redistributed and/or modified
+ * under the terms of the Apache 2.0 License OR version 2 of the GNU
+ * General Public License.
+ */
+
+#ifndef _LINUX_ASHMEM_H
+#define _LINUX_ASHMEM_H
+
+#include <linux/limits.h>
+#include <linux/ioctl.h>
+
+#define ASHMEM_NAME_LEN 256
+
+#define ASHMEM_NAME_DEF "dev/ashmem"
+
+/* Return values from ASHMEM_PIN: Was the mapping purged while unpinned? */
+#define ASHMEM_NOT_PURGED 0
+#define ASHMEM_WAS_PURGED 1
+
+/* Return values from ASHMEM_GET_PIN_STATUS: Is the mapping pinned? */
+#define ASHMEM_IS_UNPINNED 0
+#define ASHMEM_IS_PINNED 1
+
+struct ashmem_pin {
+ __u32 offset; /* offset into region, in bytes, page-aligned */
+ __u32 len; /* length forward from offset, in bytes, page-aligned */
+};
+
+#define __ASHMEMIOC 0x77
+
+#define ASHMEM_SET_NAME _IOW(__ASHMEMIOC, 1, char[ASHMEM_NAME_LEN])
+#define ASHMEM_GET_NAME _IOR(__ASHMEMIOC, 2, char[ASHMEM_NAME_LEN])
+#define ASHMEM_SET_SIZE _IOW(__ASHMEMIOC, 3, size_t)
+#define ASHMEM_GET_SIZE _IO(__ASHMEMIOC, 4)
+#define ASHMEM_SET_PROT_MASK _IOW(__ASHMEMIOC, 5, unsigned long)
+#define ASHMEM_GET_PROT_MASK _IO(__ASHMEMIOC, 6)
+#define ASHMEM_PIN _IOW(__ASHMEMIOC, 7, struct ashmem_pin)
+#define ASHMEM_UNPIN _IOW(__ASHMEMIOC, 8, struct ashmem_pin)
+#define ASHMEM_GET_PIN_STATUS _IO(__ASHMEMIOC, 9)
+#define ASHMEM_PURGE_ALL_CACHES _IO(__ASHMEMIOC, 10)
+
+#endif /* _LINUX_ASHMEM_H */
View
@@ -732,6 +732,7 @@ extern void show_free_areas(void);
int shmem_lock(struct file *file, int lock, struct user_struct *user);
struct file *shmem_file_setup(const char *name, loff_t size, unsigned long flags);
+void shmem_set_file(struct vm_area_struct *vma, struct file *file);
int shmem_zero_setup(struct vm_area_struct *);
#ifndef CONFIG_MMU
View
@@ -964,6 +964,15 @@ config SHMEM
option replaces shmem and tmpfs with the much simpler ramfs code,
which may be appropriate on small systems without swap.
+config ASHMEM
+ bool "Enable the Anonymous Shared Memory Subsystem"
+ default n
+ depends on SHMEM || TINY_SHMEM
+ help
+ The ashmem subsystem is a new shared memory allocator, similar to
+ POSIX SHM but with different behavior and sporting a simpler
+ file-based API.
+
config AIO
bool "Enable AIO support" if EMBEDDED
default y
View
@@ -24,6 +24,7 @@ obj-$(CONFIG_HUGETLBFS) += hugetlb.o
obj-$(CONFIG_NUMA) += mempolicy.o
obj-$(CONFIG_SPARSEMEM) += sparse.o
obj-$(CONFIG_SPARSEMEM_VMEMMAP) += sparse-vmemmap.o
+obj-$(CONFIG_ASHMEM) += ashmem.o
obj-$(CONFIG_SLOB) += slob.o
obj-$(CONFIG_COMPACTION) += compaction.o
obj-$(CONFIG_MMU_NOTIFIER) += mmu_notifier.o
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