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Subject[PATCH 2/3] NOMMU: Make SYSV IPC SHM use ramfs facilities on NOMMU
The attached patch makes the SYSV IPC shared memory facilities use the new
ramfs facilities on a no-MMU kernel.

The following changes are made:

(1) There are now shmem_mmap() and shmem_get_unmapped_area() functions to
allow the IPC SHM facilities to commune with the tiny-shmem and shmem
code.

(2) ramfs files now need resizing using do_truncate() rather than by modifying
the inode size directly (see shmem_file_setup()). This causes ramfs to
attempt to bind a block of pages of sufficient size to the inode.

(3) CONFIG_SYSVIPC is no longer contingent on CONFIG_MMU.

Signed-Off-By: David Howells <dhowells@redhat.com>
---
warthog>diffstat -p1 shmem-nommu-2615rc2.diff
include/linux/mm.h | 9 +++++++++
init/Kconfig | 1 -
ipc/shm.c | 18 +++++++++++++-----
mm/nommu.c | 6 ++++++
mm/shmem.c | 2 +-
mm/tiny-shmem.c | 29 ++++++++++++++++++++++++++++-
6 files changed, 57 insertions(+), 8 deletions(-)
diff -uNrp linux-2.6.15-rc2-frv/include/linux/mm.h linux-2.6.15-rc2-frv-shmem/include/linux/mm.h
--- linux-2.6.15-rc2-frv/include/linux/mm.h 2005-11-23 13:29:08.000000000 +0000
+++ linux-2.6.15-rc2-frv-shmem/include/linux/mm.h 2005-11-23 16:46:59.000000000 +0000
@@ -656,9 +656,18 @@ int shmem_lock(struct file *file, int lo
#define shmem_get_policy(a, b) (NULL)
#endif
struct file *shmem_file_setup(char *name, loff_t size, unsigned long flags);
+extern int shmem_mmap(struct file *file, struct vm_area_struct *vma);

int shmem_zero_setup(struct vm_area_struct *);

+#ifndef CONFIG_MMU
+extern unsigned long shmem_get_unmapped_area(struct file *file,
+ unsigned long addr,
+ unsigned long len,
+ unsigned long pgoff,
+ unsigned long flags);
+#endif
+
static inline int can_do_mlock(void)
{
if (capable(CAP_IPC_LOCK))
diff -uNrp linux-2.6.15-rc2-frv/init/Kconfig linux-2.6.15-rc2-frv-shmem/init/Kconfig
--- linux-2.6.15-rc2-frv/init/Kconfig 2005-11-23 12:09:23.000000000 +0000
+++ linux-2.6.15-rc2-frv-shmem/init/Kconfig 2005-11-23 16:00:57.000000000 +0000
@@ -105,7 +105,6 @@ config SWAP

config SYSVIPC
bool "System V IPC"
- depends on MMU
---help---
Inter Process Communication is a suite of library functions and
system calls which let processes (running programs) synchronize and
diff -uNrp linux-2.6.15-rc2-frv/ipc/shm.c linux-2.6.15-rc2-frv-shmem/ipc/shm.c
--- linux-2.6.15-rc2-frv/ipc/shm.c 2005-11-23 12:09:23.000000000 +0000
+++ linux-2.6.15-rc2-frv-shmem/ipc/shm.c 2005-11-23 16:45:44.000000000 +0000
@@ -157,14 +157,22 @@ static void shm_close (struct vm_area_st

static int shm_mmap(struct file * file, struct vm_area_struct * vma)
{
- file_accessed(file);
- vma->vm_ops = &shm_vm_ops;
- shm_inc(file->f_dentry->d_inode->i_ino);
- return 0;
+ int ret;
+
+ ret = shmem_mmap(file, vma);
+ if (ret == 0) {
+ vma->vm_ops = &shm_vm_ops;
+ shm_inc(file->f_dentry->d_inode->i_ino);
+ }
+
+ return ret;
}

static struct file_operations shm_file_operations = {
- .mmap = shm_mmap
+ .mmap = shm_mmap,
+#ifndef CONFIG_MMU
+ .get_unmapped_area = shmem_get_unmapped_area,
+#endif
};

static struct vm_operations_struct shm_vm_ops = {
diff -uNrp linux-2.6.15-rc2-frv/mm/nommu.c linux-2.6.15-rc2-frv-shmem/mm/nommu.c
--- linux-2.6.15-rc2-frv/mm/nommu.c 2005-11-23 12:09:24.000000000 +0000
+++ linux-2.6.15-rc2-frv-shmem/mm/nommu.c 2005-11-23 16:00:57.000000000 +0000
@@ -1177,3 +1177,9 @@ int in_gate_area_no_task(unsigned long a
{
return 0;
}
+
+struct page * filemap_nopage(struct vm_area_struct * area, unsigned long address, int *type)
+{
+ BUG();
+ return NULL;
+}
diff -uNrp linux-2.6.15-rc2-frv/mm/shmem.c linux-2.6.15-rc2-frv-shmem/mm/shmem.c
--- linux-2.6.15-rc2-frv/mm/shmem.c 2005-11-23 12:09:24.000000000 +0000
+++ linux-2.6.15-rc2-frv-shmem/mm/shmem.c 2005-11-23 16:00:57.000000000 +0000
@@ -1255,7 +1255,7 @@ out_nomem:
return retval;
}

-static int shmem_mmap(struct file *file, struct vm_area_struct *vma)
+int shmem_mmap(struct file *file, struct vm_area_struct *vma)
{
file_accessed(file);
vma->vm_ops = &shmem_vm_ops;
diff -uNrp linux-2.6.15-rc2-frv/mm/tiny-shmem.c linux-2.6.15-rc2-frv-shmem/mm/tiny-shmem.c
--- linux-2.6.15-rc2-frv/mm/tiny-shmem.c 2005-11-23 12:09:24.000000000 +0000
+++ linux-2.6.15-rc2-frv-shmem/mm/tiny-shmem.c 2005-11-23 16:46:15.000000000 +0000
@@ -81,13 +81,19 @@ struct file *shmem_file_setup(char *name
goto close_file;

d_instantiate(dentry, inode);
- inode->i_size = size;
inode->i_nlink = 0; /* It is unlinked */
+
file->f_vfsmnt = mntget(shm_mnt);
file->f_dentry = dentry;
file->f_mapping = inode->i_mapping;
file->f_op = &ramfs_file_operations;
file->f_mode = FMODE_WRITE | FMODE_READ;
+
+ /* notify everyone as to the change of file size */
+ error = do_truncate(dentry, size, file);
+ if (error < 0)
+ goto close_file;
+
return file;

close_file:
@@ -123,3 +129,24 @@ int shmem_unuse(swp_entry_t entry, struc
{
return 0;
}
+
+int shmem_mmap(struct file *file, struct vm_area_struct *vma)
+{
+ file_accessed(file);
+#ifndef CONFIG_MMU
+ return ramfs_nommu_mmap(file, vma);
+#else
+ return 0;
+#endif
+}
+
+#ifndef CONFIG_MMU
+unsigned long shmem_get_unmapped_area(struct file *file,
+ unsigned long addr,
+ unsigned long len,
+ unsigned long pgoff,
+ unsigned long flags)
+{
+ return ramfs_nommu_get_unmapped_area(file, addr, len, pgoff, flags);
+}
+#endif
-
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