[PATCH] 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>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

3 files changed, 36 insertions, 2 deletions

diff --git a/mm/nommu.c b/mm/nommu.c
index c1196812876b..c10262d68232 100644
--- a/mm/nommu.c
+++ b/mm/nommu.c
@@ -1177,3 +1177,10 @@ int in_gate_area_no_task(unsigned long addr)
 {
         return 0;
 }
+
+struct page *filemap_nopage(struct vm_area_struct *area,
+                        unsigned long address, int *type)
+{
+        BUG();
+        return NULL;
+}
diff --git a/mm/shmem.c b/mm/shmem.c
index 65c148efa2ed..a1f2f02af724 100644
--- a/mm/shmem.c
+++ b/mm/shmem.c
@@ -1270,7 +1270,7 @@ 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 --git a/mm/tiny-shmem.c b/mm/tiny-shmem.c
index b58abcf44ed6..cdc6d431972b 100644
--- a/mm/tiny-shmem.c
+++ b/mm/tiny-shmem.c
@@ -81,13 +81,19 @@ struct file *shmem_file_setup(char *name, loff_t size, unsigned long flags)
                 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, struct page *page)
 {
         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