[PATCH 5/5] NOMMU: Futher nommu shared memory support

dhowells
2004-12-09T15:10:14Z

The attached patch furthers shared memory support under !MMU conditions:

(1) tiny-shmem.c farms get_unmapped_area() and mmap() requests off to ramfs in
addition to the inode creation requests, thus supporting SYSV SHM

(2) tiny-shmem.c no longer expands the inode it allocates by writing directly
into i_size.

(3) SYSV IPC is then available on nommu.

(a) SYSV SHM requires shmem_mmap() to be provided by the backing
filesystem (tmpfs in shmem.c or tiny-shmem.c).

(b) SYSV SHM requires shmem_get_unmapped_area() to be provided by the
backing fs if under !MMU conditions.

Signed-Off-By: dhowells@redhat.com
---
diffstat nommu-shmem-2610rc2mm3-3.diff
include/linux/mm.h | 11 +++++++++++
init/Kconfig | 1 -
ipc/shm.c | 16 +++++++++++-----
mm/shmem.c | 2 +-
mm/tiny-shmem.c | 26 +++++++++++++++++++++++++-
5 files changed, 48 insertions(+), 8 deletions(-)

diff -uNrp linux-2.6.10-rc2-mm3-mmcleanup/init/Kconfig linux-2.6.10-rc2-mm3-shmem/init/Kconfig
--- linux-2.6.10-rc2-mm3-mmcleanup/init/Kconfig 2004-11-22 10:54:17.000000000 +0000
+++ linux-2.6.10-rc2-mm3-shmem/init/Kconfig 2004-12-01 17:07:36.000000000 +0000
@@ -81,7 +81,6 @@ 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-2.6.10-rc2-mm3-mmcleanup/include/linux/mm.h linux-2.6.10-rc2-mm3-shmem/include/linux/mm.h
--- linux-2.6.10-rc2-mm3-mmcleanup/include/linux/mm.h 2004-11-22 10:54:16.000000000 +0000
+++ linux-2.6.10-rc2-mm3-shmem/include/linux/mm.h 2004-12-08 16:52:24.000000000 +0000
@@ -566,9 +603,20 @@ 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 *);

+#ifdef CONFIG_MMU
+#define shmem_get_unmapped_area(f,a,l,p,fl) 0
+#else
+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-2.6.10-rc2-mm3-mmcleanup/ipc/shm.c linux-2.6.10-rc2-mm3-shmem/ipc/shm.c
--- linux-2.6.10-rc2-mm3-mmcleanup/ipc/shm.c 2004-11-22 10:54:17.000000000 +0000
+++ linux-2.6.10-rc2-mm3-shmem/ipc/shm.c 2004-12-02 15:20:36.000000000 +0000
@@ -157,14 +157,20 @@ 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,
+ .get_unmapped_area = shmem_get_unmapped_area,
};

static struct vm_operations_struct shm_vm_ops = {
diff -uNrp linux-2.6.10-rc2-mm3-mmcleanup/mm/shmem.c linux-2.6.10-rc2-mm3-shmem/mm/shmem.c
--- linux-2.6.10-rc2-mm3-mmcleanup/mm/shmem.c 2004-11-22 10:54:18.000000000 +0000
+++ linux-2.6.10-rc2-mm3-shmem/mm/shmem.c 2004-12-02 15:16:23.000000000 +0000
@@ -1246,7 +1246,7 @@ 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-2.6.10-rc2-mm3-mmcleanup/mm/tiny-shmem.c linux-2.6.10-rc2-mm3-shmem/mm/tiny-shmem.c
--- linux-2.6.10-rc2-mm3-mmcleanup/mm/tiny-shmem.c 2004-11-15 13:34:39.000000000 +0000
+++ linux-2.6.10-rc2-mm3-shmem/mm/tiny-shmem.c 2004-12-02 16:20:55.000000000 +0000
@@ -78,8 +78,13 @@ 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 */
+
+ /* notify everyone as to the change of file size */
+ error = do_truncate(dentry, size);
+ if (error < 0)
+ goto close_file;
+
file->f_vfsmnt = mntget(shm_mnt);
file->f_dentry = dentry;
file->f_mapping = inode->i_mapping;
@@ -120,3 +125,22 @@ 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
+}
+
+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);
+}