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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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