Eric Lee / smarc-ti-linux-kernel

23 Mar, 2006

1 commit

07 Jan, 2006

1 commit

  • 642fb4d1f   [PATCH] NOMMU: Provide shared-writable mmap support on ramfs ... Browse Code »

    The attached patch makes ramfs support shared-writable mmaps by:

    (1) Attempting to perform a contiguous block allocation to the requested size
    when truncate attempts to increase the file from zero size, such as
    happens when:

    fd = shm_open("/file/on/ramfs", ...):
    ftruncate(fd, size_requested);
    addr = mmap(NULL, subsize, PROT_READ|PROT_WRITE|PROT_EXEC, MAP_SHARED,
    fd, offset);

    (2) Permitting any shared-writable mapping over any contiguous set of extant
    pages. get_unmapped_area() will return the address into the actual ramfs
    pages. The mapping may start anywhere and be of any size, but may not go
    over the end of file. Multiple mappings may overlap in any way.

    (3) Not permitting a file to be shrunk if it would truncate any shared
    mappings (private mappings are copied).

    Thus this patch provides support for POSIX shared memory on NOMMU kernels,
    with certain limitations such as there being a large enough block of pages
    available to support the allocation and it only working on directly mappable
    filesystems.

    Signed-off-by: David Howells
    Signed-off-by: Andrew Morton
    Signed-off-by: Linus Torvalds

    David Howells