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    SubjectRe: [PATCH 06/19] dlm: align midcomms message buffer
    On Sat, 26 Jan 2008, Andrew Morton wrote:

    >> On Thu, 24 Jan 2008 10:50:29 -0600 David Teigland <teigland@redhat.com> wrote:
    >> From: Fabio M. Di Nitto <fabbione@ubuntu.com>
    >>
    >> gcc does not guarantee that a static buffer is 64bit aligned. This change
    >> allows sparc64 to work.
    >>
    >
    > This buffer is not static: changelog needs fixing: s/static/auto/
    >
    >> ---
    >> fs/dlm/midcomms.c | 2 +-
    >> 1 files changed, 1 insertions(+), 1 deletions(-)
    >>
    >> diff --git a/fs/dlm/midcomms.c b/fs/dlm/midcomms.c
    >> index f8c69dd..da653b5 100644
    >> --- a/fs/dlm/midcomms.c
    >> +++ b/fs/dlm/midcomms.c
    >> @@ -58,7 +58,7 @@ static void copy_from_cb(void *dst, const void *base, unsigned offset,
    >> int dlm_process_incoming_buffer(int nodeid, const void *base,
    >> unsigned offset, unsigned len, unsigned limit)
    >> {
    >> - unsigned char __tmp[DLM_INBUF_LEN];
    >> + unsigned char __tmp[DLM_INBUF_LEN] __attribute__((aligned(64)));
    >> struct dlm_header *msg = (struct dlm_header *) __tmp;
    >> int ret = 0;
    >> int err = 0;
    >
    > Why does DLM require that this thing be 64-bit aligned?
    >
    > It all looks rather ugly. Can't this stuff be implemeted within the C type
    > system somehow?
    >

    how about this one:

    From adfe3b0654583d34b0840d20a69e4306d5b98caf Mon Sep 17 00:00:00 2001
    Message-Id: <adfe3b0654583d34b0840d20a69e4306d5b98caf.1201584946.git.fabbione@ubuntu.com>
    From: Fabio M. Di Nitto <fabbione@ubuntu.com>
    Date: Tue, 29 Jan 2008 06:35:20 +0100
    Subject: [PATCH 1/1] dlm: align midcomms message buffer

    gcc does not guarantee that an auto buffer is 64bit aligned.
    This change allows sparc64 to work.

    Signed-off-by: Fabio M. Di Nitto <fabbione@ubuntu.com>
    ---
    :100644 100644 f8c69dd... 53b7af2... M fs/dlm/midcomms.c
    fs/dlm/midcomms.c | 13 ++++++++-----
    1 files changed, 8 insertions(+), 5 deletions(-)

    diff --git a/fs/dlm/midcomms.c b/fs/dlm/midcomms.c
    index f8c69dd..53b7af2 100644
    --- a/fs/dlm/midcomms.c
    +++ b/fs/dlm/midcomms.c
    @@ -58,8 +58,11 @@ static void copy_from_cb(void *dst, const void *base, unsigned offset,
    int dlm_process_incoming_buffer(int nodeid, const void *base,
    unsigned offset, unsigned len, unsigned limit)
    {
    - unsigned char __tmp[DLM_INBUF_LEN];
    - struct dlm_header *msg = (struct dlm_header *) __tmp;
    + union {
    + unsigned char __buf[DLM_INBUF_LEN];
    + struct dlm_header dlm;
    + } __tmp;
    + struct dlm_header *msg = &__tmp.dlm;
    int ret = 0;
    int err = 0;
    uint16_t msglen;
    @@ -100,8 +103,8 @@ int dlm_process_incoming_buffer(int nodeid, const void *base,
    in the buffer on the stack (which should work for most
    ordinary messages). */

    - if (msglen > sizeof(__tmp) &&
    - msg == (struct dlm_header *) __tmp) {
    + if (msglen > DLM_INBUF_LEN &&
    + msg == &__tmp.dlm) {
    msg = kmalloc(dlm_config.ci_buffer_size, GFP_KERNEL);
    if (msg == NULL)
    return ret;
    @@ -119,7 +122,7 @@ int dlm_process_incoming_buffer(int nodeid, const void *base,
    dlm_receive_buffer(msg, nodeid);
    }

    - if (msg != (struct dlm_header *) __tmp)
    + if (msg != &__tmp.dlm)
    kfree(msg);

    return err ? err : ret;
    --
    1.5.3.8

    --
    I'm going to make him an offer he can't refuse.


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