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    Subject[PATCH 49/58] staging: lustre: llite: avoid a deadlock in page write
    Date
    From: Jinshan Xiong <jinshan.xiong@intel.com>

    For a partial page write, it will have to issue a READ RPC firstly
    to get a full uptodate page. If another page is already locked by
    this thread it can easily cause deadlock.

    Signed-off-by: Jinshan Xiong <jinshan.xiong@intel.com>
    Intel-bug-id: https://jira.hpdd.intel.com/browse/LU-4873
    Reviewed-on: http://review.whamcloud.com/9928
    Reviewed-by: Bobi Jam <bobijam@gmail.com>
    Reviewed-by: Niu Yawei <yawei.niu@intel.com>
    Reviewed-by: Oleg Drokin <oleg.drokin@intel.com>
    Signed-off-by: James Simmons <jsimmons@infradead.org>
    ---
    drivers/staging/lustre/lustre/llite/rw26.c | 5 +++--
    1 files changed, 3 insertions(+), 2 deletions(-)

    diff --git a/drivers/staging/lustre/lustre/llite/rw26.c b/drivers/staging/lustre/lustre/llite/rw26.c
    index d98c7ac..c14a1b6 100644
    --- a/drivers/staging/lustre/lustre/llite/rw26.c
    +++ b/drivers/staging/lustre/lustre/llite/rw26.c
    @@ -506,8 +506,9 @@ static int ll_write_begin(struct file *file, struct address_space *mapping,
    env = lcc->lcc_env;
    io = lcc->lcc_io;

    - /* To avoid deadlock, try to lock page first. */
    - vmpage = grab_cache_page_nowait(mapping, index);
    + if (likely(to == PAGE_SIZE)) /* LU-4873 */
    + /* To avoid deadlock, try to lock page first. */
    + vmpage = grab_cache_page_nowait(mapping, index);
    if (unlikely(!vmpage || PageDirty(vmpage) || PageWriteback(vmpage))) {
    struct vvp_io *vio = vvp_env_io(env);
    struct cl_page_list *plist = &vio->u.write.vui_queue;
    --
    1.7.1
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