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    Subject[PATCH 6.0 022/862] cifs: destage dirty pages before re-reading them for cache=none
    Date
    From: Ronnie Sahlberg <lsahlber@redhat.com>

    commit bb44c31cdcac107344dd2fcc3bd0504a53575c51 upstream.

    This is the opposite case of kernel bugzilla 216301.
    If we mmap a file using cache=none and then proceed to update the mmapped
    area these updates are not reflected in a later pread() of that part of the
    file.
    To fix this we must first destage any dirty pages in the range before
    we allow the pread() to proceed.

    Cc: stable@vger.kernel.org
    Reviewed-by: Paulo Alcantara (SUSE) <pc@cjr.nz>
    Reviewed-by: Enzo Matsumiya <ematsumiya@suse.de>
    Signed-off-by: Ronnie Sahlberg <lsahlber@redhat.com>
    Signed-off-by: Steve French <stfrench@microsoft.com>
    Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
    ---
    fs/cifs/file.c | 9 +++++++++
    1 file changed, 9 insertions(+)

    --- a/fs/cifs/file.c
    +++ b/fs/cifs/file.c
    @@ -4271,6 +4271,15 @@ static ssize_t __cifs_readv(
    len = ctx->len;
    }

    + if (direct) {
    + rc = filemap_write_and_wait_range(file->f_inode->i_mapping,
    + offset, offset + len - 1);
    + if (rc) {
    + kref_put(&ctx->refcount, cifs_aio_ctx_release);
    + return -EAGAIN;
    + }
    + }
    +
    /* grab a lock here due to read response handlers can access ctx */
    mutex_lock(&ctx->aio_mutex);


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