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    SubjectRe: [PATCH] nfs: fix congestion control -v4
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    On Fri, 2007-01-26 at 00:51 -0800, Andrew Morton wrote:
    > On Fri, 26 Jan 2007 09:03:37 +0100
    > Peter Zijlstra <a.p.zijlstra@chello.nl> wrote:
    >
    > > On Thu, 2007-01-25 at 22:04 -0800, Andrew Morton wrote:
    > > > On Thu, 25 Jan 2007 21:31:43 -0800 (PST)
    > > > Christoph Lameter <clameter@sgi.com> wrote:
    > > >
    > > > > On Thu, 25 Jan 2007, Andrew Morton wrote:
    > > > >
    > > > > > atomic_t is 32-bit. Put 16TB of memory under writeback and blam.
    > > > >
    > > > > We have systems with 8TB main memory and are able to get to 16TB.
    > > >
    > > > But I bet you don't use 4k pages on 'em ;)
    > > >
    > > > > Better change it now.
    > > >
    > > > yup.
    > >
    > > I can change to atomic_long_t but that would make this patch depend on
    > > Mathieu Desnoyers' atomic.h patch series.

    ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^

    > > Do I send out a -v5 with this, or should I send an incremental patch
    > > once that hits your tree?
    >
    > A patch against next -mm would suit, thanks.


    As promised change the atomic_t in struct nfs_server to atomic_long_t in
    anticipation of machines that can handle 8+TB of (4K) pages under writeback.

    However I suspect other things in NFS will start going *bang* by then.

    Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
    ---
    fs/nfs/write.c | 4 ++--
    include/linux/nfs_fs_sb.h | 2 +-
    2 files changed, 3 insertions(+), 3 deletions(-)

    Index: linux-2.6/fs/nfs/write.c
    ===================================================================
    --- linux-2.6.orig/fs/nfs/write.c
    +++ linux-2.6/fs/nfs/write.c
    @@ -224,7 +224,7 @@ static void nfs_set_page_writeback(struc
    struct inode *inode = page->mapping->host;
    struct nfs_server *nfss = NFS_SERVER(inode);

    - if (atomic_inc_return(&nfss->writeback) >
    + if (atomic_long_inc_return(&nfss->writeback) >
    NFS_CONGESTION_ON_THRESH)
    set_bdi_congested(&nfss->backing_dev_info, WRITE);
    }
    @@ -236,7 +236,7 @@ static void nfs_end_page_writeback(struc
    struct nfs_server *nfss = NFS_SERVER(inode);

    end_page_writeback(page);
    - if (atomic_dec_return(&nfss->writeback) < NFS_CONGESTION_OFF_THRESH) {
    + if (atomic_long_dec_return(&nfss->writeback) < NFS_CONGESTION_OFF_THRESH) {
    clear_bdi_congested(&nfss->backing_dev_info, WRITE);
    congestion_end(WRITE);
    }
    Index: linux-2.6/include/linux/nfs_fs_sb.h
    ===================================================================
    --- linux-2.6.orig/include/linux/nfs_fs_sb.h
    +++ linux-2.6/include/linux/nfs_fs_sb.h
    @@ -82,7 +82,7 @@ struct nfs_server {
    struct rpc_clnt * client_acl; /* ACL RPC client handle */
    struct nfs_iostats * io_stats; /* I/O statistics */
    struct backing_dev_info backing_dev_info;
    - atomic_t writeback; /* number of writeback pages */
    + atomic_long_t writeback; /* number of writeback pages */
    int flags; /* various flags */
    unsigned int caps; /* server capabilities */
    unsigned int rsize; /* read size */

    -
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