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    Subject[176/200] NFS: Fix another nfs_wb_page() deadlock
    2.6.34-stable review patch.  If anyone has any objections, please let me know.

    ------------------

    From: Trond Myklebust <Trond.Myklebust@netapp.com>

    commit 0522f6adedd2736cbca3c0e16ca51df668993eee upstream.

    J.R. Okajima reports that the call to sync_inode() in nfs_wb_page() can
    deadlock with other writeback flush calls. It boils down to the fact
    that we cannot ever call writeback_single_inode() while holding a page
    lock (even if we do set nr_to_write to zero) since another process may
    already be waiting in the call to do_writepages(), and so will deny us
    the I_SYNC lock.

    Signed-off-by: Trond Myklebust <Trond.Myklebust@netapp.com>
    Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

    ---
    fs/nfs/write.c | 7 +++++--
    1 file changed, 5 insertions(+), 2 deletions(-)

    --- a/fs/nfs/write.c
    +++ b/fs/nfs/write.c
    @@ -1518,14 +1518,17 @@ int nfs_wb_page(struct inode *inode, str
    };
    int ret;

    - while(PagePrivate(page)) {
    + for (;;) {
    wait_on_page_writeback(page);
    if (clear_page_dirty_for_io(page)) {
    ret = nfs_writepage_locked(page, &wbc);
    if (ret < 0)
    goto out_error;
    + continue;
    }
    - ret = sync_inode(inode, &wbc);
    + if (!PagePrivate(page))
    + break;
    + ret = nfs_commit_inode(inode, FLUSH_SYNC);
    if (ret < 0)
    goto out_error;
    }



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