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    Subject[PATCH 4.4 131/135] pNFS/flexfiles: Fix list corruption if the mirror count changes
    Date
    From: Trond Myklebust <trond.myklebust@hammerspace.com>

    commit 8b04013737341442ed914b336cde866b902664ae upstream.

    If the mirror count changes in the new layout we pick up inside
    ff_layout_pg_init_write(), then we can end up adding the
    request to the wrong mirror and corrupting the mirror->pg_list.

    Fixes: d600ad1f2bdb ("NFS41: pop some layoutget errors to application")
    Cc: stable@vger.kernel.org
    Signed-off-by: Trond Myklebust <trond.myklebust@hammerspace.com>
    Signed-off-by: Anna Schumaker <Anna.Schumaker@Netapp.com>
    Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
    ---
    fs/nfs/flexfilelayout/flexfilelayout.c | 11 +++++++----
    1 file changed, 7 insertions(+), 4 deletions(-)

    diff --git a/fs/nfs/flexfilelayout/flexfilelayout.c b/fs/nfs/flexfilelayout/flexfilelayout.c
    index 6506775575aa6..17771e157e929 100644
    --- a/fs/nfs/flexfilelayout/flexfilelayout.c
    +++ b/fs/nfs/flexfilelayout/flexfilelayout.c
    @@ -855,9 +855,8 @@ ff_layout_pg_init_write(struct nfs_pageio_descriptor *pgio,
    goto out_mds;

    /* Use a direct mapping of ds_idx to pgio mirror_idx */
    - if (WARN_ON_ONCE(pgio->pg_mirror_count !=
    - FF_LAYOUT_MIRROR_COUNT(pgio->pg_lseg)))
    - goto out_mds;
    + if (pgio->pg_mirror_count != FF_LAYOUT_MIRROR_COUNT(pgio->pg_lseg))
    + goto out_eagain;

    for (i = 0; i < pgio->pg_mirror_count; i++) {
    ds = nfs4_ff_layout_prepare_ds(pgio->pg_lseg, i, true);
    @@ -869,11 +868,15 @@ ff_layout_pg_init_write(struct nfs_pageio_descriptor *pgio,
    }

    return;
    -
    +out_eagain:
    + pnfs_generic_pg_cleanup(pgio);
    + pgio->pg_error = -EAGAIN;
    + return;
    out_mds:
    pnfs_put_lseg(pgio->pg_lseg);
    pgio->pg_lseg = NULL;
    nfs_pageio_reset_write_mds(pgio);
    + pgio->pg_error = -EAGAIN;
    }

    static unsigned int
    --
    2.25.1
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