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    Subject[PATCH 1/6] nfs: "open code" the NFS direct write rescheduler
    Date
    In order to support direct asynchronous vectored writes, the write
    rescheduler in fs/nfs/direct.c must not depend on the I/O parameters in the
    controlling nfs_direct_req structure. Refactor the write rescheduler to
    use only the information in each nfs_write_data structure to redrive writes
    if the server rebooted before we can commit them.

    Signed-off-by: Chuck Lever <cel@netapp.com>
    ---

    fs/nfs/direct.c | 71 +++++++++++++++++++++++++++++++++++++++++++------------
    1 files changed, 56 insertions(+), 15 deletions(-)

    diff --git a/fs/nfs/direct.c b/fs/nfs/direct.c
    index 0980e43..0fde4bf 100644
    --- a/fs/nfs/direct.c
    +++ b/fs/nfs/direct.c
    @@ -94,8 +94,19 @@ struct nfs_direct_req {
    struct nfs_writeverf verf; /* unstable write verifier */
    };

    -static void nfs_direct_write_schedule(struct nfs_direct_req *dreq, int sync);
    static void nfs_direct_write_complete(struct nfs_direct_req *dreq, struct inode *inode);
    +static const struct rpc_call_ops nfs_write_direct_ops;
    +
    +static inline int nfs_direct_dec_outstanding(struct nfs_direct_req *dreq)
    +{
    + int result;
    +
    + spin_lock(&dreq->lock);
    + result = --dreq->outstanding;
    + spin_unlock(&dreq->lock);
    +
    + return (result == 0);
    +}

    /**
    * nfs_direct_IO - NFS address space operation for direct I/O
    @@ -428,14 +439,52 @@ static void nfs_direct_free_writedata(st
    #if defined(CONFIG_NFS_V3) || defined(CONFIG_NFS_V4)
    static void nfs_direct_write_reschedule(struct nfs_direct_req *dreq)
    {
    + struct inode *inode = dreq->inode;
    struct list_head *pos;

    - list_splice_init(&dreq->rewrite_list, &dreq->list);
    - list_for_each(pos, &dreq->list)
    - dreq->outstanding++;
    + /*
    + * Prevent I/O completion while we're still rescheduling
    + */
    + dreq->outstanding++;
    +
    dreq->count = 0;
    + list_for_each(pos, &dreq->rewrite_list) {
    + struct nfs_write_data *data =
    + list_entry(dreq->rewrite_list.next, struct nfs_write_data, pages);
    +
    + spin_lock(&dreq->lock);
    + dreq->outstanding++;
    + spin_unlock(&dreq->lock);
    +
    + nfs_fattr_init(&data->fattr);
    + data->res.count = data->args.count;
    + memset(&data->verf, 0, sizeof(data->verf));
    +
    + rpc_init_task(&data->task, NFS_CLIENT(inode), RPC_TASK_ASYNC,
    + &nfs_write_direct_ops, data);
    + NFS_PROTO(inode)->write_setup(data, FLUSH_STABLE);
    +
    + data->task.tk_priority = RPC_PRIORITY_HIGH;
    + data->task.tk_cookie = (unsigned long) inode;

    - nfs_direct_write_schedule(dreq, FLUSH_STABLE);
    + lock_kernel();
    + rpc_execute(&data->task);
    + unlock_kernel();
    +
    + dfprintk(VFS, "NFS: %5u rescheduled direct write call (req %s/%Ld, %zu bytes @ offset %Lu)\n",
    + data->task.tk_pid,
    + inode->i_sb->s_id,
    + (long long)NFS_FILEID(inode),
    + data->args.count,
    + (unsigned long long)data->args.offset);
    + }
    +
    + /*
    + * If we raced with the rescheduled I/O and lost, then
    + * all the I/O is already complete.
    + */
    + if (nfs_direct_dec_outstanding(dreq))
    + nfs_direct_write_complete(dreq, inode);
    }

    static void nfs_direct_commit_result(struct rpc_task *task, void *calldata)
    @@ -605,8 +654,6 @@ static void nfs_direct_write_result(stru
    }
    }
    }
    - /* In case we have to resend */
    - data->args.stable = NFS_FILE_SYNC;

    spin_unlock(&dreq->lock);
    }
    @@ -620,14 +667,8 @@ static void nfs_direct_write_release(voi
    struct nfs_write_data *data = calldata;
    struct nfs_direct_req *dreq = (struct nfs_direct_req *) data->req;

    - spin_lock(&dreq->lock);
    - if (--dreq->outstanding) {
    - spin_unlock(&dreq->lock);
    - return;
    - }
    - spin_unlock(&dreq->lock);
    -
    - nfs_direct_write_complete(dreq, data->inode);
    + if (nfs_direct_dec_outstanding(dreq))
    + nfs_direct_write_complete(dreq, data->inode);
    }

    static const struct rpc_call_ops nfs_write_direct_ops = {
    -
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