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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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