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SUNRPC: Eliminate side effects from rpc_malloc

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Currently rpc_malloc sets req->rq_buffer internally.  Make this a more
generic interface:  return a pointer to the new buffer (or NULL) and
make the caller set req->rq_buffer and req->rq_bufsize.  This looks much
more like kmalloc and eliminates the side effects.

To fix a potential deadlock, this patch also replaces GFP_NOFS with
GFP_NOWAIT in rpc_malloc.  This prevents async RPCs from sleeping outside
the RPC's task scheduler while allocating their buffer.

Signed-off-by: Chuck Lever <chuck.lever@oracle.com>
Signed-off-by: Trond Myklebust <Trond.Myklebust@netapp.com>
This commit is contained in:
Chuck Lever
2007-03-29 16:47:58 -04:00
committed by Trond Myklebust
parent 2bea90d43a
commit c5a4dd8b7c
5 changed files with 39 additions and 35 deletions
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65
net/sunrpc/sched.c
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@@ -741,50 +741,53 @@ static void rpc_async_schedule(struct work_struct *work)
* @task: RPC task that will use this buffer
* @size: requested byte size
*
* We try to ensure that some NFS reads and writes can always proceed
* by using a mempool when allocating 'small' buffers.
* To prevent rpciod from hanging, this allocator never sleeps,
* returning NULL if the request cannot be serviced immediately.
* The caller can arrange to sleep in a way that is safe for rpciod.
*
* Most requests are 'small' (under 2KiB) and can be serviced from a
* mempool, ensuring that NFS reads and writes can always proceed,
* and that there is good locality of reference for these buffers.
*
* In order to avoid memory starvation triggering more writebacks of
* NFS requests, we use GFP_NOFS rather than GFP_KERNEL.
* NFS requests, we avoid using GFP_KERNEL.
*/
void * rpc_malloc(struct rpc_task *task, size_t size)
void *rpc_malloc(struct rpc_task *task, size_t size)
{
struct rpc_rqst *req = task->tk_rqstp;
gfp_t gfp;
size_t *buf;
gfp_t gfp = RPC_IS_SWAPPER(task) ? GFP_ATOMIC : GFP_NOWAIT;
if (task->tk_flags & RPC_TASK_SWAPPER)
gfp = GFP_ATOMIC;
size += sizeof(size_t);
if (size <= RPC_BUFFER_MAXSIZE)
buf = mempool_alloc(rpc_buffer_mempool, gfp);
else
gfp = GFP_NOFS;
if (size > RPC_BUFFER_MAXSIZE) {
req->rq_buffer = kmalloc(size, gfp);
if (req->rq_buffer)
req->rq_bufsize = size;
} else {
req->rq_buffer = mempool_alloc(rpc_buffer_mempool, gfp);
if (req->rq_buffer)
req->rq_bufsize = RPC_BUFFER_MAXSIZE;
}
return req->rq_buffer;
buf = kmalloc(size, gfp);
*buf = size;
dprintk("RPC: %5u allocated buffer of size %u at %p\n",
task->tk_pid, size, buf);
return (void *) ++buf;
}
/**
* rpc_free - free buffer allocated via rpc_malloc
* @task: RPC task with a buffer to be freed
* @buffer: buffer to free
*
*/
void rpc_free(struct rpc_task *task)
void rpc_free(void *buffer)
{
struct rpc_rqst *req = task->tk_rqstp;
size_t size, *buf = (size_t *) buffer;
if (req->rq_buffer) {
if (req->rq_bufsize == RPC_BUFFER_MAXSIZE)
mempool_free(req->rq_buffer, rpc_buffer_mempool);
else
kfree(req->rq_buffer);
req->rq_buffer = NULL;
req->rq_bufsize = 0;
}
if (!buffer)
return;
size = *buf;
buf--;
dprintk("RPC: freeing buffer of size %u at %p\n",
size, buf);
if (size <= RPC_BUFFER_MAXSIZE)
mempool_free(buf, rpc_buffer_mempool);
else
kfree(buf);
}
/*