Commit e21d451a authored by Pierre Barre's avatar Pierre Barre Committed by Dominique Martinet
Browse files

9p: Use kvmalloc for message buffers on supported transports 

While developing a 9P server (https://github.com/Barre/ZeroFS

) and
testing it under high-load, I was running into allocation failures.
The failures occur even with plenty of free memory available because
kmalloc requires contiguous physical memory.

This results in errors like:
ls: page allocation failure: order:7, mode:0x40c40(GFP_NOFS|__GFP_COMP)

This patch introduces a transport capability flag (supports_vmalloc)
that indicates whether a transport can work with vmalloc'd buffers
(non-physically contiguous memory). Transports requiring DMA should
leave this flag as false.

The fd-based transports (tcp, unix, fd) set this flag to true, and
p9_fcall_init will use kvmalloc instead of kmalloc for these
transports. This allows the allocator to fall back to vmalloc when
contiguous physical memory is not available.

Additionally, if kmem_cache_alloc fails, the code falls back to
kvmalloc for transports that support it.

Signed-off-by: default avatarPierre Barre <pierre@barre.sh>
Reviewed-by: default avatarChristian Schoenebeck <linux_oss@crudebyte.com>
Message-ID: <d2017c29-11fb-44a5-bd0f-4204329bbefb@app.fastmail.com>
Signed-off-by: default avatarDominique Martinet <asmadeus@codewreck.org>
parent 43c36a56

include/net/9p/transport.h

+4 −0
Original line number Diff line number Diff line
@@ -24,6 +24,9 @@ 
 *                   we're less flexible when choosing the response message

 *                   size in this case

 * @def: set if this transport should be considered the default

 * @supports_vmalloc: set if this transport can work with vmalloc'd buffers

 *                    (non-physically contiguous memory). Transports requiring

 *                    DMA should leave this as false.

 * @create: member function to create a new connection on this transport

 * @close: member function to discard a connection on this transport

 * @request: member function to issue a request to the transport
@@ -44,6 +47,7 @@ struct p9_trans_module { 
	int maxsize;		/* max message size of transport */

	bool pooled_rbuffers;

	int def;		/* this transport should be default */

	bool supports_vmalloc;	/* can work with vmalloc'd buffers */

	struct module *owner;

	int (*create)(struct p9_client *client,

		      const char *devname, char *args);

net/9p/client.c

+9 −2
Original line number Diff line number Diff line
@@ -229,7 +229,14 @@ static int p9_fcall_init(struct p9_client *c, struct p9_fcall *fc, 
	if (likely(c->fcall_cache) && alloc_msize == c->msize) {

		fc->sdata = kmem_cache_alloc(c->fcall_cache, GFP_NOFS);

		fc->cache = c->fcall_cache;

		if (!fc->sdata && c->trans_mod->supports_vmalloc) {

			fc->sdata = kvmalloc(alloc_msize, GFP_NOFS);

			fc->cache = NULL;

		}

	} else {

		if (c->trans_mod->supports_vmalloc)

			fc->sdata = kvmalloc(alloc_msize, GFP_NOFS);

		else

			fc->sdata = kmalloc(alloc_msize, GFP_NOFS);

		fc->cache = NULL;

	}
@@ -252,7 +259,7 @@ void p9_fcall_fini(struct p9_fcall *fc) 
	if (fc->cache)

		kmem_cache_free(fc->cache, fc->sdata);

	else

		kfree(fc->sdata);

		kvfree(fc->sdata);

}

EXPORT_SYMBOL(p9_fcall_fini);

net/9p/trans_fd.c

+3 −0
Original line number Diff line number Diff line
@@ -1101,6 +1101,7 @@ static struct p9_trans_module p9_tcp_trans = { 
	.maxsize = MAX_SOCK_BUF,

	.pooled_rbuffers = false,

	.def = 0,

	.supports_vmalloc = true,

	.create = p9_fd_create_tcp,

	.close = p9_fd_close,

	.request = p9_fd_request,
@@ -1115,6 +1116,7 @@ static struct p9_trans_module p9_unix_trans = { 
	.name = "unix",

	.maxsize = MAX_SOCK_BUF,

	.def = 0,

	.supports_vmalloc = true,

	.create = p9_fd_create_unix,

	.close = p9_fd_close,

	.request = p9_fd_request,
@@ -1129,6 +1131,7 @@ static struct p9_trans_module p9_fd_trans = { 
	.name = "fd",

	.maxsize = MAX_SOCK_BUF,

	.def = 0,

	.supports_vmalloc = true,

	.create = p9_fd_create,

	.close = p9_fd_close,

	.request = p9_fd_request,

net/9p/trans_rdma.c

+1 −0
Original line number Diff line number Diff line
@@ -749,6 +749,7 @@ static struct p9_trans_module p9_rdma_trans = { 
	.maxsize = P9_RDMA_MAXSIZE,

	.pooled_rbuffers = true,

	.def = 0,

	.supports_vmalloc = false,

	.owner = THIS_MODULE,

	.create = rdma_create_trans,

	.close = rdma_close,

net/9p/trans_usbg.c

+1 −0
Original line number Diff line number Diff line
@@ -514,6 +514,7 @@ static struct p9_trans_module p9_usbg_trans = { 
	.close = p9_usbg_close,

	.request = p9_usbg_request,

	.cancel = p9_usbg_cancel,

	.supports_vmalloc = false,

	.owner = THIS_MODULE,

};