From: Pierre Barre Date: Thu, 16 Oct 2025 13:58:36 +0000 (+0200) Subject: 9p: Use kvmalloc for message buffers on supported transports X-Git-Tag: v6.19-rc1~60^2~9 X-Git-Url: http://git.ipfire.org/?a=commitdiff_plain;h=e21d451a82f39e91b7635c4fc3ff5ac082873ec3;p=thirdparty%2Fkernel%2Flinux.git 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: Pierre Barre Reviewed-by: Christian Schoenebeck Message-ID: Signed-off-by: Dominique Martinet --- diff --git a/include/net/9p/transport.h b/include/net/9p/transport.h index 766ec07c95999..f0981515148d6 100644 --- a/include/net/9p/transport.h +++ b/include/net/9p/transport.h @@ -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); diff --git a/net/9p/client.c b/net/9p/client.c index 5c1ca57ccd285..2a4884c880c1f 100644 --- a/net/9p/client.c +++ b/net/9p/client.c @@ -229,8 +229,15 @@ 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 { - fc->sdata = kmalloc(alloc_msize, GFP_NOFS); + if (c->trans_mod->supports_vmalloc) + fc->sdata = kvmalloc(alloc_msize, GFP_NOFS); + else + fc->sdata = kmalloc(alloc_msize, GFP_NOFS); fc->cache = NULL; } if (!fc->sdata) @@ -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); diff --git a/net/9p/trans_fd.c b/net/9p/trans_fd.c index a516745f732f7..e7334033eba5a 100644 --- a/net/9p/trans_fd.c +++ b/net/9p/trans_fd.c @@ -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, diff --git a/net/9p/trans_rdma.c b/net/9p/trans_rdma.c index b84748baf9cbe..6c5ad232c1946 100644 --- a/net/9p/trans_rdma.c +++ b/net/9p/trans_rdma.c @@ -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, diff --git a/net/9p/trans_usbg.c b/net/9p/trans_usbg.c index 468f7e8f0277b..2542ef0992333 100644 --- a/net/9p/trans_usbg.c +++ b/net/9p/trans_usbg.c @@ -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, }; diff --git a/net/9p/trans_virtio.c b/net/9p/trans_virtio.c index 0b8086f58ad55..12806207f4f03 100644 --- a/net/9p/trans_virtio.c +++ b/net/9p/trans_virtio.c @@ -803,6 +803,7 @@ static struct p9_trans_module p9_virtio_trans = { .maxsize = PAGE_SIZE * (VIRTQUEUE_NUM - 3), .pooled_rbuffers = false, .def = 1, + .supports_vmalloc = false, .owner = THIS_MODULE, }; diff --git a/net/9p/trans_xen.c b/net/9p/trans_xen.c index b9ff69c7522a1..4b1cec0ab8297 100644 --- a/net/9p/trans_xen.c +++ b/net/9p/trans_xen.c @@ -258,6 +258,7 @@ static struct p9_trans_module p9_xen_trans = { .maxsize = 1 << (XEN_9PFS_RING_ORDER + XEN_PAGE_SHIFT - 2), .pooled_rbuffers = false, .def = 1, + .supports_vmalloc = false, .create = p9_xen_create, .close = p9_xen_close, .request = p9_xen_request,