| Message ID | 0a2c16b9acf580a679f38354b5d60a68c5fb6c99.1632156835.git.linux_oss@crudebyte.com (mailing list archive) |
|---|---|
| State | Superseded |
| Delegated to: | Netdev Maintainers |
| Headers | show |
| Series | net/9p: remove msize limit in virtio transport | expand |
On Montag, 20. September 2021 18:44:20 CEST Christian Schoenebeck wrote: > Right now vq_sg_resize() used a lazy implementation following > the all-or-nothing princible. So it either resized exactly to > the requested new amount of sg lists, or it did not resize at > all. > > The problem with this is if a user supplies a very large msize > value, resize would simply fail and the user would stick to > the default maximum msize supported by the virtio transport. > > To resolve this potential issue, change vq_sg_resize() to resize > the passed sg list to whatever is possible on the machine. > > Signed-off-by: Christian Schoenebeck <linux_oss@crudebyte.com> > --- > net/9p/trans_virtio.c | 65 ++++++++++++++++++++++++++++++++++++------- > 1 file changed, 55 insertions(+), 10 deletions(-) > > diff --git a/net/9p/trans_virtio.c b/net/9p/trans_virtio.c > index 4cb75f45aa15..b9bab7ed2768 100644 > --- a/net/9p/trans_virtio.c > +++ b/net/9p/trans_virtio.c > @@ -205,24 +205,66 @@ static struct virtqueue_sg *vq_sg_alloc(unsigned int > nsgl) * amount of lists > * @_vq_sg: scatter/gather lists to be resized > * @nsgl: new amount of scatter/gather lists > + * > + * Old scatter/gather lists are retained. Only growing the size is > supported. + * If the requested amount cannot be satisfied, then lists are > increased to + * whatever is possible. > */ > static int vq_sg_resize(struct virtqueue_sg **_vq_sg, unsigned int nsgl) > { > struct virtqueue_sg *vq_sg; > + unsigned int i; > + size_t sz; > + int ret = 0; > > BUG_ON(!_vq_sg || !nsgl); > vq_sg = *_vq_sg; > + if (nsgl > VIRTQUEUE_SG_NSGL_MAX) > + nsgl = VIRTQUEUE_SG_NSGL_MAX; > if (vq_sg->nsgl == nsgl) > return 0; > + if (vq_sg->nsgl > nsgl) > + return -ENOTSUPP; > + > + vq_sg = kzalloc(sizeof(struct virtqueue_sg) + > + nsgl * sizeof(struct scatterlist *), > + GFP_KERNEL); > > - /* lazy resize implementation for now */ > - vq_sg = vq_sg_alloc(nsgl); > if (!vq_sg) > return -ENOMEM; > > - kfree(*_vq_sg); > + /* copy over old scatter gather lists */ > + sz = sizeof(struct virtqueue_sg) + > + (*_vq_sg)->nsgl * sizeof(struct scatterlist *); > + memcpy(vq_sg, *_vq_sg, sz); Missing kfree(*_vq_sg); here. > + > + vq_sg->nsgl = nsgl; > + > + for (i = (*_vq_sg)->nsgl; i < nsgl; ++i) { > + vq_sg->sgl[i] = kmalloc_array( > + SG_MAX_SINGLE_ALLOC, sizeof(struct scatterlist), > + GFP_KERNEL > + ); > + /* > + * handle failed allocation as soft error, we take whatever > + * we get > + */ > + if (!vq_sg->sgl[i]) { > + ret = -ENOMEM; > + vq_sg->nsgl = nsgl = i; > + break; > + } > + sg_init_table(vq_sg->sgl[i], SG_MAX_SINGLE_ALLOC); > + if (i) { > + /* chain the lists */ > + sg_chain(vq_sg->sgl[i - 1], SG_MAX_SINGLE_ALLOC, > + vq_sg->sgl[i]); > + } > + } > + sg_mark_end(&vq_sg->sgl[nsgl - 1][SG_MAX_SINGLE_ALLOC - 1]); > + > *_vq_sg = vq_sg; > - return 0; > + return ret; > } > > /** > @@ -839,13 +881,16 @@ p9_virtio_create(struct p9_client *client, const char > *devname, char *args) if (nsgl > chan->vq_sg->nsgl) { > /* > * if resize fails, no big deal, then just > - * continue with default msize instead > + * continue with whatever we got > */ > - if (!vq_sg_resize(&chan->vq_sg, nsgl)) { > - client->trans_maxsize = > - PAGE_SIZE * > - ((nsgl * SG_USER_PAGES_PER_LIST) - 3); > - } > + vq_sg_resize(&chan->vq_sg, nsgl); > + /* > + * actual allocation size might be less than > + * requested, so use vq_sg->nsgl instead of nsgl > + */ > + client->trans_maxsize = > + PAGE_SIZE * ((chan->vq_sg->nsgl * > + SG_USER_PAGES_PER_LIST) - 3); As with patch 6, here should probably be an additional if (chan->vq_sg->nsgl < nsgl) { pr_inf(...); } to explain the user that not all required sg lists could be allocated suiting user's requested msize option. > } > #endif /* CONFIG_ARCH_NO_SG_CHAIN */ > }
diff --git a/net/9p/trans_virtio.c b/net/9p/trans_virtio.c index 4cb75f45aa15..b9bab7ed2768 100644 --- a/net/9p/trans_virtio.c +++ b/net/9p/trans_virtio.c @@ -205,24 +205,66 @@ static struct virtqueue_sg *vq_sg_alloc(unsigned int nsgl) * amount of lists * @_vq_sg: scatter/gather lists to be resized * @nsgl: new amount of scatter/gather lists + * + * Old scatter/gather lists are retained. Only growing the size is supported. + * If the requested amount cannot be satisfied, then lists are increased to + * whatever is possible. */ static int vq_sg_resize(struct virtqueue_sg **_vq_sg, unsigned int nsgl) { struct virtqueue_sg *vq_sg; + unsigned int i; + size_t sz; + int ret = 0; BUG_ON(!_vq_sg || !nsgl); vq_sg = *_vq_sg; + if (nsgl > VIRTQUEUE_SG_NSGL_MAX) + nsgl = VIRTQUEUE_SG_NSGL_MAX; if (vq_sg->nsgl == nsgl) return 0; + if (vq_sg->nsgl > nsgl) + return -ENOTSUPP; + + vq_sg = kzalloc(sizeof(struct virtqueue_sg) + + nsgl * sizeof(struct scatterlist *), + GFP_KERNEL); - /* lazy resize implementation for now */ - vq_sg = vq_sg_alloc(nsgl); if (!vq_sg) return -ENOMEM; - kfree(*_vq_sg); + /* copy over old scatter gather lists */ + sz = sizeof(struct virtqueue_sg) + + (*_vq_sg)->nsgl * sizeof(struct scatterlist *); + memcpy(vq_sg, *_vq_sg, sz); + + vq_sg->nsgl = nsgl; + + for (i = (*_vq_sg)->nsgl; i < nsgl; ++i) { + vq_sg->sgl[i] = kmalloc_array( + SG_MAX_SINGLE_ALLOC, sizeof(struct scatterlist), + GFP_KERNEL + ); + /* + * handle failed allocation as soft error, we take whatever + * we get + */ + if (!vq_sg->sgl[i]) { + ret = -ENOMEM; + vq_sg->nsgl = nsgl = i; + break; + } + sg_init_table(vq_sg->sgl[i], SG_MAX_SINGLE_ALLOC); + if (i) { + /* chain the lists */ + sg_chain(vq_sg->sgl[i - 1], SG_MAX_SINGLE_ALLOC, + vq_sg->sgl[i]); + } + } + sg_mark_end(&vq_sg->sgl[nsgl - 1][SG_MAX_SINGLE_ALLOC - 1]); + *_vq_sg = vq_sg; - return 0; + return ret; } /** @@ -839,13 +881,16 @@ p9_virtio_create(struct p9_client *client, const char *devname, char *args) if (nsgl > chan->vq_sg->nsgl) { /* * if resize fails, no big deal, then just - * continue with default msize instead + * continue with whatever we got */ - if (!vq_sg_resize(&chan->vq_sg, nsgl)) { - client->trans_maxsize = - PAGE_SIZE * - ((nsgl * SG_USER_PAGES_PER_LIST) - 3); - } + vq_sg_resize(&chan->vq_sg, nsgl); + /* + * actual allocation size might be less than + * requested, so use vq_sg->nsgl instead of nsgl + */ + client->trans_maxsize = + PAGE_SIZE * ((chan->vq_sg->nsgl * + SG_USER_PAGES_PER_LIST) - 3); } #endif /* CONFIG_ARCH_NO_SG_CHAIN */ }
Right now vq_sg_resize() used a lazy implementation following the all-or-nothing princible. So it either resized exactly to the requested new amount of sg lists, or it did not resize at all. The problem with this is if a user supplies a very large msize value, resize would simply fail and the user would stick to the default maximum msize supported by the virtio transport. To resolve this potential issue, change vq_sg_resize() to resize the passed sg list to whatever is possible on the machine. Signed-off-by: Christian Schoenebeck <linux_oss@crudebyte.com> --- net/9p/trans_virtio.c | 65 ++++++++++++++++++++++++++++++++++++------- 1 file changed, 55 insertions(+), 10 deletions(-)