Messages in this thread | | | Date | Wed, 13 Jul 2022 05:38:38 +0900 | From | Dominique Martinet <> | Subject | Re: [PATCH v5 07/11] net/9p: limit 'msize' to KMALLOC_MAX_SIZE for all transports |
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Christian Schoenebeck wrote on Tue, Jul 12, 2022 at 04:31:26PM +0200: > This 9p client implementation is yet using linear message buffers for > most message types, i.e. they use kmalloc() et al. for allocating > continuous physical memory pages, which is usually limited to 4MB > buffers. Use KMALLOC_MAX_SIZE though instead of a hard coded 4MB for > constraining this more safely. > > Unfortunately we cannot simply replace the existing kmalloc() calls by > vmalloc() ones, because that would yield in non-logical kernel addresses > (for any vmalloc(>4MB) that is) which are in general not accessible by > hosts like QEMU. > > In future we would replace those linear buffers by scatter/gather lists > to eventually get rid of this limit (struct p9_fcall's sdata member by > p9_fcall_init() and struct p9_fid's rdir member by > v9fs_alloc_rdir_buf()). > > Signed-off-by: Christian Schoenebeck <linux_oss@crudebyte.com> > --- > > Hmm, that's a bit too simple, as we also need a bit of headroom for > transport specific overhead. So maybe this has to be handled by each > transport appropriately instead?
hm yes I'd say it's redundant with each transports max size already -- let's just keep appropriate max values in each transport.
> > net/9p/client.c | 11 +++++++++++ > 1 file changed, 11 insertions(+) > > diff --git a/net/9p/client.c b/net/9p/client.c > index 20054addd81b..fab939541c81 100644 > --- a/net/9p/client.c > +++ b/net/9p/client.c > @@ -1042,6 +1042,17 @@ struct p9_client *p9_client_create(const char *dev_name, char *options) > p9_debug(P9_DEBUG_MUX, "clnt %p trans %p msize %d protocol %d\n", > clnt, clnt->trans_mod, clnt->msize, clnt->proto_version); > > + /* > + * due to linear message buffers being used by client ATM > + */ > + if (clnt->msize > KMALLOC_MAX_SIZE) { > + clnt->msize = KMALLOC_MAX_SIZE; > + pr_info("Limiting 'msize' to %zu as this is the maximum " > + "supported by this client version.\n", > + (size_t) KMALLOC_MAX_SIZE > + ); > + } > + > err = clnt->trans_mod->create(clnt, dev_name, options); > if (err) > goto put_trans;
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