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Re: [Qemu-devel] [Qemu-block] [PATCH 3/3] blockdev: Add dynamic module l
From: |
Fam Zheng |
Subject: |
Re: [Qemu-devel] [Qemu-block] [PATCH 3/3] blockdev: Add dynamic module loading for block drivers |
Date: |
Mon, 27 Jun 2016 17:31:09 +0800 |
User-agent: |
Mutt/1.6.1 (2016-04-27) |
On Fri, 06/24 11:37, Daniel P. Berrange wrote:
> On Fri, Jun 24, 2016 at 11:04:43AM +0100, Stefan Hajnoczi wrote:
> > On Wed, Jun 22, 2016 at 05:35:54PM -0400, Colin Lord wrote:
> >
> > >
> > > @@ -447,8 +466,15 @@ int get_tmp_filename(char *filename, int size)
> > > static BlockDriver *find_hdev_driver(const char *filename)
> > > {
> > > int score_max = 0, score;
> > > + size_t i;
> > > BlockDriver *drv = NULL, *d;
> > >
> > > + for (i = 0; i < ARRAY_SIZE(block_driver_modules); ++i) {
> > > + if (block_driver_modules[i].has_probe_device) {
> > > + block_module_load_one(block_driver_modules[i].library_name);
> > > + }
> > > + }
> >
> > This patch series needs to solve probing so that we don't end up loading
> > all block drivers. Fam's suggestion for a built-in probe.c sounds good
> > to me.
>
> Do we really care if probing loads all drivers ? Last time we discussed
> this I thought we decided that because probing almost always leads to
> security vulnerabilities, no one should use it by default and so we
> don't really need to worry about optimizing it.
Does this mean we can drop "has_probe" and "has_probe_device" from the
generated header and load all modules for probe? If so, I'd like to again
stress my preference for a "simplified" code "parser":
All of current block_init() calls except quorum can be converted with this:
#define BLOCK_DRIVER_EXPORT(fmt_name, prot_name, drv) \
static void bdrv_ ## fmt_name ## _ ## prot_name(void) \
{ \
if (strlen(#fmt_name)) { \
drv->format_name = #fmt_name; \
} \
if (strlen(#prot_name)) { \
drv->protocol_name = #prot_name; \
} \
bdrv_register(&(drv)); \
} \
block_init(bdrv_ ## fmt_name ## prot_name)
curl.c:
BLOCK_DRIVER_EXPORT(http, http, bdrv_http);
BLOCK_DRIVER_EXPORT(https, https, bdrv_https);
BLOCK_DRIVER_EXPORT(ftp, ftp, bdrv_ftp);
...
iscsi.c (on top of patch 1):
BLOCK_DRIVER_EXPORT(iscsi, iscsi, bdrv_iscsi);
vmdk.c:
BLOCK_DRIVER_EXPORT(vmdk,, bdrv_vmdk);
Then the python generator greps for BLOCK_DRIVER_EXPORT, instead of 'static
BlockDriver', which is much more reliable (in the sense of whitespace subtlety,
field name changing, etc).
Fam