Date: Mon, 23 Aug 2010 17:43:32 +0300 From: Kostik Belousov <kostikbel@gmail.com> To: Ian FREISLICH <ianf@clue.co.za> Cc: Ed Schouten <ed@80386.nl>, freebsd-current@freebsd.org Subject: Re: fusefs-kmod broken? Message-ID: <20100823144332.GH2396@deviant.kiev.zoral.com.ua> In-Reply-To: <E1OnY55-0001YZ-0L@clue.co.za> References: <20100823140149.GG2396@deviant.kiev.zoral.com.ua> <201008230826.49509.jhb@freebsd.org> <E1OmUBI-0000Oy-J5@clue.co.za> <E1OnWc7-0001Kv-47@clue.co.za> <20100823132551.GE2396@deviant.kiev.zoral.com.ua> <20100823133555.GA64651@hoeg.nl> <20100823134459.GF2396@deviant.kiev.zoral.com.ua> <20100823134723.GC64651@hoeg.nl> <E1OnY55-0001YZ-0L@clue.co.za>
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[-- Attachment #1 --] On Mon, Aug 23, 2010 at 04:32:58PM +0200, Ian FREISLICH wrote: > Kostik Belousov wrote: > > > > --7hK5U8dVDlZxii7z > > Content-Type: text/plain; charset=us-ascii > > Content-Disposition: inline > > Content-Transfer-Encoding: quoted-printable > > > > On Mon, Aug 23, 2010 at 03:47:23PM +0200, Ed Schouten wrote: > > > * Kostik Belousov <kostikbel@gmail.com> wrote: > > > > On Mon, Aug 23, 2010 at 03:35:55PM +0200, Ed Schouten wrote: > > > > > * Kostik Belousov <kostikbel@gmail.com> wrote: > > > > > > Which most likely means that fusesfs filled its own struct fileops > > > > > > without properly initializing fo_truncate member. > > > > >=20 > > > > > It's a bit misleading that cdevs automatically patch the table, while > > > > > the fileops don't. Maybe it would be a good idea to patch finit() to > > > > I do not understand your first sentence. Would you please elaborate ? > > >=20 > > > Say, you create a cdev, if you don't implement all ops, it will check > > > for null pointers and return error codes accordingly. This doesn't > > > happen for fileops, which is probably one of the reasons why people > > > sometimes forget to implement them. > > >=20 > > > Wouldn't it be better to prevent this form of footshooting by adding > > > assertions? This will add some overhead for any file descriptor created, > > > but a kernel with INVARIANTS isn't meant to be fast. > > Thanks, I see it now. > > > > The cdev interface definitely falls into the public kernel interface. > > Having to fill all cdevsw methods for a random driver is too much > > burden put on the several dozens maintainers. > > > > On the other hand, file level is not much widely used by third-party > > components, and even in-tree code implements only ten different file > > types. > > > > I would not object loudly if someone put such checks as proposed > > under INVARIANTS, but also I do not see a real point in having them. > > Might be slightly better to put the checks, again under INVARIANTS, > > in the fo_XXX() wrappers. > > So, in this case is the fusefs module broken? I'm guessing it is. > I don't like the way fuse_fileops is initialised in fuse4bsd. I > would prefer for the struct to be zeroed and then the fo_xxx > implimented bits set as appropriate. That way when the struct is > changed, you don't get stung again. > > Patch attached to that makes fusefs-kmod not blowup kernels post this change. > > Ian > > -- > Ian Freislich > > Index: files/patch-fuse_module__fuse_vnops.c > =================================================================== > RCS file: /home/ncvs/ports/sysutils/fusefs-kmod/files/patch-fuse_module__fuse_vnops.c,v > retrieving revision 1.4 > diff -u -d -r1.4 patch-fuse_module__fuse_vnops.c > --- files/patch-fuse_module__fuse_vnops.c 30 Oct 2008 15:36:35 -0000 1.4 > +++ files/patch-fuse_module__fuse_vnops.c 23 Aug 2010 14:27:17 -0000 > +@@ -214,6 +214,7 @@ > + * following fields are filled from vnops, but "vnops.foo" is not > + * legitimate in a definition, so we set them at module load time > + */ > ++ .fo_truncate = NULL, > + .fo_ioctl = NULL, > + .fo_poll = NULL, > + .fo_kqfilter = NULL, Did you tested this ? I suppose that it would not change anything. Fuse, most likely, lacks real implementation of .fo_truncate method. The implementation was required for long time, otherwise file truncation would not work. [-- Attachment #2 --] -----BEGIN PGP SIGNATURE----- Version: GnuPG v1.4.10 (FreeBSD) iEYEARECAAYFAkxyiRQACgkQC3+MBN1Mb4jU1gCdGGyYoMujuWFSPy8ZM1wIVYeq 2y4An2RCVdK6QJsvTTISBOnnHUFwxYxL =73Dj -----END PGP SIGNATURE-----help
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