Date: Mon, 18 Nov 2002 20:19:30 -0800 From: Terry Lambert <tlambert2@mindspring.com> To: "Clark C. Evans" <cce@clarkevans.com> Cc: freebsd-hackers@freebsd.org Subject: Re: cd9660 and fcntl (shared locks) Message-ID: <3DD9BBD2.E622B74F@mindspring.com> References: <20021119032023.GA54980@doublegemini.com>
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"Clark C. Evans" wrote:
> When I open a file mounted via cd9660 as O_RDONLY and then flock(fd,LOCK_SH)
> it returns invalid argument; is there a reason why the cd-rom file
> system can't just return success here, make flock a no-op that is always
> successful? There are many cases where you want general code to use
> shared locks on files opened for reading to make sure that it doesn't
> get changed during the read. This general code should be useable on
> file systems mounted read only.
>
> Thoughts? Is there an easy patch?
FreeBSD implements advisory locking wrong; I've tried to get it
fixed several times, but no one is interested.
It looks like someone started to add suport, but then didn't, and
perpetuated the implementation problem.
Here is a patch which finishes adding add advisory locking support
to isofs (wrong way to do it, but only way to do it without changing
VOP_ADVLOCK semantics).
-- Terry
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Index: isofs/cd9660/cd9660_vnops.c
===================================================================
RCS file: /cvs/src/sys/isofs/cd9660/cd9660_vnops.c,v
retrieving revision 1.80
diff -c -r1.80 cd9660_vnops.c
*** isofs/cd9660/cd9660_vnops.c 28 Sep 2002 17:14:52 -0000 1.80
--- isofs/cd9660/cd9660_vnops.c 19 Nov 2002 00:13:27 -0000
***************
*** 53,58 ****
--- 53,59 ----
#include <sys/dirent.h>
#include <sys/unistd.h>
#include <sys/filio.h>
+ #include <sys/lockf.h>
#include <vm/vm.h>
#include <vm/vnode_pager.h>
***************
*** 64,69 ****
--- 65,71 ----
static int cd9660_setattr(struct vop_setattr_args *);
static int cd9660_access(struct vop_access_args *);
+ static int cd9660_advlock(struct vop_advlock_args *);
static int cd9660_getattr(struct vop_getattr_args *);
static int cd9660_ioctl(struct vop_ioctl_args *);
static int cd9660_pathconf(struct vop_pathconf_args *);
***************
*** 776,787 ****
--- 778,808 ----
}
/*
+ * Advisory record locking support
+ */
+ static int
+ cd9660_advlock(ap)
+ struct vop_advlock_args /* {
+ struct vnode *a_vp;
+ caddr_t a_id;
+ int a_op;
+ struct flock *a_fl;
+ int a_flags;
+ } */ *ap;
+ {
+ struct iso_node *ip = VTOI(ap->a_vp);
+
+ return (lf_advlock(ap, &(ip->i_lockf), ip->i_size));
+ }
+
+ /*
* Global vfs data structures for cd9660
*/
vop_t **cd9660_vnodeop_p;
static struct vnodeopv_entry_desc cd9660_vnodeop_entries[] = {
{ &vop_default_desc, (vop_t *) vop_defaultop },
{ &vop_access_desc, (vop_t *) cd9660_access },
+ { &vop_advlock_desc, (vop_t *) cd9660_advlock },
{ &vop_bmap_desc, (vop_t *) cd9660_bmap },
{ &vop_cachedlookup_desc, (vop_t *) cd9660_lookup },
{ &vop_getattr_desc, (vop_t *) cd9660_getattr },
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