On Wed, 24 Aug 2011, Rick Macklem wrote:
"afs"
The current OpenAFS codebase uses the all-caps "AFS". Judging by the
omitted text, perhaps this should change. (We also don't use VFS_SET to
set it, which I filed a bug about.)
and here is my current rendition of the patch. (I took Gleb's suggestion
and switched to fnv_32_str(). I'll leave it that way unless there is a
collision after adding any names people post to the above list.)
It sounds like people have agreed that this is a reasonable solution.
If hrs@ can confirm that testing shows it fixes the original problem
(the ZFS file handles don't change when it's loaded at different times),
I'll pass it along to re@.
Thanks for the helpful suggestions, rick
--- kern/vfs_init.c.sav 2011-06-11 18:58:33.000000000 -0400
+++ kern/vfs_init.c 2011-08-24 16:15:24.000000000 -0400
@@ -39,6 +39,7 @@ __FBSDID("$FreeBSD: head/sys/kern/vfs_in
#include <sys/param.h>
#include <sys/systm.h>
+#include <sys/fnv_hash.h>
#include <sys/kernel.h>
#include <sys/linker.h>
#include <sys/mount.h>
@@ -138,6 +139,8 @@ vfs_register(struct vfsconf *vfc)
struct sysctl_oid *oidp;
struct vfsops *vfsops;
static int once;
+ struct vfsconf *tvfc;
+ uint32_t hashval;
if (!once) {
vattr_null(&va_null);
@@ -152,7 +155,26 @@ vfs_register(struct vfsconf *vfc)
if (vfs_byname(vfc->vfc_name) != NULL)
return EEXIST;
- vfc->vfc_typenum = maxvfsconf++;
+ /*
+ * Calculate a hash on vfc_name to use for vfc_typenum. Unless
+ * a collision occurs, it is limited to 8bits since that is
+ * what ZFS uses from vfc_typenum and that also limits how sparsely
+ * distributed vfc_typenum becomes.
+ */
+ hashval = fnv_32_str(vfc->vfc_name, FNV1_32_INIT);
+ hashval &= 0xff;
+ do {
+ /* Look for and fix any collision. */
+ TAILQ_FOREACH(tvfc, &vfsconf, vfc_list) {
+ if (hashval == tvfc->vfc_typenum) {
+ hashval++; /* Can exceed 8bits, if needed. */
If we're confident that we won't ever fully fill the hash table, I would
think that this should wrap around back to zero (or one?) instead of
overflowing.
Do we need to care about something attempting to add the same vfc_name
twice? This code will happily add a second entry at the next available
index.
+ break;
+ }
+ }
+ } while (tvfc != NULL);
+ vfc->vfc_typenum = hashval;
+ if (vfc->vfc_typenum >= maxvfsconf)
+ maxvfsconf = vfc->vfc_typenum + 1;
I guess we're holding off on killing maxvfsconf until after 9.0 is out?
-Ben
TAILQ_INSERT_TAIL(&vfsconf, vfc, vfc_list);
/*
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