Messages in this thread | | | Subject | Re: [RFC v10][PATCH 09/13] Restore open file descriprtors | From | Dave Hansen <> | Date | Mon, 01 Dec 2008 17:31:08 -0800 |
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On Mon, 2008-12-01 at 13:07 -0800, Dave Hansen wrote: > > When a shared object is inserted to the hash we automatically take another > > reference to it (according to its type) for as long as it remains in the > > hash. See: 'cr_obj_ref_grab()' and 'cr_obj_ref_drop()'. So by moving that > > call higher up, we protect the struct file. > > That's kinda (and by kinda I mean really) disgusting. Hiding that two > levels deep in what is effectively the hash table code where no one will > ever see it is really bad. It also makes you lazy thinking that the > hash code will just know how to take references on whatever you give to > it. > > I think cr_obj_ref_grab() is hideous obfuscation and needs to die. > Let's just do the get_file() directly, please.
Well, I at least see why you need it now. The objhash thing is trying to be a pretty generic hash implementation and it does need to free the references up when it is destroyed. Instead of keeping a "hash of files" and a "hash of pipes" or other shared objects, there's just a single hash for everything.
One alternative here would be to have an ops-style release function that gets called instead of what we have now:
static void cr_obj_ref_drop(struct cr_objref *obj) { switch (obj->type) { case CR_OBJ_FILE: fput((struct file *) obj->ptr); break; default: BUG(); } } static void cr_obj_ref_grab(struct cr_objref *obj) { switch (obj->type) { case CR_OBJ_FILE: get_file((struct file *) obj->ptr); break; default: BUG(); } }
That would make it something like:
struct cr_obj_ops { int type; void (*release)(struct cr_objref *obj); };
void cr_release_file(struct cr_objref *obj) { struct file *file = obj->ptr; put_file(file); }
struct cr_obj_ops cr_file_ops = { .type = CR_OBJ_FILE, .release = cr_release_file, };
And the add operation becomes:
get_file(file); new = cr_obj_add_ptr(ctx, file, &objref, &cr_file_ops, 0);
with 'cr_file_ops' basically replacing the CR_OBJ_FILE that got passed before.
I like that because it only obfuscates what truly needs to be abstracted out: the release side. Hiding that get_file() is really tricky.
But, I guess we could also just kill cr_obj_ref_grab(), do the get_file() explicitly and still keep cr_obj_ref_drop() as it is now.
-- Dave
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