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Message-ID: <20080828194336.GJ9193@ghostprotocols.net>
Date: Thu, 28 Aug 2008 16:43:36 -0300
From: Arnaldo Carvalho de Melo <acme@...hat.com>
To: Gerrit Renker <gerrit@....abdn.ac.uk>
Cc: dccp@...r.kernel.org, netdev@...r.kernel.org
Subject: Re: [PATCH 03/37] dccp: List management for new feature negotiation
Em Thu, Aug 28, 2008 at 07:44:38PM +0200, Gerrit Renker escreveu:
> This adds list fields and list management functions for the new feature
> negotiation implementation. The new code is kept in parallel to the old
> code, until removed at the end of the patch set.
>
> Signed-off-by: Gerrit Renker <gerrit@....abdn.ac.uk>
> Acked-by: Ian McDonald <ian.mcdonald@...di.co.nz>
> ---
> net/dccp/feat.c | 129 +++++++++++++++++++++++++++++++++++++++++++++++++++++++
> 1 files changed, 129 insertions(+), 0 deletions(-)
>
> --- a/net/dccp/feat.c
> +++ b/net/dccp/feat.c
> @@ -147,6 +147,135 @@ static void dccp_feat_entry_destructor(struct dccp_feat_entry *entry)
> }
> }
>
> +/*
> + * List management functions
> + */
> +
> +/**
> + * dccp_feat_entry_new - Central list update routine (called by all others)
> + * @fn: list to add to
> + * @feat: feature number
> + * @is_local: whether the local (1) or remote feature with number @feat is meant
> + * The function maintains and relies on the following invariants:
> + * - each feat_num in the list is known, ie. we know its type and default value
> + * - each feat_num/is_local combination is unique (old entries are overwritten)
> + * - SP values are always freshly allocated
> + * - list is sorted in increasing order of feature number (faster lookup)
> + */
> +static struct dccp_feat_entry *
> + dccp_feat_entry_new(struct list_head *fn, u8 feat, u8 is_local)
> +{
> + struct dccp_feat_entry *entry;
> + struct list_head *pos_head = fn;
> +
> + list_for_each(pos_head, fn) {
> + entry = list_entry(pos_head, struct dccp_feat_entry, node);
Why not use list_for_each_entry()?
> + if (feat < entry->feat_num)
> + break;
> + if (entry->feat_num == feat && entry->is_local == is_local) {
> + dccp_feat_val_destructor(entry->feat_num, &entry->val);
<first reaction>
You call dccp_feat_val_destructor on entry->val, that kfrees a field and
then return it? I havent checked, but would it be safer to set the field
kfree'ed in dccp_feat_val_destructor to NULL since
dccp_feat_val_destructor is not a destructor (i.e. its not the last
function in the life of dccp_feat_val)?
Humm, and shouldn't this entry be removed from the list?
</>
I got confused with a _new routine that ends up not being a constructor
and _destructor being called on an object, then not setting what it
frees to NULL and then reusing it somehow
> + return entry;
> + }
> + }
> + entry = kmalloc(sizeof(struct dccp_feat_entry), gfp_any());
> + if (entry != NULL) {
> + entry->feat_num = feat;
> + entry->is_local = is_local;
> + list_add_tail(&entry->node, pos_head);
> + }
> + return entry;
> +}
> +
> +static struct dccp_feat_entry *dccp_feat_list_lookup(struct list_head *fn_list,
> + u8 feat_num, u8 is_local)
> +{
> + struct dccp_feat_entry *entry;
> +
> + list_for_each_entry(entry, fn_list, node)
cool, here you use list_for_each_entry :-)
> + if (entry->feat_num == feat_num && entry->is_local == is_local)
> + return entry;
> + else if (entry->feat_num > feat_num)
> + break;
> + return NULL;
> +}
Humm, wouldn't it be better to make the users of dccp_feat_entry_new
call dccp_feat_list_lookup and if it returns NULL call
dccp_feat_entry_new that now would just be what its name implies, i.e. a
constructor, doing just the kmalloc + member init?
> +/**
> + * dccp_feat_push_change - Add/overwrite a Change option in the list
> + * @fn_list: feature-negotiation list to update
> + * @feat: one of %dccp_feature_numbers
> + * @local: whether local (1) or remote (0) @feat_num is meant
> + * @needs_mandatory: whether to use Mandatory feature negotiation options
> + * @fval: pointer to NN/SP value to be inserted (will be copied)
> + */
> +static int dccp_feat_push_change(struct list_head *fn_list, u8 feat, u8 local,
> + u8 mandatory, dccp_feat_val *fval)
> +{
> + struct dccp_feat_entry *new = dccp_feat_entry_new(fn_list, feat, local);
> +
> + if (new == NULL)
> + return -ENOMEM;
> +
> + new->feat_num = feat;
> + new->is_local = local;
> + new->state = FEAT_INITIALISING;
> + new->needs_confirm = 0;
> + new->empty_confirm = 0;
> + new->val = *fval;
> + new->needs_mandatory = mandatory;
> +
> + return 0;
> +}
> +
> +/**
> + * dccp_feat_push_confirm - Add a Confirm entry to the FN list
> + * @fn_list: feature-negotiation list to add to
> + * @feat: one of %dccp_feature_numbers
> + * @local: whether local (1) or remote (0) @feat_num is being confirmed
> + * @fval: pointer to NN/SP value to be inserted or NULL
> + * Returns 0 on success, a Reset code for further processing otherwise.
> + */
> +static int dccp_feat_push_confirm(struct list_head *fn_list, u8 feat, u8 local,
> + dccp_feat_val *fval)
> +{
> + struct dccp_feat_entry *new = dccp_feat_entry_new(fn_list, feat, local);
> +
> + if (new == NULL)
> + return DCCP_RESET_CODE_TOO_BUSY;
> +
> + new->feat_num = feat;
> + new->is_local = local;
> + new->state = FEAT_STABLE; /* transition in 6.6.2 */
> + new->needs_confirm = 1;
> + new->empty_confirm = (fval == NULL);
> + new->val.nn = 0; /* zeroes the whole structure */
> + if (!new->empty_confirm)
> + new->val = *fval;
> + new->needs_mandatory = 0;
> +
> + return 0;
> +}
> +
> +static int dccp_push_empty_confirm(struct list_head *fn_list, u8 feat, u8 local)
> +{
> + return dccp_feat_push_confirm(fn_list, feat, local, NULL);
> +}
> +
> +static inline void dccp_feat_list_pop(struct dccp_feat_entry *entry)
> +{
> + list_del(&entry->node);
> + dccp_feat_entry_destructor(entry);
> +}
So dccp_feat_entry will always be embedded on other structs? i.e.
dccp_feat_entry_destructor doesn't frees its space, only fields that
points to memory allocated elsewhere
> +void dccp_feat_list_purge(struct list_head *fn_list)
> +{
> + struct dccp_feat_entry *entry, *next;
> +
> + list_for_each_entry_safe(entry, next, fn_list, node)
> + dccp_feat_entry_destructor(entry);
> + INIT_LIST_HEAD(fn_list);
> +}
Ditto, who frees the struct dccp_feat_entry instances?
- Arnaldo
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