Louis Rilling wrote:
> On Thu, Sep 04, 2008 at 04:05:22AM -0400, Oren Laadan wrote:
>> Infrastructure to handle objects that may be shared and referenced by
>> multiple tasks or other objects, e..g open files, memory address space
>> etc.
>>
>> The state of shared objects is saved once. On the first encounter, the
>> state is dumped and the object is assigned a unique identifier and also
>> stored in a hash table (indexed by its physical kenrel address). From
>> then on the object will be found in the hash and only its identifier is
>> saved.
>>
>> On restart the identifier is looked up in the hash table; if not found
>> then the state is read, the object is created, and added to the hash
>> table (this time indexed by its identifier). Otherwise, the object in
>> the hash table is used.
>>
>
> [...]
>
>> diff --git a/checkpoint/objhash.c b/checkpoint/objhash.c
>> new file mode 100644
>> index 0000000..442b08c
>> --- /dev/null
>> +++ b/checkpoint/objhash.c
>> @@ -0,0 +1,205 @@
>> +/*
>> + * Checkpoint-restart - object hash infrastructure to manage shared objects
>> + *
>> + * Copyright (C) 2008 Oren Laadan
>> + *
>> + * This file is subject to the terms and conditions of the GNU General
>> Public
>> + * License. See the file COPYING in the main directory of the Linux
>> + * distribution for more details.
>> + */
>> +
>> +#include <linux/kernel.h>
>> +#include <linux/file.h>
>> +#include <linux/hash.h>
>> +#include <linux/ckpt.h>
>> +
>> +struct cr_objref {
>> + int objref;
>> + void *ptr;
>> + unsigned short type;
>> + unsigned short flags;
>> + struct hlist_node hash;
>> +};
>> +
>> +struct cr_objhash {
>> + struct hlist_head *head;
>> + int objref_index;
>> +};
>> +
>> +#define CR_OBJHASH_NBITS 10
>> +#define CR_OBJHASH_TOTAL (1UL << CR_OBJHASH_NBITS - 1)
>
> Why -1? This makes a total number of 512 entries, which will break below with
> hashes in range 0..1023.
Ugh !!! Was fixed and tested, but sneaked back in :(
Thanks for spotting, will resend the patchset.
Oren.
>
>> +
>> +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();
>> + }
>> +}
>> +
>> +static void cr_objhash_clear(struct cr_objhash *objhash)
>> +{
>> + struct hlist_head *h = objhash->head;
>> + struct hlist_node *n, *t;
>> + struct cr_objref *obj;
>> + int i;
>> +
>> + for (i = 0; i < CR_OBJHASH_TOTAL; i++) {
>> + hlist_for_each_entry_safe(obj, n, t, &h[i], hash) {
>> + cr_obj_ref_drop(obj);
>> + kfree(obj);
>> + }
>> + }
>> +}
>> +
>> +void cr_objhash_free(struct cr_ctx *ctx)
>> +{
>> + struct cr_objhash *objhash = ctx->objhash;
>> +
>> + if (objhash) {
>> + cr_objhash_clear(objhash);
>> + kfree(objhash->head);
>> + kfree(ctx->objhash);
>> + ctx->objhash = NULL;
>> + }
>> +}
>> +
>> +int cr_objhash_alloc(struct cr_ctx *ctx)
>> +{
>> + struct cr_objhash *objhash;
>> + struct hlist_head *head;
>> +
>> + objhash = kzalloc(sizeof(*objhash), GFP_KERNEL);
>> + if (!objhash)
>> + return -ENOMEM;
>> + head = kzalloc(CR_OBJHASH_TOTAL * sizeof(*head), GFP_KERNEL);
>
> 512 entries allocated
>
>> + if (!head) {
>> + kfree(objhash);
>> + return -ENOMEM;
>> + }
>> +
>> + objhash->head = head;
>> + objhash->objref_index = 1;
>> +
>> + ctx->objhash = objhash;
>> + return 0;
>> +}
>> +
>> +static struct cr_objref *cr_obj_find_by_ptr(struct cr_ctx *ctx, void *ptr)
>> +{
>> + struct hlist_head *h;
>> + struct hlist_node *n;
>> + struct cr_objref *obj;
>> +
>> + h = &ctx->objhash->head[hash_ptr(ptr, CR_OBJHASH_NBITS)];
>
> access to entries 0..1023
>
> Louis
>
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