On Wed, May 05, 2004 at 01:55:24 +0900, Tetsuo Handa wrote:
> I see. I will try to use linked list.
> The 'const char *' data is a filename with caninicalized pathname,
> and I don't want the array not to appear the same filename in
> multiple indexes. So I will try something like this.
struct filename {
list_head list;
const char fname[1];
}
> int len = strlen(filename) + 1;
int len = strlen(filename);
> const char *cp = kmalloc(len, GFP_KERNEL);
struct filename *cp = kmalloc(sizeof(struct filename) + len, GFP_KERNEL);
> if (!cp) return;
> memmove(cp, filename, len);
list_init(&filename->list_head);
memmove(cp, filename->fname, len + 1);
> spin_lock();
> // Scan linked list.
> // Add cp to linked list if not found, kfree(cp) if found.
> spin_unlock();
The linked lists in kernel (in linux/list.h) are INTERNAL linked lists.
You need to add struct list_head as part of your data.
> > 2) Be sure to remember how kmalloc works. It can only alocate power-of-2
> > sized buffers, 32 bytes minimum, PAGE_SIZE << 5 (or something like
> I don't remember, but I thought kmalloc() with less than 32 bytes
> doesn't return NULL. I called kmalloc() with 6 bytes
> ("const char *" + "unsigned short int") and (I thought) succeeded.
> Max size I could allocate with kmalloc() is 128 * 1024 bytes,
> which is equals to PAGE_SIZE << 5.
> # I have no linux PC here to verify now.
kmalloc allocates from generic slab caches. These exist in sizes of
power-of-2, from 32 up to PAGE_SIZE << 5. When you ask some amout of
memory from kmalloc, it finds the cache with smallest larger chunks and
allocates one chunk from it.
-------------------------------------------------------------------------------
Jan 'Bulb' Hudec <bulb@ucw.cz>
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