Re: [Dri-devel] Re: [Dri-users] DRI Newbie

[Alan C. <al...@lx...>]

On Sun, 2004-06-27 at 19:49, Jos=E9 Fonseca wrote:

> And the actual code is
>=20
> #if LINUX_VERSION_CODE < 0x020500
> 		atomic_dec(&virt_to_page(page)->count);
> 		clear_bit(PG_locked, &virt_to_page(page)->flags);
> 		wake_up(&virt_to_page(page)->wait);
> #else
> 		struct page *p =3D virt_to_page(page);
> 		put_page(p);
> 		unlock_page(p);
> #endif

> Has the change that lead to the above error happened during the 2.4.x
> series or must been added by the vendor?

As of 2.4.19 the page structure reads as follows

typedef struct page {
	struct list_head list;		/* ->mapping has some page lists. */
	struct address_space *mapping;  /* The inode (or ...) we belong to. */
	unsigned long index;		/* Our offset within mapping. */
	struct page *next_hash;		/* Next page sharing our hash bucket in
                                           the pagecache hash table. */
	atomic_t count;			/* Usage count, see below. */
	unsigned long flags;		/* atomic flags, some possibly
                                           updated asynchronously */
	struct list_head lru;		/* Pageout list, eg. active_list;
                                           protected by pagemap_lru_lock
!! */
	struct page **pprev_hash;	/* Complement to *next_hash. */
	struct buffer_head * buffers;   /* Buffer maps us to a disk block. */

	/*
         * On machines where all RAM is mapped into kernel address
space,
         * we can simply calculate the virtual address. On machines with
         * highmem some memory is mapped into kernel virtual memory
         * dynamically, so we need a place to store that address.
         * Note that this field could be 16 bits on x86 ... ;)
         *
         * Architectures with slow multiplication can define
         * WANT_PAGE_VIRTUAL in asm/page.h
         */
#if defined(CONFIG_HIGHMEM) || defined(WANT_PAGE_VIRTUAL)
        void *virtual;			/* Kernel virtual address (NULL if
                                           not kmapped, ie. highmem) */
#endif /* CONFIG_HIGMEM || WANT_PAGE_VIRTUAL */
} mem_map_t;

The page fields are abstracted by the interface "wait_on_page(page)"
since at least 2.4.9. Similarly according to the 2.4.9 tree I took a
quick look at get_page/put_page are also abstracted in 2.4.

Alan