Hmm ... I've read your patch. It allows swaping by try_to_free_page ...
therefore calling try_to_free_page in __get_free_pages (linux/mm/page_alloc.c)
should be possible for GFP_BUFFER due to the changes in swaping
mechanism. But one change I'm missed in your patch... like:
--- /usr/src/linux/mm/page_alloc.c Sat Aug 17 20:19:29 1996
+++ /tmp/page_alloc.c Mon Jun 9 13:30:16 1997
@@ -214,7 +214,7 @@
return 0;
}
restore_flags(flags);
- if (priority != GFP_BUFFER && try_to_free_page(priority, dma, 1))
+ if (try_to_free_page(priority, dma, 1))
goto repeat;
return 0;
}
Without this change your patch may not have any effect on the swap behaviour.
Werner
>
> --- linux/fs/buffer.c.~1~ Thu May 29 13:15:12 1997
> +++ linux/fs/buffer.c Mon Jun 9 01:32:41 1997
> @@ -670,7 +670,7 @@
> }
>
> /* and repeat until we find something good */
> - if (grow_buffers(GFP_ATOMIC, size))
> + if (grow_buffers(GFP_BUFFER, size))
> needed -= PAGE_SIZE;
> else
> wakeup_bdflush(1);
> @@ -931,11 +931,16 @@
> * This is critical. We can't swap out pages to get
> * more buffer heads, because the swap-out may need
> * more buffer-heads itself. Thus GFP_ATOMIC.
> + *
> + * This is no longer true, it is GFP_BUFFER again, the
> + * swapping code now knows not to perform I/O when that
> + * GFP level is specified... -DaveM
> */
> +
> /* we now use kmalloc() here instead of gfp as we want
> to be able to easily release buffer heads - they
> took up quite a bit of memory (tridge) */
> - bh = (struct buffer_head *) kmalloc(sizeof(*bh),GFP_ATOMIC);
> + bh = (struct buffer_head *) kmalloc(sizeof(*bh),GFP_BUFFER);
> if (bh) {
> put_unused_buffer_head(bh);
> nr_buffer_heads++;
> --- linux/mm/vmscan.c.~1~ Mon Jun 2 17:25:12 1997
> +++ linux/mm/vmscan.c Mon Jun 9 01:33:51 1997
> @@ -68,7 +68,7 @@
> * have died while we slept).
> */
> static inline int try_to_swap_out(struct task_struct * tsk, struct vm_area_struct* vma,
> - unsigned long address, pte_t * page_table, int dma, int wait)
> + unsigned long address, pte_t * page_table, int dma, int wait, int can_do_io)
> {
> pte_t pte;
> unsigned long entry;
> @@ -100,6 +100,8 @@
> if (page_map->age)
> return 0;
> if (pte_dirty(pte)) {
> + if(!can_do_io)
> + return 0;
> if (vma->vm_ops && vma->vm_ops->swapout) {
> pid_t pid = tsk->pid;
> vma->vm_mm->rss--;
> @@ -157,7 +159,8 @@
> */
>
> static inline int swap_out_pmd(struct task_struct * tsk, struct vm_area_struct * vma,
> - pmd_t *dir, unsigned long address, unsigned long end, int dma, int wait)
> + pmd_t *dir, unsigned long address, unsigned long end, int dma, int wait,
> + int can_do_io)
> {
> pte_t * pte;
> unsigned long pmd_end;
> @@ -179,7 +182,7 @@
> do {
> int result;
> tsk->swap_address = address + PAGE_SIZE;
> - result = try_to_swap_out(tsk, vma, address, pte, dma, wait);
> + result = try_to_swap_out(tsk, vma, address, pte, dma, wait, can_do_io);
> if (result)
> return result;
> address += PAGE_SIZE;
> @@ -189,7 +192,8 @@
> }
>
> static inline int swap_out_pgd(struct task_struct * tsk, struct vm_area_struct * vma,
> - pgd_t *dir, unsigned long address, unsigned long end, int dma, int wait)
> + pgd_t *dir, unsigned long address, unsigned long end, int dma, int wait,
> + int can_do_io)
> {
> pmd_t * pmd;
> unsigned long pgd_end;
> @@ -209,7 +213,7 @@
> end = pgd_end;
>
> do {
> - int result = swap_out_pmd(tsk, vma, pmd, address, end, dma, wait);
> + int result = swap_out_pmd(tsk, vma, pmd, address, end, dma, wait, can_do_io);
> if (result)
> return result;
> address = (address + PMD_SIZE) & PMD_MASK;
> @@ -219,7 +223,7 @@
> }
>
> static int swap_out_vma(struct task_struct * tsk, struct vm_area_struct * vma,
> - pgd_t *pgdir, unsigned long start, int dma, int wait)
> + pgd_t *pgdir, unsigned long start, int dma, int wait, int can_do_io)
> {
> unsigned long end;
>
> @@ -230,7 +234,7 @@
>
> end = vma->vm_end;
> while (start < end) {
> - int result = swap_out_pgd(tsk, vma, pgdir, start, end, dma, wait);
> + int result = swap_out_pgd(tsk, vma, pgdir, start, end, dma, wait, can_do_io);
> if (result)
> return result;
> start = (start + PGDIR_SIZE) & PGDIR_MASK;
> @@ -239,7 +243,7 @@
> return 0;
> }
>
> -static int swap_out_process(struct task_struct * p, int dma, int wait)
> +static int swap_out_process(struct task_struct * p, int dma, int wait, int can_do_io)
> {
> unsigned long address;
> struct vm_area_struct* vma;
> @@ -260,7 +264,7 @@
> address = vma->vm_start;
>
> for (;;) {
> - int result = swap_out_vma(p, vma, pgd_offset(p->mm, address), address, dma, wait);
> + int result = swap_out_vma(p, vma, pgd_offset(p->mm, address), address, dma, wait, can_do_io);
> if (result)
> return result;
> vma = vma->vm_next;
> @@ -272,7 +276,7 @@
> return 0;
> }
>
> -static int swap_out(unsigned int priority, int dma, int wait)
> +static int swap_out(unsigned int priority, int dma, int wait, int gfp_level)
> {
> static int swap_task;
> int loop, counter;
> @@ -311,7 +315,7 @@
> }
> if (!--p->swap_cnt)
> swap_task++;
> - switch (swap_out_process(p, dma, wait)) {
> + switch (swap_out_process(p, dma, wait, gfp_level != GFP_BUFFER)) {
> case 0:
> if (p->swap_cnt)
> swap_task++;
> @@ -343,15 +347,22 @@
> switch (state) {
> do {
> case 0:
> + /* Don't worry here for the GFP_BUFFER case, shrink_mmap never
> + * tries to write dirty things out...
> + */
> if (shrink_mmap(i, dma))
> return 1;
> state = 1;
> case 1:
> - if (shm_swap(i, dma))
> + /* shm_swap must always perform some I/O if it succeeds
> + * in finding things to free up, so don't waste any time
> + * if we are trying to get some buffer heads...
> + */
> + if (priority != GFP_BUFFER && shm_swap(i, dma))
> return 1;
> state = 2;
> default:
> - if (swap_out(i, dma, wait))
> + if (swap_out(i, dma, wait, priority))
> return 1;
> state = 0;
> i--;
>
>