On 06/10/2012 07:51 PM, Sasha Levin wrote:
> An attempt at making frontswap_shrink shorter and more readable. This patch
> splits out walking through the swap list to find an entry with enough
> pages to unuse.
>
> Also, assert that the internal __frontswap_unuse_pages is called under swap
> lock, since that part of code was previously directly happen inside the lock.
>
> Signed-off-by: Sasha Levin <levinsasha928@xxxxxxxxx>
> ---
> mm/frontswap.c | 59 +++++++++++++++++++++++++++++++++++++-------------------
> 1 files changed, 39 insertions(+), 20 deletions(-)
>
> diff --git a/mm/frontswap.c b/mm/frontswap.c
> index 5faf840..faa43b7 100644
> --- a/mm/frontswap.c
> +++ b/mm/frontswap.c
> @@ -230,6 +230,41 @@ static unsigned long __frontswap_curr_pages(void)
> return totalpages;
> }
>
> +static int __frontswap_unuse_pages(unsigned long total, unsigned long *unused,
> + int *swapid)
Normally, we use "unsigned int type" instead of swapid.
I admit the naming is rather awkward but that should be another patch.
So let's keep consistency with swap subsystem.
> +{
> + int ret = -EINVAL;
> + struct swap_info_struct *si = NULL;
> + int si_frontswap_pages;
> + unsigned long total_pages_to_unuse = total;
> + unsigned long pages = 0, pages_to_unuse = 0;
> + int type;
> +
> + assert_spin_locked(&swap_lock);
Normally, we should use this assertion when we can't find swap_lock is hold or not easily
by complicated call depth or unexpected use-case like general function.
But I expect this function's caller is very limited, not complicated.
Just comment write down isn't enough?
> + for (type = swap_list.head; type >= 0; type = si->next) {
> + si = swap_info[type];
> + si_frontswap_pages = atomic_read(&si->frontswap_pages);
> + if (total_pages_to_unuse < si_frontswap_pages) {
> + pages = pages_to_unuse = total_pages_to_unuse;
> + } else {
> + pages = si_frontswap_pages;
> + pages_to_unuse = 0; /* unuse all */
> + }
> + /* ensure there is enough RAM to fetch pages from frontswap */
> + if (security_vm_enough_memory_mm(current->mm, pages)) {
> + ret = -ENOMEM;
Nipick:
I am not sure detailed error returning would be good.
Caller doesn't matter it now but it can consider it in future.
Hmm,
> + continue;
> + }
> + vm_unacct_memory(pages);
> + *unused = pages_to_unuse;
> + *swapid = type;
> + ret = 0;
> + break;
> + }
> +
> + return ret;
> +}
> +
> /*
> * Frontswap, like a true swap device, may unnecessarily retain pages
> * under certain circumstances; "shrink" frontswap is essentially a
> @@ -240,11 +275,9 @@ static unsigned long __frontswap_curr_pages(void)
> */
> void frontswap_shrink(unsigned long target_pages)
> {
> - struct swap_info_struct *si = NULL;
> - int si_frontswap_pages;
> unsigned long total_pages = 0, total_pages_to_unuse;
> - unsigned long pages = 0, pages_to_unuse = 0;
> - int type;
> + unsigned long pages_to_unuse = 0;
> + int type, ret;
> bool locked = false;
>
> /*
> @@ -258,22 +291,8 @@ void frontswap_shrink(unsigned long target_pages)
> if (total_pages <= target_pages)
> goto out;
> total_pages_to_unuse = total_pages - target_pages;
> - for (type = swap_list.head; type >= 0; type = si->next) {
> - si = swap_info[type];
> - si_frontswap_pages = atomic_read(&si->frontswap_pages);
> - if (total_pages_to_unuse < si_frontswap_pages) {
> - pages = pages_to_unuse = total_pages_to_unuse;
> - } else {
> - pages = si_frontswap_pages;
> - pages_to_unuse = 0; /* unuse all */
> - }
> - /* ensure there is enough RAM to fetch pages from frontswap */
> - if (security_vm_enough_memory_mm(current->mm, pages))
> - continue;
> - vm_unacct_memory(pages);
> - break;
> - }
> - if (type < 0)
> + ret = __frontswap_unuse_pages(total_pages_to_unuse, &pages_to_unuse, &type);
> + if (ret < 0)
> goto out;
> locked = false;
> spin_unlock(&swap_lock);
--
Kind regards,
Minchan Kim
--
To unsubscribe, send a message with 'unsubscribe linux-mm' in
the body to majordomo@xxxxxxxxx. For more info on Linux MM,
see: http://www.linux-mm.org/ .
Don't email: <a href=mailto:"dont@xxxxxxxxx";> email@xxxxxxxxx </a>