The frontswap_shrink works as a "partial swapoff" by using try_to_unuse(), but is has race condition with swapoff.
Of course we can fix this race issue, however, as this code is not used by anyone and not efficient, I decide drop this code. As to shrinker, a frontswap backend should implement its own shrinker if there is a real-world need. Signed-off-by: Weijie Yang <[email protected]> --- include/linux/frontswap.h | 2 - include/linux/swapfile.h | 3 -- mm/frontswap.c | 116 --------------------------------------------- mm/swapfile.c | 19 ++------ 4 files changed, 4 insertions(+), 136 deletions(-) diff --git a/include/linux/frontswap.h b/include/linux/frontswap.h index 8293262..c00b429 100644 --- a/include/linux/frontswap.h +++ b/include/linux/frontswap.h @@ -16,8 +16,6 @@ struct frontswap_ops { extern bool frontswap_enabled; extern struct frontswap_ops * frontswap_register_ops(struct frontswap_ops *ops); -extern void frontswap_shrink(unsigned long); -extern unsigned long frontswap_curr_pages(void); extern void frontswap_writethrough(bool); #define FRONTSWAP_HAS_EXCLUSIVE_GETS extern void frontswap_tmem_exclusive_gets(bool); diff --git a/include/linux/swapfile.h b/include/linux/swapfile.h index 1fd5494..5dc7c81 100644 --- a/include/linux/swapfile.h +++ b/include/linux/swapfile.h @@ -5,10 +5,7 @@ * these were static in swapfile.c but frontswap.c needs them and we don't * want to expose them to the dozens of source files that include swap.h */ -extern spinlock_t swap_lock; extern struct mutex swapon_mutex; -extern struct swap_list_t swap_list; extern struct swap_info_struct *swap_info[]; -extern int try_to_unuse(unsigned int, bool, unsigned long); #endif /* _LINUX_SWAPFILE_H */ diff --git a/mm/frontswap.c b/mm/frontswap.c index a0c68db..df067f1 100644 --- a/mm/frontswap.c +++ b/mm/frontswap.c @@ -326,122 +326,6 @@ void __frontswap_invalidate_area(unsigned type) } EXPORT_SYMBOL(__frontswap_invalidate_area); -static unsigned long __frontswap_curr_pages(void) -{ - int type; - unsigned long totalpages = 0; - struct swap_info_struct *si = NULL; - - assert_spin_locked(&swap_lock); - for (type = swap_list.head; type >= 0; type = si->next) { - si = swap_info[type]; - totalpages += atomic_read(&si->frontswap_pages); - } - return totalpages; -} - -static int __frontswap_unuse_pages(unsigned long total, unsigned long *unused, - int *swapid) -{ - 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); - 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; - continue; - } - vm_unacct_memory(pages); - *unused = pages_to_unuse; - *swapid = type; - ret = 0; - break; - } - - return ret; -} - -/* - * Used to check if it's necessory and feasible to unuse pages. - * Return 1 when nothing to do, 0 when need to shink pages, - * error code when there is an error. - */ -static int __frontswap_shrink(unsigned long target_pages, - unsigned long *pages_to_unuse, - int *type) -{ - unsigned long total_pages = 0, total_pages_to_unuse; - - assert_spin_locked(&swap_lock); - - total_pages = __frontswap_curr_pages(); - if (total_pages <= target_pages) { - /* Nothing to do */ - *pages_to_unuse = 0; - return 1; - } - total_pages_to_unuse = total_pages - target_pages; - return __frontswap_unuse_pages(total_pages_to_unuse, pages_to_unuse, type); -} - -/* - * Frontswap, like a true swap device, may unnecessarily retain pages - * under certain circumstances; "shrink" frontswap is essentially a - * "partial swapoff" and works by calling try_to_unuse to attempt to - * unuse enough frontswap pages to attempt to -- subject to memory - * constraints -- reduce the number of pages in frontswap to the - * number given in the parameter target_pages. - */ -void frontswap_shrink(unsigned long target_pages) -{ - unsigned long pages_to_unuse = 0; - int uninitialized_var(type), ret; - - /* - * we don't want to hold swap_lock while doing a very - * lengthy try_to_unuse, but swap_list may change - * so restart scan from swap_list.head each time - */ - spin_lock(&swap_lock); - ret = __frontswap_shrink(target_pages, &pages_to_unuse, &type); - spin_unlock(&swap_lock); - if (ret == 0) - try_to_unuse(type, true, pages_to_unuse); - return; -} -EXPORT_SYMBOL(frontswap_shrink); - -/* - * Count and return the number of frontswap pages across all - * swap devices. This is exported so that backend drivers can - * determine current usage without reading debugfs. - */ -unsigned long frontswap_curr_pages(void) -{ - unsigned long totalpages = 0; - - spin_lock(&swap_lock); - totalpages = __frontswap_curr_pages(); - spin_unlock(&swap_lock); - - return totalpages; -} -EXPORT_SYMBOL(frontswap_curr_pages); - static int __init init_frontswap(void) { #ifdef CONFIG_DEBUG_FS diff --git a/mm/swapfile.c b/mm/swapfile.c index 5c8a086..3023172 100644 --- a/mm/swapfile.c +++ b/mm/swapfile.c @@ -1353,7 +1353,7 @@ static int unuse_mm(struct mm_struct *mm, * Recycle to start on reaching the end, returning 0 when empty. */ static unsigned int find_next_to_unuse(struct swap_info_struct *si, - unsigned int prev, bool frontswap) + unsigned int prev) { unsigned int max = si->max; unsigned int i = prev; @@ -1379,12 +1379,6 @@ static unsigned int find_next_to_unuse(struct swap_info_struct *si, prev = 0; i = 1; } - if (frontswap) { - if (frontswap_test(si, i)) - break; - else - continue; - } count = ACCESS_ONCE(si->swap_map[i]); if (count && swap_count(count) != SWAP_MAP_BAD) break; @@ -1400,8 +1394,7 @@ static unsigned int find_next_to_unuse(struct swap_info_struct *si, * if the boolean frontswap is true, only unuse pages_to_unuse pages; * pages_to_unuse==0 means all pages; ignored if frontswap is false */ -int try_to_unuse(unsigned int type, bool frontswap, - unsigned long pages_to_unuse) +int try_to_unuse(unsigned int type) { struct swap_info_struct *si = swap_info[type]; struct mm_struct *start_mm; @@ -1438,7 +1431,7 @@ int try_to_unuse(unsigned int type, bool frontswap, * one pass through swap_map is enough, but not necessarily: * there are races when an instance of an entry might be missed. */ - while ((i = find_next_to_unuse(si, i, frontswap)) != 0) { + while ((i = find_next_to_unuse(si, i)) != 0) { if (signal_pending(current)) { retval = -EINTR; break; @@ -1613,10 +1606,6 @@ int try_to_unuse(unsigned int type, bool frontswap, * interactive performance. */ cond_resched(); - if (frontswap && pages_to_unuse > 0) { - if (!--pages_to_unuse) - break; - } } mmput(start_mm); @@ -1939,7 +1928,7 @@ SYSCALL_DEFINE1(swapoff, const char __user *, specialfile) spin_unlock(&swap_lock); set_current_oom_origin(); - err = try_to_unuse(type, false, 0); /* force all pages to be unused */ + err = try_to_unuse(type); /* force all pages to be unused */ clear_current_oom_origin(); if (err) { -- 1.7.10.4 -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [email protected] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
