From e129b5c23c2b471d47f1c5d2b8b193fc2034af43 Mon Sep 17 00:00:00 2001 From: Andrew Morton Date: Wed, 27 Sep 2006 01:50:00 -0700 Subject: [PATCH] vm: add per-zone writeout counter The VM is supposed to minimise the number of pages which get written off the LRU (for IO scheduling efficiency, and for high reclaim-success rates). But we don't actually have a clear way of showing how true this is. So add `nr_vmscan_write' to /proc/vmstat and /proc/zoneinfo - the number of pages which have been written by the vm scanner in this zone and globally. Cc: Christoph Lameter Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- mm/vmscan.c | 3 ++- 1 file changed, 2 insertions(+), 1 deletion(-) (limited to 'mm/vmscan.c') diff --git a/mm/vmscan.c b/mm/vmscan.c index 87779dda4ec6..87d340999ce8 100644 --- a/mm/vmscan.c +++ b/mm/vmscan.c @@ -19,6 +19,7 @@ #include #include #include +#include #include #include #include @@ -370,7 +371,7 @@ static pageout_t pageout(struct page *page, struct address_space *mapping) /* synchronous write or broken a_ops? */ ClearPageReclaim(page); } - + inc_zone_page_state(page, NR_VMSCAN_WRITE); return PAGE_SUCCESS; } -- cgit v1.2.2 From 0fd0e6b05aa096622f151cac2f81f2e6844fb1bb Mon Sep 17 00:00:00 2001 From: Nick Piggin Date: Wed, 27 Sep 2006 01:50:02 -0700 Subject: [PATCH] page invalidation cleanup Clean up the invalidate code, and use a common function to safely remove the page from pagecache. Signed-off-by: Nick Piggin Cc: Hugh Dickins Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- mm/vmscan.c | 27 +++++++++++++++++++++++---- 1 file changed, 23 insertions(+), 4 deletions(-) (limited to 'mm/vmscan.c') diff --git a/mm/vmscan.c b/mm/vmscan.c index 87d340999ce8..eca70310adb2 100644 --- a/mm/vmscan.c +++ b/mm/vmscan.c @@ -384,11 +384,30 @@ int remove_mapping(struct address_space *mapping, struct page *page) BUG_ON(mapping != page_mapping(page)); write_lock_irq(&mapping->tree_lock); - /* - * The non-racy check for busy page. It is critical to check - * PageDirty _after_ making sure that the page is freeable and - * not in use by anybody. (pagecache + us == 2) + * The non racy check for a busy page. + * + * Must be careful with the order of the tests. When someone has + * a ref to the page, it may be possible that they dirty it then + * drop the reference. So if PageDirty is tested before page_count + * here, then the following race may occur: + * + * get_user_pages(&page); + * [user mapping goes away] + * write_to(page); + * !PageDirty(page) [good] + * SetPageDirty(page); + * put_page(page); + * !page_count(page) [good, discard it] + * + * [oops, our write_to data is lost] + * + * Reversing the order of the tests ensures such a situation cannot + * escape unnoticed. The smp_rmb is needed to ensure the page->flags + * load is not satisfied before that of page->_count. + * + * Note that if SetPageDirty is always performed via set_page_dirty, + * and thus under tree_lock, then this ordering is not required. */ if (unlikely(page_count(page) != 2)) goto cannot_free; -- cgit v1.2.2