Messages in this thread |  | | Date | Sun, 4 Feb 2007 16:33:21 +0100 | From | Michal Hocko <> | Subject | Re: mm: how to check for kernel pages |
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On Sun, Feb 04, 2007 at 02:57:30PM +0100, Arjan van de Ven wrote: > On Sun, 2007-02-04 at 12:02 +0100, Michal Hocko wrote: > > Hi, > > is there any effective and fast way how to find out whether page > > given by its page frame number is currenly used by (mapped by) kernel? > > what do you want to use this for? The answer to your question greatly > depends on that...
Sorry for not being more precise. As a part of my thesis work I need to migrate pages. I greatly use mm/migrate.c code. I assume that not all pages can be migrated - especially those used by kernel (where direct virtual to physical mapping is used). So I intended something like following code:
/* Returns 0 if page is suitable to be migration source */ int check_migrate_page(struct page * page) { return PageBuddy(page) || PageCompound(page) || ... kernel_page(page); }
/* Steals pfn page from its current user(s) and replace it by newly * allocated page. pfn page structure is returned if page was migrated * to new location (can be reused by caller) or NULL otherwise. */ struct page * steal_page(unsigned long pfn) { int ret; struct page *page, *target_page;
page = pfn_to_page(pfn); if(!page) goto bad_page;
ret = check_migrate_page(page); if(ret) goto bad_page;
target_page = alloc_pages(flags, 0); /* uses migrate_pages function internally */ ret = do_migration(page, target_page); if(ret) goto bad_page;
/* TODO clear page frame data. */ return page; bad_page: return NULL; }
Please add me to Cc, because I am not the list member. Best regards -- Michal Hocko
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