user/sven/linux.git/include/linux/swap.h, branch ipvs/experimental

swap: rework map_swap_page() again

2009-12-15T16:53:16Z

Seems that page_io.c doesn't really need to know that page_private(page) is the swp_entry 'val'. Rework map_swap_page() to do what its name says and map a page to a page offset in the swap space. The only other caller of map_swap_page() is internal to mm/swapfile.c and it does want to map a swap entry to the 'sector'. So rename map_swap_page() to map_swap_entry(), make it 'static' and and implement map_swap_page() as a wrapper around that. Signed-off-by: Lee Schermerhorn Cc: Hugh Dickins Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds

swap_info: reorder its fields

2009-12-15T16:53:16Z

Reorder (and comment) the fields of swap_info_struct, to make better use of its cachelines: it's good for swap_duplicate() in particular if unsigned int max and swap_map are near the start. Signed-off-by: Hugh Dickins Cc: KAMEZAWA Hiroyuki Cc: Rik van Riel Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds

swap_info: note SWAP_MAP_SHMEM

2009-12-15T16:53:16Z

While we're fiddling with the swap_map values, let's assign a particular value to shmem/tmpfs swap pages: their swap counts are never incremented, and it helps swapoff's try_to_unuse() a little if it can immediately distinguish those pages from process pages. Since we've no use for SWAP_MAP_BAD | COUNT_CONTINUED, we might as well use that 0xbf value for SWAP_MAP_SHMEM. Signed-off-by: Hugh Dickins Reviewed-by: KAMEZAWA Hiroyuki Cc: Rik van Riel Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds

swap_info: swap count continuations

2009-12-15T16:53:15Z

Swap is duplicated (reference count incremented by one) whenever the same swap page is inserted into another mm (when forking finds a swap entry in place of a pte, or when reclaim unmaps a pte to insert the swap entry). swap_info_struct's vmalloc'ed swap_map is the array of these reference counts: but what happens when the unsigned short (or unsigned char since the preceding patch) is full? (and its high bit is kept for a cache flag) We then lose track of it, never freeing, leaving it in use until swapoff: at which point we _hope_ that a single pass will have found all instances, assume there are no more, and will lose user data if we're wrong. Swapping of KSM pages has not yet been enabled; but it is implemented, and makes it very easy for a user to overflow the maximum swap count: possible with ordinary process pages, but unlikely, even when pid_max has been raised from PID_MAX_DEFAULT. This patch implements swap count continuations: when the count overflows, a continuation page is allocated and linked to the original vmalloc'ed map page, and this used to hold the continuation counts for that entry and its neighbours. These continuation pages are seldom referenced: the common paths all work on the original swap_map, only referring to a continuation page when the low "digit" of a count is incremented or decremented through SWAP_MAP_MAX. Signed-off-by: Hugh Dickins Cc: KAMEZAWA Hiroyuki Cc: Rik van Riel Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds

swap_info: swap_map of chars not shorts

2009-12-15T16:53:15Z

Halve the vmalloc'ed swap_map array from unsigned shorts to unsigned chars: it's still very unusual to reach a swap count of 126, and the next patch allows it to be extended indefinitely. Signed-off-by: Hugh Dickins Reviewed-by: KAMEZAWA Hiroyuki Cc: Rik van Riel Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds

swap_info: SWAP_HAS_CACHE cleanups

2009-12-15T16:53:15Z

Though swap_count() is useful, I'm finding that swap_has_cache() and encode_swapmap() obscure what happens in the swap_map entry, just at those points where I need to understand it. Remove them, and pass more usable "usage" values to scan_swap_map(), swap_entry_free() and __swap_duplicate(), instead of the SWAP_MAP and SWAP_CACHE enum. Signed-off-by: Hugh Dickins Reviewed-by: KAMEZAWA Hiroyuki Cc: Rik van Riel Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds

swap_info: include first_swap_extent

2009-12-15T16:53:15Z

Make better use of the space by folding first swap_extent into its swap_info_struct, instead of just the list_head: swap partitions need only that one, and for others it's used as a circular list anyway. [jirislaby@gmail.com: fix crash on double swapon] Signed-off-by: Hugh Dickins Cc: KAMEZAWA Hiroyuki Cc: Rik van Riel Signed-off-by: Jiri Slaby Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds

swap_info: change to array of pointers

2009-12-15T16:53:15Z

The swap_info_struct is only 76 or 104 bytes, but it does seem wrong to reserve an array of about 30 of them in bss, when most people will want only one. Change swap_info[] to an array of pointers. That does need a "type" field in the structure: pack it as a char with next type and short prio (aha, char is unsigned by default on PowerPC). Use the (admittedly peculiar) name "type" throughout for this index. /proc/swaps does not take swap_lock: I wouldn't want it to, but do take care with barriers when adding a new item to the array (never removed). Signed-off-by: Hugh Dickins Reviewed-by: KAMEZAWA Hiroyuki Acked-by: Rik van Riel Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds

swap_info: private to swapfile.c

2009-12-15T16:53:13Z

The swap_info_struct is mostly private to mm/swapfile.c, with only one other in-tree user: get_swap_bio(). Adjust its interface to map_swap_page(), so that we can then remove get_swap_info_struct(). But there is a popular user out-of-tree, TuxOnIce: so leave the declaration of swap_info_struct in linux/swap.h. Signed-off-by: Hugh Dickins Cc: Nigel Cunningham Cc: KAMEZAWA Hiroyuki Reviewed-by: Rik van Riel Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds

mm: clear node in N_HIGH_MEMORY and stop kswapd when all memory is offlined

2009-12-15T16:53:13Z

When memory is hot-removed, its node must be cleared in N_HIGH_MEMORY if there are no present pages left. In such a situation, kswapd must also be stopped since it has nothing left to do. Signed-off-by: David Rientjes Signed-off-by: Lee Schermerhorn Cc: Christoph Lameter Cc: Yasunori Goto Cc: Mel Gorman Cc: Rafael J. Wysocki Cc: Rik van Riel Cc: KAMEZAWA Hiroyuki Cc: Lee Schermerhorn Cc: Mel Gorman Cc: Randy Dunlap Cc: Nishanth Aravamudan Cc: Andi Kleen Cc: David Rientjes Cc: Adam Litke Cc: Andy Whitcroft Cc: Eric Whitney Cc: Christoph Lameter Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds