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Date: Sat, 15 Nov 2008 01:32:39 +0100
From: "Rafael J. Wysocki" <rjw@...k.pl>
To: Nigel Cunningham <ncunningham@...a.org.au>
Cc: Len Brown <lenb@...nel.org>, Pavel Machek <pavel@...e.cz>,
Andy Whitcroft <apw@...dowen.org>,
pm list <linux-pm@...ts.linux-foundation.org>,
LKML <linux-kernel@...r.kernel.org>,
Dave Hansen <dave@...ux.vnet.ibm.com>
Subject: Re: [linux-pm] [PATCH 1/2] Hibernate: Take overlapping zones into account
On Tuesday, 11 of November 2008, Nigel Cunningham wrote:
> Hi Rafael.
>
> On Tue, 2008-11-11 at 21:31 +0100, Rafael J. Wysocki wrote:
> > From: Rafael J. Wysocki <rjw@...k.pl>
> > Subject: Hibernate: Take overlapping zones into account
> >
> > It has been requested to make hibernation work with memory
> > hotplugging enabled and for this purpose the hibernation code has to
> > be reworked to take the possible overlapping of zones into account.
> > Thus, rework the hibernation memory bitmaps code to prevent
> > duplication of PFNs from occuring and add checks to make sure that
> > one page frame will not be marked as saveable many times.
> >
> > Additionally, use list.h lists instead of open-coded lists to
> > implement the memory bitmaps.
> >
> > Signed-off-by: Rafael J. Wysocki <rjw@...k.pl>
> > Cc: Pavel Machek <pavel@...e.cz>
> > Cc: Dave Hansen <dave@...ux.vnet.ibm.com>
> > Cc: Andy Whitcroft <apw@...dowen.org>
> > ---
> > kernel/power/snapshot.c | 326 ++++++++++++++++++++++++------------------------
> > 1 file changed, 166 insertions(+), 160 deletions(-)
> >
> > Index: linux-2.6/kernel/power/snapshot.c
> > ===================================================================
> > --- linux-2.6.orig/kernel/power/snapshot.c
> > +++ linux-2.6/kernel/power/snapshot.c
> > @@ -25,6 +25,7 @@
> > #include <linux/syscalls.h>
> > #include <linux/console.h>
> > #include <linux/highmem.h>
> > +#include <linux/list.h>
> >
> > #include <asm/uaccess.h>
> > #include <asm/mmu_context.h>
> > @@ -192,12 +193,6 @@ static void *chain_alloc(struct chain_al
> > return ret;
> > }
> >
> > -static void chain_free(struct chain_allocator *ca, int clear_page_nosave)
> > -{
> > - free_list_of_pages(ca->chain, clear_page_nosave);
> > - memset(ca, 0, sizeof(struct chain_allocator));
> > -}
> > -
> > /**
> > * Data types related to memory bitmaps.
> > *
> > @@ -233,7 +228,7 @@ static void chain_free(struct chain_allo
> > #define BM_BITS_PER_BLOCK (PAGE_SIZE << 3)
> >
> > struct bm_block {
> > - struct bm_block *next; /* next element of the list */
> > + struct list_head hook; /* hook into a list of bitmap blocks */
> > unsigned long start_pfn; /* pfn represented by the first bit */
> > unsigned long end_pfn; /* pfn represented by the last bit plus 1 */
> > unsigned long *data; /* bitmap representing pages */
> > @@ -244,24 +239,15 @@ static inline unsigned long bm_block_bit
> > return bb->end_pfn - bb->start_pfn;
> > }
> >
> > -struct zone_bitmap {
> > - struct zone_bitmap *next; /* next element of the list */
> > - unsigned long start_pfn; /* minimal pfn in this zone */
> > - unsigned long end_pfn; /* maximal pfn in this zone plus 1 */
> > - struct bm_block *bm_blocks; /* list of bitmap blocks */
> > - struct bm_block *cur_block; /* recently used bitmap block */
> > -};
> > -
> > /* strcut bm_position is used for browsing memory bitmaps */
> >
> > struct bm_position {
> > - struct zone_bitmap *zone_bm;
> > struct bm_block *block;
> > int bit;
> > };
> >
> > struct memory_bitmap {
> > - struct zone_bitmap *zone_bm_list; /* list of zone bitmaps */
> > + struct list_head blocks; /* list of bitmap blocks */
> > struct linked_page *p_list; /* list of pages used to store zone
> > * bitmap objects and bitmap block
> > * objects
> > @@ -273,11 +259,7 @@ struct memory_bitmap {
> >
> > static void memory_bm_position_reset(struct memory_bitmap *bm)
> > {
> > - struct zone_bitmap *zone_bm;
> > -
> > - zone_bm = bm->zone_bm_list;
> > - bm->cur.zone_bm = zone_bm;
> > - bm->cur.block = zone_bm->bm_blocks;
> > + bm->cur.block = list_entry(bm->blocks.next, struct bm_block, hook);
> > bm->cur.bit = 0;
> > }
> >
> > @@ -285,151 +267,183 @@ static void memory_bm_free(struct memory
> >
> > /**
> > * create_bm_block_list - create a list of block bitmap objects
> > - */
> > -
> > -static inline struct bm_block *
> > -create_bm_block_list(unsigned int nr_blocks, struct chain_allocator *ca)
> > + * @nr_blocks - number of blocks to allocate
> > + * @list - list to put the allocated blocks into
> > + * @ca - chain allocator to be used for allocating memory
> > + */
> > +static int create_bm_block_list(unsigned long pages,
> > + struct list_head *list,
> > + struct chain_allocator *ca)
> > {
> > - struct bm_block *bblist = NULL;
> > + unsigned int nr_blocks = DIV_ROUND_UP(pages, BM_BITS_PER_BLOCK);
> >
> > while (nr_blocks-- > 0) {
> > struct bm_block *bb;
> >
> > bb = chain_alloc(ca, sizeof(struct bm_block));
> > if (!bb)
> > - return NULL;
> > -
> > - bb->next = bblist;
> > - bblist = bb;
> > + return -ENOMEM;
> > + list_add(&bb->hook, list);
> > }
> > - return bblist;
> > +
> > + return 0;
> > }
> >
> > +struct mem_extent {
> > + struct list_head hook;
> > + unsigned long start;
> > + unsigned long end;
> > +};
> > +
> > /**
> > - * create_zone_bm_list - create a list of zone bitmap objects
> > + * free_mem_extents - free a list of memory extents
> > + * @list - list of extents to empty
> > */
> > +static void free_mem_extents(struct list_head *list)
> > +{
> > + struct mem_extent *ext, *aux;
> >
> > -static inline struct zone_bitmap *
> > -create_zone_bm_list(unsigned int nr_zones, struct chain_allocator *ca)
> > + list_for_each_entry_safe(ext, aux, list, hook) {
> > + list_del(&ext->hook);
> > + kfree(ext);
> > + }
> > +}
> > +
> > +/**
> > + * create_mem_extents - create a list of memory extents representing
> > + * contiguous ranges of PFNs
> > + * @list - list to put the extents into
> > + * @gfp_mask - mask to use for memory allocations
> > + */
> > +static int create_mem_extents(struct list_head *list, gfp_t gfp_mask)
> > {
> > - struct zone_bitmap *zbmlist = NULL;
> > + struct zone *zone;
> >
> > - while (nr_zones-- > 0) {
> > - struct zone_bitmap *zbm;
> > + INIT_LIST_HEAD(list);
> >
> > - zbm = chain_alloc(ca, sizeof(struct zone_bitmap));
> > - if (!zbm)
> > - return NULL;
> > + for_each_zone(zone) {
> > + unsigned long zone_start, zone_end;
> > + struct mem_extent *ext, *cur, *aux;
> > +
> > + if (!populated_zone(zone))
> > + continue;
> > +
> > + zone_start = zone->zone_start_pfn;
> > + zone_end = zone->zone_start_pfn + zone->spanned_pages;
> > +
> > + list_for_each_entry(ext, list, hook)
> > + if (zone_start <= ext->end)
> > + break;
> > +
> > + if (&ext->hook == list || zone_end < ext->start) {
> > + /* New extent is necessary */
> > + struct mem_extent *new_ext;
> > +
> > + new_ext = kzalloc(sizeof(struct mem_extent), gfp_mask);
> > + if (!new_ext) {
> > + free_mem_extents(list);
> > + return -ENOMEM;
> > + }
> > + new_ext->start = zone_start;
> > + new_ext->end = zone_end;
> > + list_add_tail(&new_ext->hook, &ext->hook);
>
> Is list_add_tail right? You seem to be relying on the list being ordered
> in the list_for_each_entry above.
Yes, I do and it is right. From list.h:
/**
* list_add_tail - add a new entry
* @new: new entry to be added
* @head: list head to add it before
*
* Insert a new entry before the specified head.
> > + continue;
> > + }
> >
> > - zbm->next = zbmlist;
> > - zbmlist = zbm;
> > + /* Merge this zone's range of PFNs with the existing one */
> > + if (zone_start < ext->start)
> > + ext->start = zone_start;
> > + if (zone_end > ext->end)
> > + ext->end = zone_end;
> > +
> > + /* More merging may be possible */
> > + cur = ext;
> > + list_for_each_entry_safe_continue(cur, aux, list, hook) {
> > + if (zone_end < cur->start)
> > + break;
> > + if (zone_end < cur->end)
> > + ext->end = cur->end;
> > + list_del(&cur->hook);
>
> kfree?
Yes, it should be here, thanks.
> > + }
> > }
> > - return zbmlist;
> > +
> > + return 0;
> > }
> >
> > /**
> > * memory_bm_create - allocate memory for a memory bitmap
> > */
> > -
> > static int
> > memory_bm_create(struct memory_bitmap *bm, gfp_t gfp_mask, int safe_needed)
> > {
> > struct chain_allocator ca;
> > - struct zone *zone;
> > - struct zone_bitmap *zone_bm;
> > - struct bm_block *bb;
> > - unsigned int nr;
> > + struct list_head mem_extents;
> > + struct mem_extent *ext;
> > + int error;
> >
> > chain_init(&ca, gfp_mask, safe_needed);
> > + INIT_LIST_HEAD(&bm->blocks);
> >
> > - /* Compute the number of zones */
> > - nr = 0;
> > - for_each_zone(zone)
> > - if (populated_zone(zone))
> > - nr++;
> > -
> > - /* Allocate the list of zones bitmap objects */
> > - zone_bm = create_zone_bm_list(nr, &ca);
> > - bm->zone_bm_list = zone_bm;
> > - if (!zone_bm) {
> > - chain_free(&ca, PG_UNSAFE_CLEAR);
> > - return -ENOMEM;
> > - }
> > + error = create_mem_extents(&mem_extents, gfp_mask);
> > + if (error)
> > + return error;
> >
> > - /* Initialize the zone bitmap objects */
> > - for_each_zone(zone) {
> > - unsigned long pfn;
> > + list_for_each_entry(ext, &mem_extents, hook) {
> > + struct bm_block *bb;
> > + unsigned long pfn = ext->start;
> > + unsigned long pages = ext->end - ext->start;
> >
> > - if (!populated_zone(zone))
> > - continue;
> > + bb = list_entry(bm->blocks.prev, struct bm_block, hook);
> >
> > - zone_bm->start_pfn = zone->zone_start_pfn;
> > - zone_bm->end_pfn = zone->zone_start_pfn + zone->spanned_pages;
> > - /* Allocate the list of bitmap block objects */
> > - nr = DIV_ROUND_UP(zone->spanned_pages, BM_BITS_PER_BLOCK);
> > - bb = create_bm_block_list(nr, &ca);
> > - zone_bm->bm_blocks = bb;
> > - zone_bm->cur_block = bb;
> > - if (!bb)
> > - goto Free;
> > + error = create_bm_block_list(pages, bm->blocks.prev, &ca);
> > + if (error)
> > + goto Error;
> >
> > - nr = zone->spanned_pages;
> > - pfn = zone->zone_start_pfn;
> > - /* Initialize the bitmap block objects */
> > - while (bb) {
> > - unsigned long *ptr;
> > -
> > - ptr = get_image_page(gfp_mask, safe_needed);
> > - bb->data = ptr;
> > - if (!ptr)
> > - goto Free;
> > + list_for_each_entry_continue(bb, &bm->blocks, hook) {
> > + bb->data = get_image_page(gfp_mask, safe_needed);
> > + if (!bb->data) {
> > + error = -ENOMEM;
> > + goto Error;
> > + }
> >
> > bb->start_pfn = pfn;
> > - if (nr >= BM_BITS_PER_BLOCK) {
> > + if (pages >= BM_BITS_PER_BLOCK) {
> > pfn += BM_BITS_PER_BLOCK;
> > - nr -= BM_BITS_PER_BLOCK;
> > + pages -= BM_BITS_PER_BLOCK;
> > } else {
> > /* This is executed only once in the loop */
> > - pfn += nr;
> > + pfn += pages;
> > }
> > bb->end_pfn = pfn;
> > - bb = bb->next;
> > }
> > - zone_bm = zone_bm->next;
> > }
> > +
> > bm->p_list = ca.chain;
> > memory_bm_position_reset(bm);
> > - return 0;
> > + Exit:
> > + free_mem_extents(&mem_extents);
> > + return error;
> >
> > - Free:
> > + Error:
> > bm->p_list = ca.chain;
> > memory_bm_free(bm, PG_UNSAFE_CLEAR);
> > - return -ENOMEM;
> > + goto Exit;
> > }
> >
> > /**
> > * memory_bm_free - free memory occupied by the memory bitmap @bm
> > */
> > -
> > static void memory_bm_free(struct memory_bitmap *bm, int clear_nosave_free)
> > {
> > - struct zone_bitmap *zone_bm;
> > + struct bm_block *bb;
> >
> > - /* Free the list of bit blocks for each zone_bitmap object */
> > - zone_bm = bm->zone_bm_list;
> > - while (zone_bm) {
> > - struct bm_block *bb;
> > + list_for_each_entry(bb, &bm->blocks, hook)
> > + if (bb->data)
> > + free_image_page(bb->data, clear_nosave_free);
> >
> > - bb = zone_bm->bm_blocks;
> > - while (bb) {
> > - if (bb->data)
> > - free_image_page(bb->data, clear_nosave_free);
> > - bb = bb->next;
> > - }
> > - zone_bm = zone_bm->next;
> > - }
> > free_list_of_pages(bm->p_list, clear_nosave_free);
> > - bm->zone_bm_list = NULL;
> > +
> > + INIT_LIST_HEAD(&bm->blocks);
> > }
> >
> > /**
> > @@ -437,38 +451,33 @@ static void memory_bm_free(struct memory
> > * to given pfn. The cur_zone_bm member of @bm and the cur_block member
> > * of @bm->cur_zone_bm are updated.
> > */
> > -
> > static int memory_bm_find_bit(struct memory_bitmap *bm, unsigned long pfn,
> > void **addr, unsigned int *bit_nr)
> > {
> > - struct zone_bitmap *zone_bm;
> > struct bm_block *bb;
> >
> > - /* Check if the pfn is from the current zone */
> > - zone_bm = bm->cur.zone_bm;
> > - if (pfn < zone_bm->start_pfn || pfn >= zone_bm->end_pfn) {
> > - zone_bm = bm->zone_bm_list;
> > - /* We don't assume that the zones are sorted by pfns */
> > - while (pfn < zone_bm->start_pfn || pfn >= zone_bm->end_pfn) {
> > - zone_bm = zone_bm->next;
> > -
> > - if (!zone_bm)
> > - return -EFAULT;
> > - }
> > - bm->cur.zone_bm = zone_bm;
> > - }
> > - /* Check if the pfn corresponds to the current bitmap block */
> > - bb = zone_bm->cur_block;
> > + /*
> > + * Check if the pfn corresponds to the current bitmap block and find
> > + * the block where it fits if this is not the case.
> > + */
> > + bb = bm->cur.block;
> > if (pfn < bb->start_pfn)
> > - bb = zone_bm->bm_blocks;
> > + list_for_each_entry_continue_reverse(bb, &bm->blocks, hook)
> > + if (pfn >= bb->start_pfn)
> > + break;
> > +
> > + if (pfn >= bb->end_pfn)
> > + list_for_each_entry_continue(bb, &bm->blocks, hook)
> > + if (pfn >= bb->start_pfn && pfn < bb->end_pfn)
> > + break;
> >
> > - while (pfn >= bb->end_pfn) {
> > - bb = bb->next;
> > + if (&bb->hook == &bm->blocks)
> > + return -EFAULT;
> >
> > - BUG_ON(!bb);
> > - }
> > - zone_bm->cur_block = bb;
> > + /* The block has been found */
> > + bm->cur.block = bb;
> > pfn -= bb->start_pfn;
> > + bm->cur.bit = pfn + 1;
> > *bit_nr = pfn;
> > *addr = bb->data;
> > return 0;
> > @@ -530,29 +539,21 @@ static int memory_bm_test_bit(struct mem
> >
> > static unsigned long memory_bm_next_pfn(struct memory_bitmap *bm)
> > {
> > - struct zone_bitmap *zone_bm;
> > struct bm_block *bb;
> > int bit;
> >
> > + bb = bm->cur.block;
> > do {
> > - bb = bm->cur.block;
> > - do {
> > - bit = bm->cur.bit;
> > - bit = find_next_bit(bb->data, bm_block_bits(bb), bit);
> > - if (bit < bm_block_bits(bb))
> > - goto Return_pfn;
> > -
> > - bb = bb->next;
> > - bm->cur.block = bb;
> > - bm->cur.bit = 0;
> > - } while (bb);
> > - zone_bm = bm->cur.zone_bm->next;
> > - if (zone_bm) {
> > - bm->cur.zone_bm = zone_bm;
> > - bm->cur.block = zone_bm->bm_blocks;
> > - bm->cur.bit = 0;
> > - }
> > - } while (zone_bm);
> > + bit = bm->cur.bit;
> > + bit = find_next_bit(bb->data, bm_block_bits(bb), bit);
> > + if (bit < bm_block_bits(bb))
> > + goto Return_pfn;
> > +
> > + bb = list_entry(bb->hook.next, struct bm_block, hook);
> > + bm->cur.block = bb;
> > + bm->cur.bit = 0;
> > + } while (&bb->hook != &bm->blocks);
> > +
> > memory_bm_position_reset(bm);
> > return BM_END_OF_MAP;
>
> Is anything above here related to the hotplug memory support? If not,
> perhaps this could be two patches?
This one I already answered.
Thanks,
Rafael
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