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mm, swap: add swap_cluster_list
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This is a code clean up patch without functionality changes.  The
swap_cluster_list data structure and its operations are introduced to
provide some better encapsulation for the free cluster and discard cluster
list operations.  This avoid some code duplication, improved the code
readability, and reduced the total line number.

Link: http://lkml.kernel.org/r/[email protected]
Signed-off-by: "Huang, Ying" <[email protected]>
Acked-by: Minchan Kim <[email protected]>
Acked-by: Rik van Riel <[email protected]>
Cc: Tim Chen <[email protected]>
Cc: Hugh Dickins <[email protected]>
Cc: Shaohua Li <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>
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@yhuang-intel @hnaz
yhuang-intel authored and hnaz committed Sep 21, 2016
1 parent 1907501 commit c07787e
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Showing 2 changed files with 68 additions and 74 deletions.
11 changes: 7 additions & 4 deletions include/linux/swap.h
View file
Original file line number Diff line number Diff line change
Expand Up @@ -191,6 +191,11 @@ struct percpu_cluster {
unsigned int next; /* Likely next allocation offset */
};

struct swap_cluster_list {
struct swap_cluster_info head;
struct swap_cluster_info tail;
};

/*
* The in-memory structure used to track swap areas.
*/
Expand All @@ -203,8 +208,7 @@ struct swap_info_struct {
unsigned int max; /* extent of the swap_map */
unsigned char *swap_map; /* vmalloc'ed array of usage counts */
struct swap_cluster_info *cluster_info; /* cluster info. Only for SSD */
struct swap_cluster_info free_cluster_head; /* free cluster list head */
struct swap_cluster_info free_cluster_tail; /* free cluster list tail */
struct swap_cluster_list free_clusters; /* free clusters list */
unsigned int lowest_bit; /* index of first free in swap_map */
unsigned int highest_bit; /* index of last free in swap_map */
unsigned int pages; /* total of usable pages of swap */
Expand Down Expand Up @@ -235,8 +239,7 @@ struct swap_info_struct {
* first.
*/
struct work_struct discard_work; /* discard worker */
struct swap_cluster_info discard_cluster_head; /* list head of discard clusters */
struct swap_cluster_info discard_cluster_tail; /* list tail of discard clusters */
struct swap_cluster_list discard_clusters; /* discard clusters list */
};

/* linux/mm/workingset.c */
Expand Down
131 changes: 61 additions & 70 deletions mm/swapfile.c
View file
Original file line number Diff line number Diff line change
Expand Up @@ -257,6 +257,52 @@ static inline void cluster_set_null(struct swap_cluster_info *info)
info->data = 0;
}

static inline bool cluster_list_empty(struct swap_cluster_list *list)
{
return cluster_is_null(&list->head);
}

static inline unsigned int cluster_list_first(struct swap_cluster_list *list)
{
return cluster_next(&list->head);
}

static void cluster_list_init(struct swap_cluster_list *list)
{
cluster_set_null(&list->head);
cluster_set_null(&list->tail);
}

static void cluster_list_add_tail(struct swap_cluster_list *list,
struct swap_cluster_info *ci,
unsigned int idx)
{
if (cluster_list_empty(list)) {
cluster_set_next_flag(&list->head, idx, 0);
cluster_set_next_flag(&list->tail, idx, 0);
} else {
unsigned int tail = cluster_next(&list->tail);
cluster_set_next(&ci[tail], idx);
cluster_set_next_flag(&list->tail, idx, 0);
}
}

static unsigned int cluster_list_del_first(struct swap_cluster_list *list,
struct swap_cluster_info *ci)
{
unsigned int idx;

idx = cluster_next(&list->head);
if (cluster_next(&list->tail) == idx) {
cluster_set_null(&list->head);
cluster_set_null(&list->tail);
} else
cluster_set_next_flag(&list->head,
cluster_next(&ci[idx]), 0);

return idx;
}

/* Add a cluster to discard list and schedule it to do discard */
static void swap_cluster_schedule_discard(struct swap_info_struct *si,
unsigned int idx)
Expand All @@ -270,17 +316,7 @@ static void swap_cluster_schedule_discard(struct swap_info_struct *si,
memset(si->swap_map + idx * SWAPFILE_CLUSTER,
SWAP_MAP_BAD, SWAPFILE_CLUSTER);

if (cluster_is_null(&si->discard_cluster_head)) {
cluster_set_next_flag(&si->discard_cluster_head,
idx, 0);
cluster_set_next_flag(&si->discard_cluster_tail,
idx, 0);
} else {
unsigned int tail = cluster_next(&si->discard_cluster_tail);
cluster_set_next(&si->cluster_info[tail], idx);
cluster_set_next_flag(&si->discard_cluster_tail,
idx, 0);
}
cluster_list_add_tail(&si->discard_clusters, si->cluster_info, idx);

schedule_work(&si->discard_work);
}
Expand All @@ -296,35 +332,16 @@ static void swap_do_scheduled_discard(struct swap_info_struct *si)

info = si->cluster_info;

while (!cluster_is_null(&si->discard_cluster_head)) {
idx = cluster_next(&si->discard_cluster_head);

cluster_set_next_flag(&si->discard_cluster_head,
cluster_next(&info[idx]), 0);
if (cluster_next(&si->discard_cluster_tail) == idx) {
cluster_set_null(&si->discard_cluster_head);
cluster_set_null(&si->discard_cluster_tail);
}
while (!cluster_list_empty(&si->discard_clusters)) {
idx = cluster_list_del_first(&si->discard_clusters, info);
spin_unlock(&si->lock);

discard_swap_cluster(si, idx * SWAPFILE_CLUSTER,
SWAPFILE_CLUSTER);

spin_lock(&si->lock);
cluster_set_flag(&info[idx], CLUSTER_FLAG_FREE);
if (cluster_is_null(&si->free_cluster_head)) {
cluster_set_next_flag(&si->free_cluster_head,
idx, 0);
cluster_set_next_flag(&si->free_cluster_tail,
idx, 0);
} else {
unsigned int tail;

tail = cluster_next(&si->free_cluster_tail);
cluster_set_next(&info[tail], idx);
cluster_set_next_flag(&si->free_cluster_tail,
idx, 0);
}
cluster_list_add_tail(&si->free_clusters, info, idx);
memset(si->swap_map + idx * SWAPFILE_CLUSTER,
0, SWAPFILE_CLUSTER);
}
Expand Down Expand Up @@ -353,13 +370,8 @@ static void inc_cluster_info_page(struct swap_info_struct *p,
if (!cluster_info)
return;
if (cluster_is_free(&cluster_info[idx])) {
VM_BUG_ON(cluster_next(&p->free_cluster_head) != idx);
cluster_set_next_flag(&p->free_cluster_head,
cluster_next(&cluster_info[idx]), 0);
if (cluster_next(&p->free_cluster_tail) == idx) {
cluster_set_null(&p->free_cluster_tail);
cluster_set_null(&p->free_cluster_head);
}
VM_BUG_ON(cluster_list_first(&p->free_clusters) != idx);
cluster_list_del_first(&p->free_clusters, cluster_info);
cluster_set_count_flag(&cluster_info[idx], 0, 0);
}

Expand Down Expand Up @@ -398,14 +410,7 @@ static void dec_cluster_info_page(struct swap_info_struct *p,
}

cluster_set_flag(&cluster_info[idx], CLUSTER_FLAG_FREE);
if (cluster_is_null(&p->free_cluster_head)) {
cluster_set_next_flag(&p->free_cluster_head, idx, 0);
cluster_set_next_flag(&p->free_cluster_tail, idx, 0);
} else {
unsigned int tail = cluster_next(&p->free_cluster_tail);
cluster_set_next(&cluster_info[tail], idx);
cluster_set_next_flag(&p->free_cluster_tail, idx, 0);
}
cluster_list_add_tail(&p->free_clusters, cluster_info, idx);
}
}

Expand All @@ -421,8 +426,8 @@ scan_swap_map_ssd_cluster_conflict(struct swap_info_struct *si,
bool conflict;

offset /= SWAPFILE_CLUSTER;
conflict = !cluster_is_null(&si->free_cluster_head) &&
offset != cluster_next(&si->free_cluster_head) &&
conflict = !cluster_list_empty(&si->free_clusters) &&
offset != cluster_list_first(&si->free_clusters) &&
cluster_is_free(&si->cluster_info[offset]);

if (!conflict)
Expand All @@ -447,11 +452,11 @@ static void scan_swap_map_try_ssd_cluster(struct swap_info_struct *si,
new_cluster:
cluster = this_cpu_ptr(si->percpu_cluster);
if (cluster_is_null(&cluster->index)) {
if (!cluster_is_null(&si->free_cluster_head)) {
cluster->index = si->free_cluster_head;
if (!cluster_list_empty(&si->free_clusters)) {
cluster->index = si->free_clusters.head;
cluster->next = cluster_next(&cluster->index) *
SWAPFILE_CLUSTER;
} else if (!cluster_is_null(&si->discard_cluster_head)) {
} else if (!cluster_list_empty(&si->discard_clusters)) {
/*
* we don't have free cluster but have some clusters in
* discarding, do discard now and reclaim them
Expand Down Expand Up @@ -2292,10 +2297,8 @@ static int setup_swap_map_and_extents(struct swap_info_struct *p,

nr_good_pages = maxpages - 1; /* omit header page */

cluster_set_null(&p->free_cluster_head);
cluster_set_null(&p->free_cluster_tail);
cluster_set_null(&p->discard_cluster_head);
cluster_set_null(&p->discard_cluster_tail);
cluster_list_init(&p->free_clusters);
cluster_list_init(&p->discard_clusters);

for (i = 0; i < swap_header->info.nr_badpages; i++) {
unsigned int page_nr = swap_header->info.badpages[i];
Expand Down Expand Up @@ -2341,19 +2344,7 @@ static int setup_swap_map_and_extents(struct swap_info_struct *p,
for (i = 0; i < nr_clusters; i++) {
if (!cluster_count(&cluster_info[idx])) {
cluster_set_flag(&cluster_info[idx], CLUSTER_FLAG_FREE);
if (cluster_is_null(&p->free_cluster_head)) {
cluster_set_next_flag(&p->free_cluster_head,
idx, 0);
cluster_set_next_flag(&p->free_cluster_tail,
idx, 0);
} else {
unsigned int tail;

tail = cluster_next(&p->free_cluster_tail);
cluster_set_next(&cluster_info[tail], idx);
cluster_set_next_flag(&p->free_cluster_tail,
idx, 0);
}
cluster_list_add_tail(&p->free_clusters, cluster_info, idx);
}
idx++;
if (idx == nr_clusters)
Expand Down

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