In current implementation, grow_buffers() uses alloc_page() to
allocate the buffers for each stripe_head, i.e. allocate a page
for each dev[i] in stripe_head.
After setting stripe_size as a configurable value by writing
sysfs entry, it means that we always allocate 64K buffers, but
just use 4K of them when stripe_size is 4K in 64KB arm64.
To avoid wasting memory, we try to let multiple sh->dev share
one real page. That means, multiple sh->dev[i].page will point
to the only page with different offset. Example of 64K PAGE_SIZE
and 4K stripe_size as following:
64K PAGE_SIZE
+---+---+---+---+------------------------------+
| | | | |
| | | | |
+-+-+-+-+-+-+-+-+------------------------------+
^ ^ ^ ^
| | | +----------------------------+
| | | |
| | +-------------------+ |
| | | |
| +----------+ | |
| | | |
+-+ | | |
| | | |
+-----+-----+------+-----+------+-----+------+------+
sh | offset(0) | offset(4K) | offset(8K) | offset(12K) |
+ +-----------+------------+------------+-------------+
+----> dev[0].page dev[1].page dev[2].page dev[3].page
A new 'pages' array will be added into stripe_head to record shared
page used by this stripe_head. Allocate them when grow_buffers()
and free them when shrink_buffers().
After trying to share page, the users of sh->dev[i].page need to take
care of the related page offset: page of issued bio and page passed
to xor compution functions. But thanks for previous different page offset
supported. Here, we just need to set correct dev[i].offset.
Signed-off-by: Yufen Yu <yuyufen@xxxxxxxxxx>
---
drivers/md/raid5.c | 89 ++++++++++++++++++++++++++++++++++++++++++++--
drivers/md/raid5.h | 28 ++++++++++++++-
2 files changed, 114 insertions(+), 3 deletions(-)
diff --git a/drivers/md/raid5.c b/drivers/md/raid5.c
index 8ed4610deeb2..c038be864257 100644
--- a/drivers/md/raid5.c
+++ b/drivers/md/raid5.c
@@ -448,13 +448,74 @@ static struct stripe_head *get_free_stripe(struct r5conf *conf, int hash)
return sh;
}
-static void shrink_buffers(struct stripe_head *sh)
+#if PAGE_SIZE != DEFAULT_STRIPE_SIZE
+static void free_stripe_pages(struct stripe_head *sh)
+{
+ int i;
+ struct page *p;
+
+ /* Have not allocate page pool */
+ if (!sh->pages)
+ return;
+
+ for (i = 0; i < sh->nr_pages; i++) {
+ p = sh->pages[i];
+ if (p)
+ put_page(p);
+ sh->pages[i] = NULL;
+ }
+}
+
+static int alloc_stripe_pages(struct stripe_head *sh, gfp_t gfp)
{
+ int i;
struct page *p;
+
+ for (i = 0; i < sh->nr_pages; i++) {
+ /* The page have allocated. */
+ if (sh->pages[i])
+ continue;
+
+ p = alloc_page(gfp);
+ if (!p) {
+ free_stripe_pages(sh);
+ return -ENOMEM;
+ }
+ sh->pages[i] = p;
+ }
+ return 0;
+}
+
+static int
+init_stripe_shared_pages(struct stripe_head *sh, struct r5conf *conf, int disks)
+{
+ int nr_pages, cnt;
+
+ if (sh->pages)
+ return 0;
+
+ /* Each of the sh->dev[i] need one conf->stripe_size */
+ cnt = PAGE_SIZE / conf->stripe_size;
+ nr_pages = (disks + cnt - 1) / cnt;
+
+ sh->pages = kcalloc(nr_pages, sizeof(struct page *), GFP_KERNEL);
+ if (!sh->pages)
+ return -ENOMEM;
+ sh->nr_pages = nr_pages;
+ sh->stripes_per_page = cnt;
+ return 0;
+}
+#endif
+
+static void shrink_buffers(struct stripe_head *sh)
+{
int i;
int num = sh->raid_conf->pool_size;
+#if PAGE_SIZE == DEFAULT_STRIPE_SIZE
for (i = 0; i < num ; i++) {
+ struct page *p;
+
WARN_ON(sh->dev[i].page != sh->dev[i].orig_page);
p = sh->dev[i].page;
if (!p)
@@ -462,6 +523,11 @@ static void shrink_buffers(struct stripe_head *sh)
sh->dev[i].page = NULL;
put_page(p);
}
+#else
+ for (i = 0; i < num; i++)
+ sh->dev[i].page = NULL;
+ free_stripe_pages(sh); /* Free pages */
+#endif
}
static int grow_buffers(struct stripe_head *sh, gfp_t gfp)
@@ -469,6 +535,7 @@ static int grow_buffers(struct stripe_head *sh, gfp_t gfp)
int i;
int num = sh->raid_conf->pool_size;
+#if PAGE_SIZE == DEFAULT_STRIPE_SIZE
for (i = 0; i < num; i++) {
struct page *page;
@@ -479,7 +546,16 @@ static int grow_buffers(struct stripe_head *sh, gfp_t gfp)
sh->dev[i].orig_page = page;
sh->dev[i].offset = 0;
}
+#else
+ if (alloc_stripe_pages(sh, gfp))
+ return -ENOMEM;
+ for (i = 0; i < num; i++) {
+ sh->dev[i].page = raid5_get_dev_page(sh, i);
+ sh->dev[i].orig_page = sh->dev[i].page;
+ sh->dev[i].offset = raid5_get_page_offset(sh, i);
+ }
+#endif
return 0;
}
@@ -2205,6 +2281,9 @@ static void raid_run_ops(struct stripe_head *sh, unsigned long ops_request)
static void free_stripe(struct kmem_cache *sc, struct stripe_head *sh)
{
+#if PAGE_SIZE != DEFAULT_STRIPE_SIZE
+ kfree(sh->pages);
+#endif
if (sh->ppl_page)
__free_page(sh->ppl_page);
kmem_cache_free(sc, sh);
@@ -2238,9 +2317,15 @@ static struct stripe_head *alloc_stripe(struct kmem_cache *sc, gfp_t gfp,
sh->ppl_page = alloc_page(gfp);
if (!sh->ppl_page) {
free_stripe(sc, sh);
- sh = NULL;
+ return NULL;
}
}
+#if PAGE_SIZE != DEFAULT_STRIPE_SIZE
+ if (init_stripe_shared_pages(sh, conf, disks)) {
+ free_stripe(sc, sh);
+ return NULL;
+ }
+#endif
}
return sh;
}
diff --git a/drivers/md/raid5.h b/drivers/md/raid5.h
index 6afdd3a78580..5c05acf20e1f 100644
--- a/drivers/md/raid5.h
+++ b/drivers/md/raid5.h
@@ -195,6 +195,7 @@ enum reconstruct_states {
reconstruct_state_result,
};
+#define DEFAULT_STRIPE_SIZE 4096
struct stripe_head {
struct hlist_node hash;
struct list_head lru; /* inactive_list or handle_list */
@@ -246,6 +247,13 @@ struct stripe_head {
int target, target2;
enum sum_check_flags zero_sum_result;
} ops;
+
+#if PAGE_SIZE != DEFAULT_STRIPE_SIZE
+ /* These pages will be used by bios in dev[i] */
+ struct page **pages;
+ int nr_pages; /* page array size */
+ int stripes_per_page;
+#endif
struct r5dev {
/* rreq and rvec are used for the replacement device when
* writing data to both devices.
@@ -473,7 +481,6 @@ struct disk_info {
*/
#define NR_STRIPES 256
-#define DEFAULT_STRIPE_SIZE 4096
#if PAGE_SIZE == DEFAULT_STRIPE_SIZE
#define STRIPE_SIZE PAGE_SIZE
@@ -772,6 +779,25 @@ static inline int algorithm_is_DDF(int layout)
return layout >= 8 && layout <= 10;
}
+#if PAGE_SIZE != DEFAULT_STRIPE_SIZE
+/*
+ * Return offset of the corresponding page for r5dev.
+ */
+static inline int raid5_get_page_offset(struct stripe_head *sh, int disk_idx)
+{
+ return (disk_idx % sh->stripes_per_page) * RAID5_STRIPE_SIZE(sh->raid_conf);
+}
+
+/*
+ * Return corresponding page address for r5dev.
+ */
+static inline struct page *
+raid5_get_dev_page(struct stripe_head *sh, int disk_idx)
+{
+ return sh->pages[disk_idx / sh->stripes_per_page];
+}
+#endif
+
extern void md_raid5_kick_device(struct r5conf *conf);
extern int raid5_set_cache_size(struct mddev *mddev, int size);
extern sector_t raid5_compute_blocknr(struct stripe_head *sh, int i, int previous);
--
2.25.4
