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Date: Tue, 14 Jul 2015 12:28:52 +0300
From: Dmitry Safonov <0x7f454c46@...il.com>
To: sjennings@...iantweb.net
Cc: akpm@...ux-foundation.org, hannes@...xchg.org,
vdavydov@...allels.com, mhocko@...e.cz, hughd@...gle.com,
0x7f454c46@...il.com, minchan@...nel.org, tj@...nel.org,
axboe@...com, hch@....de, dh.herrmann@...il.com,
linux-kernel@...r.kernel.org, linux-mm@...ck.org
Subject: [PATCH] mm: swap: zswap: maybe_preload & refactoring
zswap_get_swap_cache_page and read_swap_cache_async have pretty the same
code with only significant difference in return value and usage of
swap_readpage.
I made helper function __read_swap_cache_async with the common code.
Behavior change: now zswap_get_swap_cache_page will use
radix_tree_maybe_preload instead radix_tree_preload. Looks like, this
wasn't changed only by the reason of code duplication.
Signed-off-by: Dmitry Safonov <0x7f454c46@...il.com>
---
include/linux/swap.h | 3 +++
mm/swap_state.c | 37 ++++++++++++++++++--------
mm/zswap.c | 73 +++++-----------------------------------------------
3 files changed, 35 insertions(+), 78 deletions(-)
diff --git a/include/linux/swap.h b/include/linux/swap.h
index 3887472..cd2926e 100644
--- a/include/linux/swap.h
+++ b/include/linux/swap.h
@@ -398,6 +398,9 @@ extern void free_pages_and_swap_cache(struct page **, int);
extern struct page *lookup_swap_cache(swp_entry_t);
extern struct page *read_swap_cache_async(swp_entry_t, gfp_t,
struct vm_area_struct *vma, unsigned long addr);
+extern struct page *__read_swap_cache_async(swp_entry_t, gfp_t,
+ struct vm_area_struct *vma, unsigned long addr,
+ bool *new_page_allocated);
extern struct page *swapin_readahead(swp_entry_t, gfp_t,
struct vm_area_struct *vma, unsigned long addr);
diff --git a/mm/swap_state.c b/mm/swap_state.c
index 8bc8e66..d504adb 100644
--- a/mm/swap_state.c
+++ b/mm/swap_state.c
@@ -288,17 +288,14 @@ struct page * lookup_swap_cache(swp_entry_t entry)
return page;
}
-/*
- * Locate a page of swap in physical memory, reserving swap cache space
- * and reading the disk if it is not already cached.
- * A failure return means that either the page allocation failed or that
- * the swap entry is no longer in use.
- */
-struct page *read_swap_cache_async(swp_entry_t entry, gfp_t gfp_mask,
- struct vm_area_struct *vma, unsigned long addr)
+struct page *__read_swap_cache_async(swp_entry_t entry, gfp_t gfp_mask,
+ struct vm_area_struct *vma, unsigned long addr,
+ bool *new_page_allocated)
{
struct page *found_page, *new_page = NULL;
+ struct address_space *swapper_space = swap_address_space(entry);
int err;
+ *new_page_allocated = false;
do {
/*
@@ -306,8 +303,7 @@ struct page *read_swap_cache_async(swp_entry_t entry, gfp_t gfp_mask,
* called after lookup_swap_cache() failed, re-calling
* that would confuse statistics.
*/
- found_page = find_get_page(swap_address_space(entry),
- entry.val);
+ found_page = find_get_page(swapper_space, entry.val);
if (found_page)
break;
@@ -366,7 +362,7 @@ struct page *read_swap_cache_async(swp_entry_t entry, gfp_t gfp_mask,
* Initiate read into locked page and return.
*/
lru_cache_add_anon(new_page);
- swap_readpage(new_page);
+ *new_page_allocated = true;
return new_page;
}
radix_tree_preload_end();
@@ -384,6 +380,25 @@ struct page *read_swap_cache_async(swp_entry_t entry, gfp_t gfp_mask,
return found_page;
}
+/*
+ * Locate a page of swap in physical memory, reserving swap cache space
+ * and reading the disk if it is not already cached.
+ * A failure return means that either the page allocation failed or that
+ * the swap entry is no longer in use.
+ */
+struct page *read_swap_cache_async(swp_entry_t entry, gfp_t gfp_mask,
+ struct vm_area_struct *vma, unsigned long addr)
+{
+ bool page_was_allocated;
+ struct page *retpage = __read_swap_cache_async(entry, gfp_mask,
+ vma, addr, &page_was_allocated);
+
+ if (page_was_allocated)
+ swap_readpage(retpage);
+
+ return retpage;
+}
+
static unsigned long swapin_nr_pages(unsigned long offset)
{
static unsigned long prev_offset;
diff --git a/mm/zswap.c b/mm/zswap.c
index 2d5727b..09208c7 100644
--- a/mm/zswap.c
+++ b/mm/zswap.c
@@ -446,75 +446,14 @@ enum zswap_get_swap_ret {
static int zswap_get_swap_cache_page(swp_entry_t entry,
struct page **retpage)
{
- struct page *found_page, *new_page = NULL;
- struct address_space *swapper_space = swap_address_space(entry);
- int err;
+ bool page_was_allocated;
- *retpage = NULL;
- do {
- /*
- * First check the swap cache. Since this is normally
- * called after lookup_swap_cache() failed, re-calling
- * that would confuse statistics.
- */
- found_page = find_get_page(swapper_space, entry.val);
- if (found_page)
- break;
-
- /*
- * Get a new page to read into from swap.
- */
- if (!new_page) {
- new_page = alloc_page(GFP_KERNEL);
- if (!new_page)
- break; /* Out of memory */
- }
-
- /*
- * call radix_tree_preload() while we can wait.
- */
- err = radix_tree_preload(GFP_KERNEL);
- if (err)
- break;
-
- /*
- * Swap entry may have been freed since our caller observed it.
- */
- err = swapcache_prepare(entry);
- if (err == -EEXIST) { /* seems racy */
- radix_tree_preload_end();
- continue;
- }
- if (err) { /* swp entry is obsolete ? */
- radix_tree_preload_end();
- break;
- }
-
- /* May fail (-ENOMEM) if radix-tree node allocation failed. */
- __set_page_locked(new_page);
- SetPageSwapBacked(new_page);
- err = __add_to_swap_cache(new_page, entry);
- if (likely(!err)) {
- radix_tree_preload_end();
- lru_cache_add_anon(new_page);
- *retpage = new_page;
- return ZSWAP_SWAPCACHE_NEW;
- }
- radix_tree_preload_end();
- ClearPageSwapBacked(new_page);
- __clear_page_locked(new_page);
- /*
- * add_to_swap_cache() doesn't return -EEXIST, so we can safely
- * clear SWAP_HAS_CACHE flag.
- */
- swapcache_free(entry);
- } while (err != -ENOMEM);
-
- if (new_page)
- page_cache_release(new_page);
- if (!found_page)
+ *retpage = __read_swap_cache_async(entry, GFP_KERNEL,
+ NULL, 0, &page_was_allocated);
+ if (page_was_allocated)
+ return ZSWAP_SWAPCACHE_NEW;
+ if (!*retpage)
return ZSWAP_SWAPCACHE_FAIL;
- *retpage = found_page;
return ZSWAP_SWAPCACHE_EXIST;
}
--
2.4.5
--
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