[PATCH] Fixing address space lock contention in 2.6.11

From: Peter Chubb
Date: Wed Mar 02 2005 - 21:10:27 EST


Hi,
As part of the Gelato scalability focus group, we've been running
OSDL's Re-AIM7 benchmark with an I/O intensive load with varying
numbers of processors. The current kernel shows severe contention on
the tree_lock in the address space structure when running on tmpfs or
ext2 on a RAM disk.


Lockstat output for a 12-way:

SPINLOCKS HOLD WAIT
UTIL CON MEAN( MAX ) MEAN( MAX )(% CPU) TOTAL NOWAIT SPIN RJECT NAME

5.5% 0.4us(3177us) 28us( 20ms)(44.2%) 131821954 94.5% 5.5% 0.00% *TOTAL*

72.3% 13.1% 0.5us( 9.5us) 29us( 20ms)(42.5%) 50542055 86.9% 13.1% 0% find_lock_page+0x30
23.8% 0% 385us(3177us) 0us 23235 100% 0% 0% exit_mmap+0x50
11.5% 0.82% 0.1us( 101us) 17us(5670us)( 1.6%) 50665658 99.2% 0.82% 0% dnotify_parent+0x70


Replacing the spinlock with a multi-reader lock fixes this problem,
without unduly affecting anything else.

Here are the benchmark results (jobs per minute at a 50-client level,
average of 5 runs, standard deviation in parens) on an HP Olympia with
3 cells, 12 processors, and dnotify turned off (after this spinlock,
the spinlock in dnotify_parent is the worst contended for this workload).

tmpfs............... ext2...............
#CPUs spinlock rwlock spinlock rwlock
1 7556(15) 7588(17) +0.42% 3744(20) 3791(16) +1.25%
2 13743(31) 13791(33) +0.35% 6405(30) 6413(24) +0.12%
4 23334(111) 22881(154) -2% 9648(51) 9595(50) -0.55%
8 33580(240) 36163(190) +7.7% 13183(63) 13070(68) -0.85%
12 28748(170) 44064(238)+53% 12681(49) 14504(105)+14%

And on a pentium3 single processsor:
1 4177(4) 4169(2) -0.2% 3811(4) 3820(3) +0.23%

I'm not sure what's happening in the 4-processor case. The important
thing to note is that with a spinlock, the benchmark shows worse
performance for a 12 than for an 8-way box; with the patch, the 12 way
performs better, as expected. We've done some runs with 16-way as
well; without the patch below, the 16-way performs worse than the
12-way.

Anyway, here's the patch to convert the address space lock to a
rwlock, and allow multiple processes to scan an address-space's radix
tree at once.

===== drivers/mtd/devices/block2mtd.c 1.4 vs edited =====
--- 1.4/drivers/mtd/devices/block2mtd.c 2005-02-02 19:27:37 +11:00
+++ edited/drivers/mtd/devices/block2mtd.c 2005-02-22 14:28:23 +11:00
@@ -59,7 +59,7 @@ void cache_readahead(struct address_spac

end_index = ((isize - 1) >> PAGE_CACHE_SHIFT);

- spin_lock_irq(&mapping->tree_lock);
+ read_lock_irq(&mapping->tree_lock);
for (i = 0; i < PAGE_READAHEAD; i++) {
pagei = index + i;
if (pagei > end_index) {
@@ -71,16 +71,16 @@ void cache_readahead(struct address_spac
break;
if (page)
continue;
- spin_unlock_irq(&mapping->tree_lock);
+ read_unlock_irq(&mapping->tree_lock);
page = page_cache_alloc_cold(mapping);
- spin_lock_irq(&mapping->tree_lock);
+ read_lock_irq(&mapping->tree_lock);
if (!page)
break;
page->index = pagei;
list_add(&page->lru, &page_pool);
ret++;
}
- spin_unlock_irq(&mapping->tree_lock);
+ read_unlock_irq(&mapping->tree_lock);
if (ret)
read_cache_pages(mapping, &page_pool, filler, NULL);
}
===== fs/buffer.c 1.271 vs edited =====
--- 1.271/fs/buffer.c 2005-02-18 20:44:07 +11:00
+++ edited/fs/buffer.c 2005-02-22 14:31:41 +11:00
@@ -875,7 +875,7 @@ int __set_page_dirty_buffers(struct page
spin_unlock(&mapping->private_lock);

if (!TestSetPageDirty(page)) {
- spin_lock_irq(&mapping->tree_lock);
+ read_lock_irq(&mapping->tree_lock);
if (page->mapping) { /* Race with truncate? */
if (!mapping->backing_dev_info->memory_backed)
inc_page_state(nr_dirty);
@@ -883,7 +883,7 @@ int __set_page_dirty_buffers(struct page
page_index(page),
PAGECACHE_TAG_DIRTY);
}
- spin_unlock_irq(&mapping->tree_lock);
+ read_unlock_irq(&mapping->tree_lock);
__mark_inode_dirty(mapping->host, I_DIRTY_PAGES);
}

===== fs/inode.c 1.143 vs edited =====
--- 1.143/fs/inode.c 2005-01-21 16:02:13 +11:00
+++ edited/fs/inode.c 2005-02-22 14:16:33 +11:00
@@ -196,7 +196,7 @@ void inode_init_once(struct inode *inode
sema_init(&inode->i_sem, 1);
init_rwsem(&inode->i_alloc_sem);
INIT_RADIX_TREE(&inode->i_data.page_tree, GFP_ATOMIC);
- spin_lock_init(&inode->i_data.tree_lock);
+ rwlock_init(&inode->i_data.tree_lock);
spin_lock_init(&inode->i_data.i_mmap_lock);
INIT_LIST_HEAD(&inode->i_data.private_list);
spin_lock_init(&inode->i_data.private_lock);
===== include/asm-arm/cacheflush.h 1.18 vs edited =====
--- 1.18/include/asm-arm/cacheflush.h 2004-11-05 21:53:14 +11:00
+++ edited/include/asm-arm/cacheflush.h 2005-02-22 14:31:05 +11:00
@@ -312,9 +312,9 @@ flush_cache_page(struct vm_area_struct *
extern void flush_dcache_page(struct page *);

#define flush_dcache_mmap_lock(mapping) \
- spin_lock_irq(&(mapping)->tree_lock)
+ write_lock_irq(&(mapping)->tree_lock)
#define flush_dcache_mmap_unlock(mapping) \
- spin_unlock_irq(&(mapping)->tree_lock)
+ write_unlock_irq(&(mapping)->tree_lock)

#define flush_icache_user_range(vma,page,addr,len) \
flush_dcache_page(page)
===== include/asm-parisc/cacheflush.h 1.13 vs edited =====
--- 1.13/include/asm-parisc/cacheflush.h 2004-12-25 10:40:22 +11:00
+++ edited/include/asm-parisc/cacheflush.h 2005-02-22 14:31:41 +11:00
@@ -57,9 +57,9 @@ flush_user_icache_range(unsigned long st
extern void flush_dcache_page(struct page *page);

#define flush_dcache_mmap_lock(mapping) \
- spin_lock_irq(&(mapping)->tree_lock)
+ write_lock_irq(&(mapping)->tree_lock)
#define flush_dcache_mmap_unlock(mapping) \
- spin_unlock_irq(&(mapping)->tree_lock)
+ write_unlock_irq(&(mapping)->tree_lock)

#define flush_icache_page(vma,page) do { flush_kernel_dcache_page(page_address(page)); flush_kernel_icache_page(page_address(page)); } while (0)

===== include/linux/fs.h 1.376 vs edited =====
--- 1.376/include/linux/fs.h 2005-02-04 01:42:40 +11:00
+++ edited/include/linux/fs.h 2005-02-22 14:31:41 +11:00
@@ -334,7 +334,7 @@ struct backing_dev_info;
struct address_space {
struct inode *host; /* owner: inode, block_device */
struct radix_tree_root page_tree; /* radix tree of all pages */
- spinlock_t tree_lock; /* and spinlock protecting it */
+ rwlock_t tree_lock; /* and multi-reader lock protecting it */
unsigned int i_mmap_writable;/* count VM_SHARED mappings */
struct prio_tree_root i_mmap; /* tree of private and shared mappings */
struct list_head i_mmap_nonlinear;/*list VM_NONLINEAR mappings */
===== mm/filemap.c 1.292 vs edited =====
--- 1.292/mm/filemap.c 2005-02-15 05:31:41 +11:00
+++ edited/mm/filemap.c 2005-02-22 14:31:41 +11:00
@@ -126,9 +126,9 @@ void remove_from_page_cache(struct page
if (unlikely(!PageLocked(page)))
PAGE_BUG(page);

- spin_lock_irq(&mapping->tree_lock);
+ write_lock_irq(&mapping->tree_lock);
__remove_from_page_cache(page);
- spin_unlock_irq(&mapping->tree_lock);
+ write_unlock_irq(&mapping->tree_lock);
}

static int sync_page(void *word)
@@ -349,7 +349,7 @@ int add_to_page_cache(struct page *page,
int error = radix_tree_preload(gfp_mask & ~__GFP_HIGHMEM);

if (error == 0) {
- spin_lock_irq(&mapping->tree_lock);
+ write_lock_irq(&mapping->tree_lock);
error = radix_tree_insert(&mapping->page_tree, offset, page);
if (!error) {
page_cache_get(page);
@@ -359,7 +359,7 @@ int add_to_page_cache(struct page *page,
mapping->nrpages++;
pagecache_acct(1);
}
- spin_unlock_irq(&mapping->tree_lock);
+ write_unlock_irq(&mapping->tree_lock);
radix_tree_preload_end();
}
return error;
@@ -472,11 +472,11 @@ struct page * find_get_page(struct addre
{
struct page *page;

- spin_lock_irq(&mapping->tree_lock);
+ read_lock_irq(&mapping->tree_lock);
page = radix_tree_lookup(&mapping->page_tree, offset);
if (page)
page_cache_get(page);
- spin_unlock_irq(&mapping->tree_lock);
+ read_unlock_irq(&mapping->tree_lock);
return page;
}

@@ -489,11 +489,11 @@ struct page *find_trylock_page(struct ad
{
struct page *page;

- spin_lock_irq(&mapping->tree_lock);
+ read_lock_irq(&mapping->tree_lock);
page = radix_tree_lookup(&mapping->page_tree, offset);
if (page && TestSetPageLocked(page))
page = NULL;
- spin_unlock_irq(&mapping->tree_lock);
+ read_unlock_irq(&mapping->tree_lock);
return page;
}

@@ -515,15 +515,15 @@ struct page *find_lock_page(struct addre
{
struct page *page;

- spin_lock_irq(&mapping->tree_lock);
+ read_lock_irq(&mapping->tree_lock);
repeat:
page = radix_tree_lookup(&mapping->page_tree, offset);
if (page) {
page_cache_get(page);
if (TestSetPageLocked(page)) {
- spin_unlock_irq(&mapping->tree_lock);
+ read_unlock_irq(&mapping->tree_lock);
lock_page(page);
- spin_lock_irq(&mapping->tree_lock);
+ read_lock_irq(&mapping->tree_lock);

/* Has the page been truncated while we slept? */
if (page->mapping != mapping || page->index != offset) {
@@ -533,7 +533,7 @@ repeat:
}
}
}
- spin_unlock_irq(&mapping->tree_lock);
+ read_unlock_irq(&mapping->tree_lock);
return page;
}

@@ -607,12 +607,12 @@ unsigned find_get_pages(struct address_s
unsigned int i;
unsigned int ret;

- spin_lock_irq(&mapping->tree_lock);
+ read_lock_irq(&mapping->tree_lock);
ret = radix_tree_gang_lookup(&mapping->page_tree,
(void **)pages, start, nr_pages);
for (i = 0; i < ret; i++)
page_cache_get(pages[i]);
- spin_unlock_irq(&mapping->tree_lock);
+ read_unlock_irq(&mapping->tree_lock);
return ret;
}

@@ -626,14 +626,14 @@ unsigned find_get_pages_tag(struct addre
unsigned int i;
unsigned int ret;

- spin_lock_irq(&mapping->tree_lock);
+ read_lock_irq(&mapping->tree_lock);
ret = radix_tree_gang_lookup_tag(&mapping->page_tree,
(void **)pages, *index, nr_pages, tag);
for (i = 0; i < ret; i++)
page_cache_get(pages[i]);
if (ret)
*index = pages[ret - 1]->index + 1;
- spin_unlock_irq(&mapping->tree_lock);
+ read_unlock_irq(&mapping->tree_lock);
return ret;
}

===== mm/page-writeback.c 1.96 vs edited =====
--- 1.96/mm/page-writeback.c 2005-01-26 08:50:13 +11:00
+++ edited/mm/page-writeback.c 2005-02-22 14:31:41 +11:00
@@ -601,7 +601,7 @@ int __set_page_dirty_nobuffers(struct pa
struct address_space *mapping2;

if (mapping) {
- spin_lock_irq(&mapping->tree_lock);
+ read_lock_irq(&mapping->tree_lock);
mapping2 = page_mapping(page);
if (mapping2) { /* Race with truncate? */
BUG_ON(mapping2 != mapping);
@@ -610,7 +610,7 @@ int __set_page_dirty_nobuffers(struct pa
radix_tree_tag_set(&mapping->page_tree,
page_index(page), PAGECACHE_TAG_DIRTY);
}
- spin_unlock_irq(&mapping->tree_lock);
+ read_unlock_irq(&mapping->tree_lock);
if (mapping->host) {
/* !PageAnon && !swapper_space */
__mark_inode_dirty(mapping->host,
@@ -685,17 +685,17 @@ int test_clear_page_dirty(struct page *p
unsigned long flags;

if (mapping) {
- spin_lock_irqsave(&mapping->tree_lock, flags);
+ read_lock_irqsave(&mapping->tree_lock, flags);
if (TestClearPageDirty(page)) {
radix_tree_tag_clear(&mapping->page_tree,
page_index(page),
PAGECACHE_TAG_DIRTY);
- spin_unlock_irqrestore(&mapping->tree_lock, flags);
+ read_unlock_irqrestore(&mapping->tree_lock, flags);
if (!mapping->backing_dev_info->memory_backed)
dec_page_state(nr_dirty);
return 1;
}
- spin_unlock_irqrestore(&mapping->tree_lock, flags);
+ read_unlock_irqrestore(&mapping->tree_lock, flags);
return 0;
}
return TestClearPageDirty(page);
@@ -742,15 +742,15 @@ int __clear_page_dirty(struct page *page
if (mapping) {
unsigned long flags;

- spin_lock_irqsave(&mapping->tree_lock, flags);
+ read_lock_irqsave(&mapping->tree_lock, flags);
if (TestClearPageDirty(page)) {
radix_tree_tag_clear(&mapping->page_tree,
page_index(page),
PAGECACHE_TAG_DIRTY);
- spin_unlock_irqrestore(&mapping->tree_lock, flags);
+ read_unlock_irqrestore(&mapping->tree_lock, flags);
return 1;
}
- spin_unlock_irqrestore(&mapping->tree_lock, flags);
+ read_unlock_irqrestore(&mapping->tree_lock, flags);
return 0;
}
return TestClearPageDirty(page);
@@ -764,13 +764,13 @@ int test_clear_page_writeback(struct pag
if (mapping) {
unsigned long flags;

- spin_lock_irqsave(&mapping->tree_lock, flags);
+ read_lock_irqsave(&mapping->tree_lock, flags);
ret = TestClearPageWriteback(page);
if (ret)
radix_tree_tag_clear(&mapping->page_tree,
page_index(page),
PAGECACHE_TAG_WRITEBACK);
- spin_unlock_irqrestore(&mapping->tree_lock, flags);
+ read_unlock_irqrestore(&mapping->tree_lock, flags);
} else {
ret = TestClearPageWriteback(page);
}
@@ -785,7 +785,7 @@ int test_set_page_writeback(struct page
if (mapping) {
unsigned long flags;

- spin_lock_irqsave(&mapping->tree_lock, flags);
+ read_lock_irqsave(&mapping->tree_lock, flags);
ret = TestSetPageWriteback(page);
if (!ret)
radix_tree_tag_set(&mapping->page_tree,
@@ -795,7 +795,7 @@ int test_set_page_writeback(struct page
radix_tree_tag_clear(&mapping->page_tree,
page_index(page),
PAGECACHE_TAG_DIRTY);
- spin_unlock_irqrestore(&mapping->tree_lock, flags);
+ read_unlock_irqrestore(&mapping->tree_lock, flags);
} else {
ret = TestSetPageWriteback(page);
}
@@ -813,9 +813,9 @@ int mapping_tagged(struct address_space
unsigned long flags;
int ret;

- spin_lock_irqsave(&mapping->tree_lock, flags);
+ read_lock_irqsave(&mapping->tree_lock, flags);
ret = radix_tree_tagged(&mapping->page_tree, tag);
- spin_unlock_irqrestore(&mapping->tree_lock, flags);
+ read_unlock_irqrestore(&mapping->tree_lock, flags);
return ret;
}
EXPORT_SYMBOL(mapping_tagged);
===== mm/readahead.c 1.56 vs edited =====
--- 1.56/mm/readahead.c 2005-01-12 11:42:34 +11:00
+++ edited/mm/readahead.c 2005-02-22 14:31:41 +11:00
@@ -274,7 +274,7 @@ __do_page_cache_readahead(struct address
/*
* Preallocate as many pages as we will need.
*/
- spin_lock_irq(&mapping->tree_lock);
+ read_lock_irq(&mapping->tree_lock);
for (page_idx = 0; page_idx < nr_to_read; page_idx++) {
unsigned long page_offset = offset + page_idx;

@@ -285,16 +285,16 @@ __do_page_cache_readahead(struct address
if (page)
continue;

- spin_unlock_irq(&mapping->tree_lock);
+ read_unlock_irq(&mapping->tree_lock);
page = page_cache_alloc_cold(mapping);
- spin_lock_irq(&mapping->tree_lock);
+ read_lock_irq(&mapping->tree_lock);
if (!page)
break;
page->index = page_offset;
list_add(&page->lru, &page_pool);
ret++;
}
- spin_unlock_irq(&mapping->tree_lock);
+ read_unlock_irq(&mapping->tree_lock);

/*
* Now start the IO. We ignore I/O errors - if the page is not
===== mm/swap_state.c 1.82 vs edited =====
--- 1.82/mm/swap_state.c 2005-01-31 17:19:53 +11:00
+++ edited/mm/swap_state.c 2005-02-22 14:31:41 +11:00
@@ -35,7 +35,7 @@ static struct backing_dev_info swap_back

struct address_space swapper_space = {
.page_tree = RADIX_TREE_INIT(GFP_ATOMIC|__GFP_NOWARN),
- .tree_lock = SPIN_LOCK_UNLOCKED,
+ .tree_lock = RW_LOCK_UNLOCKED,
.a_ops = &swap_aops,
.i_mmap_nonlinear = LIST_HEAD_INIT(swapper_space.i_mmap_nonlinear),
.backing_dev_info = &swap_backing_dev_info,
@@ -76,7 +76,7 @@ static int __add_to_swap_cache(struct pa
BUG_ON(PagePrivate(page));
error = radix_tree_preload(gfp_mask);
if (!error) {
- spin_lock_irq(&swapper_space.tree_lock);
+ write_lock_irq(&swapper_space.tree_lock);
error = radix_tree_insert(&swapper_space.page_tree,
entry.val, page);
if (!error) {
@@ -87,7 +87,7 @@ static int __add_to_swap_cache(struct pa
total_swapcache_pages++;
pagecache_acct(1);
}
- spin_unlock_irq(&swapper_space.tree_lock);
+ write_unlock_irq(&swapper_space.tree_lock);
radix_tree_preload_end();
}
return error;
@@ -214,9 +214,9 @@ void delete_from_swap_cache(struct page

entry.val = page->private;

- spin_lock_irq(&swapper_space.tree_lock);
+ write_lock_irq(&swapper_space.tree_lock);
__delete_from_swap_cache(page);
- spin_unlock_irq(&swapper_space.tree_lock);
+ write_unlock_irq(&swapper_space.tree_lock);

swap_free(entry);
page_cache_release(page);
@@ -315,13 +315,13 @@ struct page * lookup_swap_cache(swp_entr
{
struct page *page;

- spin_lock_irq(&swapper_space.tree_lock);
+ read_lock_irq(&swapper_space.tree_lock);
page = radix_tree_lookup(&swapper_space.page_tree, entry.val);
if (page) {
page_cache_get(page);
INC_CACHE_INFO(find_success);
}
- spin_unlock_irq(&swapper_space.tree_lock);
+ read_unlock_irq(&swapper_space.tree_lock);
INC_CACHE_INFO(find_total);
return page;
}
@@ -344,12 +344,12 @@ struct page *read_swap_cache_async(swp_e
* called after lookup_swap_cache() failed, re-calling
* that would confuse statistics.
*/
- spin_lock_irq(&swapper_space.tree_lock);
+ read_lock_irq(&swapper_space.tree_lock);
found_page = radix_tree_lookup(&swapper_space.page_tree,
entry.val);
if (found_page)
page_cache_get(found_page);
- spin_unlock_irq(&swapper_space.tree_lock);
+ read_unlock_irq(&swapper_space.tree_lock);
if (found_page)
break;

===== mm/swapfile.c 1.125 vs edited =====
--- 1.125/mm/swapfile.c 2005-01-12 11:42:36 +11:00
+++ edited/mm/swapfile.c 2005-02-22 14:31:41 +11:00
@@ -292,10 +292,10 @@ static int exclusive_swap_page(struct pa
/* Is the only swap cache user the cache itself? */
if (p->swap_map[swp_offset(entry)] == 1) {
/* Recheck the page count with the swapcache lock held.. */
- spin_lock_irq(&swapper_space.tree_lock);
+ read_lock_irq(&swapper_space.tree_lock);
if (page_count(page) == 2)
retval = 1;
- spin_unlock_irq(&swapper_space.tree_lock);
+ read_unlock_irq(&swapper_space.tree_lock);
}
swap_info_put(p);
}
@@ -363,13 +363,13 @@ int remove_exclusive_swap_page(struct pa
retval = 0;
if (p->swap_map[swp_offset(entry)] == 1) {
/* Recheck the page count with the swapcache lock held.. */
- spin_lock_irq(&swapper_space.tree_lock);
+ write_lock_irq(&swapper_space.tree_lock);
if ((page_count(page) == 2) && !PageWriteback(page)) {
__delete_from_swap_cache(page);
SetPageDirty(page);
retval = 1;
}
- spin_unlock_irq(&swapper_space.tree_lock);
+ write_unlock_irq(&swapper_space.tree_lock);
}
swap_info_put(p);

@@ -393,12 +393,12 @@ void free_swap_and_cache(swp_entry_t ent
p = swap_info_get(entry);
if (p) {
if (swap_entry_free(p, swp_offset(entry)) == 1) {
- spin_lock_irq(&swapper_space.tree_lock);
+ read_lock_irq(&swapper_space.tree_lock);
page = radix_tree_lookup(&swapper_space.page_tree,
entry.val);
if (page && TestSetPageLocked(page))
page = NULL;
- spin_unlock_irq(&swapper_space.tree_lock);
+ read_unlock_irq(&swapper_space.tree_lock);
}
swap_info_put(p);
}
===== mm/truncate.c 1.20 vs edited =====
--- 1.20/mm/truncate.c 2005-02-06 07:51:43 +11:00
+++ edited/mm/truncate.c 2005-02-22 14:31:41 +11:00
@@ -76,15 +76,15 @@ invalidate_complete_page(struct address_
if (PagePrivate(page) && !try_to_release_page(page, 0))
return 0;

- spin_lock_irq(&mapping->tree_lock);
+ write_lock_irq(&mapping->tree_lock);
if (PageDirty(page)) {
- spin_unlock_irq(&mapping->tree_lock);
+ write_unlock_irq(&mapping->tree_lock);
return 0;
}

BUG_ON(PagePrivate(page));
__remove_from_page_cache(page);
- spin_unlock_irq(&mapping->tree_lock);
+ write_unlock_irq(&mapping->tree_lock);
ClearPageUptodate(page);
page_cache_release(page); /* pagecache ref */
return 1;
===== mm/vmscan.c 1.240 vs edited =====
--- 1.240/mm/vmscan.c 2005-02-04 11:53:32 +11:00
+++ edited/mm/vmscan.c 2005-02-22 14:31:41 +11:00
@@ -475,7 +475,7 @@ static int shrink_list(struct list_head
if (!mapping)
goto keep_locked; /* truncate got there first */

- spin_lock_irq(&mapping->tree_lock);
+ write_lock_irq(&mapping->tree_lock);

/*
* The non-racy check for busy page. It is critical to check
@@ -483,7 +483,7 @@ static int shrink_list(struct list_head
* not in use by anybody. (pagecache + us == 2)
*/
if (page_count(page) != 2 || PageDirty(page)) {
- spin_unlock_irq(&mapping->tree_lock);
+ write_unlock_irq(&mapping->tree_lock);
goto keep_locked;
}

@@ -491,7 +491,7 @@ static int shrink_list(struct list_head
if (PageSwapCache(page)) {
swp_entry_t swap = { .val = page->private };
__delete_from_swap_cache(page);
- spin_unlock_irq(&mapping->tree_lock);
+ write_unlock_irq(&mapping->tree_lock);
swap_free(swap);
__put_page(page); /* The pagecache ref */
goto free_it;
@@ -499,7 +499,7 @@ static int shrink_list(struct list_head
#endif /* CONFIG_SWAP */

__remove_from_page_cache(page);
- spin_unlock_irq(&mapping->tree_lock);
+ write_unlock_irq(&mapping->tree_lock);
__put_page(page);

free_it:
-
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