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Subject[PATCH 9/12] tmpfs: convert mem_cgroup shmem to radix-swap
Remove mem_cgroup_shmem_charge_fallback(): it was only required
when we had to move swappage to filecache with GFP_NOWAIT.

Remove the GFP_NOWAIT special case from mem_cgroup_cache_charge(),
by moving its call out from shmem_add_to_page_cache() to two of thats
three callers. But leave it doing mem_cgroup_uncharge_cache_page() on
error: although asymmetrical, it's easier for all 3 callers to handle.

These two changes would also be appropriate if anyone were
to start using shmem_read_mapping_page_gfp() with GFP_NOWAIT.

Remove mem_cgroup_get_shmem_target(): mc_handle_file_pte() can test
radix_tree_exceptional_entry() to get what it needs for itself.

Signed-off-by: Hugh Dickins <hughd@google.com>
---
include/linux/memcontrol.h | 8 ---
include/linux/shmem_fs.h | 2
mm/memcontrol.c | 66 +++------------------------
mm/shmem.c | 83 ++++-------------------------------
4 files changed, 20 insertions(+), 139 deletions(-)
--- linux.orig/include/linux/memcontrol.h 2011-06-13 13:26:07.126099155 -0700
+++ linux/include/linux/memcontrol.h 2011-06-13 13:30:05.951283422 -0700
@@ -76,8 +76,6 @@ extern void mem_cgroup_uncharge_end(void

extern void mem_cgroup_uncharge_page(struct page *page);
extern void mem_cgroup_uncharge_cache_page(struct page *page);
-extern int mem_cgroup_shmem_charge_fallback(struct page *page,
- struct mm_struct *mm, gfp_t gfp_mask);

extern void mem_cgroup_out_of_memory(struct mem_cgroup *mem, gfp_t gfp_mask);
int task_in_mem_cgroup(struct task_struct *task, const struct mem_cgroup *mem);
@@ -206,12 +204,6 @@ static inline void mem_cgroup_uncharge_c
{
}

-static inline int mem_cgroup_shmem_charge_fallback(struct page *page,
- struct mm_struct *mm, gfp_t gfp_mask)
-{
- return 0;
-}
-
static inline void mem_cgroup_add_lru_list(struct page *page, int lru)
{
}
--- linux.orig/include/linux/shmem_fs.h 2011-06-13 13:28:25.822786909 -0700
+++ linux/include/linux/shmem_fs.h 2011-06-14 00:45:20.625161293 -0700
@@ -57,8 +57,6 @@ extern struct page *shmem_read_mapping_p
pgoff_t index, gfp_t gfp_mask);
extern void shmem_truncate_range(struct inode *inode, loff_t start, loff_t end);
extern int shmem_unuse(swp_entry_t entry, struct page *page);
-extern void mem_cgroup_get_shmem_target(struct inode *inode, pgoff_t pgoff,
- struct page **pagep, swp_entry_t *ent);

static inline struct page *shmem_read_mapping_page(
struct address_space *mapping, pgoff_t index)
--- linux.orig/mm/memcontrol.c 2011-06-13 13:26:07.446100738 -0700
+++ linux/mm/memcontrol.c 2011-06-14 00:50:17.346633542 -0700
@@ -35,7 +35,6 @@
#include <linux/limits.h>
#include <linux/mutex.h>
#include <linux/rbtree.h>
-#include <linux/shmem_fs.h>
#include <linux/slab.h>
#include <linux/swap.h>
#include <linux/swapops.h>
@@ -2690,30 +2689,6 @@ int mem_cgroup_cache_charge(struct page
return 0;
if (PageCompound(page))
return 0;
- /*
- * Corner case handling. This is called from add_to_page_cache()
- * in usual. But some FS (shmem) precharges this page before calling it
- * and call add_to_page_cache() with GFP_NOWAIT.
- *
- * For GFP_NOWAIT case, the page may be pre-charged before calling
- * add_to_page_cache(). (See shmem.c) check it here and avoid to call
- * charge twice. (It works but has to pay a bit larger cost.)
- * And when the page is SwapCache, it should take swap information
- * into account. This is under lock_page() now.
- */
- if (!(gfp_mask & __GFP_WAIT)) {
- struct page_cgroup *pc;
-
- pc = lookup_page_cgroup(page);
- if (!pc)
- return 0;
- lock_page_cgroup(pc);
- if (PageCgroupUsed(pc)) {
- unlock_page_cgroup(pc);
- return 0;
- }
- unlock_page_cgroup(pc);
- }

if (unlikely(!mm))
mm = &init_mm;
@@ -3303,31 +3278,6 @@ void mem_cgroup_end_migration(struct mem
cgroup_release_and_wakeup_rmdir(&mem->css);
}

-/*
- * A call to try to shrink memory usage on charge failure at shmem's swapin.
- * Calling hierarchical_reclaim is not enough because we should update
- * last_oom_jiffies to prevent pagefault_out_of_memory from invoking global OOM.
- * Moreover considering hierarchy, we should reclaim from the mem_over_limit,
- * not from the memcg which this page would be charged to.
- * try_charge_swapin does all of these works properly.
- */
-int mem_cgroup_shmem_charge_fallback(struct page *page,
- struct mm_struct *mm,
- gfp_t gfp_mask)
-{
- struct mem_cgroup *mem;
- int ret;
-
- if (mem_cgroup_disabled())
- return 0;
-
- ret = mem_cgroup_try_charge_swapin(mm, page, gfp_mask, &mem);
- if (!ret)
- mem_cgroup_cancel_charge_swapin(mem); /* it does !mem check */
-
- return ret;
-}
-
#ifdef CONFIG_DEBUG_VM
static struct page_cgroup *lookup_page_cgroup_used(struct page *page)
{
@@ -5086,15 +5036,17 @@ static struct page *mc_handle_file_pte(s
pgoff = pte_to_pgoff(ptent);

/* page is moved even if it's not RSS of this task(page-faulted). */
- if (!mapping_cap_swap_backed(mapping)) { /* normal file */
- page = find_get_page(mapping, pgoff);
- } else { /* shmem/tmpfs file. we should take account of swap too. */
- swp_entry_t ent;
- mem_cgroup_get_shmem_target(inode, pgoff, &page, &ent);
+ page = find_get_page(mapping, pgoff);
+
+#ifdef CONFIG_SWAP
+ /* shmem/tmpfs may report page out on swap: account for that too. */
+ if (radix_tree_exceptional_entry(page)) {
+ swp_entry_t swap = radix_to_swp_entry(page);
if (do_swap_account)
- entry->val = ent.val;
+ *entry = swap;
+ page = find_get_page(&swapper_space, swap.val);
}
-
+#endif
return page;
}

--- linux.orig/mm/shmem.c 2011-06-13 13:29:55.115229689 -0700
+++ linux/mm/shmem.c 2011-06-14 00:45:20.685161581 -0700
@@ -262,15 +262,11 @@ static int shmem_add_to_page_cache(struc
struct address_space *mapping,
pgoff_t index, gfp_t gfp, void *expected)
{
- int error;
+ int error = 0;

VM_BUG_ON(!PageLocked(page));
VM_BUG_ON(!PageSwapBacked(page));

- error = mem_cgroup_cache_charge(page, current->mm,
- gfp & GFP_RECLAIM_MASK);
- if (error)
- goto out;
if (!expected)
error = radix_tree_preload(gfp & GFP_RECLAIM_MASK);
if (!error) {
@@ -300,7 +296,6 @@ static int shmem_add_to_page_cache(struc
}
if (error)
mem_cgroup_uncharge_cache_page(page);
-out:
return error;
}

@@ -660,7 +655,6 @@ int shmem_unuse(swp_entry_t swap, struct
* Charge page using GFP_KERNEL while we can wait, before taking
* the shmem_swaplist_mutex which might hold up shmem_writepage().
* Charged back to the user (not to caller) when swap account is used.
- * shmem_add_to_page_cache() will be called with GFP_NOWAIT.
*/
error = mem_cgroup_cache_charge(page, current->mm, GFP_KERNEL);
if (error)
@@ -954,8 +948,11 @@ repeat:
goto failed;
}

- error = shmem_add_to_page_cache(page, mapping, index,
- gfp, swp_to_radix_entry(swap));
+ error = mem_cgroup_cache_charge(page, current->mm,
+ gfp & GFP_RECLAIM_MASK);
+ if (!error)
+ error = shmem_add_to_page_cache(page, mapping, index,
+ gfp, swp_to_radix_entry(swap));
if (error)
goto failed;

@@ -990,8 +987,11 @@ repeat:

SetPageSwapBacked(page);
__set_page_locked(page);
- error = shmem_add_to_page_cache(page, mapping, index,
- gfp, NULL);
+ error = mem_cgroup_cache_charge(page, current->mm,
+ gfp & GFP_RECLAIM_MASK);
+ if (!error)
+ error = shmem_add_to_page_cache(page, mapping, index,
+ gfp, NULL);
if (error)
goto decused;
lru_cache_add_anon(page);
@@ -2448,42 +2448,6 @@ out4:
return error;
}

-#ifdef CONFIG_CGROUP_MEM_RES_CTLR
-/**
- * mem_cgroup_get_shmem_target - find page or swap assigned to the shmem file
- * @inode: the inode to be searched
- * @index: the page offset to be searched
- * @pagep: the pointer for the found page to be stored
- * @swapp: the pointer for the found swap entry to be stored
- *
- * If a page is found, refcount of it is incremented. Callers should handle
- * these refcount.
- */
-void mem_cgroup_get_shmem_target(struct inode *inode, pgoff_t index,
- struct page **pagep, swp_entry_t *swapp)
-{
- struct shmem_inode_info *info = SHMEM_I(inode);
- struct page *page = NULL;
- swp_entry_t swap = {0};
-
- if ((index << PAGE_CACHE_SHIFT) >= i_size_read(inode))
- goto out;
-
- spin_lock(&info->lock);
-#ifdef CONFIG_SWAP
- swap = shmem_get_swap(info, index);
- if (swap.val)
- page = find_get_page(&swapper_space, swap.val);
- else
-#endif
- page = find_get_page(inode->i_mapping, index);
- spin_unlock(&info->lock);
-out:
- *pagep = page;
- *swapp = swap;
-}
-#endif
-
#else /* !CONFIG_SHMEM */

/*
@@ -2529,31 +2493,6 @@ void shmem_truncate_range(struct inode *
}
EXPORT_SYMBOL_GPL(shmem_truncate_range);

-#ifdef CONFIG_CGROUP_MEM_RES_CTLR
-/**
- * mem_cgroup_get_shmem_target - find page or swap assigned to the shmem file
- * @inode: the inode to be searched
- * @index: the page offset to be searched
- * @pagep: the pointer for the found page to be stored
- * @swapp: the pointer for the found swap entry to be stored
- *
- * If a page is found, refcount of it is incremented. Callers should handle
- * these refcount.
- */
-void mem_cgroup_get_shmem_target(struct inode *inode, pgoff_t index,
- struct page **pagep, swp_entry_t *swapp)
-{
- struct page *page = NULL;
-
- if ((index << PAGE_CACHE_SHIFT) >= i_size_read(inode))
- goto out;
- page = find_get_page(inode->i_mapping, index);
-out:
- *pagep = page;
- *swapp = (swp_entry_t){0};
-}
-#endif
-
#define shmem_vm_ops generic_file_vm_ops
#define shmem_file_operations ramfs_file_operations
#define shmem_get_inode(sb, dir, mode, dev, flags) ramfs_get_inode(sb, dir, mode, dev)

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