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tmpfs: convert mem_cgroup shmem to radix-swap
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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 <[email protected]>
Acked-by: Rik van Riel <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>
Signed-off-by: Linus Torvalds <[email protected]>
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@torvalds
Hugh Dickins authored and torvalds committed Aug 4, 2011
1 parent 54af604 commit aa3b189
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Showing 4 changed files with 20 additions and 139 deletions.
8 changes: 0 additions & 8 deletions include/linux/memcontrol.h
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Original file line number Diff line number Diff line change
Expand Up @@ -86,8 +86,6 @@ 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);
Expand Down Expand Up @@ -225,12 +223,6 @@ static inline void mem_cgroup_uncharge_cache_page(struct page *page)
{
}

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)
{
}
Expand Down
2 changes: 0 additions & 2 deletions include/linux/shmem_fs.h
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Original file line number Diff line number Diff line change
Expand Up @@ -57,8 +57,6 @@ extern struct page *shmem_read_mapping_page_gfp(struct address_space *mapping,
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)
Expand Down
66 changes: 9 additions & 57 deletions mm/memcontrol.c
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Original file line number Diff line number Diff line change
Expand Up @@ -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>
Expand Down Expand Up @@ -2873,30 +2872,6 @@ int mem_cgroup_cache_charge(struct page *page, struct mm_struct *mm,
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;
Expand Down Expand Up @@ -3486,31 +3461,6 @@ void mem_cgroup_end_migration(struct mem_cgroup *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)
{
Expand Down Expand Up @@ -5330,15 +5280,17 @@ static struct page *mc_handle_file_pte(struct vm_area_struct *vma,
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;
}

Expand Down
83 changes: 11 additions & 72 deletions mm/shmem.c
View file
Original file line number Diff line number Diff line change
Expand Up @@ -262,15 +262,11 @@ static int shmem_add_to_page_cache(struct page *page,
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) {
Expand Down Expand Up @@ -300,7 +296,6 @@ static int shmem_add_to_page_cache(struct page *page,
}
if (error)
mem_cgroup_uncharge_cache_page(page);
out:
return error;
}

Expand Down Expand Up @@ -660,7 +655,6 @@ int shmem_unuse(swp_entry_t swap, struct page *page)
* 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)
Expand Down Expand Up @@ -954,8 +948,11 @@ static int shmem_getpage_gfp(struct inode *inode, pgoff_t index,
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;

Expand Down Expand Up @@ -990,8 +987,11 @@ static int shmem_getpage_gfp(struct inode *inode, pgoff_t index,

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);
Expand Down Expand Up @@ -2442,42 +2442,6 @@ int __init shmem_init(void)
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 */

/*
Expand Down Expand Up @@ -2523,31 +2487,6 @@ void shmem_truncate_range(struct inode *inode, loff_t lstart, loff_t lend)
}
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)
Expand Down

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