Re: [PATCH 6/9] readahead: clean up and simplify the code forfilemap page fault readahead
From: Andrew Morton
Date: Fri Apr 10 2009 - 19:55:24 EST
On Fri, 10 Apr 2009 14:10:03 +0800
Wu Fengguang <fengguang.wu@xxxxxxxxx> wrote:
> @@ -1553,18 +1581,18 @@ retry_find:
> if (unlikely(!PageUptodate(page)))
> goto page_not_uptodate;
>
> - /* Must recheck i_size under page lock */
> + /*
> + * Found the page and have a reference on it.
> + * We must recheck i_size under page lock.
> + */
> size = (i_size_read(inode) + PAGE_CACHE_SIZE - 1) >> PAGE_CACHE_SHIFT;
> - if (unlikely(vmf->pgoff >= size)) {
> + if (unlikely(offset >= size)) {
> unlock_page(page);
> page_cache_release(page);
> return VM_FAULT_SIGBUS;
> }
This hunk broke
mm-update_page_reclaim_stat-is-called-from-page-fault-path.patch.
I fixed it thusly:
/*
* Found the page and have a reference on it.
* We must recheck i_size under page lock.
*/
size = (i_size_read(inode) + PAGE_CACHE_SIZE - 1) >> PAGE_CACHE_SHIFT;
if (unlikely(offset >= size)) {
unlock_page(page);
page_cache_release(page);
return VM_FAULT_SIGBUS;
}
+ update_page_reclaim_stat(page);
ra->prev_pos = (loff_t)offset << PAGE_CACHE_SHIFT;
vmf->page = page;
return ret | VM_FAULT_LOCKED;
which seems logical to me.
Although now I look at it, it seems that
mm-update_page_reclaim_stat-is-called-from-page-fault-path.patch should
go into 2.6.30?
Ah. But I have a note here that I didn't like it, because it adds lots
of new spinlocking to fastpaths. So I'll leave things as they stand
until we have had a little talk about that.
From: KOSAKI Motohiro <kosaki.motohiro@xxxxxxxxxxxxxx>
Unfortunately, the following two patches had conflicting concepts.
1. commit 9ff473b9a72942c5ac0ad35607cae28d8d59ed7a
(vmscan: evict streaming IO first)
2. commit bf3f3bc5e734706730c12a323f9b2068052aa1f0
(mm: don't mark_page_accessed in fault path)
(1) requires that a page fault update reclaim stat via
mark_page_accessed(), but
(2) removed mark_page_accessed().
However, (1) actually only needed to update reclaim stat, but not activate
the page. Then, the fault-path can call update_page_reclaim_stat() to
solve this conflict.
Signed-off-by: KOSAKI Motohiro <kosaki.motohiro@xxxxxxxxxxxxxx>
Cc: Nick Piggin <npiggin@xxxxxxx>
Cc: Hugh Dickins <hugh@xxxxxxxxxxx>
Cc: Rik van Riel <riel@xxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
include/linux/swap.h | 1 +
mm/filemap.c | 2 +-
mm/memory.c | 2 ++
mm/swap.c | 24 +++++++++++++++++++-----
4 files changed, 23 insertions(+), 6 deletions(-)
diff -puN include/linux/swap.h~mm-update_page_reclaim_stat-is-called-from-page-fault-path include/linux/swap.h
--- a/include/linux/swap.h~mm-update_page_reclaim_stat-is-called-from-page-fault-path
+++ a/include/linux/swap.h
@@ -179,6 +179,7 @@ extern void __lru_cache_add(struct page
extern void lru_cache_add_lru(struct page *, enum lru_list lru);
extern void activate_page(struct page *);
extern void mark_page_accessed(struct page *);
+extern void update_page_reclaim_stat(struct page *page);
extern void lru_add_drain(void);
extern int lru_add_drain_all(void);
extern void rotate_reclaimable_page(struct page *page);
diff -puN mm/filemap.c~mm-update_page_reclaim_stat-is-called-from-page-fault-path mm/filemap.c
--- a/mm/filemap.c~mm-update_page_reclaim_stat-is-called-from-page-fault-path
+++ a/mm/filemap.c
@@ -1595,7 +1595,7 @@ retry_find:
page_cache_release(page);
return VM_FAULT_SIGBUS;
}
-
+ update_page_reclaim_stat(page);
ra->prev_pos = (loff_t)offset << PAGE_CACHE_SHIFT;
vmf->page = page;
return ret | VM_FAULT_LOCKED;
diff -puN mm/memory.c~mm-update_page_reclaim_stat-is-called-from-page-fault-path mm/memory.c
--- a/mm/memory.c~mm-update_page_reclaim_stat-is-called-from-page-fault-path
+++ a/mm/memory.c
@@ -2507,6 +2507,8 @@ static int do_swap_page(struct mm_struct
try_to_free_swap(page);
unlock_page(page);
+ update_page_reclaim_stat(page);
+
if (write_access) {
ret |= do_wp_page(mm, vma, address, page_table, pmd, ptl, pte);
if (ret & VM_FAULT_ERROR)
diff -puN mm/swap.c~mm-update_page_reclaim_stat-is-called-from-page-fault-path mm/swap.c
--- a/mm/swap.c~mm-update_page_reclaim_stat-is-called-from-page-fault-path
+++ a/mm/swap.c
@@ -151,8 +151,9 @@ void rotate_reclaimable_page(struct pag
}
}
-static void update_page_reclaim_stat(struct zone *zone, struct page *page,
- int file, int rotated)
+static void update_page_reclaim_stat_locked(struct zone *zone,
+ struct page *page,
+ int file, int rotated)
{
struct zone_reclaim_stat *reclaim_stat = &zone->reclaim_stat;
struct zone_reclaim_stat *memcg_reclaim_stat;
@@ -171,6 +172,19 @@ static void update_page_reclaim_stat(str
memcg_reclaim_stat->recent_rotated[file]++;
}
+void update_page_reclaim_stat(struct page *page)
+{
+ struct zone *zone = page_zone(page);
+
+ spin_lock_irq(&zone->lru_lock);
+ /* if the page isn't reclaimable, it doesn't update reclaim stat */
+ if (PageLRU(page) && !PageUnevictable(page)) {
+ update_page_reclaim_stat_locked(zone, page,
+ !!page_is_file_cache(page), 1);
+ }
+ spin_unlock_irq(&zone->lru_lock);
+}
+
/*
* FIXME: speed this up?
*/
@@ -182,14 +196,14 @@ void activate_page(struct page *page)
if (PageLRU(page) && !PageActive(page) && !PageUnevictable(page)) {
int file = page_is_file_cache(page);
int lru = LRU_BASE + file;
- del_page_from_lru_list(zone, page, lru);
+ del_page_from_lru_list(zone, page, lru);
SetPageActive(page);
lru += LRU_ACTIVE;
add_page_to_lru_list(zone, page, lru);
__count_vm_event(PGACTIVATE);
- update_page_reclaim_stat(zone, page, !!file, 1);
+ update_page_reclaim_stat_locked(zone, page, !!file, 1);
}
spin_unlock_irq(&zone->lru_lock);
}
@@ -427,7 +441,7 @@ void ____pagevec_lru_add(struct pagevec
file = is_file_lru(lru);
if (active)
SetPageActive(page);
- update_page_reclaim_stat(zone, page, file, active);
+ update_page_reclaim_stat_locked(zone, page, file, active);
add_page_to_lru_list(zone, page, lru);
}
if (zone)
_
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