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Subject[PATCH v2 12/12] mm: a few small updates for radix-swap
Remove PageSwapBacked (!page_is_file_cache) cases from
add_to_page_cache_locked() and add_to_page_cache_lru():
those pages now go through shmem_add_to_page_cache().

Remove a comment on maximum tmpfs size from fsstack_copy_inode_size(),
and add a comment on swap entries to invalidate_mapping_pages().

And mincore_page() uses find_get_page() on what might be shmem or a
tmpfs file: allow for a radix_tree_exceptional_entry(), and proceed to
find_get_page() on swapper_space if so (oh, swapper_space needs #ifdef).

v2: Fix NULL dereference I introduced in mincore_page().

Signed-off-by: Hugh Dickins <hughd@google.com>
---
fs/stack.c | 5 +----
mm/filemap.c | 21 +++------------------
mm/mincore.c | 10 ++++++----
mm/truncate.c | 8 ++++++++
4 files changed, 18 insertions(+), 26 deletions(-)
--- linux.orig/fs/stack.c 2011-06-14 01:22:10.768120780 -0700
+++ linux/fs/stack.c 2011-06-14 01:23:26.088494288 -0700
@@ -29,10 +29,7 @@ void fsstack_copy_inode_size(struct inod
*
* We don't actually know what locking is used at the lower level;
* but if it's a filesystem that supports quotas, it will be using
- * i_lock as in inode_add_bytes(). tmpfs uses other locking, and
- * its 32-bit is (just) able to exceed 2TB i_size with the aid of
- * holes; but its i_blocks cannot carry into the upper long without
- * almost 2TB swap - let's ignore that case.
+ * i_lock as in inode_add_bytes().
*/
if (sizeof(i_blocks) > sizeof(long))
spin_lock(&src->i_lock);
--- linux.orig/mm/filemap.c 2011-06-14 01:22:10.768120780 -0700
+++ linux/mm/filemap.c 2011-06-14 01:23:26.088494288 -0700
@@ -33,7 +33,6 @@
#include <linux/cpuset.h>
#include <linux/hardirq.h> /* for BUG_ON(!in_atomic()) only */
#include <linux/memcontrol.h>
-#include <linux/mm_inline.h> /* for page_is_file_cache() */
#include <linux/cleancache.h>
#include "internal.h"

@@ -465,6 +464,7 @@ int add_to_page_cache_locked(struct page
int error;

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

error = mem_cgroup_cache_charge(page, current->mm,
gfp_mask & GFP_RECLAIM_MASK);
@@ -482,8 +482,6 @@ int add_to_page_cache_locked(struct page
if (likely(!error)) {
mapping->nrpages++;
__inc_zone_page_state(page, NR_FILE_PAGES);
- if (PageSwapBacked(page))
- __inc_zone_page_state(page, NR_SHMEM);
spin_unlock_irq(&mapping->tree_lock);
} else {
page->mapping = NULL;
@@ -505,22 +503,9 @@ int add_to_page_cache_lru(struct page *p
{
int ret;

- /*
- * Splice_read and readahead add shmem/tmpfs pages into the page cache
- * before shmem_readpage has a chance to mark them as SwapBacked: they
- * need to go on the anon lru below, and mem_cgroup_cache_charge
- * (called in add_to_page_cache) needs to know where they're going too.
- */
- if (mapping_cap_swap_backed(mapping))
- SetPageSwapBacked(page);
-
ret = add_to_page_cache(page, mapping, offset, gfp_mask);
- if (ret == 0) {
- if (page_is_file_cache(page))
- lru_cache_add_file(page);
- else
- lru_cache_add_anon(page);
- }
+ if (ret == 0)
+ lru_cache_add_file(page);
return ret;
}
EXPORT_SYMBOL_GPL(add_to_page_cache_lru);
--- linux.orig/mm/mincore.c 2011-06-14 01:22:10.768120780 -0700
+++ linux/mm/mincore.c 2011-06-14 17:41:15.760211585 -0700
@@ -69,12 +69,14 @@ static unsigned char mincore_page(struct
* file will not get a swp_entry_t in its pte, but rather it is like
* any other file mapping (ie. marked !present and faulted in with
* tmpfs's .fault). So swapped out tmpfs mappings are tested here.
- *
- * However when tmpfs moves the page from pagecache and into swapcache,
- * it is still in core, but the find_get_page below won't find it.
- * No big deal, but make a note of it.
*/
page = find_get_page(mapping, pgoff);
+#ifdef CONFIG_SWAP
+ if (radix_tree_exceptional_entry(page)) {
+ swp_entry_t swap = radix_to_swp_entry(page);
+ page = find_get_page(&swapper_space, swap.val);
+ }
+#endif
if (page) {
present = PageUptodate(page);
page_cache_release(page);
--- linux.orig/mm/truncate.c 2011-06-14 01:22:10.768120780 -0700
+++ linux/mm/truncate.c 2011-06-14 01:23:26.092494303 -0700
@@ -331,6 +331,14 @@ unsigned long invalidate_mapping_pages(s
unsigned long count = 0;
int i;

+ /*
+ * Note: this function may get called on a shmem/tmpfs mapping:
+ * pagevec_lookup() might then return 0 prematurely (because it
+ * got a gangful of swap entries); but it's hardly worth worrying
+ * about - it can rarely have anything to free from such a mapping
+ * (most pages are dirty), and already skips over any difficulties.
+ */
+
pagevec_init(&pvec, 0);
while (index <= end && pagevec_lookup(&pvec, mapping, index,
min(end - index, (pgoff_t)PAGEVEC_SIZE - 1) + 1)) {

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