The patch titled
Ramfs and Ram Disk pages are unevictable
has been added to the -mm tree. Its filename is
ramfs-and-ram-disk-pages-are-unevictable.patch
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The current -mm tree may be found at http://userweb.kernel.org/~akpm/mmotm/
------------------------------------------------------
Subject: Ramfs and Ram Disk pages are unevictable
From: Lee Schermerhorn <Lee.Schermerhorn@xxxxxx>
Christoph Lameter pointed out that ram disk pages also clutter the LRU
lists. When vmscan finds them dirty and tries to clean them, the ram disk
writeback function just redirties the page so that it goes back onto the
active list. Round and round she goes...
Define new address_space flag [shares address_space flags member with
mapping's gfp mask] to indicate that the address space contains all
unevictable pages. This will provide for efficient testing of ramdisk
pages in page_evictable().
Also provide wrapper functions to set/test the unevictable state to
minimize #ifdefs in ramdisk driver and any other users of this facility.
Set the unevictable state on address_space structures for new ramdisk
inodes. Test the unevictable state in page_evictable() to cull
unevictable pages.
Similarly, ramfs pages are unevictable. Set the 'unevictable'
address_space flag for new ramfs inodes.
These changes depend on [CONFIG_]UNEVICTABLE_LRU.
Signed-off-by: Lee Schermerhorn <lee.schermerhorn@xxxxxx>
Signed-off-by: Rik van Riel <riel@xxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
drivers/block/brd.c | 13 +++++++++++++
fs/ramfs/inode.c | 1 +
include/linux/pagemap.h | 22 ++++++++++++++++++++++
mm/vmscan.c | 5 +++++
4 files changed, 41 insertions(+)
diff -puN drivers/block/brd.c~ramfs-and-ram-disk-pages-are-unevictable drivers/block/brd.c
--- a/drivers/block/brd.c~ramfs-and-ram-disk-pages-are-unevictable
+++ a/drivers/block/brd.c
@@ -374,8 +374,21 @@ static int brd_ioctl(struct inode *inode
return error;
}
+/*
+ * brd_open():
+ * Just mark the mapping as containing unevictable pages
+ */
+static int brd_open(struct inode *inode, struct file *filp)
+{
+ struct address_space *mapping = inode->i_mapping;
+
+ mapping_set_unevictable(mapping);
+ return 0;
+}
+
static struct block_device_operations brd_fops = {
.owner = THIS_MODULE,
+ .open = brd_open,
.ioctl = brd_ioctl,
#ifdef CONFIG_BLK_DEV_XIP
.direct_access = brd_direct_access,
diff -puN fs/ramfs/inode.c~ramfs-and-ram-disk-pages-are-unevictable fs/ramfs/inode.c
--- a/fs/ramfs/inode.c~ramfs-and-ram-disk-pages-are-unevictable
+++ a/fs/ramfs/inode.c
@@ -61,6 +61,7 @@ struct inode *ramfs_get_inode(struct sup
inode->i_mapping->a_ops = &ramfs_aops;
inode->i_mapping->backing_dev_info = &ramfs_backing_dev_info;
mapping_set_gfp_mask(inode->i_mapping, GFP_HIGHUSER);
+ mapping_set_unevictable(inode->i_mapping);
inode->i_atime = inode->i_mtime = inode->i_ctime = CURRENT_TIME;
switch (mode & S_IFMT) {
default:
diff -puN include/linux/pagemap.h~ramfs-and-ram-disk-pages-are-unevictable include/linux/pagemap.h
--- a/include/linux/pagemap.h~ramfs-and-ram-disk-pages-are-unevictable
+++ a/include/linux/pagemap.h
@@ -31,6 +31,28 @@ static inline void mapping_set_error(str
}
}
+#ifdef CONFIG_UNEVICTABLE_LRU
+#define AS_UNEVICTABLE (__GFP_BITS_SHIFT + 2) /* e.g., ramdisk, SHM_LOCK */
+
+static inline void mapping_set_unevictable(struct address_space *mapping)
+{
+ set_bit(AS_UNEVICTABLE, &mapping->flags);
+}
+
+static inline int mapping_unevictable(struct address_space *mapping)
+{
+ if (mapping && (mapping->flags & AS_UNEVICTABLE))
+ return 1;
+ return 0;
+}
+#else
+static inline void mapping_set_unevictable(struct address_space *mapping) { }
+static inline int mapping_unevictable(struct address_space *mapping)
+{
+ return 0;
+}
+#endif
+
static inline gfp_t mapping_gfp_mask(struct address_space * mapping)
{
return (__force gfp_t)mapping->flags & __GFP_BITS_MASK;
diff -puN mm/vmscan.c~ramfs-and-ram-disk-pages-are-unevictable mm/vmscan.c
--- a/mm/vmscan.c~ramfs-and-ram-disk-pages-are-unevictable
+++ a/mm/vmscan.c
@@ -2354,6 +2354,8 @@ int zone_reclaim(struct zone *zone, gfp_
* lists vs unevictable list.
*
* Reasons page might not be evictable:
+ * (1) page's mapping marked unevictable
+ *
* TODO - later patches
*/
int page_evictable(struct page *page, struct vm_area_struct *vma)
@@ -2361,6 +2363,9 @@ int page_evictable(struct page *page, st
VM_BUG_ON(PageUnevictable(page));
+ if (mapping_unevictable(page_mapping(page)))
+ return 0;
+
/* TODO: test page [!]evictable conditions */
return 1;
_
Patches currently in -mm which might be from Lee.Schermerhorn@xxxxxx are
vmscan-move-isolate_lru_page-to-vmscanc.patch
vmscan-free-swap-space-on-swap-in-activation.patch
vmscan-split-lru-lists-into-anon-file-sets.patch
unevictable-lru-infrastructure.patch
unevictable-lru-page-statistics.patch
ramfs-and-ram-disk-pages-are-unevictable.patch
shm_locked-pages-are-unevictable.patch
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