Ramfs and Ram Disk pages are unevictable (ba9ddf49) · Commits · 戴 / test

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... With the ram disk driver [rd.c] replaced by the newer 'brd.c', this is no longer the case, as ram disk pages are no longer maintained on the lru. [This makes them unmigratable for defrag or memory hot remove, but that can be addressed by a separate patch series.] However, the ramfs pages behave like ram disk pages used to, so: 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 ramfs pages in page_evictable(). Also provide wrapper functions to set/test the unevictable state to minimize #ifdefs in ramfs driver and any other users of this facility. Set the unevictable state on address_space structures for new ramfs inodes. Test the unevictable state in page_evictable() to cull unevictable pages. These changes depend on [CONFIG_]UNEVICTABLE_LRU. [riel@redhat.com: undo the brd.c part] Signed-off-by:

Lee Schermerhorn <lee.schermerhorn@hp.com> Signed-off-by:

Rik van Riel <riel@redhat.com> Debugged-by:

Nick Piggin <nickpiggin@yahoo.com.au> Signed-off-by:

Andrew Morton <akpm@linux-foundation.org> Signed-off-by:

Linus Torvalds <torvalds@linux-foundation.org>

fs/ramfs/inode.c

+1 −0

Original line number	Diff line number	Diff line
		@@ -61,6 +61,7 @@ struct inode ramfs_get_inode(struct super_block sb, int mode, dev_t dev)
		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:

include/linux/pagemap.h

+22 −0

Original line number	Diff line number	Diff line
		@@ -32,6 +32,28 @@ static inline void mapping_set_error(struct address_space *mapping, int error)
		}
		}

		#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;

mm/vmscan.c

+5 −0

Original line number	Diff line number	Diff line
		@@ -2332,11 +2332,16 @@ int zone_reclaim(struct zone *zone, gfp_t gfp_mask, unsigned int order)
		* 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)
		{

		if (mapping_unevictable(page_mapping(page)))
		return 0;

		/* TODO: test page [!]evictable conditions */

		return 1;

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