[PATCH] truncate/invalidate_inode_pages rewrite

Rewrite these functions to use gang lookup.

- This probably has similar performance to the old code in the common case.

- It will be vastly quicker than current code for the worst case
  (single-page truncate).

- invalidate_inode_pages() has been changed.  It used to use
  page_count(page) as the "is it mapped into pagetables" heuristic.  It
  now uses the (page->pte.direct != 0) heuristic.

- Removes the worst cause of scheduling latency in the kernel.

- It's a big code cleanup.

- invalidate_inode_pages() has been changed to take an address_space
  *, not an inode *.

- the maximum hold times for mapping->page_lock are enormously reduced,
  making it quite feasible to turn this into an irq-safe lock.  Which, it
  seems, is a requirement for sane AIO<->direct-io integration, as well
  as possibly other AIO things.

(Thanks Hugh for fixing a bug in this one as well).

(Christoph added some stuff too)

3 files changed, 7 insertions, 1 deletions

diff --git a/include/linux/fs.h b/include/linux/fs.h
index 56f2bab87d7f..f0ba1e96325c 100644
--- a/include/linux/fs.h
+++ b/include/linux/fs.h
@@ -1140,7 +1140,7 @@ extern int full_check_disk_change(struct block_device *);
 extern int __check_disk_change(dev_t);
 extern int invalidate_inodes(struct super_block *);
 extern int invalidate_device(kdev_t, int);
-extern void invalidate_inode_pages(struct inode *);
+extern void invalidate_inode_pages(struct address_space *mapping);
 extern void invalidate_inode_pages2(struct address_space *mapping);
 extern void write_inode_now(struct inode *, int);
 extern int filemap_fdatawrite(struct address_space *);
diff --git a/include/linux/pagemap.h b/include/linux/pagemap.h
index bfc986131fe6..1fe640eaf601 100644
--- a/include/linux/pagemap.h
+++ b/include/linux/pagemap.h
@@ -41,6 +41,9 @@ extern struct page * find_trylock_page(struct address_space *mapping,
 				unsigned long index);
 extern struct page * find_or_create_page(struct address_space *mapping,
 				unsigned long index, unsigned int gfp_mask);
+extern unsigned int find_get_pages(struct address_space *mapping,
+				pgoff_t start, unsigned int nr_pages,
+				struct page **pages);
 
 /*
  * Returns locked page at given index in given cache, creating it if needed.
diff --git a/include/linux/pagevec.h b/include/linux/pagevec.h
index 278689b2fb2a..0207270b0fe7 100644
--- a/include/linux/pagevec.h
+++ b/include/linux/pagevec.h
@@ -8,6 +8,7 @@
 #define PAGEVEC_SIZE	16
 
 struct page;
+struct address_space;
 
 struct pagevec {
 	unsigned nr;
@@ -21,6 +22,8 @@ void __pagevec_lru_add(struct pagevec *pvec);
 void lru_add_drain(void);
 void pagevec_deactivate_inactive(struct pagevec *pvec);
 void pagevec_strip(struct pagevec *pvec);
+unsigned int pagevec_lookup(struct pagevec *pvec, struct address_space *mapping,
+		pgoff_t start, unsigned int nr_pages);
 
 static inline void pagevec_init(struct pagevec *pvec)
 {