mm: implement ->map_pages for page cache

filemap_map_pages() is generic implementation of ->map_pages() for
filesystems who uses page cache.

It should be safe to use filemap_map_pages() for ->map_pages() if
filesystem use filemap_fault() for ->fault().

Signed-off-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
Acked-by: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Mel Gorman <mgorman@suse.de>
Cc: Rik van Riel <riel@redhat.com>
Cc: Andi Kleen <ak@linux.intel.com>
Cc: Matthew Wilcox <matthew.r.wilcox@intel.com>
Cc: Dave Hansen <dave.hansen@linux.intel.com>
Cc: Alexander Viro <viro@zeniv.linux.org.uk>
Cc: Dave Chinner <david@fromorbit.com>
Cc: Ning Qu <quning@gmail.com>
Cc: Hugh Dickins <hughd@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

1 files changed, 74 insertions, 0 deletions

diff --git a/mm/filemap.c b/mm/filemap.c
index 21781f1fe52b..3f9b5fbb623f 100644
--- a/mm/filemap.c
+++ b/mm/filemap.c
@@ -33,6 +33,7 @@
 #include <linux/hardirq.h> /* for BUG_ON(!in_atomic()) only */
 #include <linux/memcontrol.h>
 #include <linux/cleancache.h>
+#include <linux/rmap.h>
 #include "internal.h"
 
 #define CREATE_TRACE_POINTS
@@ -2064,6 +2065,78 @@ page_not_uptodate:
 }
 EXPORT_SYMBOL(filemap_fault);
 
+void filemap_map_pages(struct vm_area_struct *vma, struct vm_fault *vmf)
+{
+        struct radix_tree_iter iter;
+        void **slot;
+        struct file *file = vma->vm_file;
+        struct address_space *mapping = file->f_mapping;
+        loff_t size;
+        struct page *page;
+        unsigned long address = (unsigned long) vmf->virtual_address;
+        unsigned long addr;
+        pte_t *pte;
+
+        rcu_read_lock();
+        radix_tree_for_each_slot(slot, &mapping->page_tree, &iter, vmf->pgoff) {
+                if (iter.index > vmf->max_pgoff)
+                        break;
+repeat:
+                page = radix_tree_deref_slot(slot);
+                if (unlikely(!page))
+                        goto next;
+                if (radix_tree_exception(page)) {
+                        if (radix_tree_deref_retry(page))
+                                break;
+                        else
+                                goto next;
+                }
+
+                if (!page_cache_get_speculative(page))
+                        goto repeat;
+
+                /* Has the page moved? */
+                if (unlikely(page != *slot)) {
+                        page_cache_release(page);
+                        goto repeat;
+                }
+
+                if (!PageUptodate(page) ||
+                                PageReadahead(page) ||
+                                PageHWPoison(page))
+                        goto skip;
+                if (!trylock_page(page))
+                        goto skip;
+
+                if (page->mapping != mapping || !PageUptodate(page))
+                        goto unlock;
+
+                size = i_size_read(mapping->host) + PAGE_CACHE_SIZE - 1;
+                if (page->index >= size >> PAGE_CACHE_SHIFT)
+                        goto unlock;
+
+                pte = vmf->pte + page->index - vmf->pgoff;
+                if (!pte_none(*pte))
+                        goto unlock;
+
+                if (file->f_ra.mmap_miss > 0)
+                        file->f_ra.mmap_miss--;
+                addr = address + (page->index - vmf->pgoff) * PAGE_SIZE;
+                do_set_pte(vma, addr, page, pte, false, false);
+                unlock_page(page);
+                goto next;
+unlock:
+                unlock_page(page);
+skip:
+                page_cache_release(page);
+next:
+                if (iter.index == vmf->max_pgoff)
+                        break;
+        }
+        rcu_read_unlock();
+}
+EXPORT_SYMBOL(filemap_map_pages);
+
 int filemap_page_mkwrite(struct vm_area_struct *vma, struct vm_fault *vmf)
 {
         struct page *page = vmf->page;
@@ -2093,6 +2166,7 @@ EXPORT_SYMBOL(filemap_page_mkwrite);
 
 const struct vm_operations_struct generic_file_vm_ops = {
         .fault          = filemap_fault,
+        .map_pages      = filemap_map_pages,
         .page_mkwrite   = filemap_page_mkwrite,
         .remap_pages    = generic_file_remap_pages,
 };