ocfs2: shared writeable mmap

Implement cluster consistent shared writeable mappings using the
->page_mkwrite() callback.

Signed-off-by: Mark Fasheh <mark.fasheh@oracle.com>

1 files changed, 41 insertions, 15 deletions

diff --git a/fs/ocfs2/aops.c b/fs/ocfs2/aops.c
index fc723fb9c981..b8869fd0884f 100644
--- a/fs/ocfs2/aops.c
+++ b/fs/ocfs2/aops.c
@@ -1034,7 +1034,8 @@ out:
  */
 static int ocfs2_grab_pages_for_write(struct address_space *mapping,
                                       struct ocfs2_write_ctxt *wc,
-                                      u32 cpos, loff_t user_pos, int new)
+                                      u32 cpos, loff_t user_pos, int new,
+                                      struct page *mmap_page)
 {
         int ret = 0, i;
         unsigned long start, target_index, index;
@@ -1058,11 +1059,36 @@ static int ocfs2_grab_pages_for_write(struct address_space *mapping,
         for(i = 0; i < wc->w_num_pages; i++) {
                 index = start + i;
 
-                wc->w_pages[i] = find_or_create_page(mapping, index, GFP_NOFS);
-                if (!wc->w_pages[i]) {
-                        ret = -ENOMEM;
-                        mlog_errno(ret);
-                        goto out;
+                if (index == target_index && mmap_page) {
+                        /*
+                         * ocfs2_pagemkwrite() is a little different
+                         * and wants us to directly use the page
+                         * passed in.
+                         */
+                        lock_page(mmap_page);
+
+                        if (mmap_page->mapping != mapping) {
+                                unlock_page(mmap_page);
+                                /*
+                                 * Sanity check - the locking in
+                                 * ocfs2_pagemkwrite() should ensure
+                                 * that this code doesn't trigger.
+                                 */
+                                ret = -EINVAL;
+                                mlog_errno(ret);
+                                goto out;
+                        }
+
+                        page_cache_get(mmap_page);
+                        wc->w_pages[i] = mmap_page;
+                } else {
+                        wc->w_pages[i] = find_or_create_page(mapping, index,
+                                                             GFP_NOFS);
+                        if (!wc->w_pages[i]) {
+                                ret = -ENOMEM;
+                                mlog_errno(ret);
+                                goto out;
+                        }
                 }
 
                 if (index == target_index)
@@ -1213,10 +1239,10 @@ static void ocfs2_set_target_boundaries(struct ocfs2_super *osb,
         }
 }
 
-static int ocfs2_write_begin_nolock(struct address_space *mapping,
-                                    loff_t pos, unsigned len, unsigned flags,
-                                    struct page **pagep, void **fsdata,
-                                    struct buffer_head *di_bh)
+int ocfs2_write_begin_nolock(struct address_space *mapping,
+                             loff_t pos, unsigned len, unsigned flags,
+                             struct page **pagep, void **fsdata,
+                             struct buffer_head *di_bh, struct page *mmap_page)
 {
         int ret, i, credits = OCFS2_INODE_UPDATE_CREDITS;
         unsigned int num_clusters = 0, clusters_to_alloc = 0;
@@ -1318,7 +1344,7 @@ static int ocfs2_write_begin_nolock(struct address_space *mapping,
          * extent.
          */
         ret = ocfs2_grab_pages_for_write(mapping, wc, wc->w_cpos, pos,
-                                         clusters_to_alloc);
+                                         clusters_to_alloc, mmap_page);
         if (ret) {
                 mlog_errno(ret);
                 goto out_commit;
@@ -1386,7 +1412,7 @@ int ocfs2_write_begin(struct file *file, struct address_space *mapping,
         }
 
         ret = ocfs2_write_begin_nolock(mapping, pos, len, flags, pagep,
-                                       fsdata, di_bh);
+                                       fsdata, di_bh, NULL);
         if (ret) {
                 mlog_errno(ret);
                 goto out_fail_data;
@@ -1407,9 +1433,9 @@ out_fail:
         return ret;
 }
 
-static int ocfs2_write_end_nolock(struct address_space *mapping,
-                                  loff_t pos, unsigned len, unsigned copied,
-                                  struct page *page, void *fsdata)
+int ocfs2_write_end_nolock(struct address_space *mapping,
+                           loff_t pos, unsigned len, unsigned copied,
+                           struct page *page, void *fsdata)
 {
         int i;
         unsigned from, to, start = pos & (PAGE_CACHE_SIZE - 1);