5 files changed, 75 insertions, 0 deletions

diff --git a/fs/nilfs2/mdt.c b/fs/nilfs2/mdt.c
index 0066468609da..532f85acf273 100644
--- a/fs/nilfs2/mdt.c
+++ b/fs/nilfs2/mdt.c
@@ -622,6 +622,72 @@ int nilfs_mdt_save_to_shadow_map(struct inode *inode)
         return ret;
 }
 
+int nilfs_mdt_freeze_buffer(struct inode *inode, struct buffer_head *bh)
+{
+        struct nilfs_shadow_map *shadow = NILFS_MDT(inode)->mi_shadow;
+        struct buffer_head *bh_frozen;
+        struct page *page;
+        int blkbits = inode->i_blkbits;
+        int ret = -ENOMEM;
+
+        page = grab_cache_page(&shadow->frozen_data, bh->b_page->index);
+        if (!page)
+                return ret;
+
+        if (!page_has_buffers(page))
+                create_empty_buffers(page, 1 << blkbits, 0);
+
+        bh_frozen = nilfs_page_get_nth_block(page, bh_offset(bh) >> blkbits);
+        if (bh_frozen) {
+                if (!buffer_uptodate(bh_frozen))
+                        nilfs_copy_buffer(bh_frozen, bh);
+                if (list_empty(&bh_frozen->b_assoc_buffers)) {
+                        list_add_tail(&bh_frozen->b_assoc_buffers,
+                                      &shadow->frozen_buffers);
+                        set_buffer_nilfs_redirected(bh);
+                } else {
+                        brelse(bh_frozen); /* already frozen */
+                }
+                ret = 0;
+        }
+        unlock_page(page);
+        page_cache_release(page);
+        return ret;
+}
+
+struct buffer_head *
+nilfs_mdt_get_frozen_buffer(struct inode *inode, struct buffer_head *bh)
+{
+        struct nilfs_shadow_map *shadow = NILFS_MDT(inode)->mi_shadow;
+        struct buffer_head *bh_frozen = NULL;
+        struct page *page;
+        int n;
+
+        page = find_lock_page(&shadow->frozen_data, bh->b_page->index);
+        if (page) {
+                if (page_has_buffers(page)) {
+                        n = bh_offset(bh) >> inode->i_blkbits;
+                        bh_frozen = nilfs_page_get_nth_block(page, n);
+                }
+                unlock_page(page);
+                page_cache_release(page);
+        }
+        return bh_frozen;
+}
+
+static void nilfs_release_frozen_buffers(struct nilfs_shadow_map *shadow)
+{
+        struct list_head *head = &shadow->frozen_buffers;
+        struct buffer_head *bh;
+
+        while (!list_empty(head)) {
+                bh = list_first_entry(head, struct buffer_head,
+                                      b_assoc_buffers);
+                list_del_init(&bh->b_assoc_buffers);
+                brelse(bh); /* drop ref-count to make it releasable */
+        }
+}
+
 /**
  * nilfs_mdt_restore_from_shadow_map - restore dirty pages and bmap state
  * @inode: inode of the metadata file
@@ -658,6 +724,7 @@ void nilfs_mdt_clear_shadow_map(struct inode *inode)
         struct nilfs_shadow_map *shadow = mi->mi_shadow;
 
         down_write(&mi->mi_sem);
+        nilfs_release_frozen_buffers(shadow);
         truncate_inode_pages(&shadow->frozen_data, 0);
         truncate_inode_pages(&shadow->frozen_btnodes, 0);
         up_write(&mi->mi_sem);
diff --git a/fs/nilfs2/mdt.h b/fs/nilfs2/mdt.h
index e7f0d158c527..e60bbfe899f1 100644
--- a/fs/nilfs2/mdt.h
+++ b/fs/nilfs2/mdt.h
@@ -100,6 +100,9 @@ int nilfs_mdt_setup_shadow_map(struct inode *inode,
 int nilfs_mdt_save_to_shadow_map(struct inode *inode);
 void nilfs_mdt_restore_from_shadow_map(struct inode *inode);
 void nilfs_mdt_clear_shadow_map(struct inode *inode);
+int nilfs_mdt_freeze_buffer(struct inode *inode, struct buffer_head *bh);
+struct buffer_head *nilfs_mdt_get_frozen_buffer(struct inode *inode,
+                                                struct buffer_head *bh);
 
 #define nilfs_mdt_mark_buffer_dirty(bh) nilfs_mark_buffer_dirty(bh)
 
diff --git a/fs/nilfs2/page.c b/fs/nilfs2/page.c
index 6384ac14c0c8..7083344ac881 100644
--- a/fs/nilfs2/page.c
+++ b/fs/nilfs2/page.c
@@ -131,6 +131,7 @@ void nilfs_forget_buffer(struct buffer_head *bh)
         lock_buffer(bh);
         clear_buffer_nilfs_volatile(bh);
         clear_buffer_nilfs_checked(bh);
+        clear_buffer_nilfs_redirected(bh);
         clear_buffer_dirty(bh);
         if (nilfs_page_buffers_clean(page))
                 __nilfs_clear_page_dirty(page);
@@ -483,6 +484,7 @@ void nilfs_clear_dirty_pages(struct address_space *mapping)
                                 clear_buffer_dirty(bh);
                                 clear_buffer_nilfs_volatile(bh);
                                 clear_buffer_nilfs_checked(bh);
+                                clear_buffer_nilfs_redirected(bh);
                                 clear_buffer_uptodate(bh);
                                 clear_buffer_mapped(bh);
                                 unlock_buffer(bh);
diff --git a/fs/nilfs2/page.h b/fs/nilfs2/page.h
index 6ec4f498fc2b..fb9e8a8a2038 100644
--- a/fs/nilfs2/page.h
+++ b/fs/nilfs2/page.h
@@ -35,12 +35,14 @@ enum {
         BH_NILFS_Node,
         BH_NILFS_Volatile,
         BH_NILFS_Checked,
+        BH_NILFS_Redirected,
 };
 
 BUFFER_FNS(NILFS_Allocated, nilfs_allocated)    /* nilfs private buffers */
 BUFFER_FNS(NILFS_Node, nilfs_node)              /* nilfs node buffers */
 BUFFER_FNS(NILFS_Volatile, nilfs_volatile)
 BUFFER_FNS(NILFS_Checked, nilfs_checked)        /* buffer is verified */
+BUFFER_FNS(NILFS_Redirected, nilfs_redirected)  /* redirected to a copy */
 
 
 void nilfs_mark_buffer_dirty(struct buffer_head *bh);
diff --git a/fs/nilfs2/segment.c b/fs/nilfs2/segment.c
index b75306d642c2..91dc0668ec83 100644
--- a/fs/nilfs2/segment.c
+++ b/fs/nilfs2/segment.c
@@ -1908,6 +1908,7 @@ static void nilfs_segctor_complete_write(struct nilfs_sc_info *sci)
                         set_buffer_uptodate(bh);
                         clear_buffer_dirty(bh);
                         clear_buffer_nilfs_volatile(bh);
+                        clear_buffer_nilfs_redirected(bh);
                         if (bh == segbuf->sb_super_root) {
                                 if (bh->b_page != bd_page) {
                                         end_page_writeback(bd_page);