1 files changed, 77 insertions, 1 deletions

diff --git a/fs/gfs2/bmap.c b/fs/gfs2/bmap.c
index 72b19c5d7807..d20d41e1c028 100644
--- a/fs/gfs2/bmap.c
+++ b/fs/gfs2/bmap.c
@@ -22,12 +22,12 @@
 #include "glock.h"
 #include "inode.h"
 #include "meta_io.h"
-#include "page.h"
 #include "quota.h"
 #include "rgrp.h"
 #include "trans.h"
 #include "dir.h"
 #include "util.h"
+#include "ops_address.h"
 
 /* This doesn't need to be that large as max 64 bit pointers in a 4k
  * block is 512, so __u16 is fine for that. It saves stack space to
@@ -885,6 +885,82 @@ static int do_grow(struct gfs2_inode *ip, uint64_t size)
         return error;
 }
 
+
+/**
+ * gfs2_block_truncate_page - Deal with zeroing out data for truncate
+ *
+ * This is partly borrowed from ext3.
+ */
+static int gfs2_block_truncate_page(struct address_space *mapping)
+{
+        struct inode *inode = mapping->host;
+        struct gfs2_inode *ip = GFS2_I(inode);
+        struct gfs2_sbd *sdp = GFS2_SB(inode);
+        loff_t from = inode->i_size;
+        unsigned long index = from >> PAGE_CACHE_SHIFT;
+        unsigned offset = from & (PAGE_CACHE_SIZE-1);
+        unsigned blocksize, iblock, length, pos;
+        struct buffer_head *bh;
+        struct page *page;
+        void *kaddr;
+        int err;
+
+        page = grab_cache_page(mapping, index);
+        if (!page)
+                return 0;
+
+        blocksize = inode->i_sb->s_blocksize;
+        length = blocksize - (offset & (blocksize - 1));
+        iblock = index << (PAGE_CACHE_SHIFT - inode->i_sb->s_blocksize_bits);
+
+        if (!page_has_buffers(page))
+                create_empty_buffers(page, blocksize, 0);
+
+        /* Find the buffer that contains "offset" */
+        bh = page_buffers(page);
+        pos = blocksize;
+        while (offset >= pos) {
+                bh = bh->b_this_page;
+                iblock++;
+                pos += blocksize;
+        }
+
+        err = 0;
+
+        if (!buffer_mapped(bh)) {
+                gfs2_get_block(inode, iblock, bh, 0);
+                /* unmapped? It's a hole - nothing to do */
+                if (!buffer_mapped(bh))
+                        goto unlock;
+        }
+
+        /* Ok, it's mapped. Make sure it's up-to-date */
+        if (PageUptodate(page))
+                set_buffer_uptodate(bh);
+
+        if (!buffer_uptodate(bh)) {
+                err = -EIO;
+                ll_rw_block(READ, 1, &bh);
+                wait_on_buffer(bh);
+                /* Uhhuh. Read error. Complain and punt. */
+                if (!buffer_uptodate(bh))
+                        goto unlock;
+        }
+
+        if (sdp->sd_args.ar_data == GFS2_DATA_ORDERED || gfs2_is_jdata(ip))
+                gfs2_trans_add_bh(ip->i_gl, bh, 0);
+
+        kaddr = kmap_atomic(page, KM_USER0);
+        memset(kaddr + offset, 0, length);
+        flush_dcache_page(page);
+        kunmap_atomic(kaddr, KM_USER0);
+
+unlock:
+        unlock_page(page);
+        page_cache_release(page);
+        return err;
+}
+
 static int trunc_start(struct gfs2_inode *ip, uint64_t size)
 {
         struct gfs2_sbd *sdp = GFS2_SB(&ip->i_inode);