[PATCH] reiserfs_write_full_page() should not get_block past eof

reiserfs_write_full_page does zero bytes in the file past eof, but it may
call get_block on those buffers as well.  On machines where the page size
is larger than the blocksize, this can result in mmaped files incorrectly
growing up to a block boundary during writepage.

The fix is to avoid calling get_block for any blocks that are entirely past
eof

Signed-off-by: Chris Mason <mason@suse.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

1 files changed, 12 insertions, 2 deletions

diff --git a/fs/reiserfs/inode.c b/fs/reiserfs/inode.c
index ac57305b1afc..52f1e2136546 100644
--- a/fs/reiserfs/inode.c
+++ b/fs/reiserfs/inode.c
@@ -2340,6 +2340,7 @@ static int reiserfs_write_full_page(struct page *page,
         unsigned long end_index = inode->i_size >> PAGE_CACHE_SHIFT;
         int error = 0;
         unsigned long block;
+        sector_t last_block;
         struct buffer_head *head, *bh;
         int partial = 0;
         int nr = 0;
@@ -2387,10 +2388,19 @@ static int reiserfs_write_full_page(struct page *page,
         }
         bh = head;
         block = page->index << (PAGE_CACHE_SHIFT - s->s_blocksize_bits);
+        last_block = (i_size_read(inode) - 1) >> inode->i_blkbits;
         /* first map all the buffers, logging any direct items we find */
         do {
-                if ((checked || buffer_dirty(bh)) && (!buffer_mapped(bh) ||
-                                                      (buffer_mapped(bh)
+                if (block > last_block) {
+                        /*
+                         * This can happen when the block size is less than
+                         * the page size.  The corresponding bytes in the page
+                         * were zero filled above
+                         */
+                        clear_buffer_dirty(bh);
+                        set_buffer_uptodate(bh);
+                } else if ((checked || buffer_dirty(bh)) &&
+                           (!buffer_mapped(bh) || (buffer_mapped(bh)
                                                        && bh->b_blocknr ==
                                                        0))) {
                         /* not mapped yet, or it points to a direct item, search