There is a typo in gfs2_page_mkwrite()
gfs2_write_alloc_required() expects pos to be the offset in bytes. However,
instead of the page index being shifted by by PAGE_CACHE_SHIFT, it was shifted
by (PAGE_CACHE_SIZE - inode->i_blkbits).  This patch simply shifts the page
index by the proper amount.
Signed-off-by: Benjamin Marzinski <bmarzins@redhat.com>
Signed-off-by: Steven Whitehouse <swhiteho@redhat.com>
        struct gfs2_inode *ip = GFS2_I(inode);
        struct gfs2_sbd *sdp = GFS2_SB(inode);
        unsigned long last_index;
-       u64 pos = page->index << (PAGE_CACHE_SIZE - inode->i_blkbits);
+       u64 pos = page->index << PAGE_CACHE_SHIFT;
        unsigned int data_blocks, ind_blocks, rblocks;
        int alloc_required = 0;
        struct gfs2_holder gh;