[GFS2] Fix a size calculation error

Fix a size calculation error.
The size was incorrect being computed as a
negative length and then being passed to an
unsigned parameter.

This in turn would cause the allocator to
think it needed enough meta data to store
a gigabyte file for every file created.

Signed-off-by: Russell Cattelan <cattelan@redhat.com>
Signed-off-by: Steven Whitehouse <swhiteho@redhat.com>

1 files changed, 4 insertions, 2 deletions

diff --git a/fs/gfs2/ops_address.c b/fs/gfs2/ops_address.c
index 4fb743f4e4a4..bdf56cf66224 100644
--- a/fs/gfs2/ops_address.c
+++ b/fs/gfs2/ops_address.c
@@ -370,15 +370,17 @@ static int gfs2_prepare_write(struct file *file, struct page *page,
         loff_t pos = ((loff_t)page->index << PAGE_CACHE_SHIFT) + from;
         loff_t end = ((loff_t)page->index << PAGE_CACHE_SHIFT) + to;
         struct gfs2_alloc *al;
+        unsigned int write_len = to - from;
+
 
         gfs2_holder_init(ip->i_gl, LM_ST_EXCLUSIVE, GL_ATIME|GL_AOP, &ip->i_gh);
         error = gfs2_glock_nq_m_atime(1, &ip->i_gh);
         if (error)
                 goto out_uninit;
 
-        gfs2_write_calc_reserv(ip, to - from, &data_blocks, &ind_blocks);
+        gfs2_write_calc_reserv(ip, write_len, &data_blocks, &ind_blocks);
 
-        error = gfs2_write_alloc_required(ip, pos, from - to, &alloc_required);
+        error = gfs2_write_alloc_required(ip, pos, write_len, &alloc_required);
         if (error)
                 goto out_unlock;