[GFS2] Fix for mmap() bug in readpage

Fix for Red Hat bz 205307. Don't need to lock in readpage if
the higher level code has already grabbed the lock.

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

1 files changed, 5 insertions, 2 deletions

diff --git a/fs/gfs2/ops_address.c b/fs/gfs2/ops_address.c
index 6f9ac5e6e3f..25d7025e43c 100644
--- a/fs/gfs2/ops_address.c
+++ b/fs/gfs2/ops_address.c
@@ -218,14 +218,16 @@ static int gfs2_readpage(struct file *file, struct page *page)
 {
         struct gfs2_inode *ip = GFS2_I(page->mapping->host);
         struct gfs2_sbd *sdp = GFS2_SB(page->mapping->host);
+        struct gfs2_file *gf = NULL;
         struct gfs2_holder gh;
         int error;
         int do_unlock = 0;
 
         if (likely(file != &gfs2_internal_file_sentinel)) {
                 if (file) {
-                        struct gfs2_file *gf = file->private_data;
+                        gf = file->private_data;
                         if (test_bit(GFF_EXLOCK, &gf->f_flags))
+                                /* gfs2_sharewrite_nopage has grabbed the ip->i_gl already */
                                 goto skip_lock;
                 }
                 gfs2_holder_init(ip->i_gl, LM_ST_SHARED, GL_ATIME|GL_AOP, &gh);
@@ -245,7 +247,8 @@ skip_lock:
         if (unlikely(test_bit(SDF_SHUTDOWN, &sdp->sd_flags)))
                 error = -EIO;
 
-        if (file != &gfs2_internal_file_sentinel) {
+        if (gf && !test_bit(GFF_EXLOCK, &gf->f_flags) &&
+            file != &gfs2_internal_file_sentinel) {
                 gfs2_glock_dq_m(1, &gh);
                 gfs2_holder_uninit(&gh);
         }