md: fix loading of out-of-date bitmap.

When md is loading a bitmap which it knows is out of date, it fills
each page with 1s and writes it back out again.  However the
write_page call makes used of bitmap->file_pages and
bitmap->last_page_size which haven't been set correctly yet.  So this
can sometimes fail.

Move the setting of file_pages and last_page_size to before the call
to write_page.

This bug can cause the assembly on an array to fail, thus making the
data inaccessible.  Hence I think it is a suitable candidate for
-stable.

Cc: stable@kernel.org
Reported-by: Vojtech Pavlik <vojtech@suse.cz>
Signed-off-by: NeilBrown <neilb@suse.de>

1 files changed, 4 insertions, 7 deletions

diff --git a/drivers/md/bitmap.c b/drivers/md/bitmap.c
index 1fb91edc7de2..bc1d64b7b63b 100644
--- a/drivers/md/bitmap.c
+++ b/drivers/md/bitmap.c
@@ -986,6 +986,9 @@ static int bitmap_init_from_disk(struct bitmap *bitmap, sector_t start)
                         oldindex = index;
                         oldpage = page;
 
+                        bitmap->filemap[bitmap->file_pages++] = page;
+                        bitmap->last_page_size = count;
+
                         if (outofdate) {
                                 /*
                                  * if bitmap is out of date, dirty the
@@ -998,15 +1001,9 @@ static int bitmap_init_from_disk(struct bitmap *bitmap, sector_t start)
                                 write_page(bitmap, page, 1);
 
                                 ret = -EIO;
-                                if (bitmap->flags & BITMAP_WRITE_ERROR) {
-                                        /* release, page not in filemap yet */
-                                        put_page(page);
+                                if (bitmap->flags & BITMAP_WRITE_ERROR)
                                         goto err;
-                                }
                         }
-
-                        bitmap->filemap[bitmap->file_pages++] = page;
-                        bitmap->last_page_size = count;
                 }
                 paddr = kmap_atomic(page, KM_USER0);
                 if (bitmap->flags & BITMAP_HOSTENDIAN)