ext4: Use new buffer_head flag to check uninit group bitmaps initialization

For uninit block group, the on-disk bitmap is not initialized. That
implies we cannot depend on the uptodate flag on the bitmap
buffer_head to find bitmap validity.  Use a new buffer_head flag which
would be set after we properly initialize the bitmap.  This also
prevents (re-)initializing the uninit group bitmap every time we call 
ext4_read_block_bitmap().

Signed-off-by: Aneesh Kumar K.V <aneesh.kumar@linux.vnet.ibm.com>
Signed-off-by: "Theodore Ts'o" <tytso@mit.edu>
Cc: stable@kernel.org

1 files changed, 22 insertions, 2 deletions

diff --git a/fs/ext4/mballoc.c b/fs/ext4/mballoc.c
index aac33590ac64..18a52d39d094 100644
--- a/fs/ext4/mballoc.c
+++ b/fs/ext4/mballoc.c
@@ -794,22 +794,42 @@ static int ext4_mb_init_cache(struct page *page, char *incore)
                 if (bh[i] == NULL)
                         goto out;
 
-                if (buffer_uptodate(bh[i]) &&
-                    !(desc->bg_flags & cpu_to_le16(EXT4_BG_BLOCK_UNINIT)))
+                if (bitmap_uptodate(bh[i]))
                         continue;
 
                 lock_buffer(bh[i]);
+                if (bitmap_uptodate(bh[i])) {
+                        unlock_buffer(bh[i]);
+                        continue;
+                }
                 spin_lock(sb_bgl_lock(EXT4_SB(sb), first_group + i));
                 if (desc->bg_flags & cpu_to_le16(EXT4_BG_BLOCK_UNINIT)) {
                         ext4_init_block_bitmap(sb, bh[i],
                                                 first_group + i, desc);
+                        set_bitmap_uptodate(bh[i]);
                         set_buffer_uptodate(bh[i]);
                         spin_unlock(sb_bgl_lock(EXT4_SB(sb), first_group + i));
                         unlock_buffer(bh[i]);
                         continue;
                 }
                 spin_unlock(sb_bgl_lock(EXT4_SB(sb), first_group + i));
+                if (buffer_uptodate(bh[i])) {
+                        /*
+                         * if not uninit if bh is uptodate,
+                         * bitmap is also uptodate
+                         */
+                        set_bitmap_uptodate(bh[i]);
+                        unlock_buffer(bh[i]);
+                        continue;
+                }
                 get_bh(bh[i]);
+                /*
+                 * submit the buffer_head for read. We can
+                 * safely mark the bitmap as uptodate now.
+                 * We do it here so the bitmap uptodate bit
+                 * get set with buffer lock held.
+                 */
+                set_bitmap_uptodate(bh[i]);
                 bh[i]->b_end_io = end_buffer_read_sync;
                 submit_bh(READ, bh[i]);
                 mb_debug("read bitmap for group %u\n", first_group + i);