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 aac33590ac6..18a52d39d09 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);