jbd2: add COW fields to struct jbd2_journal_handle

Add fields needed for the copy-on-write ext4 development work.

The h_cowing flag is used by ext4 snapshots code to mark the task in
COWING state.

The h_XXX_credits fields are used to track buffer credits usage
(accounted by COW and non-COW operations).

The h_cow_XXX fields are used as per task debugging counters.

Merging this commit into mainline will allow users to test ext4
snapshots as a standalone module, without the need to patch and
install a development kernel.

Signed-off-by: Amir Goldstein <amir73il@users.sf.net>
Signed-off-by: "Theodore Ts'o" <tytso@mit.edu>

1 files changed, 25 insertions, 3 deletions

diff --git a/include/linux/jbd2.h b/include/linux/jbd2.h
index 27e79c27ba08..a32dcaec04e1 100644
--- a/include/linux/jbd2.h
+++ b/include/linux/jbd2.h
@@ -432,13 +432,35 @@ struct jbd2_journal_handle
         int                     h_err;
 
         /* Flags [no locking] */
-        unsigned int    h_sync:         1;      /* sync-on-close */
-        unsigned int    h_jdata:        1;      /* force data journaling */
-        unsigned int    h_aborted:      1;      /* fatal error on handle */
+        unsigned int    h_sync:1;       /* sync-on-close */
+        unsigned int    h_jdata:1;      /* force data journaling */
+        unsigned int    h_aborted:1;    /* fatal error on handle */
+        unsigned int    h_cowing:1;     /* COWing block to snapshot */
+
+        /* Number of buffers requested by user:
+         * (before adding the COW credits factor) */
+        unsigned int    h_base_credits:14;
+
+        /* Number of buffers the user is allowed to dirty:
+         * (counts only buffers dirtied when !h_cowing) */
+        unsigned int    h_user_credits:14;
+
 
 #ifdef CONFIG_DEBUG_LOCK_ALLOC
         struct lockdep_map      h_lockdep_map;
 #endif
+
+#ifdef CONFIG_JBD2_DEBUG
+        /* COW debugging counters: */
+        unsigned int h_cow_moved; /* blocks moved to snapshot */
+        unsigned int h_cow_copied; /* blocks copied to snapshot */
+        unsigned int h_cow_ok_jh; /* blocks already COWed during current
+                                     transaction */
+        unsigned int h_cow_ok_bitmap; /* blocks not set in COW bitmap */
+        unsigned int h_cow_ok_mapped;/* blocks already mapped in snapshot */
+        unsigned int h_cow_bitmaps; /* COW bitmaps created */
+        unsigned int h_cow_excluded; /* blocks set in exclude bitmap */
+#endif
 };