ext4: Clean up ext4_get_blocks() so it does not depend on bh_result->b_state

The ext4_get_blocks() function was depending on the value of
bh_result->b_state as an input parameter to decide whether or not
update the delalloc accounting statistics by calling
ext4_da_update_reserve_space().  We now use a separate flag,
EXT4_GET_BLOCKS_UPDATE_RESERVE_SPACE, to requests this update, so that
all callers of ext4_get_blocks() can clear map_bh.b_state before
calling ext4_get_blocks() without worrying about any consistency
issues.

Signed-off-by: "Theodore Ts'o" <tytso@mit.edu>

2 files changed, 41 insertions, 30 deletions

diff --git a/fs/ext4/ext4.h b/fs/ext4/ext4.h
index 17feb4ac633a..d164f1294e5f 100644
--- a/fs/ext4/ext4.h
+++ b/fs/ext4/ext4.h
@@ -318,16 +318,21 @@ struct ext4_new_group_data {
  */
         /* Allocate any needed blocks and/or convert an unitialized
            extent to be an initialized ext4 */
-#define EXT4_GET_BLOCKS_CREATE                  1
+#define EXT4_GET_BLOCKS_CREATE                  0x0001
         /* Request the creation of an unitialized extent */
-#define EXT4_GET_BLOCKS_UNINIT_EXT              2
+#define EXT4_GET_BLOCKS_UNINIT_EXT              0x0002
 #define EXT4_GET_BLOCKS_CREATE_UNINIT_EXT       (EXT4_GET_BLOCKS_UNINIT_EXT|\
                                                  EXT4_GET_BLOCKS_CREATE)
         /* Update the ext4_inode_info i_disksize field */
-#define EXT4_GET_BLOCKS_EXTEND_DISKSIZE         4
+#define EXT4_GET_BLOCKS_EXTEND_DISKSIZE         0x0004
         /* Caller is from the delayed allocation writeout path,
-           so the filesystem blocks have already been accounted for */
-#define EXT4_GET_BLOCKS_DELALLOC_RESERVE        8
+           so set the magic i_delalloc_reserve_flag after taking the 
+           inode allocation semaphore for */
+#define EXT4_GET_BLOCKS_DELALLOC_RESERVE        0x0008
+        /* Call ext4_da_update_reserve_space() after successfully 
+           allocating the blocks */
+#define EXT4_GET_BLOCKS_UPDATE_RESERVE_SPACE    0x0010
+
 
 /*
  * ioctl commands
diff --git a/fs/ext4/inode.c b/fs/ext4/inode.c
index bfe50a22363b..d7b7480682b9 100644
--- a/fs/ext4/inode.c
+++ b/fs/ext4/inode.c
@@ -1234,16 +1234,15 @@ int ext4_get_blocks(handle_t *handle, struct inode *inode, sector_t block,
                 }
         }
 
-        if (flags & EXT4_GET_BLOCKS_DELALLOC_RESERVE) {
+        if (flags & EXT4_GET_BLOCKS_DELALLOC_RESERVE)
                 EXT4_I(inode)->i_delalloc_reserved_flag = 0;
-                /*
-                 * Update reserved blocks/metadata blocks
-                 * after successful block allocation
-                 * which were deferred till now
-                 */
-                if ((retval > 0) && buffer_delay(bh))
-                        ext4_da_update_reserve_space(inode, retval);
-        }
+
+        /*
+         * Update reserved blocks/metadata blocks after successful
+         * block allocation which had been deferred till now.
+         */
+        if ((retval > 0) && (flags & EXT4_GET_BLOCKS_UPDATE_RESERVE_SPACE))
+                ext4_da_update_reserve_space(inode, retval);
 
         up_write((&EXT4_I(inode)->i_data_sem));
         return retval;
@@ -2015,7 +2014,7 @@ static void ext4_print_free_blocks(struct inode *inode)
  */
 static int mpage_da_map_blocks(struct mpage_da_data *mpd)
 {
-        int err, blks;
+        int err, blks, get_blocks_flags;
         struct buffer_head new;
         sector_t next = mpd->b_blocknr;
         unsigned max_blocks = mpd->b_size >> mpd->inode->i_blkbits;
@@ -2040,23 +2039,30 @@ static int mpage_da_map_blocks(struct mpage_da_data *mpd)
         BUG_ON(!handle);
 
         /*
-         * We need to make sure the BH_Delay flag is passed down to
-         * ext4_da_get_block_write(), since it calls ext4_get_blocks()
-         * with the EXT4_GET_BLOCKS_DELALLOC_RESERVE flag.  This flag
-         * causes ext4_get_blocks() to call
-         * ext4_da_update_reserve_space() if the passed buffer head
-         * has the BH_Delay flag set.  In the future, once we clean up
-         * the interfaces to ext4_get_blocks(), we should pass in a
-         * separate flag which requests that the delayed allocation
-         * statistics should be updated, instead of depending on the
-         * state information getting passed down via the map_bh's
-         * state bitmasks plus the magic
-         * EXT4_GET_BLOCKS_DELALLOC_RESERVE flag.
+         * Call ext4_get_blocks() to allocate any delayed allocation
+         * blocks, or to convert an uninitialized extent to be
+         * initialized (in the case where we have written into
+         * one or more preallocated blocks).
+         *
+         * We pass in the magic EXT4_GET_BLOCKS_DELALLOC_RESERVE to
+         * indicate that we are on the delayed allocation path.  This
+         * affects functions in many different parts of the allocation
+         * call path.  This flag exists primarily because we don't
+         * want to change *many* call functions, so ext4_get_blocks()
+         * will set the magic i_delalloc_reserved_flag once the
+         * inode's allocation semaphore is taken.
+         *
+         * If the blocks in questions were delalloc blocks, set
+         * EXT4_GET_BLOCKS_DELALLOC_RESERVE so the delalloc accounting
+         * variables are updated after the blocks have been allocated.
          */
-        new.b_state = mpd->b_state & (1 << BH_Delay);
+        new.b_state = 0;
+        get_blocks_flags = (EXT4_GET_BLOCKS_CREATE |
+                            EXT4_GET_BLOCKS_DELALLOC_RESERVE);
+        if (mpd->b_state & (1 << BH_Delay))
+                get_blocks_flags |= EXT4_GET_BLOCKS_UPDATE_RESERVE_SPACE;
         blks = ext4_get_blocks(handle, mpd->inode, next, max_blocks,
-                               &new, EXT4_GET_BLOCKS_CREATE|
-                               EXT4_GET_BLOCKS_DELALLOC_RESERVE);
+                               &new, get_blocks_flags);
         if (blks < 0) {
                 err = blks;
                 /*