ext4: fix the number of credits needed for ext4_unlink() and ext4_rmdir()

The ext4_unlink() and ext4_rmdir() don't actually release the blocks
associated with the file/directory. This gets done in a separate jbd2
handle called via ext4_evict_inode(). Thus, we don't need to reserve
lots of journal credits for the truncate.

Note that using too many journal credits is non-optimal because it can
leading to the journal transmit getting closed too early, before it is
strictly necessary.

Signed-off-by: "Theodore Ts'o" <[e-mail]>
Reviewed-by: Jan Kara <[e-mail]>

fs/ext4/ext4_jbd2.h

···
 #define EXT4_META_TRANS_BLOCKS(sb)	(EXT4_XATTR_TRANS_BLOCKS + \
 					EXT4_MAXQUOTAS_TRANS_BLOCKS(sb))
 
-/* Delete operations potentially hit one directory's namespace plus an
- * entire inode, plus arbitrary amounts of bitmap/indirection data.  Be
- * generous.  We can grow the delete transaction later if necessary. */
-
-#define EXT4_DELETE_TRANS_BLOCKS(sb)	(2 * EXT4_DATA_TRANS_BLOCKS(sb) + 64)
-
 /* Define an arbitrary limit for the amount of data we will anticipate
  * writing to any given transaction.  For unbounded transactions such as
  * write(2) and truncate(2) we can write more than this, but we always

fs/ext4/namei.c

···
 		goto end_rmdir;
 
 	handle = ext4_journal_start(dir, EXT4_HT_DIR,
-				    EXT4_DELETE_TRANS_BLOCKS(dir->i_sb));
+				    EXT4_DATA_TRANS_BLOCKS(dir->i_sb));
 	if (IS_ERR(handle)) {
 		retval = PTR_ERR(handle);
 		handle = NULL;
···
 		goto end_unlink;
 
 	handle = ext4_journal_start(dir, EXT4_HT_DIR,
-				    EXT4_DELETE_TRANS_BLOCKS(dir->i_sb));
+				    EXT4_DATA_TRANS_BLOCKS(dir->i_sb));
 	if (IS_ERR(handle)) {
 		retval = PTR_ERR(handle);
 		handle = NULL;