ext4, jbd2: Provide accessor function for handle credits

Provide accessor function to get number of credits available in a handle
and use it from ext4. Later, computation of available credits won't be
so straightforward.
Reviewed-by: Theodore Ts'o <tytso@mit.edu>
Signed-off-by: Jan Kara <jack@suse.cz>
Link: https://lore.kernel.org/r/20191105164437.32602-11-jack@suse.czSigned-off-by: Theodore Ts'o <tytso@mit.edu>

fs/ext4/ext4_jbd2.c

@@ -119,8 +119,8 @@ handle_t *__ext4_journal_start_reserved(handle_t *handle, unsigned int line,
 		return ext4_get_nojournal();
 
 	sb = handle->h_journal->j_private;
-	trace_ext4_journal_start_reserved(sb, handle->h_buffer_credits,
-					  _RET_IP_);
+	trace_ext4_journal_start_reserved(sb,
+				jbd2_handle_buffer_credits(handle), _RET_IP_);
 	err = ext4_journal_check_start(sb);
 	if (err < 0) {
 		jbd2_journal_free_reserved(handle);
@@ -138,10 +138,10 @@ int __ext4_journal_ensure_credits(handle_t *handle, int check_cred,
 {
 	if (!ext4_handle_valid(handle))
 		return 0;
-	if (handle->h_buffer_credits >= check_cred)
+	if (jbd2_handle_buffer_credits(handle) >= check_cred)
 		return 0;
 	return ext4_journal_extend(handle,
-				   extend_cred - handle->h_buffer_credits);
+			   extend_cred - jbd2_handle_buffer_credits(handle));
 }
 
 static void ext4_journal_abort_handle(const char *caller, unsigned int line,
@@ -289,7 +289,7 @@ int __ext4_handle_dirty_metadata(const char *where, unsigned int line,
 				       handle->h_type,
 				       handle->h_line_no,
 				       handle->h_requested_credits,
-				       handle->h_buffer_credits, err);
+				       jbd2_handle_buffer_credits(handle), err);
 				return err;
 			}
 			ext4_error_inode(inode, where, line,
@@ -300,7 +300,8 @@ int __ext4_handle_dirty_metadata(const char *where, unsigned int line,
 					 handle->h_type,
 					 handle->h_line_no,
 					 handle->h_requested_credits,
-					 handle->h_buffer_credits, err);
+					 jbd2_handle_buffer_credits(handle),
+					 err);
 		}
 	} else {
 		if (inode)

fs/ext4/ext4_jbd2.h

@@ -288,13 +288,6 @@ static inline int ext4_handle_is_aborted(handle_t *handle)
 	return 0;
 }
 
-static inline int ext4_handle_has_enough_credits(handle_t *handle, int needed)
-{
-	if (ext4_handle_valid(handle) && handle->h_buffer_credits < needed)
-		return 0;
-	return 1;
-}
-
 #define ext4_journal_start_sb(sb, type, nblocks)			\
 	__ext4_journal_start_sb((sb), __LINE__, (type), (nblocks), 0)
 

fs/ext4/xattr.c

@@ -2314,7 +2314,7 @@ ext4_xattr_set_handle(handle_t *handle, struct inode *inode, int name_index,
 						   flags & XATTR_CREATE);
 		brelse(bh);
 
-		if (!ext4_handle_has_enough_credits(handle, credits)) {
+		if (jbd2_handle_buffer_credits(handle) < credits) {
 			error = -ENOSPC;
 			goto cleanup;
 		}

include/linux/jbd2.h

@@ -1645,6 +1645,12 @@ static inline tid_t  jbd2_get_latest_transaction(journal_t *journal)
 	return tid;
 }
 
+
+static inline int jbd2_handle_buffer_credits(handle_t *handle)
+{
+	return handle->h_buffer_credits;
+}
+
 #ifdef __KERNEL__
 
 #define buffer_trace_init(bh)	do {} while (0)