btrfs: put initial index value of a directory in a constant

At btrfs_set_inode_index_count() we refer twice to the number 2 as the
initial index value for a directory (when it's empty), with a proper
comment explaining the reason for that value. In the next patch I'll
have to use that magic value in the directory logging code, so put
the value in a #define at btrfs_inode.h, to avoid hardcoding the
magic value again at tree-log.c.

Signed-off-by: Filipe Manana <fdmanana@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>

diff --git a/fs/btrfs/btrfs_inode.h b/fs/btrfs/btrfs_inode.h
index b3e46aa..6d4f42b 100644 (file)
--- a/fs/btrfs/btrfs_inode.h
+++ b/fs/btrfs/btrfs_inode.h
@@ -13,6 +13,13 @@
 #include "ordered-data.h"
 #include "delayed-inode.h"
 
+/*
+ * Since we search a directory based on f_pos (struct dir_context::pos) we have
+ * to start at 2 since '.' and '..' have f_pos of 0 and 1 respectively, so
+ * everybody else has to start at 2 (see btrfs_real_readdir() and dir_emit_dots()).
+ */
+#define BTRFS_DIR_START_INDEX 2
+
 /*
  * ordered_data_close is set by truncate when a file that used
  * to have good data has been truncated to zero.  When it is set
@@ -173,8 +180,9 @@ struct btrfs_inode {
        u64 disk_i_size;
 
        /*
-        * if this is a directory then index_cnt is the counter for the index
-        * number for new files that are created
+        * If this is a directory then index_cnt is the counter for the index
+        * number for new files that are created. For an empty directory, this
+        * must be initialized to BTRFS_DIR_START_INDEX.
         */
        u64 index_cnt;
 

diff --git a/fs/btrfs/inode.c b/fs/btrfs/inode.c
index 5bbea5e..5c7aeb5 100644 (file)
--- a/fs/btrfs/inode.c
+++ b/fs/btrfs/inode.c
@@ -5971,14 +5971,8 @@ static int btrfs_set_inode_index_count(struct btrfs_inode *inode)
                goto out;
        ret = 0;
 
-       /*
-        * MAGIC NUMBER EXPLANATION:
-        * since we search a directory based on f_pos we have to start at 2
-        * since '.' and '..' have f_pos of 0 and 1 respectively, so everybody
-        * else has to start at 2
-        */
        if (path->slots[0] == 0) {
-               inode->index_cnt = 2;
+               inode->index_cnt = BTRFS_DIR_START_INDEX;
                goto out;
        }
 
@@ -5989,7 +5983,7 @@ static int btrfs_set_inode_index_count(struct btrfs_inode *inode)
 
        if (found_key.objectid != btrfs_ino(inode) ||
            found_key.type != BTRFS_DIR_INDEX_KEY) {
-               inode->index_cnt = 2;
+               inode->index_cnt = BTRFS_DIR_START_INDEX;
                goto out;
        }