linux-ext4 - Re: [PATCH v3] Add largedir feature

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Date:   Tue, 4 Jul 2017 13:56:17 -0400
From:   Theodore Ts'o <tytso@....edu>
To:     Artem Blagodarenko <artem.blagodarenko@...il.com>
Cc:     linux-ext4@...r.kernel.org, adilger.kernel@...ger.ca,
        alexey.lyashkov@...il.com, ebiggers3@...il.com,
        Yang Sheng <yang.sheng@...el.com>,
        Artem Blagodarenko <artem.blagodarenko@...gate.com>
Subject: Re: [PATCH v3] Add largedir feature

On Sat, May 06, 2017 at 02:19:21PM -0400, Artem Blagodarenko wrote:
> From: Artem Blagodarenko <artem.blagodarenko@...il.com>
> 
> This INCOMPAT_LARGEDIR feature allows larger directories to be created
> in ldiskfs, both with directory sizes over 2GB and and a maximum htree
> depth of 3 instead of the current limit of 2. These features are needed
> in order to exceed the current limit of approximately 10M entries in a
> single directory.
> 
> Signed-off-by: Yang Sheng <yang.sheng@...el.com>
> Signed-off-by: Artem Blagodarenko <artem.blagodarenko@...gate.com>

I'm going to fold the following minor fix-up to this patch before I
send it to Linus.

					- Ted

diff --git a/fs/ext4/ext4_jbd2.h b/fs/ext4/ext4_jbd2.h
index f97611171023..5e61e464d71c 100644
--- a/fs/ext4/ext4_jbd2.h
+++ b/fs/ext4/ext4_jbd2.h
@@ -77,7 +77,14 @@
 
 #define EXT4_RESERVE_TRANS_BLOCKS	12U
 
-#define EXT4_INDEX_EXTRA_TRANS_BLOCKS	8
+/*
+ * Number of credits needed if we need to insert an entry into a
+ * directory.  For each new index block, we need 4 blocks (old index
+ * block, new index block, bitmap block, bg summary).  For normal
+ * htree directories there are 2 levels; if the largedir feature
+ * enabled it's 3 levels.
+ */
+#define EXT4_INDEX_EXTRA_TRANS_BLOCKS	12U
 
 #ifdef CONFIG_QUOTA
 /* Amount of blocks needed for quota update - we know that the structure was