linux-ext4 - [PATCH] misc/mke2fs.8.in: Correct valid cluster-size values

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Date:   Fri, 18 Aug 2023 08:31:39 +0000
From:   Srivathsa Dara <srivathsa.d.dara@...cle.com>
To:     tytso@....edu, adilger.kernel@...ger.ca
Cc:     rajesh.sivaramasubramaniom@...cle.com, junxiao.bi@...cle.com,
        linux-ext4@...r.kernel.org
Subject: [PATCH] misc/mke2fs.8.in: Correct valid cluster-size values

According to the mke2fs man page, the supported cluster-size values
for an ext4 filesystem are 2048 to 256M bytes. However, this is not
the case.

When mkfs is run to create a filesystem with following specifications:
* 1k blocksize and cluster-size greater than 32M
* 2k blocksize and cluster-size greater than 64M
* 4k blocksize and cluster-size greater than 128M
mkfs fails with "Invalid argument passed to ext2 library while trying
to create journal" error. In general, when the cluster-size to blocksize
ratio is greater than 32k, mkfs fails with this error.

Went through the code and found out that the function
`ext2fs_new_range()` is the source of this error. This is because when
the cluster-size to blocksize ratio exceeds 32k, the length argument
to the function `ext2fs_new_range()` results in 0. Hence, the error.

This patch corrects the valid cluster-size values.
---
 misc/mke2fs.8.in | 6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

diff --git a/misc/mke2fs.8.in b/misc/mke2fs.8.in
index e6bfc6d6..b5b02144 100644
--- a/misc/mke2fs.8.in
+++ b/misc/mke2fs.8.in
@@ -230,9 +230,9 @@ test is used instead of a fast read-only test.
 .TP
 .B \-C " cluster-size"
 Specify the size of cluster in bytes for filesystems using the bigalloc
-feature.  Valid cluster-size values are from 2048 to 256M bytes per
-cluster.  This can only be specified if the bigalloc feature is
-enabled.  (See the
+feature.  Valid cluster-size values are from 2048 to 128M bytes per 
+cluster based on filesystem blocksize. This can only be specified if the
+bigalloc feature is enabled.  (See the
 .B ext4 (5)
 man page for more details about bigalloc.)   The default cluster size if
 bigalloc is enabled is 16 times the block size.
-- 
2.31.1