linux-ext4 - [RESEND PATCH] debugfs/htree.c: In do_dx_hash() read hash_seed, hash

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Date:   Thu, 24 Aug 2023 06:56:34 +0000
From:   Srivathsa Dara <srivathsa.d.dara@...cle.com>
To:     tytso@....edu, adilger.kernel@...ger.ca
Cc:     linux-ext4@...r.kernel.org, rajesh.sivaramasubramaniom@...cle.com,
        junxiao.bi@...cle.com
Subject: [RESEND PATCH] debugfs/htree.c: In do_dx_hash() read hash_seed, hash_version directly from superblock

debugfs hash command computes the hash for the given filename. It takes hash_seed and
hash_version (i.e hash algorithm) as arguments. User has to refer to the superblock to
get these values used by the filesystem. If the arguments are not given then debugfs
computes hash assuming both hash_seed and hash_version are zeros. In most of the cases
this assumption will be different from the actual hash_seed and hash_version used by the
filesystem. In general user will be in need of hash computed from hash_seed and hash_version
of the filesystem. So, instead of assuming hash_seed and hash_version as zero when the
arguments are not provided, read these directly from the superblock to simplify the task of user.

Example:
Before:-
debugfs:  hash -s 524e5394-e2a3-43fa-b192-79720b1fe3e1 -h half_md4 file1
Hash of file1 is 0x4a8d8c94 (minor 0x17a37f43)

After improvement:-
debugfs:  hash file1
Hash of file1 is 0x4a8d8c94 (minor 0x17a37f43)

Signed-off-by: Srivathsa Dara <srivathsa.d.dara@...cle.com>
---
 debugfs/htree.c | 7 ++++++-
 1 file changed, 6 insertions(+), 1 deletion(-)

diff --git a/debugfs/htree.c b/debugfs/htree.c
index 7fae7f11..2d881c74 100644
--- a/debugfs/htree.c
+++ b/debugfs/htree.c
@@ -316,7 +316,12 @@ void do_dx_hash(int argc, char *argv[], int sci_idx EXT2FS_ATTR((unused)),
 	int		hash_flags = 0;
 	const struct ext2fs_nls_table *encoding = NULL;

-	hash_seed[0] = hash_seed[1] = hash_seed[2] = hash_seed[3] = 0;
+	hash_seed[0] = current_fs->super->s_hash_seed[0];
+	hash_seed[1] = current_fs->super->s_hash_seed[1];
+	hash_seed[2] = current_fs->super->s_hash_seed[2];
+	hash_seed[3] = current_fs->super->s_hash_seed[3];
+
+	hash_version = current_fs->super->s_def_hash_version;

 	reset_getopt();
 	while ((c = getopt(argc, argv, "h:s:ce:")) != EOF) {
-- 
2.31.1