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From: Srivathsa Dara <srivathsa.d.dara@oracle.com>
To: Theodore Ts'o <tytso@mit.edu>
CC: "adilger.kernel@dilger.ca" <adilger.kernel@dilger.ca>,
        "linux-ext4@vger.kernel.org" <linux-ext4@vger.kernel.org>,
        Rajesh
 Sivaramasubramaniom <rajesh.sivaramasubramaniom@oracle.com>,
        Junxiao Bi
	<junxiao.bi@oracle.com>
Subject: RE: [External] : Re: [RESEND PATCH] debugfs/htree.c: In do_dx_hash()
 read hash_seed, hash_version directly from superblock
Thread-Topic: [External] : Re: [RESEND PATCH] debugfs/htree.c: In do_dx_hash()
 read hash_seed, hash_version directly from superblock
Thread-Index: AQHZ1lhVKTt2yfxi/kuE3HFdK46bD7CXopsAgAIBcOA=
Date: Mon, 4 Dec 2023 11:55:02 +0000
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Hi Ted,
Thank you for considering the patch and improving it.=20
I'll make sure that I follow the proper patch formatting for
my future patches.

Thanks,
Srivathsa Dara

-----Original Message-----
From: Theodore Ts'o <tytso@mit.edu>=20
Sent: Sunday, December 3, 2023 10:45 AM
To: Srivathsa Dara <srivathsa.d.dara@oracle.com>
Cc: adilger.kernel@dilger.ca; linux-ext4@vger.kernel.org; Rajesh Sivaramasu=
bramaniom <rajesh.sivaramasubramaniom@oracle.com>; Junxiao Bi <junxiao.bi@o=
racle.com>
Subject: [External] : Re: [RESEND PATCH] debugfs/htree.c: In do_dx_hash() r=
ead hash_seed, hash_version directly from superblock

On Thu, Aug 24, 2023 at 06:56:34AM +0000, Srivathsa Dara wrote:
> diff --git a/debugfs/htree.c b/debugfs/htree.c index=20
> 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 =3D 0;
>  	const struct ext2fs_nls_table *encoding =3D NULL;
> =20
> -	hash_seed[0] =3D hash_seed[1] =3D hash_seed[2] =3D hash_seed[3] =3D 0;
> +	hash_seed[0] =3D current_fs->super->s_hash_seed[0];
> +	hash_seed[1] =3D current_fs->super->s_hash_seed[1];
> +	hash_seed[2] =3D current_fs->super->s_hash_seed[2];
> +	hash_seed[3] =3D current_fs->super->s_hash_seed[3];
> +
> +	hash_version =3D current_fs->super->s_def_hash_version;
> =20
>  	reset_getopt();
>  	while ((c =3D getopt(argc, argv, "h:s:ce:")) !=3D EOF) {

The problem with this patch is that if a file system is not opened, then cu=
rrent_fs is NULL.  As a result:

% gdb -q debugfs
Reading symbols from debugfs...
(gdb) run
Starting program: /build/e2fsprogs/debugfs/debugfs [Thread debugging using =
libthread_db enabled] Using host libthread_db library "/lib/x86_64-linux-gn=
u/libthread_db.so.1".
debugfs 1.47.0 (5-Feb-2023)
debugfs:  dx_hash test1

Program received signal SIGSEGV, Segmentation fault.
0x000055555556f73d in do_dx_hash (argc=3D2, argv=3D0x5555555d38d0, sci_idx=
=3D1, infop=3D0x0)
    at /usr/projects/e2fsprogs/e2fsprogs/debugfs/htree.c:343
343             hash_seed[0] =3D current_fs->super->s_hash_seed[0];


To address this, I've fixed up your patch slightly.  (See below for the fix=
 up, as well as the final patch.)

Also, in the future, please make sure that the first line of the commit is =
a summary of the patch, no longer than 75 characters, and that the text is =
wrapped to no more than 75 characters.  (I personally use 72 characters, bu=
t 75 is what suggested in the Linux Kernel's submitting patches documentati=
on[1] in the "The Canonical Patch Format" section.)

[1] https://urldefense.com/v3/__https://docs.kernel.org/process/submitting-=
patches.html__;!!ACWV5N9M2RV99hQ!Pfb7MqoeE6NAhDDwRgjeGOuOZJ5NozX9970IvoER0R=
4oDpPXfKVMC3Mmq_TzfqTesrPbvRy6gI5sxFlEQo4$=20

					- Ted