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Date:   Thu, 3 Oct 2019 18:58:12 +0300
From:   Благодаренко Артём 
        <artem.blagodarenko@...il.com>
To:     Andreas Dilger <adilger@...ger.ca>
Cc:     linux-ext4 <linux-ext4@...r.kernel.org>, adilger.kernel@...ger.ca
Subject: Re: [PATCH] ext2fs: add ext2fs_read_sb that returns superblock

Thanks.

Sorry, not good new call time for me, but I can join occasionally.
I joined today, but too late.

Best regards,
Artem Blagodarenko.

> On 3 Oct 2019, at 18:55, Andreas Dilger <adilger@...ger.ca> wrote:
> 
> We just discussed this on the ext4 developer concall today, and Ted is looking into it. 
> 
> Cheers, Andreas
> 
>> On Oct 3, 2019, at 09:47, Благодаренко Артём <artem.blagodarenko@...il.com> wrote:
>> 
>> Hello,
>> 
>> Does anybody wants to give any feedback for this?
>> e2label became really faster on large partitions with this patch. Probably it can be useful.
>> 
>> Ted, what do you think?
>> 
>> Thanks,
>> Artem Blagodarenko.
>> 
>> 
>> 
>>> On 5 Sep 2019, at 14:01, Artem Blagodarenko <artem.blagodarenko@...il.com> wrote:
>>> 
>>> tune2fs is used to make e2label duties.  ext2fs_open2() reads group
>>> descriptors which are not used during disk label obtaining, but takes
>>> a lot of time on large partitions.
>>> 
>>> This patch adds ext2fs_read_sb(), there only initialized superblock
>>> is returned This saves time dramatically.
>>> 
>>> Signed-off-by: Artem Blagodarenko <c17828@...y.com>
>>> Cray-bug-id: LUS-5777
>>> ---
>>> lib/ext2fs/ext2fs.h |  2 ++
>>> lib/ext2fs/openfs.c | 16 ++++++++++++++++
>>> misc/tune2fs.c      | 23 +++++++++++++++--------
>>> 3 files changed, 33 insertions(+), 8 deletions(-)
>>> 
>>> diff --git a/lib/ext2fs/ext2fs.h b/lib/ext2fs/ext2fs.h
>>> index 59fd9742..3a63b74d 100644
>>> --- a/lib/ext2fs/ext2fs.h
>>> +++ b/lib/ext2fs/ext2fs.h
>>> @@ -1630,6 +1630,8 @@ extern int ext2fs_journal_sb_start(int blocksize);
>>> extern errcode_t ext2fs_open(const char *name, int flags, int superblock,
>>>                unsigned int block_size, io_manager manager,
>>>                ext2_filsys *ret_fs);
>>> +extern errcode_t ext2fs_read_sb(const char *name, io_manager manager,
>>> +                struct ext2_super_block * super);
>>> extern errcode_t ext2fs_open2(const char *name, const char *io_options,
>>>                 int flags, int superblock,
>>>                 unsigned int block_size, io_manager manager,
>>> diff --git a/lib/ext2fs/openfs.c b/lib/ext2fs/openfs.c
>>> index 51b54a44..95f45d84 100644
>>> --- a/lib/ext2fs/openfs.c
>>> +++ b/lib/ext2fs/openfs.c
>>> @@ -99,6 +99,22 @@ static void block_sha_map_free_entry(void *data)
>>>   return;
>>> }
>>> 
>>> +errcode_t ext2fs_read_sb(const char *name, io_manager manager,
>>> +             struct ext2_super_block * super)
>>> +{
>>> +    io_channel    io;
>>> +    errcode_t    retval = 0;
>>> +
>>> +    retval = manager->open(name, 0, &io);
>>> +    if (!retval) {
>>> +        retval = io_channel_read_blk(io, 1, -SUPERBLOCK_SIZE,
>>> +                     super);
>>> +        io_channel_close(io);
>>> +    }
>>> +
>>> +    return retval;
>>> +}
>>> +
>>> /*
>>> *  Note: if superblock is non-zero, block-size must also be non-zero.
>>> *    Superblock and block_size can be zero to use the default size.
>>> diff --git a/misc/tune2fs.c b/misc/tune2fs.c
>>> index 7d2d38d7..fea607e1 100644
>>> --- a/misc/tune2fs.c
>>> +++ b/misc/tune2fs.c
>>> @@ -2879,6 +2879,21 @@ int tune2fs_main(int argc, char **argv)
>>> #endif
>>>       io_ptr = unix_io_manager;
>>> 
>>> +    if (print_label) {
>>> +        /* For e2label emulation */
>>> +        struct ext2_super_block sb;
>>> +
>>> +        /* Read only superblock. Nothing else metters.*/
>>> +        retval = ext2fs_read_sb(device_name, io_ptr, &sb);
>>> +        if (!retval) {
>>> +            printf("%.*s\n", (int) sizeof(sb.s_volume_name),
>>> +                   sb.s_volume_name);
>>> +        }
>>> +
>>> +        remove_error_table(&et_ext2_error_table);
>>> +        return retval;
>>> +    }
>>> +
>>> retry_open:
>>>   if ((open_flag & EXT2_FLAG_RW) == 0 || f_flag)
>>>       open_flag |= EXT2_FLAG_SKIP_MMP;
>>> @@ -2972,14 +2987,6 @@ retry_open:
>>>   sb = fs->super;
>>>   fs->flags &= ~EXT2_FLAG_MASTER_SB_ONLY;
>>> 
>>> -    if (print_label) {
>>> -        /* For e2label emulation */
>>> -        printf("%.*s\n", (int) sizeof(sb->s_volume_name),
>>> -               sb->s_volume_name);
>>> -        remove_error_table(&et_ext2_error_table);
>>> -        goto closefs;
>>> -    }
>>> -
>>>   retval = ext2fs_check_if_mounted(device_name, &mount_flags);
>>>   if (retval) {
>>>       com_err("ext2fs_check_if_mount", retval,
>>> -- 
>>> 2.14.3
>>> 
>> 

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