Re: [PATCH] jbd2: move more common code into journal_init_common()

[Geliang Tang <geliangtang@gmail.com>]

On Thu, Sep 15, 2016 at 03:58:18PM -0400, Theodore Ts'o wrote:
> On Thu, Sep 15, 2016 at 12:03:09PM -0400, Theodore Ts'o wrote:
> > On Wed, Sep 07, 2016 at 03:16:24PM +0200, Jan Kara wrote:
> > > On Wed 07-09-16 20:41:13, Geliang Tang wrote:
> > > > There are some repetitive code in jbd2_journal_init_dev() and
> > > > jbd2_journal_init_inode(). So this patch moves the common code into
> > > > journal_init_common() helper to simplify the code. And fix the coding
> > > > style warnings reported by checkpatch.pl by the way.
> > > > 
> > > > Signed-off-by: Geliang Tang <geliangtang@gmail.com>
> > > 
> > > The patch looks good to me. You can add:
> > > 
> > > Reviewed-by: Jan Kara <jack@suse.cz>
> > 
> > Applied, thanks.
> > 
> 
> Hi Geiliang,
> 
> This patch is causing a WARN_ON:
> 
> [   13.923139] ------------[ cut here ]------------
> [   13.924644] WARNING: CPU: 0 PID: 2534 at /usr/projects/linux/ext4/fs/proc/generic.c:369 __proc_create+0xe1/0x156
> [   13.926751] name len 0
> [   13.927283] Modules linked in:
> [   13.927954] CPU: 0 PID: 2534 Comm: mount Tainted: G        W       4.8.0-rc4-00139-g52c4278 #685
> [   13.929809] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS Debian-1.8.2-1 04/01/2014
> [   13.931643]  00000000 00000246 f3c1dd3c c13faa3e f3c1dd68 c11cc9c1 f3c1dd54 c1087d00
> [   13.933425]  00000171 f4727b0c f3c1ddac f5183bc0 f3c1dd70 c1087d44 00000009 00000000
> [   13.935199]  f3c1dd68 c1969704 f3c1dd84 f3c1dda0 c11cc9c1 c19696d9 00000171 c1969704
> [   13.936987] Call Trace:
> [   13.937507]  [<c13faa3e>] dump_stack+0x73/0xa5
> [   13.938438]  [<c11cc9c1>] ? __proc_create+0xe1/0x156
> [   13.939503]  [<c1087d00>] __warn+0xbc/0xd3
> [   13.940404]  [<c1087d44>] warn_slowpath_fmt+0x2d/0x32
> [   13.941470]  [<c11cc9c1>] __proc_create+0xe1/0x156
> [   13.942461]  [<c11ccc8d>] proc_mkdir_data+0x2c/0x6e
> [   13.943484]  [<c11cccf6>] proc_mkdir+0x13/0x15
> [   13.944425]  [<c122a597>] journal_init_common+0x1a8/0x26a
> [   13.945539]  [<c122a753>] jbd2_journal_init_inode+0xa9/0xfd
> [   13.946702]  [<c11fa5cf>] ext4_fill_super+0x18e5/0x2a92
> [   13.947794]  [<c1402d01>] ? bitmap_string.isra.6+0xa9/0xc1
> [   13.948926]  [<c117ec1f>] mount_bdev+0x114/0x15f
> [   13.950333]  [<c11f48c4>] ext4_mount+0x15/0x17
> [   13.951985]  [<c11f8cea>] ? ext4_calculate_overhead+0x30e/0x30e
> [   13.954172]  [<c117f49d>] mount_fs+0x58/0x115
> [   13.955789]  [<c11943cb>] vfs_kern_mount+0x4c/0xae
> [   13.957588]  [<c11966dc>] do_mount+0x6b0/0x8d7
> [   13.959270]  [<c1405620>] ? _copy_from_user+0x44/0x57
> [   13.961140]  [<c1150873>] ? strndup_user+0x31/0x42
> [   13.962919]  [<c1196aab>] SyS_mount+0x57/0x7b
> [   13.964609]  [<c10015b2>] do_int80_syscall_32+0x4d/0x5f
> [   13.966555]  [<c16f6ccb>] entry_INT80_32+0x2f/0x2f
> [   13.968402] ---[ end trace 2eb7cc6d9a94f309 ]---
> [   14.017482] EXT4-fs (vdc): mounted filesystem with ordered data mode. Opts: (null)
> 
> The problem is that journal->j_devname isn't initialized until *after*
> journal_init_common(), and it's used by jbd2_stats_proc_init(), which
> is called by journal_init_common().
> 
> To fix it I applied the following fix on top of your patch.
> 
>        	    	    		      	     - Ted
> 
> diff --git a/fs/jbd2/journal.c b/fs/jbd2/journal.c
> index 07e14ef..927da49 100644
> --- a/fs/jbd2/journal.c
> +++ b/fs/jbd2/journal.c
> @@ -1141,13 +1141,11 @@ static journal_t *journal_init_common(struct block_device *bdev,
>  	journal->j_fs_dev = fs_dev;
>  	journal->j_blk_offset = start;
>  	journal->j_maxlen = len;
> -	jbd2_stats_proc_init(journal);
>  	n = journal->j_blocksize / sizeof(journal_block_tag_t);
>  	journal->j_wbufsize = n;
>  	journal->j_wbuf = kmalloc_array(n, sizeof(struct buffer_head *),
>  					GFP_KERNEL);
>  	if (!journal->j_wbuf) {
> -		jbd2_stats_proc_exit(journal);
>  		kfree(journal);
>  		return NULL;
>  	}
> @@ -1157,7 +1155,6 @@ static journal_t *journal_init_common(struct block_device *bdev,
>  		pr_err("%s: Cannot get buffer for journal superblock\n",
>  			__func__);
>  		kfree(journal->j_wbuf);
> -		jbd2_stats_proc_exit(journal);
>  		kfree(journal);
>  		return NULL;
>  	}
> @@ -1202,6 +1199,7 @@ journal_t *jbd2_journal_init_dev(struct block_device *bdev,
>  
>  	bdevname(journal->j_dev, journal->j_devname);
>  	strreplace(journal->j_devname, '/', '!');
> +	jbd2_stats_proc_init(journal);
>  
>  	return journal;
>  }
> @@ -1241,6 +1239,7 @@ journal_t *jbd2_journal_init_inode(struct inode *inode)
>  	bdevname(journal->j_dev, journal->j_devname);
>  	p = strreplace(journal->j_devname, '/', '!');
>  	sprintf(p, "-%lu", journal->j_inode->i_ino);
> +	jbd2_stats_proc_init(journal);
>  
>  	return journal;
>  }

Thanks Ted, this looks fine to me.

-Geliang