Message-ID: <20151202111915.GC22125@quack.suse.cz>
Date:	Wed, 2 Dec 2015 12:19:15 +0100
From:	Jan Kara <jack@...e.cz>
To:	Junxiao Bi <junxiao.bi@...cle.com>
Cc:	linux-ext4@...r.kernel.org, tytso@....edu, jack@...e.cz,
	ocfs2-devel@....oracle.com
Subject: Re: [PATCH V2] jbd2: fix null committed data return in undo_access

On Wed 02-12-15 14:54:15, Junxiao Bi wrote:
> commit de92c8caf16c ("jbd2: speedup jbd2_journal_get_[write|undo]_access()")
> introduced jbd2_write_access_granted() to improve write|undo_access
> speed, but missed to check the status of b_committed_data which caused
> a kernel panic on ocfs2.
> 
> [ 6538.405938] ------------[ cut here ]------------
> [ 6538.406686] kernel BUG at fs/ocfs2/suballoc.c:2400!
> [ 6538.406686] invalid opcode: 0000 [#1] SMP
> [ 6538.406686] Modules linked in: ocfs2 nfsd lockd grace nfs_acl auth_rpcgss sunrpc autofs4 ocfs2_dlmfs ocfs2_stack_o2cb ocfs2_dlm ocfs2_nodemanager ocfs2_stackglue configfs sd_mod sg ip6t_REJECT nf_reject_ipv6 nf_conntrack_ipv6 nf_defrag_ipv6 xt_state nf_conntrack ip6table_filter ip6_tables be2iscsi iscsi_boot_sysfs bnx2i cnic uio cxgb4i cxgb4 cxgb3i libcxgbi cxgb3 mdio ib_iser rdma_cm ib_cm iw_cm ib_sa ib_mad ib_core ib_addr ipv6 iscsi_tcp libiscsi_tcp libiscsi scsi_transport_iscsi ppdev xen_kbdfront xen_netfront xen_fbfront parport_pc parport pcspkr i2c_piix4 acpi_cpufreq ext4 jbd2 mbcache xen_blkfront floppy pata_acpi ata_generic ata_piix cirrus ttm drm_kms_helper drm fb_sys_fops sysimgblt sysfillrect i2c_core syscopyarea dm_mirror dm_region_hash dm_log dm_mod
> [ 6538.406686] CPU: 1 PID: 16265 Comm: mmap_truncate Not tainted 4.3.0 #1
> [ 6538.406686] Hardware name: Xen HVM domU, BIOS 4.3.1OVM 05/14/2014
> [ 6538.406686] task: ffff88007c2bab00 ti: ffff880075b78000 task.ti: ffff880075b78000
> [ 6538.406686] RIP: 0010:[<ffffffffa06a286b>]  [<ffffffffa06a286b>] ocfs2_block_group_clear_bits+0x23b/0x250 [ocfs2]
> [ 6538.406686] RSP: 0018:ffff880075b7b7f8  EFLAGS: 00010246
> [ 6538.406686] RAX: ffff8800760c5b40 RBX: ffff88006c06a000 RCX: ffffffffa06e6df0
> [ 6538.406686] RDX: 0000000000000000 RSI: ffff88007a6f6ea0 RDI: ffff88007a760430
> [ 6538.406686] RBP: ffff880075b7b878 R08: 0000000000000002 R09: 0000000000000001
> [ 6538.406686] R10: ffffffffa06769be R11: 0000000000000000 R12: 0000000000000001
> [ 6538.406686] R13: ffffffffa06a1750 R14: 0000000000000001 R15: ffff88007a6f6ea0
> [ 6538.406686] FS:  00007f17fde30720(0000) GS:ffff88007f040000(0000) knlGS:0000000000000000
> [ 6538.406686] CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
> [ 6538.406686] CR2: 0000000000601730 CR3: 000000007aea0000 CR4: 00000000000406e0
> [ 6538.406686] Stack:
> [ 6538.406686]  ffff88007c2bb5b0 ffff880075b7b8e0 ffff88007a7604b0 ffff88006c640800
> [ 6538.406686]  ffff88007a7604b0 ffff880075d77390 0000000075b7b878 ffffffffa06a309d
> [ 6538.406686]  ffff880075d752d8 ffff880075b7b990 ffff880075b7b898 0000000000000000
> [ 6538.406686] Call Trace:
> [ 6538.406686]  [<ffffffffa06a309d>] ? ocfs2_read_group_descriptor+0x6d/0xa0 [ocfs2]
> [ 6538.406686]  [<ffffffffa06a3654>] _ocfs2_free_suballoc_bits+0xe4/0x320 [ocfs2]
> [ 6538.406686]  [<ffffffffa06a1750>] ? ocfs2_put_slot+0xf0/0xf0 [ocfs2]
> [ 6538.406686]  [<ffffffffa06a397e>] _ocfs2_free_clusters+0xee/0x210 [ocfs2]
> [ 6538.406686]  [<ffffffffa06a1750>] ? ocfs2_put_slot+0xf0/0xf0 [ocfs2]
> [ 6538.406686]  [<ffffffffa06a1750>] ? ocfs2_put_slot+0xf0/0xf0 [ocfs2]
> [ 6538.406686]  [<ffffffffa0682d50>] ? ocfs2_extend_trans+0x50/0x1a0 [ocfs2]
> [ 6538.406686]  [<ffffffffa06a3ad5>] ocfs2_free_clusters+0x15/0x20 [ocfs2]
> [ 6538.406686]  [<ffffffffa065072c>] ocfs2_replay_truncate_records+0xfc/0x290 [ocfs2]
> [ 6538.406686]  [<ffffffffa06843ac>] ? ocfs2_start_trans+0xec/0x1d0 [ocfs2]
> [ 6538.406686]  [<ffffffffa0654600>] __ocfs2_flush_truncate_log+0x140/0x2d0 [ocfs2]
> [ 6538.406686]  [<ffffffffa0654394>] ? ocfs2_reserve_blocks_for_rec_trunc.clone.0+0x44/0x170 [ocfs2]
> [ 6538.406686]  [<ffffffffa065acd4>] ocfs2_remove_btree_range+0x374/0x630 [ocfs2]
> [ 6538.406686]  [<ffffffffa017486b>] ? jbd2_journal_stop+0x25b/0x470 [jbd2]
> [ 6538.406686]  [<ffffffffa065d5b5>] ocfs2_commit_truncate+0x305/0x670 [ocfs2]
> [ 6538.406686]  [<ffffffffa0683430>] ? ocfs2_journal_access_eb+0x20/0x20 [ocfs2]
> [ 6538.406686]  [<ffffffffa067adb7>] ocfs2_truncate_file+0x297/0x380 [ocfs2]
> [ 6538.406686]  [<ffffffffa01759e4>] ? jbd2_journal_begin_ordered_truncate+0x64/0xc0 [jbd2]
> [ 6538.406686]  [<ffffffffa067c7a2>] ocfs2_setattr+0x572/0x860 [ocfs2]
> [ 6538.406686]  [<ffffffff810e4a3f>] ? current_fs_time+0x3f/0x50
> [ 6538.406686]  [<ffffffff812124b7>] notify_change+0x1d7/0x340
> [ 6538.406686]  [<ffffffff8121abf9>] ? generic_getxattr+0x79/0x80
> [ 6538.406686]  [<ffffffff811f5876>] do_truncate+0x66/0x90
> [ 6538.406686]  [<ffffffff81120e30>] ? __audit_syscall_entry+0xb0/0x110
> [ 6538.406686]  [<ffffffff811f5bb3>] do_sys_ftruncate.clone.0+0xf3/0x120
> [ 6538.406686]  [<ffffffff811f5bee>] SyS_ftruncate+0xe/0x10
> [ 6538.406686]  [<ffffffff816aa2ae>] entry_SYSCALL_64_fastpath+0x12/0x71
> [ 6538.406686] Code: 28 48 81 ee b0 04 00 00 48 8b 92 50 fb ff ff 48 8b 80 b0 03 00 00 48 39 90 88 00 00 00 0f 84 30 fe ff ff 0f 0b eb fe 0f 0b eb fe <0f> 0b 0f 1f 00 eb fb 66 66 66 66 66 2e 0f 1f 84 00 00 00 00 00
> [ 6538.406686] RIP  [<ffffffffa06a286b>] ocfs2_block_group_clear_bits+0x23b/0x250 [ocfs2]
> [ 6538.406686]  RSP <ffff880075b7b7f8>
> [ 6538.691128] ---[ end trace 31cd7011d6770d7e ]---
> [ 6538.694492] Kernel panic - not syncing: Fatal exception
> [ 6538.695484] Kernel Offset: disabled
> 
> Fixes: de92c8caf16c("jbd2: speedup jbd2_journal_get_[write|undo]_access()")
> Cc: <stable@...r.kernel.org>
> Signed-off-by: Junxiao Bi <junxiao.bi@...cle.com>

The patch looks good. You can add:

Reviewed-by: Jan Kara <jack@...e.cz>

								Honza
> ---
>  fs/jbd2/transaction.c |   10 +++++++---
>  1 file changed, 7 insertions(+), 3 deletions(-)
> 
> diff --git a/fs/jbd2/transaction.c b/fs/jbd2/transaction.c
> index 6b8338e..fb5014f 100644
> --- a/fs/jbd2/transaction.c
> +++ b/fs/jbd2/transaction.c
> @@ -1009,7 +1009,8 @@ out:
>  }
>  
>  /* Fast check whether buffer is already attached to the required transaction */
> -static bool jbd2_write_access_granted(handle_t *handle, struct buffer_head *bh)
> +static bool jbd2_write_access_granted(handle_t *handle, struct buffer_head *bh,
> +							bool undo)
>  {
>  	struct journal_head *jh;
>  	bool ret = false;
> @@ -1036,6 +1037,9 @@ static bool jbd2_write_access_granted(handle_t *handle, struct buffer_head *bh)
>  	jh = READ_ONCE(bh->b_private);
>  	if (!jh)
>  		goto out;
> +	/* For undo access buffer must have data copied */
> +	if (undo && !jh->b_committed_data)
> +		goto out;
>  	if (jh->b_transaction != handle->h_transaction &&
>  	    jh->b_next_transaction != handle->h_transaction)
>  		goto out;
> @@ -1073,7 +1077,7 @@ int jbd2_journal_get_write_access(handle_t *handle, struct buffer_head *bh)
>  	struct journal_head *jh;
>  	int rc;
>  
> -	if (jbd2_write_access_granted(handle, bh))
> +	if (jbd2_write_access_granted(handle, bh, false))
>  		return 0;
>  
>  	jh = jbd2_journal_add_journal_head(bh);
> @@ -1210,7 +1214,7 @@ int jbd2_journal_get_undo_access(handle_t *handle, struct buffer_head *bh)
>  	char *committed_data = NULL;
>  
>  	JBUFFER_TRACE(jh, "entry");
> -	if (jbd2_write_access_granted(handle, bh))
> +	if (jbd2_write_access_granted(handle, bh, true))
>  		return 0;
>  
>  	jh = jbd2_journal_add_journal_head(bh);
> -- 
> 1.7.9.5
> 
-- 
Jan Kara <jack@...e.com>
SUSE Labs, CR
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