Re: [PATCH -next v2] ext4: fix warning in 'ext4_da_release_space'

[Jan Kara]

On Tue 18-10-22 10:27:01, Ye Bin wrote:
> Syzkaller report issue as follows:
> EXT4-fs (loop0): Free/Dirty block details
> EXT4-fs (loop0): free_blocks=0
> EXT4-fs (loop0): dirty_blocks=0
> EXT4-fs (loop0): Block reservation details
> EXT4-fs (loop0): i_reserved_data_blocks=0
> EXT4-fs warning (device loop0): ext4_da_release_space:1527: ext4_da_release_space: ino 18, to_free 1 with only 0 reserved data blocks
> ------------[ cut here ]------------
> WARNING: CPU: 0 PID: 92 at fs/ext4/inode.c:1528 ext4_da_release_space+0x25e/0x370 fs/ext4/inode.c:1524
> Modules linked in:
> CPU: 0 PID: 92 Comm: kworker/u4:4 Not tainted 6.0.0-syzkaller-09423-g493ffd6605b2 #0
> Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 09/22/2022
> Workqueue: writeback wb_workfn (flush-7:0)
> RIP: 0010:ext4_da_release_space+0x25e/0x370 fs/ext4/inode.c:1528
> RSP: 0018:ffffc900015f6c90 EFLAGS: 00010296
> RAX: 42215896cd52ea00 RBX: 0000000000000000 RCX: 42215896cd52ea00
> RDX: 0000000000000000 RSI: 0000000080000001 RDI: 0000000000000000
> RBP: 1ffff1100e907d96 R08: ffffffff816aa79d R09: fffff520002bece5
> R10: fffff520002bece5 R11: 1ffff920002bece4 R12: ffff888021fd2000
> R13: ffff88807483ecb0 R14: 0000000000000001 R15: ffff88807483e740
> FS:  0000000000000000(0000) GS:ffff8880b9a00000(0000) knlGS:0000000000000000
> CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
> CR2: 00005555569ba628 CR3: 000000000c88e000 CR4: 00000000003506f0
> DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
> DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
> Call Trace:
>  <TASK>
>  ext4_es_remove_extent+0x1ab/0x260 fs/ext4/extents_status.c:1461
>  mpage_release_unused_pages+0x24d/0xef0 fs/ext4/inode.c:1589
>  ext4_writepages+0x12eb/0x3be0 fs/ext4/inode.c:2852
>  do_writepages+0x3c3/0x680 mm/page-writeback.c:2469
>  __writeback_single_inode+0xd1/0x670 fs/fs-writeback.c:1587
>  writeback_sb_inodes+0xb3b/0x18f0 fs/fs-writeback.c:1870
>  wb_writeback+0x41f/0x7b0 fs/fs-writeback.c:2044
>  wb_do_writeback fs/fs-writeback.c:2187 [inline]
>  wb_workfn+0x3cb/0xef0 fs/fs-writeback.c:2227
>  process_one_work+0x877/0xdb0 kernel/workqueue.c:2289
>  worker_thread+0xb14/0x1330 kernel/workqueue.c:2436
>  kthread+0x266/0x300 kernel/kthread.c:376
>  ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:306
>  </TASK>
> 
> Above issue may happens as follows:
> ext4_da_write_begin
>   ext4_create_inline_data
>     ext4_clear_inode_flag(inode, EXT4_INODE_EXTENTS);
>     ext4_set_inode_flag(inode, EXT4_INODE_INLINE_DATA);
> __ext4_ioctl
>   ext4_ext_migrate -> will lead to eh->eh_entries not zero, and set extent flag
> ext4_da_write_begin
>   ext4_da_convert_inline_data_to_extent
>     ext4_da_write_inline_data_begin
>       ext4_da_map_blocks
>         ext4_insert_delayed_block
> 	  if (!ext4_es_scan_clu(inode, &ext4_es_is_delonly, lblk))
> 	    if (!ext4_es_scan_clu(inode, &ext4_es_is_mapped, lblk))
> 	      ext4_clu_mapped(inode, EXT4_B2C(sbi, lblk)); -> will return 1
> 	       allocated = true;
>           ext4_es_insert_delayed_block(inode, lblk, allocated);
> ext4_writepages
>   mpage_map_and_submit_extent(handle, &mpd, &give_up_on_write); -> return -ENOSPC
>   mpage_release_unused_pages(&mpd, give_up_on_write); -> give_up_on_write == 1
>     ext4_es_remove_extent
>       ext4_da_release_space(inode, reserved);
>         if (unlikely(to_free > ei->i_reserved_data_blocks))
> 	  -> to_free == 1  but ei->i_reserved_data_blocks == 0
> 	  -> then trigger warning as above
> 
> To solve above issue, forbid inode do migrate which has inline data.
> 
> Reported-by: syzbot+c740bb18df70ad00952e@xxxxxxxxxxxxxxxxxxxxxxxxx
> Signed-off-by: Ye Bin <yebin10@xxxxxxxxxx>

Yeah, makes sense. Feel free to add:

Reviewed-by: Jan Kara <jack@xxxxxxx>

								Honza 

> ---
>  fs/ext4/migrate.c | 3 ++-
>  1 file changed, 2 insertions(+), 1 deletion(-)
> 
> diff --git a/fs/ext4/migrate.c b/fs/ext4/migrate.c
> index 0a220ec9862d..a19a9661646e 100644
> --- a/fs/ext4/migrate.c
> +++ b/fs/ext4/migrate.c
> @@ -424,7 +424,8 @@ int ext4_ext_migrate(struct inode *inode)
>  	 * already is extent-based, error out.
>  	 */
>  	if (!ext4_has_feature_extents(inode->i_sb) ||
> -	    (ext4_test_inode_flag(inode, EXT4_INODE_EXTENTS)))
> +	    ext4_test_inode_flag(inode, EXT4_INODE_EXTENTS) ||
> +	    ext4_has_inline_data(inode))
>  		return -EINVAL;
>  
>  	if (S_ISLNK(inode->i_mode) && inode->i_blocks == 0)
> -- 
> 2.31.1
> 
-- 
Jan Kara <jack@xxxxxxxx>
SUSE Labs, CR