Re: [PATCH -next] ext4: fix bug_on in ext4_writepages

Jan Kara
2022-05-09T13:01:16Z

On Thu 05-05-22 21:57:08, Ye Bin wrote:
> we got issue as follows:
> EXT4-fs error (device loop0): ext4_mb_generate_buddy:1141: group 0, block bitmap and bg descriptor inconsistent: 25 vs 31513 free cls
> ------------[ cut here ]------------
> kernel BUG at fs/ext4/inode.c:2708!
> invalid opcode: 0000 [#1] PREEMPT SMP KASAN PTI
> CPU: 2 PID: 2147 Comm: rep Not tainted 5.18.0-rc2-next-20220413+ #155
> RIP: 0010:ext4_writepages+0x1977/0x1c10
> RSP: 0018:ffff88811d3e7880 EFLAGS: 00010246
> RAX: 0000000000000000 RBX: 0000000000000001 RCX: ffff88811c098000
> RDX: 0000000000000000 RSI: ffff88811c098000 RDI: 0000000000000002
> RBP: ffff888128140f50 R08: ffffffffb1ff6387 R09: 0000000000000000
> R10: 0000000000000007 R11: ffffed10250281ea R12: 0000000000000001
> R13: 00000000000000a4 R14: ffff88811d3e7bb8 R15: ffff888128141028
> FS: 00007f443aed9740(0000) GS:ffff8883aef00000(0000) knlGS:0000000000000000
> CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
> CR2: 0000000020007200 CR3: 000000011c2a4000 CR4: 00000000000006e0
> DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
> DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
> Call Trace:
> <TASK>
> do_writepages+0x130/0x3a0
> filemap_fdatawrite_wbc+0x83/0xa0
> filemap_flush+0xab/0xe0
> ext4_alloc_da_blocks+0x51/0x120
> __ext4_ioctl+0x1534/0x3210
> __x64_sys_ioctl+0x12c/0x170
> do_syscall_64+0x3b/0x90
>
> It may happen as follows:
> 1. write inline_data inode
> vfs_write
> new_sync_write
> ext4_file_write_iter
> ext4_buffered_write_iter
> generic_perform_write
> ext4_da_write_begin
> ext4_da_write_inline_data_begin -> If inline data size too
> small will allocate block to write, then mapping will has
> dirty page
> ext4_da_convert_inline_data_to_extent ->clear EXT4_STATE_MAY_INLINE_DATA
> 2. fallocate
> do_vfs_ioctl
> ioctl_preallocate
> vfs_fallocate
> ext4_fallocate
> ext4_convert_inline_data
> ext4_convert_inline_data_nolock
> ext4_map_blocks -> fail will goto restore data
> ext4_restore_inline_data
> ext4_create_inline_data
> ext4_write_inline_data
> ext4_set_inode_state -> set inode EXT4_STATE_MAY_INLINE_DATA
> 3. writepages
> __ext4_ioctl
> ext4_alloc_da_blocks
> filemap_flush
> filemap_fdatawrite_wbc
> do_writepages
> ext4_writepages
> if (ext4_has_inline_data(inode))
> BUG_ON(ext4_test_inode_state(inode, EXT4_STATE_MAY_INLINE_DATA))
>
> To solved this issue, record origin 'EXT4_STATE_MAY_INLINE_DATA' flag, then pass
> value to 'ext4_restore_inline_data', 'ext4_restore_inline_data' will
> decide to if recovery 'EXT4_STATE_MAY_INLINE_DATA' flag according to parameter.
>
> Signed-off-by: Ye Bin <yebin10@huawei.com>

Thanks for the patch. I agree it will fix the crash you have spotted but
I'm somewhat wondering whether it would not be simpler to just move the
call to ext4_destroy_inline_data_nolock() in
ext4_convert_inline_data_nolock() later, after we have done writing
data_bh. That way we can completely remove ext4_restore_inline_data() and
as a consequence avoid problems. What do you think?

Honza

> ---
> fs/ext4/inline.c | 13 +++++++++----
> 1 file changed, 9 insertions(+), 4 deletions(-)
>
> diff --git a/fs/ext4/inline.c b/fs/ext4/inline.c
> index 9c076262770d..407061c79adc 100644
> --- a/fs/ext4/inline.c
> +++ b/fs/ext4/inline.c
> @@ -1125,8 +1125,8 @@ static int ext4_update_inline_dir(handle_t *handle, struct inode *dir,
> }
>
> static void ext4_restore_inline_data(handle_t *handle, struct inode *inode,
> - struct ext4_iloc *iloc,
> - void *buf, int inline_size)
> + struct ext4_iloc *iloc, void *buf,
> + int inline_size, bool has_data)
> {
> int ret;
>
> @@ -1138,7 +1138,8 @@ static void ext4_restore_inline_data(handle_t *handle, struct inode *inode,
> return;
> }
> ext4_write_inline_data(inode, iloc, buf, 0, inline_size);
> - ext4_set_inode_state(inode, EXT4_STATE_MAY_INLINE_DATA);
> + if (has_data)
> + ext4_set_inode_state(inode, EXT4_STATE_MAY_INLINE_DATA);
> }
>
> static int ext4_finish_convert_inline_dir(handle_t *handle,
> @@ -1194,6 +1195,7 @@ static int ext4_convert_inline_data_nolock(handle_t *handle,
> struct buffer_head *data_bh = NULL;
> struct ext4_map_blocks map;
> int inline_size;
> + bool has_data;
>
> inline_size = ext4_get_inline_size(inode);
> buf = kmalloc(inline_size, GFP_NOFS);
> @@ -1222,6 +1224,8 @@ static int ext4_convert_inline_data_nolock(handle_t *handle,
> if (error)
> goto out;
>
> + has_data = !!ext4_test_inode_state(inode, EXT4_STATE_MAY_INLINE_DATA);
> +
> map.m_lblk = 0;
> map.m_len = 1;
> map.m_flags = 0;
> @@ -1262,7 +1266,8 @@ static int ext4_convert_inline_data_nolock(handle_t *handle,
> unlock_buffer(data_bh);
> out_restore:
> if (error)
> - ext4_restore_inline_data(handle, inode, iloc, buf, inline_size);
> + ext4_restore_inline_data(handle, inode, iloc, buf,
> + inline_size, has_data);
>
> out:
> brelse(data_bh);
> --
> 2.31.1