ext4: fix bug_on in ext4_writepages

In the Linux kernel, the following vulnerability has been resolved:

ext4: fix bug_on in ext4_writepages

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))

The root cause of this issue is we destory inline data until call

ext4_writepages under delay allocation mode. But there maybe already

convert from inline to extent. To solve this issue, we call

filemap_flush first..