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Date: Fri, 6 May 2022 20:48:44 +0800 From: yebin <yebin10@...wei.com> To: Jan Kara <jack@...e.cz> CC: <tytso@....edu>, <adilger.kernel@...ger.ca>, <linux-ext4@...r.kernel.org>, <linux-kernel@...r.kernel.org>, <lczerner@...hat.com> Subject: Re: [PATCH -next] ext4: fix bug_on in ext4_writepages On 2022/5/6 16:50, Jan Kara wrote: > On Fri 06-05-22 09:27:25, yebin wrote: >> On 2022/5/5 23:47, Jan Kara wrote: >>> 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@...wei.com> >>> I think this will get also fixed by a patch from your colleague I've >>> reviewed here [1], won't it? >>> >>> [1] https://lore.kernel.org/all/20220428165725.mvjh6mx7gr5vekqe@quack3.lan >>> >> The issue I fixed is not the same as the isuue my colleague fixed. > OK, maybe I've jumped to conclusion too early but the fix I've referenced > above will protect ext4_convert_inline_data() in ext4_fallocate() with > inode->i_rwsem so I think the race you describe with ext4_da_write_begin() > cannot happen. The inline conversion path with be entered either from > ext4_da_write_begin() or from ext4_fallocate() but not from both. If I'm > missing something, please explain how you think the problem happens with > the above fix applied... Thanks! > > Honza It's happen as follows: step1: ext4_file_write_iter ext4_buffered_write_iter generic_perform_write ext4_da_write_begin if (ext4_test_inode_state(inode, EXT4_STATE_MAY_INLINE_DATA)) ext4_da_write_inline_data_begin ext4_da_convert_inline_data_to_extent __block_write_begin ext4_clear_inode_state(inode, EXT4_STATE_MAY_INLINE_DATA); ->clear EXT4_STATE_MAY_INLINE_DATA flag, If inline data size too small will allocate block to write, then mapping will has dirty page ext4_da_write_end generic_write_end step2: vfs_fallocate ext4_fallocate ext4_convert_inline_data if (ext4_has_inline_data(inode)) -> This condition is satisfied 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 step3: do_writepages ext4_writepages if (ext4_has_inline_data(inode)) BUG_ON(ext4_test_inode_state(inode, EXT4_STATE_MAY_INLINE_DATA)) As we call "ext4_destroy_inline_data" to destory inline data when delay allocation. So,if we call fallocate before writepages while ext4_map_blocks return failed, will lead to above issue. This issue does not require concurrency conditions. >>>> --- >>>> 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 >>>>
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