On Tue 26-04-22 22:06:58, Baokun Li wrote:
> Hulk Robot reported a BUG_ON:
> ==================================================================
> EXT4-fs error (device loop3): ext4_mb_generate_buddy:805: group 0,
> block bitmap and bg descriptor inconsistent: 25 vs 31513 free clusters
> kernel BUG at fs/ext4/ext4_jbd2.c:53!
> invalid opcode: 0000 [#1] SMP KASAN PTI
> CPU: 0 PID: 25371 Comm: syz-executor.3 Not tainted 5.10.0+ #1
> RIP: 0010:ext4_put_nojournal fs/ext4/ext4_jbd2.c:53 [inline]
> RIP: 0010:__ext4_journal_stop+0x10e/0x110 fs/ext4/ext4_jbd2.c:116
> [...]
> Call Trace:
> ext4_write_inline_data_end+0x59a/0x730 fs/ext4/inline.c:795
> generic_perform_write+0x279/0x3c0 mm/filemap.c:3344
> ext4_buffered_write_iter+0x2e3/0x3d0 fs/ext4/file.c:270
> ext4_file_write_iter+0x30a/0x11c0 fs/ext4/file.c:520
> do_iter_readv_writev+0x339/0x3c0 fs/read_write.c:732
> do_iter_write+0x107/0x430 fs/read_write.c:861
> vfs_writev fs/read_write.c:934 [inline]
> do_pwritev+0x1e5/0x380 fs/read_write.c:1031
> [...]
> ==================================================================
>
> Above issue may happen as follows:
> cpu1 cpu2
> __________________________|__________________________
> do_pwritev
> vfs_writev
> do_iter_write
> ext4_file_write_iter
> ext4_buffered_write_iter
> generic_perform_write
> ext4_da_write_begin
> vfs_fallocate
> ext4_fallocate
> ext4_convert_inline_data
> ext4_convert_inline_data_nolock
> ext4_destroy_inline_data_nolock
> clear EXT4_STATE_MAY_INLINE_DATA
> ext4_map_blocks
> ext4_ext_map_blocks
> ext4_mb_new_blocks
> ext4_mb_regular_allocator
> ext4_mb_good_group_nolock
> ext4_mb_init_group
> ext4_mb_init_cache
> ext4_mb_generate_buddy --> error
> ext4_test_inode_state(inode, EXT4_STATE_MAY_INLINE_DATA)
> ext4_restore_inline_data
> set EXT4_STATE_MAY_INLINE_DATA
> ext4_block_write_begin
> ext4_da_write_end
> ext4_test_inode_state(inode, EXT4_STATE_MAY_INLINE_DATA)
> ext4_write_inline_data_end
> handle=NULL
> ext4_journal_stop(handle)
> __ext4_journal_stop
> ext4_put_nojournal(handle)
> ref_cnt = (unsigned long)handle
> BUG_ON(ref_cnt == 0) ---> BUG_ON
>
> The lock held by ext4_convert_inline_data is xattr_sem, but the lock
> held by generic_perform_write is i_rwsem. Therefore, the two locks can
> be concurrent. To solve above issue, we just add inode_lock in
> ext4_convert_inline_data.
>
> Fixes: 0c8d414f163f ("ext4: let fallocate handle inline data correctly")
> Cc: [email protected]
> Reported-by: Hulk Robot <[email protected]>
> Signed-off-by: Baokun Li <[email protected]>
Thanks for the report and the patch. I agree inode_lock is needed to
protect the conversion. However you cannot lock it inside
ext4_convert_inline_data() because it is often called with inode_lock
already held (in fact in most of the other cases as far as I have checked).
So the right fix is to reorganize ext4_fallocate() a bit to do something
like:
ext4_clear_inode_state(inode, EXT4_STATE_MAY_INLINE_DATA);
if (ext4_has_inline_data(inode)) {
inode_lock(inode);
ret = ext4_convert_inline_data(inode);
inode_unlock(inode);
if (ret)
goto exit;
}
and remove similar handling from ext4_punch_hole() (and make sure it uses
the new handling in ext4_fallocate()).
Honza
--
Jan Kara <[email protected]>
SUSE Labs, CR