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[BUG] There is a syzbot report that the ASSERT() inside write_dev_supers() got triggered: assertion failed: folio_order(folio) == 0, in fs/btrfs/disk-io.c:3858 ------------[ cut here ]------------ kernel BUG at fs/btrfs/disk-io.c:3858! Oops: invalid opcode: 0000 [#1] SMP KASAN NOPTI CPU: 0 UID: 0 PID: 6730 Comm: syz-executor378 Not tainted 6.14.0-syzkaller-03565-gf6e0150b2003 #0 PREEMPT(full) Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 1.16.3-debian-1.16.3-2~bpo12+1 04/01/2014 RIP: 0010:write_dev_supers fs/btrfs/disk-io.c:3858 [inline] RIP: 0010:write_all_supers+0x400f/0x4090 fs/btrfs/disk-io.c:4155 Call Trace: <TASK> btrfs_commit_transaction+0x1eda/0x3750 fs/btrfs/transaction.c:2528 btrfs_quota_enable+0xfcc/0x21a0 fs/btrfs/qgroup.c:1226 btrfs_ioctl_quota_ctl+0x144/0x1c0 fs/btrfs/ioctl.c:3677 vfs_ioctl fs/ioctl.c:51 [inline] __do_sys_ioctl fs/ioctl.c:906 [inline] __se_sys_ioctl+0xf1/0x160 fs/ioctl.c:892 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline] do_syscall_64+0xf3/0x230 arch/x86/entry/syscall_64.c:94 entry_SYSCALL_64_after_hwframe+0x77/0x7f RIP: 0033:0x7f5ad1f20289 </TASK> ---[ end trace 0000000000000000 ]--- [CAUSE] Since commitf93ee0df51("btrfs: convert super block writes to folio in write_dev_supers()") and commitc94b7349b8("btrfs: convert super block writes to folio in wait_dev_supers()"), the super block writeback path is converted to use folio. Since the original code is using page based interfaces, we have an "ASSERT(folio_order(folio) == 0);" added to make sure everything is not changed. But the folio here is not from any btrfs inode, but from the block device, and we have no control on the folio order in bdev, the device can choose whatever folio size they want/need. E.g. the bdev may even have a block size of multiple pages. So the ASSERT() is triggered. [FIX] The super block writeback path has taken larger folios into consideration, so there is no need for the ASSERT(). And since commitbc00965dbf("btrfs: count super block write errors in device instead of tracking folio error state"), the wait path no longer checks the folio status but only wait for the folio writeback to finish, there is nothing requiring the ASSERT() either. So we can remove both ASSERT()s safely now. Reported-by: syzbot+34122898a11ab689518a@syzkaller.appspotmail.com Signed-off-by: Qu Wenruo <wqu@suse.com> Reviewed-by: David Sterba <dsterba@suse.com> Signed-off-by: David Sterba <dsterba@suse.com>
Linux kernel
============
There are several guides for kernel developers and users. These guides can
be rendered in a number of formats, like HTML and PDF. Please read
Documentation/admin-guide/README.rst first.
In order to build the documentation, use ``make htmldocs`` or
``make pdfdocs``. The formatted documentation can also be read online at:
https://www.kernel.org/doc/html/latest/
There are various text files in the Documentation/ subdirectory,
several of them using the reStructuredText markup notation.
Please read the Documentation/process/changes.rst file, as it contains the
requirements for building and running the kernel, and information about
the problems which may result by upgrading your kernel.