KCSAN: data-race in ext4_setattr / mpage_process_page_bufs (2)

[syzbot]

Hello,

syzbot found the following issue on:

HEAD commit: 325d0eab Merge branch 'akpm' (patches from Andrew)
git tree: upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=161f7e9b900000
kernel config: https://syzkaller.appspot.com/x/.config?x=71d95d75ec48fd6f
dashboard link: https://syzkaller.appspot.com/bug?extid=d8c674e306c5fd82145e
compiler: clang version 11.0.0 (https://github.com/llvm/llvm-project.git ca2dcbd030eadbf0aa9b660efe864ff08af6e18b)
CC: [adilger...@dilger.ca linux...@vger.kernel.org linux-...@vger.kernel.org ty...@mit.edu]

Unfortunately, I don't have any reproducer for this issue yet.

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+d8c674...@syzkaller.appspotmail.com

==================================================================
BUG: KCSAN: data-race in ext4_setattr / mpage_process_page_bufs

write to 0xffff8880bbbda1f8 of 8 bytes by task 27492 on cpu 0:
i_size_write include/linux/fs.h:876 [inline]
ext4_setattr+0xd63/0xec0 fs/ext4/inode.c:5386
notify_change+0x7d7/0xa80 fs/attr.c:336
do_truncate+0xe0/0x120 fs/open.c:64
handle_truncate fs/namei.c:2909 [inline]
do_open fs/namei.c:3255 [inline]
path_openat+0x1a31/0x20a0 fs/namei.c:3368
do_filp_open+0xbd/0x1d0 fs/namei.c:3395
do_sys_openat2+0x33b/0x500 fs/open.c:1168
do_sys_open fs/open.c:1184 [inline]
__do_sys_creat fs/open.c:1258 [inline]
__se_sys_creat fs/open.c:1252 [inline]
__x64_sys_creat+0x62/0x80 fs/open.c:1252
do_syscall_64+0x39/0x80 arch/x86/entry/common.c:46
entry_SYSCALL_64_after_hwframe+0x44/0xa9

read to 0xffff8880bbbda1f8 of 8 bytes by task 27486 on cpu 1:
i_size_read include/linux/fs.h:854 [inline]
mpage_process_page_bufs+0x34/0x600 fs/ext4/inode.c:2173
mpage_prepare_extent_to_map+0x4ec/0x650 fs/ext4/inode.c:2607
ext4_writepages+0x97d/0x1ef0 fs/ext4/inode.c:2779
do_writepages+0x7b/0x150 mm/page-writeback.c:2352
__filemap_fdatawrite_range+0x19b/0x1d0 mm/filemap.c:422
file_write_and_wait_range+0x9f/0x120 mm/filemap.c:761
ext4_sync_file+0xfc/0x6e0 fs/ext4/fsync.c:151
vfs_fsync_range+0x107/0x120 fs/sync.c:200
generic_write_sync include/linux/fs.h:2747 [inline]
ext4_buffered_write_iter+0x369/0x3b0 fs/ext4/file.c:276
ext4_file_write_iter+0x768/0x1060 include/linux/fs.h:784
call_write_iter include/linux/fs.h:1882 [inline]
new_sync_write fs/read_write.c:503 [inline]
vfs_write+0x665/0x6f0 fs/read_write.c:578
ksys_write+0xce/0x180 fs/read_write.c:631
__do_sys_write fs/read_write.c:643 [inline]
__se_sys_write fs/read_write.c:640 [inline]
__x64_sys_write+0x3e/0x50 fs/read_write.c:640
do_syscall_64+0x39/0x80 arch/x86/entry/common.c:46
entry_SYSCALL_64_after_hwframe+0x44/0xa9

Reported by Kernel Concurrency Sanitizer on:
CPU: 1 PID: 27486 Comm: syz-executor.3 Not tainted 5.9.0-rc5-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
==================================================================


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[syzbot]

Auto-closing this bug as obsolete.
Crashes did not happen for a while, no reproducer and no activity.