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BUG: KCSAN: data-race in __mark_inode_dirty / writeback_single_inode

write to 0xffff888130fca7a0 of 8 bytes by task 27639 on cpu 0:
 writeback_single_inode+0x148/0x3e0 fs/fs-writeback.c:1726
 sync_inode_metadata+0x57/0x80 fs/fs-writeback.c:2748
 ext4_fsync_nojournal fs/ext4/fsync.c:92 [inline]
 ext4_sync_file+0x359/0x670 fs/ext4/fsync.c:170
 vfs_fsync_range+0x107/0x120 fs/sync.c:200
 generic_write_sync include/linux/fs.h:2955 [inline]
 ext4_buffered_write_iter+0x3af/0x400 fs/ext4/file.c:277
 ext4_file_write_iter+0x2e7/0x11a0
 call_write_iter include/linux/fs.h:2163 [inline]
 do_iter_readv_writev+0x2cd/0x370 fs/read_write.c:729
 do_iter_write+0x192/0x5c0 fs/read_write.c:855
 vfs_iter_write+0x4c/0x70 fs/read_write.c:896
 iter_file_splice_write+0x40a/0x750 fs/splice.c:689
 do_splice_from fs/splice.c:767 [inline]
 direct_splice_actor+0x80/0xa0 fs/splice.c:936
 splice_direct_to_actor+0x345/0x650 fs/splice.c:891
 do_splice_direct+0xf5/0x170 fs/splice.c:979
 do_sendfile+0x618/0xb90 fs/read_write.c:1249
 __do_sys_sendfile64 fs/read_write.c:1314 [inline]
 __se_sys_sendfile64 fs/read_write.c:1300 [inline]
 __x64_sys_sendfile64+0xf2/0x130 fs/read_write.c:1300
 do_syscall_x64 arch/x86/entry/common.c:50 [inline]
 do_syscall_64+0x3d/0x90 arch/x86/entry/common.c:80
 entry_SYSCALL_64_after_hwframe+0x44/0xae

read to 0xffff888130fca7a0 of 8 bytes by task 27628 on cpu 1:
 __mark_inode_dirty+0xda/0x6a0 fs/fs-writeback.c:2419
 mark_buffer_dirty+0x143/0x200 fs/buffer.c:1112
 __block_commit_write fs/buffer.c:2079 [inline]
 block_write_end+0x13d/0x260 fs/buffer.c:2158
 generic_write_end+0x5e/0x180 fs/buffer.c:2172
 ext4_da_write_end+0x59b/0x730 fs/ext4/inode.c:3116
 generic_perform_write+0x23a/0x3d0 mm/filemap.c:3781
 ext4_buffered_write_iter+0x305/0x400 fs/ext4/file.c:269
 ext4_file_write_iter+0x2e7/0x11a0
 call_write_iter include/linux/fs.h:2163 [inline]
 do_iter_readv_writev+0x2cd/0x370 fs/read_write.c:729
 do_iter_write+0x192/0x5c0 fs/read_write.c:855
 vfs_iter_write+0x4c/0x70 fs/read_write.c:896
 iter_file_splice_write+0x40a/0x750 fs/splice.c:689
 do_splice_from fs/splice.c:767 [inline]
 direct_splice_actor+0x80/0xa0 fs/splice.c:936
 splice_direct_to_actor+0x345/0x650 fs/splice.c:891
 do_splice_direct+0xf5/0x170 fs/splice.c:979
 do_sendfile+0x618/0xb90 fs/read_write.c:1249
 __do_sys_sendfile64 fs/read_write.c:1314 [inline]
 __se_sys_sendfile64 fs/read_write.c:1300 [inline]
 __x64_sys_sendfile64+0xf2/0x130 fs/read_write.c:1300
 do_syscall_x64 arch/x86/entry/common.c:50 [inline]
 do_syscall_64+0x3d/0x90 arch/x86/entry/common.c:80
 entry_SYSCALL_64_after_hwframe+0x44/0xae

value changed: 0x0000000000000007 -> 0x0000000000000084

Reported by Kernel Concurrency Sanitizer on:
CPU: 1 PID: 27628 Comm: syz-executor.3 Tainted: G        W         5.14.0-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
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