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BUG: KCSAN: data-race in ext4_punch_hole / xas_set_mark

write to 0xffff88812503cb54 of 4 bytes by task 8251 on cpu 1:
 xa_mark_set lib/xarray.c:69 [inline]
 xas_set_mark lib/xarray.c:886 [inline]
 xas_set_mark+0x14d/0x160 lib/xarray.c:870
 __xa_set_mark+0xd3/0x100 lib/xarray.c:1706
 __set_page_dirty+0x152/0x270 fs/buffer.c:624
 mark_buffer_dirty+0x27f/0x2c0 fs/buffer.c:1152
 __block_commit_write.isra.0+0x11f/0x170 fs/buffer.c:2081
 block_write_end+0x6d/0x140 fs/buffer.c:2159
 generic_write_end+0x8a/0x1f0 fs/buffer.c:2173
 ext4_da_write_end+0x158/0x620 fs/ext4/inode.c:3092
 generic_perform_write+0x1d3/0x320 mm/filemap.c:3298
 ext4_buffered_write_iter+0x143/0x290 fs/ext4/file.c:270
 ext4_file_write_iter+0xfa/0xd70 fs/ext4/file.c:642
 call_write_iter include/linux/fs.h:1901 [inline]
 new_sync_write+0x388/0x4a0 fs/read_write.c:483
 __vfs_write+0xb1/0xc0 fs/read_write.c:496
 vfs_write fs/read_write.c:558 [inline]
 vfs_write+0x18a/0x390 fs/read_write.c:542
 ksys_write+0xd5/0x1b0 fs/read_write.c:611
 __do_sys_write fs/read_write.c:623 [inline]
 __se_sys_write fs/read_write.c:620 [inline]
 __x64_sys_write+0x4c/0x60 fs/read_write.c:620
 do_syscall_64+0xcc/0x3a0 arch/x86/entry/common.c:294
 entry_SYSCALL_64_after_hwframe+0x44/0xa9

read to 0xffff88812503cb54 of 4 bytes by task 8253 on cpu 0:
 mapping_tagged include/linux/fs.h:521 [inline]
 ext4_punch_hole+0x110/0xab0 fs/ext4/inode.c:3956
 ext4_fallocate+0x28b/0x21a0 fs/ext4/extents.c:4865
 vfs_fallocate+0x3be/0x650 fs/open.c:309
 ksys_fallocate+0x61/0xa0 fs/open.c:332
 __do_sys_fallocate fs/open.c:340 [inline]
 __se_sys_fallocate fs/open.c:338 [inline]
 __x64_sys_fallocate+0x5e/0x80 fs/open.c:338
 do_syscall_64+0xcc/0x3a0 arch/x86/entry/common.c:294
 entry_SYSCALL_64_after_hwframe+0x44/0xa9

Reported by Kernel Concurrency Sanitizer on:
CPU: 0 PID: 8253 Comm: syz-executor.5 Not tainted 5.6.0-rc1-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
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