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BUG: KCSAN: data-race in fat_bmap / generic_write_end

write to 0xffff88813bc16240 of 8 bytes by task 22812 on cpu 1:
 i_size_write include/linux/fs.h:932 [inline]
 generic_write_end+0x94/0x230 fs/buffer.c:2292
 fat_write_end+0x4e/0x160 fs/fat/inode.c:244
 generic_perform_write+0x267/0x410 mm/filemap.c:3980
 __generic_file_write_iter+0xa1/0x120 mm/filemap.c:4064
 generic_file_write_iter+0x7d/0x1c0 mm/filemap.c:4090
 do_iter_write+0x4b4/0x7b0 fs/read_write.c:860
 vfs_iter_write+0x56/0x70 fs/read_write.c:901
 iter_file_splice_write+0x462/0x7e0 fs/splice.c:736
 do_splice_from fs/splice.c:933 [inline]
 direct_splice_actor+0x8a/0xb0 fs/splice.c:1142
 splice_direct_to_actor+0x31d/0x690 fs/splice.c:1088
 do_splice_direct+0x10d/0x190 fs/splice.c:1194
 do_sendfile+0x3b6/0x9a0 fs/read_write.c:1254
 __do_sys_sendfile64 fs/read_write.c:1322 [inline]
 __se_sys_sendfile64 fs/read_write.c:1308 [inline]
 __x64_sys_sendfile64+0x110/0x150 fs/read_write.c:1308
 do_syscall_x64 arch/x86/entry/common.c:50 [inline]
 do_syscall_64+0x41/0xc0 arch/x86/entry/common.c:80
 entry_SYSCALL_64_after_hwframe+0x63/0xcd

read to 0xffff88813bc16240 of 8 bytes by task 22820 on cpu 0:
 i_size_read include/linux/fs.h:910 [inline]
 is_exceed_eof fs/fat/cache.c:340 [inline]
 fat_bmap+0x1d2/0x290 fs/fat/cache.c:375
 __fat_get_block fs/fat/inode.c:129 [inline]
 fat_get_block+0xd1/0x5e0 fs/fat/inode.c:190
 do_mpage_readpage+0x478/0xd90 fs/mpage.c:234
 mpage_readahead+0x1ad/0x2d0 fs/mpage.c:382
 fat_readahead+0x1c/0x20 fs/fat/inode.c:210
 read_pages+0x9f/0x530 mm/readahead.c:160
 page_cache_ra_unbounded+0x224/0x2e0
 do_page_cache_ra mm/readahead.c:299 [inline]
 force_page_cache_ra+0x18e/0x1d0 mm/readahead.c:330
 force_page_cache_readahead mm/internal.h:130 [inline]
 generic_fadvise+0x2c7/0x460 mm/fadvise.c:106
 vfs_fadvise+0x73/0x80 mm/fadvise.c:185
 ksys_readahead mm/readahead.c:741 [inline]
 __do_sys_readahead mm/readahead.c:749 [inline]
 __se_sys_readahead mm/readahead.c:747 [inline]
 __x64_sys_readahead+0x117/0x170 mm/readahead.c:747
 do_syscall_x64 arch/x86/entry/common.c:50 [inline]
 do_syscall_64+0x41/0xc0 arch/x86/entry/common.c:80
 entry_SYSCALL_64_after_hwframe+0x63/0xcd

value changed: 0x00000000000ba0b7 -> 0x00000000000ba8b2

Reported by Kernel Concurrency Sanitizer on:
CPU: 0 PID: 22820 Comm: syz-executor.1 Not tainted 6.6.0-rc5-syzkaller-00267-g9a3dad63edbe #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 09/06/2023
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