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BUG: KCSAN: data-race in fat_bmap / generic_write_end

write to 0xffff8881290d09e8 of 8 bytes by task 16608 on cpu 1:
 i_size_write include/linux/fs.h:886 [inline]
 generic_write_end+0xb1/0x350 fs/buffer.c:2168
 fat_write_end+0x4a/0x150 fs/fat/inode.c:249
 generic_perform_write+0x264/0x3f0 mm/filemap.c:3764
 __generic_file_write_iter+0x172/0x280 mm/filemap.c:3849
 generic_file_write_iter+0x79/0x1c0 mm/filemap.c:3913
 do_iter_write+0x494/0x750 fs/read_write.c:861
 vfs_iter_write+0x4c/0x70 fs/read_write.c:902
 iter_file_splice_write+0x44a/0x7c0 fs/splice.c:686
 do_splice_from fs/splice.c:764 [inline]
 direct_splice_actor+0x80/0xa0 fs/splice.c:931
 splice_direct_to_actor+0x305/0x620 fs/splice.c:886
 do_splice_direct+0xfb/0x180 fs/splice.c:974
 do_sendfile+0x3bf/0x910 fs/read_write.c:1255
 __do_sys_sendfile64 fs/read_write.c:1323 [inline]
 __se_sys_sendfile64 fs/read_write.c:1309 [inline]
 __x64_sys_sendfile64+0x10c/0x150 fs/read_write.c:1309
 do_syscall_x64 arch/x86/entry/common.c:50 [inline]
 do_syscall_64+0x2b/0x70 arch/x86/entry/common.c:80
 entry_SYSCALL_64_after_hwframe+0x63/0xcd

read to 0xffff8881290d09e8 of 8 bytes by task 16601 on cpu 0:
 i_size_read include/linux/fs.h:864 [inline]
 is_exceed_eof fs/fat/cache.c:340 [inline]
 fat_bmap+0x1cc/0x290 fs/fat/cache.c:375
 __fat_get_block fs/fat/inode.c:129 [inline]
 fat_get_block+0xcf/0x600 fs/fat/inode.c:190
 do_mpage_readpage+0x539/0xcf0 fs/mpage.c:208
 mpage_readahead+0x19f/0x2c0 fs/mpage.c:361
 fat_readahead+0x18/0x20 fs/fat/inode.c:215
 read_pages+0xa6/0x560 mm/readahead.c:161
 page_cache_ra_unbounded+0x12a/0x320 mm/readahead.c:242
 do_page_cache_ra mm/readahead.c:300 [inline]
 page_cache_ra_order mm/readahead.c:560 [inline]
 ondemand_readahead+0x541/0x6d0 mm/readahead.c:682
 page_cache_sync_ra+0xdc/0xf0 mm/readahead.c:709
 page_cache_sync_readahead include/linux/pagemap.h:1213 [inline]
 filemap_get_pages mm/filemap.c:2581 [inline]
 filemap_read+0x3fd/0x1510 mm/filemap.c:2675
 generic_file_read_iter+0x72/0x320 mm/filemap.c:2821
 call_read_iter include/linux/fs.h:2180 [inline]
 generic_file_splice_read+0xde/0x2b0 fs/splice.c:309
 do_splice_to fs/splice.c:793 [inline]
 splice_direct_to_actor+0x26c/0x620 fs/splice.c:865
 do_splice_direct+0xfb/0x180 fs/splice.c:974
 do_sendfile+0x3bf/0x910 fs/read_write.c:1255
 __do_sys_sendfile64 fs/read_write.c:1323 [inline]
 __se_sys_sendfile64 fs/read_write.c:1309 [inline]
 __x64_sys_sendfile64+0x10c/0x150 fs/read_write.c:1309
 do_syscall_x64 arch/x86/entry/common.c:50 [inline]
 do_syscall_64+0x2b/0x70 arch/x86/entry/common.c:80
 entry_SYSCALL_64_after_hwframe+0x63/0xcd

value changed: 0x000000000021b000 -> 0x000000000021c000

Reported by Kernel Concurrency Sanitizer on:
CPU: 0 PID: 16601 Comm: syz-executor.1 Not tainted 6.1.0-syzkaller-02754-g9b93f5069fd9-dirty #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 10/26/2022
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