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BUG: KCSAN: data-race in fat_bmap / generic_write_end

write to 0xffff888122a113c8 of 8 bytes by task 9012 on cpu 0:
 i_size_write include/linux/fs.h:878 [inline]
 generic_write_end+0x98/0x230 fs/buffer.c:2183
 fat_write_end+0x4a/0x150 fs/fat/inode.c:249
 generic_perform_write+0x26a/0x3f0 mm/filemap.c:3798
 __generic_file_write_iter+0x172/0x280 mm/filemap.c:3883
 generic_file_write_iter+0x75/0x130 mm/filemap.c:3947
 do_iter_readv_writev+0x27b/0x300
 do_iter_write+0x16f/0x5c0 fs/read_write.c:852
 vfs_iter_write+0x4c/0x70 fs/read_write.c:893
 iter_file_splice_write+0x44a/0x7c0 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+0x345/0x660 fs/splice.c:891
 do_splice_direct+0xfb/0x180 fs/splice.c:979
 do_sendfile+0x3ad/0x900 fs/read_write.c:1246
 __do_sys_sendfile64 fs/read_write.c:1311 [inline]
 __se_sys_sendfile64 fs/read_write.c:1297 [inline]
 __x64_sys_sendfile64+0x10c/0x150 fs/read_write.c:1297
 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+0x44/0xae

read to 0xffff888122a113c8 of 8 bytes by task 9025 on cpu 1:
 i_size_read include/linux/fs.h:856 [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+0x3e8/0xf20 fs/mpage.c:203
 mpage_readahead+0x18b/0x3f0 fs/mpage.c:356
 fat_readahead+0x18/0x20 fs/fat/inode.c:215
 read_pages+0xa0/0x7c0 mm/readahead.c:157
 page_cache_ra_unbounded+0x11f/0x2e0 mm/readahead.c:234
 do_page_cache_ra mm/readahead.c:291 [inline]
 page_cache_ra_order mm/readahead.c:546 [inline]
 ondemand_readahead+0x5df/0x780 mm/readahead.c:668
 page_cache_sync_ra+0x1a4/0x1b0 mm/readahead.c:695
 page_cache_sync_readahead include/linux/pagemap.h:1185 [inline]
 filemap_get_pages mm/filemap.c:2592 [inline]
 filemap_read+0x3e5/0x1400 mm/filemap.c:2679
 generic_file_read_iter+0x72/0x320 mm/filemap.c:2825
 call_read_iter include/linux/fs.h:2044 [inline]
 generic_file_splice_read+0x1de/0x2c0 fs/splice.c:311
 do_splice_to fs/splice.c:796 [inline]
 splice_direct_to_actor+0x2ac/0x660 fs/splice.c:870
 do_splice_direct+0xfb/0x180 fs/splice.c:979
 do_sendfile+0x3ad/0x900 fs/read_write.c:1246
 __do_sys_sendfile64 fs/read_write.c:1311 [inline]
 __se_sys_sendfile64 fs/read_write.c:1297 [inline]
 __x64_sys_sendfile64+0x10c/0x150 fs/read_write.c:1297
 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+0x44/0xae

value changed: 0x000000000011d000 -> 0x000000000011e000

Reported by Kernel Concurrency Sanitizer on:
CPU: 1 PID: 9025 Comm: syz-executor.3 Not tainted 5.18.0-rc7-syzkaller-00119-gb015dcd62b86-dirty #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
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