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BUG: KCSAN: data-race in shmem_getattr / shmem_recalc_inode

read-write to 0xffff8881176f1750 of 8 bytes by task 18724 on cpu 0:
 shmem_recalc_inode+0x3f/0x1f0 mm/shmem.c:444
 shmem_alloc_and_add_folio mm/shmem.c:2013 [inline]
 shmem_get_folio_gfp+0x7a8/0xd60 mm/shmem.c:2579
 shmem_get_folio mm/shmem.c:2685 [inline]
 shmem_fallocate+0x628/0x920 mm/shmem.c:3801
 vfs_fallocate+0x3b6/0x450 fs/open.c:339
 ksys_fallocate fs/open.c:363 [inline]
 __do_sys_fallocate fs/open.c:368 [inline]
 __se_sys_fallocate fs/open.c:366 [inline]
 __x64_sys_fallocate+0x7a/0xd0 fs/open.c:366
 x64_sys_call+0x1cd4/0x3000 arch/x86/include/generated/asm/syscalls_64.h:286
 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
 do_syscall_64+0xc0/0x2a0 arch/x86/entry/syscall_64.c:94
 entry_SYSCALL_64_after_hwframe+0x77/0x7f

read to 0xffff8881176f1750 of 8 bytes by task 18726 on cpu 1:
 shmem_getattr+0x41/0x200 mm/shmem.c:1285
 vfs_getattr_nosec+0x146/0x1e0 fs/stat.c:213
 vfs_getattr+0x48/0x60 fs/stat.c:262
 vfs_statx_path+0x28/0x140 fs/stat.c:299
 vfs_statx+0xc4/0x170 fs/stat.c:356
 vfs_fstatat fs/stat.c:375 [inline]
 vfs_lstat include/linux/fs.h:3163 [inline]
 __do_sys_newlstat fs/stat.c:528 [inline]
 __se_sys_newlstat+0x66/0x3f0 fs/stat.c:522
 __x64_sys_newlstat+0x31/0x40 fs/stat.c:522
 x64_sys_call+0x1f49/0x3000 arch/x86/include/generated/asm/syscalls_64.h:7
 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
 do_syscall_64+0xc0/0x2a0 arch/x86/entry/syscall_64.c:94
 entry_SYSCALL_64_after_hwframe+0x77/0x7f

value changed: 0x0000000000001b0b -> 0x0000000000001b0c

Reported by Kernel Concurrency Sanitizer on:
CPU: 1 UID: 0 PID: 18726 Comm: syz.1.3929 Tainted: G        W           syzkaller #0 PREEMPT(voluntary) 
Tainted: [W]=WARN
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 10/25/2025
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