efivarfs: fsync file variable store on write#304
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write_file() persists the RAM-backed EFI variable store to a file on the ESP via buffered fopen()/fwrite()/fclose(), with no explicit flush to storage. The data can remain dirty in the page cache and be lost on a power loss before the kernel's periodic writeback runs, even though efi_update_var_file() is invoked synchronously from efivarfs_set_variable() and efivarfs_del_variable(). Add an explicit fflush()+fsync() after the write loop so the variable store file is durable on disk before write_file() returns. Signed-off-by: Balaji Selvanathan <balaji.selvanathan@oss.qualcomm.com>
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write_file() persists the RAM-backed EFI variable store to a file on the ESP via buffered fopen()/fwrite()/fclose(), with no explicit flush to storage. The data can remain dirty in the page cache and be lost on a power loss before the kernel's periodic writeback runs, even though efi_update_var_file() is invoked synchronously from efivarfs_set_variable() and efivarfs_del_variable().
Add an explicit fflush()+fsync() after the write loop so the variable store file is durable on disk before write_file() returns.