ksmbd: round SetAllocation to the advertised allocation unit

SetAllocation rounds requests to 512-byte blocks, although
FS_SIZE_INFORMATION advertises the filesystem's f_bsize as its
allocation unit. For example, on a filesystem with a 4 KiB unit, a
1000-byte request can truncate an 8 KiB file to 1024 bytes instead of
4 KiB.

Round the request to the advertised unit and use the same result for
the block-count decision, fallocate, truncate, and the size stored on
the open handle. Validate the unit and rounded size before either
operation. Use DIV_ROUND_UP_ULL() so the calculation works on 32-bit
kernels.

This does not change the existing block-count decision for whether to
call fallocate. In particular, success does not yet guarantee
reservation of holes within the requested range on a sparse file.

Fixes: e2f34481b24d ("cifsd: add server-side procedures for SMB3")
Signed-off-by: DaeMyung Kang <charsyam@gmail.com>
Signed-off-by: Namjae Jeon <linkinjeon@kernel.org>

0 files changed, 0 insertions, 0 deletions