[PATCH 0/7] smb/client: fix fallocate allocation handling

[Huiwen He <huiwen.he@linux.dev>]

From: Huiwen He <hehuiwen@kylinos.cn>

CIFS fallocate can return success without allocating the requested space.
It can also derive i_blocks from EOF, making sparse files appear fully
allocated.

This series propagates sparse conversion failures, corrects i_blocks
accounting, and verifies server allocation after EOF-extending mode 0
fallocate. It also reduces the memory used by zero-write emulation and
supports small ranges starting at EOF.

General arbitrary-range preallocation remains unsupported because SMB2
provides no equivalent operation. Small ranges can be emulated by writing
zeroes.

Tested against Samba with xfstests. With `strict allocate=yes`,
generic/496, generic/568 and generic/701 pass with server allocation
verified. generic/495 was used to verify that EOF extension no longer
inflates i_blocks.

With `strict allocate=no`, requests whose allocation cannot be verified
fail instead of reporting false preallocation success.

Huiwen He (7):
  smb/client: name the default fallocate mode
  smb/client: handle smb2_set_sparse() failure in EOF-extending
    fallocate
  smb/client: handle smb2_set_sparse() failure in non-extending
    fallocate
  smb/client: do not account EOF extension as allocation
  smb/client: verify allocation after EOF-extending fallocate
  smb/client: reduce fallocate zero buffer allocation
  smb/client: emulate small fallocate ranges at EOF

 fs/smb/client/inode.c     |  13 +++-
 fs/smb/client/smb2ops.c   | 128 +++++++++++++++++++++++++++++++++-----
 fs/smb/client/smb2pdu.c   |  19 ++++++
 fs/smb/client/smb2proto.h |   3 +
 fs/smb/common/fscc.h      |   5 ++
 5 files changed, 151 insertions(+), 17 deletions(-)

-- 
2.43.0