On Thu, Jan 13, 2022 at 03:20:32PM +0000, David Howells wrote:
David Howells <dhowells@xxxxxxxxxx> wrote:
If I do the following:
mount //carina/test /xfstest.test -o user=shares,pass=foobar,noperm,vers=3.0,mfsymlinks,actimeo=0
/usr/sbin/xfs_io -f -t \
-c "pwrite -S 0x41 0 4096"
-c "pwrite -S 0x42 4096 4096"
-c "fzero 0 4096" \
-c "pread 0 8192" \
/xfstest.test/008.7067
...
31 0.321638749 192.168.6.2 -> 192.168.6.1 SMB2 206 Ioctl Request FSCTL_SET_ZERO_DATA File: 008.7067
So what I see is that Samba does:
fallocate(24, FALLOC_FL_KEEP_SIZE|FALLOC_FL_PUNCH_HOLE, 0, 4096) = 0
for this... but that's not what cifs was asked to do. Should Samba be using
FALLOC_FL_ZERO_RANGE instead?
This is from fsctl_zero_data() in Samba. We have:
/*
* MS-FSCC <58> Section 2.3.67
* This FSCTL sets the range of bytes to zero (0) without extending the
* file size.
*
* The VFS_FALLOCATE_FL_KEEP_SIZE flag is used to satisfy this
* constraint.
*/
mode = VFS_FALLOCATE_FL_PUNCH_HOLE | VFS_FALLOCATE_FL_KEEP_SIZE;
ret = SMB_VFS_FALLOCATE(fsp, mode, zdata_info.file_off, len);
if (ret == -1) {
status = map_nt_error_from_unix_common(errno);
DEBUG(2, ("zero-data fallocate(0x%x) failed: %s\n", mode,
strerror(errno)));
return status;
}
if (!fsp->fsp_flags.is_sparse && lp_strict_allocate(SNUM(fsp->conn))) {
/*
* File marked non-sparse and "strict allocate" is enabled -
* allocate the range that we just punched out.
* In future FALLOC_FL_ZERO_RANGE could be used exclusively for
* this, but it's currently only supported on XFS and ext4.
*
* The newly allocated range still won't be found by SEEK_DATA
* for QAR, but stat.st_blocks will reflect it.
*/
ret = SMB_VFS_FALLOCATE(fsp, VFS_FALLOCATE_FL_KEEP_SIZE,
zdata_info.file_off, len);
Note the "currently only supported on XFS and ext4" problem
with FALLOC_FL_ZERO_RANGE.
