punching holes in files

Steve French smfrench at gmail.com
Thu Nov 1 19:16:25 GMT 2007

madvise_remove (in Linux) is used to free the backing store associated
with pages (punching a hole in a file).   This is one of the vfs
operations that we do not send over the wire to Samba (so this call
would return -ENOSYS locally).   Any thoughts on whether this could be
done with an obscure SetFileInfo level or FCNTL or whether it is worth
adding to the CIFS POSIX Extensions?

A second interesting question is whether to implement fallocate over
the wire.  sys_fallocate takes a range (and also a flag which
indicates whether to extend the size beyond end of file).
SET_FILE_ALLOCATION_INFO takes a size field rather than a range.  For
the case of the range starting at zero, we could simply call Trans2
set pathinfo (or file info) with SET_FILE_ALLOCATION_INFO.   Should we
add a CIFS POSIX Extension operation for this too?

By the way it looks like OCFS2 (not just ext4) implement these.



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