11 Apr
2019
11 Apr
'19
9:49 p.m.
On Apr 11, 2019, at 8:57 AM, Richard Tobin <richard(a)inf.ed.ac.uk> wrote:
You still had to read all those unallocated blocks as zeroes
if you wanted to copy such a "holey" file. I believe it was
Solaris (may be just for zfs?) that added SEEK_HOLE and
SEEK_DATA lseek whence values.
This could've been hidden if only mmap was allowed on files.
Or alternately read/write buffering was done by the kernel
or the {network,file}-server - which can avoid copying in
cases where it makes sense.
When did the Unix filesystem add the semantics
for "files with holes" (large,
sparse files)?
It was there in the first edition:
https://www.bell-labs.com/usr/dmr/www/pdfs/man51.pdf