* Re: [TUHS] Unix filesystem semantics history - files with holes
@ 2019-04-11 15:57 Richard Tobin
2019-04-11 19:09 ` William Corcoran
2019-04-11 19:49 ` Bakul Shah
0 siblings, 2 replies; 5+ messages in thread
From: Richard Tobin @ 2019-04-11 15:57 UTC (permalink / raw)
To: Erik E. Fair, The Eunuchs Hysterical Society
> 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
The FILE SYSTEM (V) man page includes a last paragraph identical to
that of FILSYS (V) in seventh edition:
If block b in a file exists, it is not necessary that all blocks
less than b exist. A zero block number either in the address words
of the the i-node or in an indirect block indicates that the
corresponding block has never been allocated. Such a missing block
reads as if it contained all zero words.
The first edition indirect blocks were a bit different though: if the
file was bigger than 8 blocks (4kB), all the blocks in the inode were
(singly) indirect.
-- Richard
--
The University of Edinburgh is a charitable body, registered in
Scotland, with registration number SC005336.
^ permalink raw reply [flat|nested] 5+ messages in thread
* Re: [TUHS] Unix filesystem semantics history - files with holes
2019-04-11 15:57 [TUHS] Unix filesystem semantics history - files with holes Richard Tobin
@ 2019-04-11 19:09 ` William Corcoran
2019-04-11 19:49 ` Bakul Shah
1 sibling, 0 replies; 5+ messages in thread
From: William Corcoran @ 2019-04-11 19:09 UTC (permalink / raw)
To: Richard Tobin; +Cc: The Eunuchs Hysterical Society
Sparse files: “Thin Provisioning” way ahead of its time. Combined with the patented SUID: The UNIX marvels never cease.
It just goes to show that all this marketing BS touted today has already been done before.
Bill Corcoran
On Apr 11, 2019, at 12:36 PM, Richard Tobin <richard@inf.ed.ac.uk> wrote:
>> 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
>
> The FILE SYSTEM (V) man page includes a last paragraph identical to
> that of FILSYS (V) in seventh edition:
>
> If block b in a file exists, it is not necessary that all blocks
> less than b exist. A zero block number either in the address words
> of the the i-node or in an indirect block indicates that the
> corresponding block has never been allocated. Such a missing block
> reads as if it contained all zero words.
>
> The first edition indirect blocks were a bit different though: if the
> file was bigger than 8 blocks (4kB), all the blocks in the inode were
> (singly) indirect.
>
> -- Richard
>
> --
> The University of Edinburgh is a charitable body, registered in
> Scotland, with registration number SC005336.
>
^ permalink raw reply [flat|nested] 5+ messages in thread
* Re: [TUHS] Unix filesystem semantics history - files with holes
2019-04-11 15:57 [TUHS] Unix filesystem semantics history - files with holes Richard Tobin
2019-04-11 19:09 ` William Corcoran
@ 2019-04-11 19:49 ` Bakul Shah
1 sibling, 0 replies; 5+ messages in thread
From: Bakul Shah @ 2019-04-11 19:49 UTC (permalink / raw)
To: The Eunuchs Hysterical Society
On Apr 11, 2019, at 8:57 AM, Richard Tobin <richard@inf.ed.ac.uk> wrote:
>
>> 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
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.
^ permalink raw reply [flat|nested] 5+ messages in thread
* [TUHS] Unix filesystem semantics history - files with holes
@ 2019-04-11 2:37 Erik E. Fair
2019-04-11 5:28 ` Ronald Natalie
0 siblings, 1 reply; 5+ messages in thread
From: Erik E. Fair @ 2019-04-11 2:37 UTC (permalink / raw)
To: The Eunuchs Hysterical Society
When did the Unix filesystem add the semantics for "files with holes" (large,
sparse files)?
Just an idle question that was sparked by a conversation I had today.
Erik <fair@clock.org>
^ permalink raw reply [flat|nested] 5+ messages in thread
* Re: [TUHS] Unix filesystem semantics history - files with holes
2019-04-11 2:37 Erik E. Fair
@ 2019-04-11 5:28 ` Ronald Natalie
0 siblings, 0 replies; 5+ messages in thread
From: Ronald Natalie @ 2019-04-11 5:28 UTC (permalink / raw)
To: Erik E. Fair; +Cc: The Eunuchs Hysterical Society
Define large? It appears that filesystems going back to Research V4 supported sparse files. The maximum file size went up from 2**24 in V6 to 2**32 in V7, and then broke that barrier in several of the subsequent file systems.
> On Apr 10, 2019, at 10:37 PM, Erik E. Fair <fair-tuhs@netbsd.org> wrote:
>
> When did the Unix filesystem add the semantics for "files with holes" (large,
> sparse files)?
>
> Just an idle question that was sparked by a conversation I had today.
>
> Erik <fair@clock.org>
^ permalink raw reply [flat|nested] 5+ messages in thread
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2019-04-11 15:57 [TUHS] Unix filesystem semantics history - files with holes Richard Tobin
2019-04-11 19:09 ` William Corcoran
2019-04-11 19:49 ` Bakul Shah
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2019-04-11 2:37 Erik E. Fair
2019-04-11 5:28 ` Ronald Natalie
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