<div dir="ltr"><br><div class="gmail_extra"><br><br><div class="gmail_quote">On Sat, Mar 29, 2014 at 4:31 PM, Sankar P <span dir="ltr"><<a href="mailto:sankar.curiosity@gmail.com" target="_blank">sankar.curiosity@gmail.com</a>></span> wrote:<br>
<blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex">2014-03-28 23:11 GMT+05:30 Rishi Agrawal <<a href="mailto:rishi.b.agrawal@gmail.com">rishi.b.agrawal@gmail.com</a>>:<br>
<div class="">> Hi Sankar,<br>
><br>
> Have you written any code further. I read your file system's code and learnt<br>
> a lot from it.<br>
><br>
<br>
</div>Good to know that you have learnt from it. I stopped at a logical<br>
closure where the filesystem is at a usable state.<br>
<br>
I did not write any code further as I am spending my personal time on<br>
changing diapers for my newborn :)<br>
<br>
Whatever little time I get, I tend to do it in trivial user space<br>
applications. Extending the filesystem requires long hours of<br>
learning, context maintenance, focus etc. So I deferred it for a later<br>
stage. I will be happy to get some patches though :)<br>
<div class="HOEnZb"><div class="h5"><br>
><br>
><br>
> On Thu, Aug 8, 2013 at 8:36 PM, Sankar P <<a href="mailto:sankar.curiosity@gmail.com">sankar.curiosity@gmail.com</a>> wrote:<br>
>><br>
>> okay. Thanks. I will update this list once I write enough code for the<br>
>> next release :)<br>
>><br>
>> On Thu, Aug 8, 2013 at 4:59 PM, Greg Freemyer <<a href="mailto:greg.freemyer@gmail.com">greg.freemyer@gmail.com</a>><br>
>> wrote:<br>
>> ><br>
>> ><br>
>> > Sankar P <<a href="mailto:sankar.curiosity@gmail.com">sankar.curiosity@gmail.com</a>> wrote:<br>
>> >>On Thu, Aug 8, 2013 at 3:55 AM, Greg Freemyer <<a href="mailto:greg.freemyer@gmail.com">greg.freemyer@gmail.com</a>><br>
>> >>wrote:<br>
>> > <snip><br>
>> >>><br>
>> >>> I just read your todo's.<br>
>> >>><br>
>> >>> Multi-block files should come before extents and/or mmap support. I<br>
>> >>> guess you realize that ext2 and ext3 are NOT extent based<br>
>> >>filesystems.<br>
>> >>> ext4 is the first extent based one.<br>
>> >>><br>
>> >>> So its:<br>
>> >>> ext2 - block based filesystem<br>
>> >>> ext3 - block based with a journal<br>
>> >>> ext4 - extent based with a journal<br>
>> >>><br>
>> >>> In reality the current ext4 driver has a matrix of supported<br>
>> >>features.<br>
>> >>> There are flag bits which tell you which features a specific<br>
>> >>> filesystem instance supports. You may want to atleast look at those<br>
>> >>> feature flags to get an idea of the kinds of features ext4 supports.<br>
>> >>><br>
>> >>> If you don't have lseek() support for read, you need to get it added.<br>
>> >>> lseek() is pretty trivial for reads so there is not much reason not<br>
>> >>to<br>
>> >>> have it as the very next step.<br>
>> >>><br>
>> >>> For write, it means you have to implement a read/modify/write cycle<br>
>> >>in<br>
>> >>> your filesystem. I gather you don't have that.<br>
>> >>><br>
>> >>> With just those todo's I go in this order:<br>
>> >>><br>
>> >>> - lseek() support with read (trivial)<br>
>> >>> - partial block write support (requires read/modify/write logic, so<br>
>> >>not trivial)<br>
>> >>> - lseek() support for write (trivial now you have partial block write<br>
>> >>support)<br>
>> >>> - multi-block support, requires a major refactor most likely.<br>
>> >>><br>
>> >><br>
>> >>Thank you so much for the detailed response.<br>
>> >><br>
>> >>I will go in this order as this seem to be logically progressive nicely<br>
>> >>iiuc.<br>
>> >><br>
>> >>When do you think I should bring in support for mmap and page-caching<br>
>> >>that Rajat in the above plan ?<br>
>> >><br>
>> >>Thanks.<br>
>> ><br>
>> > I've never done a FS from scratch so I'm not sure, but I would delay<br>
>> > them as long as you can.<br>
>> ><br>
>> > I suspect you will need cache support to properly handle writes on a<br>
>> > multi block file, so as you work on that feature you may decide "now is the<br>
>> > time" for the cache.<br>
>> ><br>
>> > Mmap should be last.<br>
>> ><br>
>> > Greg<br>
>> > --<br>
>> > Sent from my Android phone with K-9 Mail. Please excuse my brevity.<br>
>><br>
>><br>
>><br>
>> --<br>
>> Sankar P<br>
>> <a href="http://psankar.blogspot.com" target="_blank">http://psankar.blogspot.com</a><br>
>><br>
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><br>
><br>
><br>
><br>
> --<br>
> Regards,<br>
> Rishi Agrawal<br>
<br>
<br>
<br>
--<br>
Sankar P<br>
<a href="http://psankar.blogspot.com" target="_blank">http://psankar.blogspot.com</a><br>
</div></div></blockquote></div><br></div><div class="gmail_extra">I identified one memory leak while reading the code. Will send the patch.<br clear="all"></div><div class="gmail_extra"><br>-- <br>Regards,<br>Rishi Agrawal<br>
</div></div>