okay. Thanks. I will update this list once I write enough code for the next release :) On Thu, Aug 8, 2013 at 4:59 PM, Greg Freemyer <greg.freemyer@xxxxxxxxx> wrote: > > > Sankar P <sankar.curiosity@xxxxxxxxx> wrote: >>On Thu, Aug 8, 2013 at 3:55 AM, Greg Freemyer <greg.freemyer@xxxxxxxxx> >>wrote: > <snip> >>> >>> I just read your todo's. >>> >>> Multi-block files should come before extents and/or mmap support. I >>> guess you realize that ext2 and ext3 are NOT extent based >>filesystems. >>> ext4 is the first extent based one. >>> >>> So its: >>> ext2 - block based filesystem >>> ext3 - block based with a journal >>> ext4 - extent based with a journal >>> >>> In reality the current ext4 driver has a matrix of supported >>features. >>> There are flag bits which tell you which features a specific >>> filesystem instance supports. You may want to atleast look at those >>> feature flags to get an idea of the kinds of features ext4 supports. >>> >>> If you don't have lseek() support for read, you need to get it added. >>> lseek() is pretty trivial for reads so there is not much reason not >>to >>> have it as the very next step. >>> >>> For write, it means you have to implement a read/modify/write cycle >>in >>> your filesystem. I gather you don't have that. >>> >>> With just those todo's I go in this order: >>> >>> - lseek() support with read (trivial) >>> - partial block write support (requires read/modify/write logic, so >>not trivial) >>> - lseek() support for write (trivial now you have partial block write >>support) >>> - multi-block support, requires a major refactor most likely. >>> >> >>Thank you so much for the detailed response. >> >>I will go in this order as this seem to be logically progressive nicely >>iiuc. >> >>When do you think I should bring in support for mmap and page-caching >>that Rajat in the above plan ? >> >>Thanks. > > I've never done a FS from scratch so I'm not sure, but I would delay them as long as you can. > > I suspect you will need cache support to properly handle writes on a multi block file, so as you work on that feature you may decide "now is the time" for the cache. > > Mmap should be last. > > Greg > -- > Sent from my Android phone with K-9 Mail. Please excuse my brevity. -- Sankar P http://psankar.blogspot.com _______________________________________________ Kernelnewbies mailing list Kernelnewbies@xxxxxxxxxxxxxxxxx http://lists.kernelnewbies.org/mailman/listinfo/kernelnewbies
