From mboxrd@z Thu Jan 1 00:00:00 1970 From: Hans Reiser Subject: Re: tail policy question Date: Thu, 13 Nov 2003 21:12:04 -0800 Message-ID: <3FB46424.4000300@namesys.com> References: <3FB22E06.9070500@namesys.com> <20031114170604.GQ1278@backtop.namesys.com> Mime-Version: 1.0 Content-Transfer-Encoding: 7bit Return-path: list-help: list-unsubscribe: list-post: Errors-To: flx@namesys.com In-Reply-To: <20031114170604.GQ1278@backtop.namesys.com> List-Id: Content-Type: text/plain; charset="us-ascii"; format="flowed" To: Alex Zarochentsev Cc: Zhihui Zhang , reiserfs-list@namesys.com, vs@namesys.com Alex Zarochentsev wrote: >On Thu, Nov 13, 2003 at 01:34:07PM -0500, Zhihui Zhang wrote: > > >>Thanks for your and Alex's reply. I poke around a little bit more and >>find out that the mkfs.c does use ITEM_TAIL40_ID, which happens to have >>the same value as TAIL_ID (0x6) in the kernel file. >> >> > >they are from different name spaces. > > > > >>However, I am confused >>when I see the following in plugin.h: >> >>PLUGIN_BY_ID(item_plugin, REISER4_ITEM_PLUGIN_TYPE, item); >>PLUGIN_BY_ID(tail_plugin, REISER4_TAIL_PLUGIN_TYPE, tail); >> >> > >IFAIK above defines service functions for plugins of different types, >it does not define concrete plugins. tail_plugin_type should be named >as tail_policy_plugin for better understanding. > > > >>The item plugin has TAIL_ID if the item is of tail type. So what is the >>use of a separate tail_plugin? Plus, the tail_plugin has three IDs >>defined: NEVER, ALWAYS, and DEFAULT, none of which has a value of 0x6. My >>guess is that the item plugin for tails are used to manage tails (merge, >>split, read, write?), >> >> > >yes > > > >>while the tail_plugin is used to decide if a >>conversion between tail format and extent format is needed. If so, the >>reiser4.h file should have: >> >>#define REISER4_TAIL_PLUGIN (DEFAULT_TAIL_ID) >> >>instead of >> >>#define REISER4_TAIL_PLUGIN (ALWAYS_TAIL_ID) >> >>Does this make sense? Please clarify this for me. Thanks. >> >> > >what i would like to see: >rename *_TAIL_ID to *_TAIL_POLICY_ID >DEFAULT_TAIL_POLICY__ID renamed to SMART_TAIL_POLICY_ID > > 16K_TAIL_POLICY is more informative.... >#define REISER4_TAIL_POLICY_PLUGIN (one of SMART_TAIL_POLICY_ID ALWAYS_TAIL_POLICY_ID, > NEVER_TAIL_POLICY_ID) > >Does it make things more clear? > >Thanks. > > -- Hans