From: Patrick Farrell Date: Tue, 16 Aug 2016 20:19:12 +0000 (-0400) Subject: staging: lustre: fld: add fld description documentation X-Git-Tag: v4.9-rc1~119^2~1078 X-Git-Url: https://git.karo-electronics.de/?a=commitdiff_plain;h=aa08b0e3c7ae977ed9384f63ded2743e0aee1c7e;p=karo-tx-linux.git staging: lustre: fld: add fld description documentation Add subsystem description from Di Wang to header file. Signed-off-by: Patrick Farrell Intel-bug-id: https://jira.hpdd.intel.com/browse/LU-5153 Reviewed-on: http://review.whamcloud.com/10631 Reviewed-by: wangdi Reviewed-by: John L. Hammond Reviewed-by: Oleg Drokin Signed-off-by: James Simmons Signed-off-by: Greg Kroah-Hartman --- diff --git a/drivers/staging/lustre/lustre/fld/fld_internal.h b/drivers/staging/lustre/lustre/fld/fld_internal.h index f0efe5b9fbec..08eaec735d6f 100644 --- a/drivers/staging/lustre/lustre/fld/fld_internal.h +++ b/drivers/staging/lustre/lustre/fld/fld_internal.h @@ -31,6 +31,25 @@ * * lustre/fld/fld_internal.h * + * Subsystem Description: + * FLD is FID Location Database, which stores where (IE, on which MDT) + * FIDs are located. + * The database is basically a record file, each record consists of a FID + * sequence range, MDT/OST index, and flags. The FLD for the whole FS + * is only stored on the sequence controller(MDT0) right now, but each target + * also has its local FLD, which only stores the local sequence. + * + * The FLD subsystem usually has two tasks: + * 1. maintain the database, i.e. when the sequence controller allocates + * new sequence ranges to some nodes, it will call the FLD API to insert the + * location information in FLDB. + * + * 2. Handle requests from other nodes, i.e. if client needs to know where + * the FID is located, if it can not find the information in the local cache, + * it will send a FLD lookup RPC to the FLD service, and the FLD service will + * look up the FLDB entry and return the location information to client. + * + * * Author: Yury Umanets * Author: Tom WangDi */