> I'm sorry, but I have absolutely no idea what this > means. > > From the rationale it sounds like s390 stashes some kind of > label or > bootable area at the end of a minidisk, which is visible to > the Linux > program accessing the device file, and that mke2fs is > supposed to > somehow recognize the RECOMP area (how?), figure out how > big is it > (how?) and when mke2fs is not given a filesystem size, to > pick by > default a new filesystem size which hdoesn't overwrite > the RECOMP > area. > > Did I guess this correctly? If so, you're going to > have to tell me > how to do this, or better yet, supply code (patches) which > does this.
You got it right. In the CMS label record for an ECKD DASD minidisk, there are two fields of interest: ADTCYL and ADTMCYL. ADTMCYL is the total size of the minidisk in cylinders, including the RECOMP area, if there is one. ADTCYL is the number of cylinders used by the filesystem. Normally, these two values are the same. But if the minidisk has been formatted with the RECOMP option, the two values will be different. ADTCYL will be less than ADTMCYL. The difference will be the size of the RECOMP area, in cylinders. I'm not a C programmer, but I found this structure mapping on the internet at http://people.redhat.com/zaitcev/linux/linux-2.4.18-pre7-cmsfs.diff. Perhaps it will be helpful to you. I suspect, though I haven't looked at the source code, that there is probably already a similar data structure defined for mke2fs that it is using now. + * Mock ADTSECT for the CMS FS for Linux. + * Based on: http://www.vm.ibm.com/pubs/cmsdacb/ADTSECT.HTML + * noting offset 144 (0x90) for 80 bytes (0x50) + */ +typedef struct CMSFSADT +{ + char ADTIDENT[4] ; /* VOL START / LABEL IDENTIFIER */ + char ADTID[6] ; /* VOL START / VOL IDENTIFIER */ + char ADTVER[2] ; /* VERSION LEVEL */ + char ADTDBSIZ[4] ; /* DISK BLOCK SIZE */ + char ADTDOP[4] ; /* DISK ORIGIN POINTER */ + char ADTCYL[4] ; /* NUM OF FORMATTED CYL ON DISK */ + char ADTMCYL[4] ; /* MAX NUM FORMATTED CYL ON DISK */ + char ADTNUM[4] ; /* Number of Blocks on disk */ + char ADTUSED[4] ; /* Number of Blocks used */ + char ADTFSTSZ[4] ; /* SIZE OF FST */ + char ADTNFST[4] ; /* NUMBER OF FST'S PER BLOCK */ + char ADTDCRED[6] ; /* DISK CREATION DATE (YYMMDDHHMMSS) */ + char ADTFLGL[1] ; /* LABEL FLAG BYTE (ADTFLGL) */ +#define ADTCNTRY 0x01 /* Century for disk creation + date (0=19, 1=20), corresponds to + ADTDCRED. */ + char reserved[1] ; + char ADTOFFST[4] ; /* DISK OFFSET WHEN RESERVED */ + char ADTAMNB[4] ; /* ALLOC MAP BLOCK WITH NEXT HOLE */ + char ADTAMND[4] ; /* DISP INTO HBLK DATA OF NEXT HOLE */ + char ADTAMUP[4] ; /* DISP INTO USER PART OF ALLOC MAP */ + char ADTOFCNT[4] ; /* Count of SFS open files for this ADT */ + char ADTSFNAM[8] ; /* NAME OF SHARED SEGMENT */ +} CMSFSADT ; + +#define ADTLABSZ 0x00000050 /* LENGTH OF THE LABEL PORTION */ + +/* + MAPPING OF VOLUME LABEL +0090 144 Dbl-Word 8 * (0) +0090 144 Character 4 ADTIDENT VOL START / LABEL IDENTIFIER +0094 148 Character 6 ADTID VOL START / VOL IDENTIFIER +009A 154 Character 2 ADTVER VERSION LEVEL +009C 156 Signed 4 ADTDBSIZ DISK BLOCK SIZE +00A0 160 Signed 4 ADTDOP DISK ORIGIN POINTER +00A4 164 Signed 4 ADTCYL NUM OF FORMATTED CYL ON DISK +00A8 168 Signed 4 ADTMCYL MAX NUM FORMATTED CYL ON DISK +00AC 172 Signed 4 ADTNUM Number of Blocks assigned to the + minidisk or, in the case of an + SFS top directory, the number of + blocks assigned to the containing + filespace. This field is not set + for SFS subdirectories except as + a byproduct of the ADT Lookup + function, which queries the space + values for subdirs and also + leaves these values in the ADT + space fields. +00B0 176 Signed 4 ADTUSED Number of Blocks used in the + minidisk or, in the case of an + SFS top directory, the number of + blocks consumed in the containing + filespace. This field is not set + for SFS subdirectories except as + a byproduct of the ADT Lookup + function, which queries the space + values for subdirs and also + leaves these values in the ADT + space fields. +00B4 180 Signed 4 ADTFSTSZ SIZE OF FST +00B8 184 Signed 4 ADTNFST NUMBER OF FST'S PER BLOCK +00BC 188 Character 6 ADTDCRED DISK CREATION DATE (YYMMDDHHMMSS) +00C2 194 Bitstring 1 ADTFLGL LABEL FLAG BYTE (ADTFLGL) + EQUATES FOR ADT LABEL FLAG BYTE (ADTFLGL) + .... ...1 ADTCNTRY X'01' Century for disk creation + date (0=19, 1=20), corresponds to + ADTDCRED. +00C3 195 Character 1 * RESERVED +00C4 196 Signed 4 ADTOFFST DISK OFFSET WHEN RESERVED +00C8 200 Signed 4 ADTAMNB ALLOC MAP BLOCK WITH NEXT HOLE +00CC 204 Signed 4 ADTAMND DISP INTO HBLK DATA OF NEXT HOLE +00D0 208 Signed 4 ADTAMUP DISP INTO USER PART OF ALLOC MAP +00D4 212 Signed 4 ADTOFCNT Count of SFS open files for this + ADT NOTE: ADTOFCNT IS NOT REALLY + PART OF THE VOLUME LABEL - IT IS + NOT USED FOR MINIDISKS. +00D8 216 Character 8 ADTSFNAM NAME OF SHARED SEGMENT + 00000050 ADTLABSZ *-ADTIDENT LENGTH OF THE LABEL + PORTION + +* +---------------------------+---------------------------+ +* 90 | ADTIDENT | ADTID- | +* +-------------+-------------+---------------------------+ +* 98 | -(094) | ADTVER | ADTDBSIZ | +* +-------------+-------------+---------------------------+ +* A0 | ADTDOP | ADTCYL | +* +---------------------------+---------------------------+ +* A8 | ADTMCYL | ADTNUM | +* +---------------------------+---------------------------+ +* B0 | ADTUSED | ADTFSTSZ | +* +---------------------------+---------------------------+ +* B8 | ADTNFST | ADTDCRED- | +* +-------------+------+------+---------------------------+ +* C0 | -(0BC) |:FLGL |//////| ADTOFFST | +* +-------------+------+------+---------------------------+ +* C8 | ADTAMNB | ADTAMND | +* +---------------------------+---------------------------+ +* D0 | ADTAMUP | ADTOFCNT | +* +---------------------------+---------------------------+ +* D8 | ADTSFNAM | +* +-------------------------------------------------------+ +* E0 +* + +This information is based on VM/ESA 2.4.0. +Last updated on 12 Aug 1999 at 11:17:01 EDT. +Copyright IBM Corporation, 1990, 1999 + -- To UNSUBSCRIBE, email to [EMAIL PROTECTED] with a subject of "unsubscribe". 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