IV96475: DATA LOSS WHEN USING "TAR" TO ARCHIVE FILES WITH "-S" OPTION

APAR status

• Closed as program error.

Error description

• Users archived their files using tar command with -S
  option,
  then extracted files from the archive and found the data
  in
  files corrupted. This is because the tar command with -S
  option would check whether a file is a sparse file before
  archiving it and would handle sparse file efficiently by
  directly writing zero data into archive for holes. Here
  GPFS
  data-in-inode files are incorrectly determined as sparse
  files since the tar command is comparing the file size
  and
  stat() st_blocks, and file size is non-zero and st_blocks
  is
  zero for data-in-inode files, hence like a real sparse
  file.
  

Local fix

Problem summary

• Users archived their files using tar command with -S option,
  then extracted files from the archive and found the data in
  files corrupted. This is because the tar command with -S option
  would check whether a file is a sparse file before archiving it
  and would handle sparse file efficiently by directly writing
  zero data into archive for holes. Here GPFS data-in-inode files
  are incorrectly determined as sparse files since the tar command
  is comparing the file size and stat() st_blocks, and file size
  is non-zero and st_blocks is zero for data-in-inode files,
  hence like a real sparse file.
  

Problem conclusion

• Changed the stat() behavior to return fake block count on stat()
  st_blocks for data-in-inode files. Introduced an undocumented
  configuration parameter "showFakeBlockCountForDataInInodeOnStat"
  to give users an interface to revert to the old behavior on
  stat() st_blocks for data-in-inode file.
  

Temporary fix

Comments

APAR Information

• APAR is sysrouted FROM one or more of the following:

• APAR is sysrouted TO one or more of the following:

  IV96488

Fix information

• Fixed component name

  SPECTRUM SCALE

• Fixed component ID

  5725Q01LX

Applicable component levels

• R420 PSY

     UP