IJ01911: FILE SIZE MAY NOT BE UPDATED CORRECTLY AFTER A TRUNCATE CALL

APAR status

• Closed as program error.

Error description

• If a truncate() call is used to set the size of a file to
  something larger than the size the last write left it at,
  the filesystem may not correctly update the size of the
  file.
  
  Reported in:
  Spectrum Scale 4.2.3.2 on RHEL 7.3 x86_64
  
  Known Impact:
  If an application is expecting a file to be of a certain
  size, and a later stat() call shows the size of that file
  to be something different, that may cause the application
  to believe that the file is corrupt.
  
  Verification steps:
  One example to recreate this issue is to use a 4 MiB
  block
  size for the data pool in a filesystem, and use the
  following test program to demonstrate the problem:
  
  main()
  {
     system("dd if=/dev/zero bs=1 seek=22864437303 count=1
  of=/gpfs2/test");
     truncate("/gpfs2/test", 22868010952);
  }
  
  # ls -l /gpfs2/test
  -rw-r--r-- 1 root root 22867345408 Nov  9 12:00
  /gpfs2/test
  
  22864437303 bytes are written to the file, the size of
  the file is set to 22868010952 by truncate(), but stat()
  (ls) shows the file size as 22867345408.
  

Local fix

Problem summary

• In rare case, truncate() does not set file size
  correctly. The file size is set to full block boundary,
  the fragment is lost.
  

Problem conclusion

• Fix the logic error.
  

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:

  IJ03091

Fix information

• Fixed component name

  SPECTRUM SCALE

• Fixed component ID

  5725Q01LX

Applicable component levels