1. 25 May, 2005 23 commits
  2. 24 May, 2005 1 commit
  3. 23 May, 2005 15 commits
  4. 21 May, 2005 1 commit
    • Suparna Bhattacharya's avatar
      [PATCH] fix for __generic_file_aio_read() to return 0 on EOF · b5c44c21
      Suparna Bhattacharya authored
      I came across the following problem while running ltp-aiodio testcases from
      ltp-full-20050405 on linux-2.6.12-rc3-mm3.  I tried running the tests with
      EXT3 as well as JFS filesystems.
      
      One or two fsx-linux testcases were hung after some time.  These testcases
      were hanging at wait_for_all_aios().
      
      Debugging shows that there were some iocbs which were not getting completed
      eventhough the last retry for those returned -EIOCBQUEUED.  Also all such
      pending iocbs represented READ operation.
      
      Further debugging revealed that all such iocbs hit EOF in the DIO layer.
      To be more precise, the "pos" from which they were trying to read was
      greater than the "size" of the file.  So the generic_file_direct_IO
      returned 0.
      
      This happens rarely as there is already a check in
      __generic_file_aio_read(), for whether "pos" < "size" before calling direct
      IO routine.
      
      >size = i_size_read(inode);
      >if (pos < size) {
      >	  retval = generic_file_direct_IO(READ, iocb,
      >                               iov, pos, nr_segs);
      
      But for READ, we are taking the inode->i_sem only in the DIO layer.  So it
      is possible that some other process can change the size of the file before
      we take the i_sem.  In such a case ( when "pos" > "size"), the
      __generic_file_aio_read() would return -EIOCBQUEUED even though there were
      no I/O requests submitted by the DIO layer.  This would cause the AIO layer
      to expect aio_complete() for THE iocb, which doesnot happen.  And thus the
      test hangs forever, waiting for an I/O completion, where there are no
      requests submitted at all.
      
      The following patch makes __generic_file_aio_read() return 0 (instead of
      returning -EIOCBQUEUED), on getting 0 from generic_file_direct_IO(), so
      that the AIO layer does the aio_complete().
      
      Testing:
      
      I have tested the patch on a SMP machine(with 2 Pentium 4 (HT)) running
      linux-2.6.12-rc3-mm3.  I ran the ltp-aiodio testcases and none of the
      fsx-linux tests hung.  Also the aio-stress tests ran without any problem.
      Signed-off-by: default avatarSuzuki K P <suzuki@in.ibm.com>
      Signed-off-by: default avatarSuparna Bhattacharya <suparna@in.ibm.com>
      Signed-off-by: default avatarAndrew Morton <akpm@osdl.org>
      Signed-off-by: default avatarLinus Torvalds <torvalds@osdl.org>
      b5c44c21